uht plant

UHT PLANT

A PROJECT REPORT

B.Tech Electrical

Submited byHafiz Muhammad Assad Iqbal

Tahir JavedMuhammad Umer

BACHLORSIN

Electrical TechnologyYear2012

PROJECT SUPERVISOR

Mr. Muhammad Naveed

PRESTON INSTITUTE OF MANAGEMENT SCIENCE AND

TECHNOLOGY

APPROVED ON:

SIGN: -------------------------------------

NAME: -----------------------------------

INTERNAL EXAMINER:

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NAME: -----------------------------------

EXTERNAL EXAMINER:

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NAME: -------------------------------------

DECLARATION

We hereby declare that no portion of the work referred to in this project Thesis has been

submitted in support of an application for another degree or qualification of this of any other

university or other institute action of learning. If any act of plagiarism found, we are fully

responsible for every disciplinary action taken against us depending upon seriousness of the

proven offence, even the cancellation

COPYRIGHT STATEMENT

Copyright in text of this thesis rests with the student author. Copies (by any process)

either in full, or of extracts, may be made only in accordance with instructions given

by the author and lodged in the Library of PIMSAT. Details may be obtained by the

Librarian. This page must from part of any such copies made. Further copies (by any

process) of copies made in accordance with such instructions may not be made

without the permission (in writing) of the author.

The ownership of any intellectual property right which may be described in this thesis

is vested in PIMSAT, subject to any prior agreement to the country, and may not be

made available for use any parties without the written permission of the PIMSAT,

which will prescribe the term and conditions of any such agreement

ACKNOWLEDGEMENT

We are thankful to ALLAH and many different people for helping us creating

this project.

Thanks to our families for their trust and understanding.

Our friends (who have always been a source of inspiration) have helped

to create a wonderful academic climate.

DEDICATED TO

Our dearest and most respected parents and teachers. Whose efforts and prayers

are great source of strength to us in every noble venture? Theirs love inspired us

to the higher idea of life.

ABSTRACT

The report is all about the research conducted by the group and the subsequent

implementation of the project in the form of human tracking. The human tracking system

offer the capability of searing a specific person in a multy story building without spending

much time.

Milk deposits from an ultra-high-temperature (UHT) plant were analysed for protein, fat and

minerals. The physical appearance and composition of the deposits was found to vary with

modifications of the plant. For each particular arrangement of the plant, a characteristic

pattern of deposits occurred. Possible mechanisms involved in the formation of the deposits

are discussed.

Ultra-high temperature ceramics are the ideal materials for extreme conditions owing to their

very high melting points and good thermo-mechanical properties at high temperatures. For

these reasons, they are widely known as materials for aerospace applications. This paper

presents a comparative spectral characterization of zirconium, hafnium, and tantalum

carbides ultra-high temperature ceramics for concentrating solar power applications. Room-

temperature reflectance spectra have been measured from the ultraviolet wavelength region

to the mid-infrared band. Using these spectral properties, the ceramics were evaluated as

sunlight absorbers in receivers for high-temperature thermodynamic solar plants.

LIST OF CONTENTS

Chapter 1

The Heat Treatment Processes

1.1 Introduction 15

1.2 Microbiology 17

1.3 Bacteria 17

1.4 Molds 20

1.4.1 Yeast 20

1.5 Bacteria Phages 20

1.6 Toxicity 21

1.7 Pasteurization 21

1.8 Extended Shelf Life / Ultra Pasteurization 22

1.9 UHT Treatment 23

1.10 Sterilization 24

1.11 EU Classification 25

1.12 Process Evaluation 27

1.13 The Logarithmic Reduction of spores and Sterilizing

Efficiency 27

1.14 Terms & Expressions to Characterize Heat Treatment

Processes 28

1.15 Residence Time 29

1.16 Chemical & Bacteriological changes at High

Temperature 31

Chapter 2

PT 100

2.1. Introduction 33

2.2. Features 33

2.3. Getting Started 34

2.4. Hardware Setup 35

2.5. Software Setup 36

2.6. Evaluation Board 37

2.6.1. The Constant Current Source 37

2.6.2. RTD Signal Chain 39

2.7. Types of PT 100 40

2.8. Technical Data 43

2.9. Cabling 43

2.9.1. Line Resistance 43

2.9.2. Line Compensation 44

2.10. Measuring Junction Location 46

2.11. Wiring of PT 100 Sensors 47

2.11.1. Two Wire Connection 47

2.11.2. Three Wire Connection 48

2.11.3. Four Wire Connection 48

Chapter 3

Solenoid Valve


3.2. Magnetic Field of an infinite solenoid inside 51

3.3. Outside 53

3.4. Quantitative Description 53

3.5. Magnetic Field and vector potential for finite continuous

solenoid 54

3.6. Inductance of a solenoid 56

3.7. Electromechanical Solenoids 57

3.8. Rotary Solenoid 58

3.8.1. Rotary Voice Call 59

3.8.2. Pneumatic Solenoid Valves 59

3.8.3. Hydraulic Solenoid Valves 59

3.8.4. Automobile Starter Solenoid 60

3.9. Switching Functions & Symbols 60

3.9.1. Normally Closed (NC) 60

3.10. Latching or Bi-Stable 61

3.10.1. Number of Ways 61

3.11. Electric Position Indicator 62

3.11.1. Features 62

3.12. Dust Collector Valves & Blow Tubes 63

3.12.1. Features 63

3.12.2. Dust Collector Cleaning 63

Chapter 4

Line Heat System


4.2. Milk Samples 66

4.3. Sample Preparation 67

4.3.1. Panelists 67

4.4. Descriptive Orientation Sessions 67

4.5. Line Separation 67

4.6. Determining Sensory Properties 69

4.7. Experimental Design and Statistical Analysis 69

Chapter 5

Temperature Controller

5.1. Basic of Temperature Control 73

5.2. Practical Considerations 73

5.3. Types of Control 74

5.4. More about control Theory 75

5.5. Power Control 76

5.6. Outputs 76

5.7. Solid State Relays 77

5.7.1. Thyrister Power Controllers 77

5.8. Phase Angle 77

5.9. Final Remarks 82

Chapter 6

Jomo Controller

6.1.Introduction 84

6.2. Tolerance Limits 86

6.3. Temperature Limiter 88

6.4. Applications 88

6.5. Brief Description 89

6.6. Functional Description 90

6.7. Binary Input 90

6.8. Analog Output 91

6.9. Instrument Description Transmitter 91

6.10. Schematic Arrangement of the Standard Cell 93

List of Figure

Figure 1.1: Temperature profiles for pasteurization processes 22

Figure 1.2. Temperature profiles for direct infusion, high heat infusion &

indirect UHT process. 23

Figure 1.3. Temperature profiles for conventional in-container

sterilization 25

Figure. 1.4 Holding Tube 30

Figure 1.5. Deposit in UHT Plants 31

Figure 2.1. PT 100 RTD Evaluation Board Simplified Block Diagram 34

Figure 2.2. Simplified PT 100 RTD Evaluation Board Schematic 35

Figure 2.3: Microsoft Excel-Based GUI 36

Figure 2.4. Constant Current Source 37

Figure 2.5. External RTD Connections 38

Figure 2.6: Hardware Status 39

Figure 2.7. Length of the wire 47

Figure 3.1. Solenoid Coil 50

Figure 3.2. Solenoid inside with 3 loops 51

Figure 3.3 Solenoid outside 52

Figure 3.4. Magnetic Field Continuous Solenoid 54

Figure : 3.5. Electric Indicator 62

Figure 4.1 Line Separation 68

Figure 4.2. Principal Component Analysis 71

Figure 5.1. Phase Angle 78

Figure 5.2. The response of a PI algorithm to a step in error 81

Figure 6.1. Jomo Characteristics 85

Figure 6.2. Torelance Band as a Function of the temperature 87

Figure 6.3. TB/TW 88

Figure 6.4. Block Diagram Brief Description 89

Figure 6.5. Jumo Digital Meter. 91

Figure 6.6 Measuring Cell. 93

List of Table

Table 1.1: A variety of dairy, food & beverage products and their suitability for

treatment in thermal heat processing systems 16

Table 1.2. Present legislation according to EU directive 92/46 “IDF & EU suggestions

for Dual Chemical Criteria” 26

List of Symbol

3.1. Normally Closed 61

CHAPTER # 1

THE HEAT

TREATMENT

PROCESSES

Chapter # 1 The Heat Treatment Processes

1.1. Introduction

As one of the most complete food products of all, dairy products are very important in human

nutrition. But dairy products are also highly perishable and would easily lose their nutritional

value, flavor and appearance if protective measures were not taken. Consequently, the dairy

industry is one of the most advanced industries in the food processing area, taking care of the

milk from when it leaves the udder of the cow — through transportation to the dairy,

processing, packaging, and distribution — until it reaches the consumer. The technology of

producing long-life products is today applied throughout the food and beverage industries,

and in many cases, the processing plants are designed for multipurpose operation. When

aseptic technology was introduced more than 35 years ago, it revolutionized the food

industry by making it possible to distribute high quality food products over long distances in

a cost-effective way. The heart of aseptic technology for production of long-life dairy

products is aseptic processing. Since its introduction this concept has been developed and

refined to a point where any need in respect of capacity, product viscosity, particulate

content, acidity or sensitivity to heat treatment can be met while securing high quality, long-

life products. APV was one of the pioneers in aseptic processing and over the years we have

developed a wide range of processing concepts to satisfy all the needs of the industry. In this

Technology Update, we will first discuss some of the micro-biological factors which must be

considered in all aseptic processing, together with the heating processes most commonly

used for reducing micro-organisms in dairy products: pasteurization, sterilization and ultra

high temperature (UHT) treatment. So-called commercial sterility is the aim of all UHT

processes, and the extent to which this is achieved in a particular process can be measured,

notably by reference to the bacteriological effect (B*) and the chemical effect (C*) of such

processes. These factors are explained in the section “Process Evaluation”. The main part of

the Technology Update is devoted to an analysis of the processing systems of most interest to

the dairy, food and beverage industries: Indirect Plate Sterilizer, Indirect Tubular Sterilizer,

Steam Infusion Sterilizer, High Heat Infusion Sterilizer, Instant Infusion Pasteurizer, Steam

Injection Sterilizer and Indirect Scraped Surface Heat Exchanger (SSHE) Sterilizer. In each

case we describe the system, discuss its advantages and limitations, and list a number of


products for which the system in question is particularly suitable The Pilot UHT Plant is able

to combine most of the aseptic processes in one unit, which provides an efficient tool for

pilot trials and product development. In aseptic processing, special consideration must be

given to some of the auxiliary equipment required. Aseptic tanks are not

Table 1.1: A variety of dairy, food & beverage products and their suitability for treatment in

thermal heat processing systems

A necessary requirement but often serves as a useful buffer for sterilized products. The area

of extended shelf life products is becoming increasingly important. APV has developed

concepts, offering the industry and consumers new solutions and exciting opportunities. With

the large number of options available it becomes important to be able to choose the solution

which provides the best quality product at a reasonable cost, giving safe and trouble free

operation. A separate section has been made to cover this subject. The process control system


is not only necessary, it must Incorporate up-to-date technology — not least on the software

side. Special attention must be given to the subsequent filling and packaging of aseptically

processed products. Finally, we address the area of product development. APV’s worldwide

capabilities in respect to product testing makes it possible to work closely with customers in

their efforts to upgrade production and launch new products. This Technology Update purely

deals with the indirect and direct heat transfer processes. APV also manufactures various

types of electrical — or “electro heat” thermal processing equipment such as ohmic heating.

This is dealt with in a separate Technology Update.

1.2. Microbiology

The key to production of long-life products with aseptic technology is a detailed

understanding of the microbiology of food. Using the example of the dairy industry, the milk

in the udder of a healthy cow is free from bacteria, but as soon as the milk comes into contact

with the air it becomes contaminated with micro-organisms. If the temperature is favorable,

the micro-organisms multiply and very soon the milk will turn sour (or putrefy), developing

an unpleasant flavor. To prevent this from happening, the raw milk is subjected to heat

treatment. The term “aseptic” is usually defined as “free from or keeping away” disease-

producing or putrefying micro-organisms. In the food industry the terms “aseptic”, “sterile”

and “commercially sterile” are often used interchangeably. This is not strictly correct.

Sterilization means 100% destruction of all living organisms, including their spores, and this

is very difficult to achieve. “Commercial sterility” means that the product is free from

microorganisms which grow and consequently contribute to the deterioration of the product.

Micro-organisms are extremely small and can only be seen under a microscope. However,

hundreds or thousands of individual cells or groups of cells can form colonies — which are

visible to the naked eye — and some colonies have colors, shapes, textures or odors which

make the organism identifiable.

1.3. Bacteria

The term “bacteria” strictly means rod-shaped micro-organisms only, but is also used in a

loose sense to include all microorganisms except yeast and molds. The individual bacterium

varies in size from 0.5 to 3 micron. The groups of bacteria which are most important in the


dairy industry are the lactic acid, coli form, butyric acid, and putrefaction bacteria. The

bacterial count in milk coming from the farm varies from a few thousand bacteria/ml for

high-quality milk; to several million if the standard of cleaning, disinfection and chilling is

poor. For milk to be classified as top quality, the CFU (Colony Forming Units) should be less

than 100,000/ml. Bacteria are single-celled organisms which normally multiply by binary

fission, i.e. splitting in two. The simplest and most common way to classify bacteria is

according to their appearance and shape.

However, in order to be able to see bacteria, they must first be stained and then studied under

a microscope at a magnification of approximately 1,000 X. Based on a method of staining,

developed by the Danish Bacteriologist Gram, bacteria are divided into Gram negative (red)

and Gram positive (blue). The three characteristic shapes of bacteria are spherical, rod

shaped and spiral. Diplococcic arrange themselves in pairs; staphylococci form clusters,

while streptococci form chains. Another way of classification is according to temperature

preference:

• Psychotropic bacteria (cold tolerant) reproduce at temperatures of 45°F or below.

• Psychrophilic bacteria (cold loving) have an optimum growth temperature below 68°F.

• Mesophilic bacteria (loving the middle range) have optimum growth temperatures between

68°F and 111°F.

• Thermophilic bacteria (heat loving) have their optimum growth temperatures between

113°F and 140°F.

• Thermoduric bacteria (heat enduring) can tolerate high temperatures — above 150°F. They

do not grow and reproduce at high temperatures, but can resist them without being killed.

Bacteria can only develop within certain temperature limits, which vary from one species to

another. Temperatures below the minimum cause growth to stop, but do not kill the bacteria.

They are, however, damaged by repeated freezing and thawing. If the temperature is raised

above the maximum, the bacteria are soon killed by heat. Most cells die within a few seconds

of being exposed to 158°F, but some bacteria can survive heating to 185°F for 15 minutes,

even though they do not form spores. A third way of classifying micro-organisms is by their

oxygen requirement. The availability of oxygen is vital to the metabolism of all organisms.


Some bacteria consume oxygen from the atmosphere; they are called aerobic bacteria.

However, to some bacteria free oxygen is a poison; they are called anaerobic bacteria and

obtain the oxygen they need from chemical compounds in their food supply. Some bacteria

consume free oxygen if it is present, but they can also grow in the absence of oxygen; they

are called facultative anaerobic. The acidity of the nutrient substrate for bacteria is also

important. Sensitivity to pH changes varies from one species to another, but most bacteria

prefer a growth environment with a pH around 7. Furthermore, the salt and/or sugar

concentration of a substrate has an important influence on the growth of bacteria. The higher

the concentration, the more growth is inhibited. This is caused by the high osmotic pressure

which will draw water out from the cell, thereby dehydrating it. Osmotic pressure is used as a

means of food preservation in sweetened condensed milk, salted fish and fruit preserves like

jam and marmalade. Spores. The spore is a form of protection against adverse conditions,

e.g. heat and cold, lack of moisture, lack of nutrients, or presence of disinfectants. Only a few

bacteria are spore forming e.g. Bacillus and Clostridium. The spores germinate back into a

vegetative cell and start reproduction when conditions become favorable again. The spores

have no metabolism and can survive for years in dry air and are much more resistant to

adverse conditions than bacteria. This includes heat treatment, and it takes typically 20

minutes at 248°F to kill them with 100 percent certainty. The UHT time/temperature

combination reduces the number of bacteria spores by a minimum of log 9, leaving very few

bacteria spores in UHT treated products.

Enzymes. When milk leaves the udder it contains enzymes, the so-called original enzymes.

Enzymes are also produced by the bacteria in the milk, the so-called bacterial enzymes.

Enzymes are not micro-organisms but are formed as a result of the metabolism of micro-

organisms. The ability of enzymes to trigger chemical reactions can be important when UHT

products are produced. Some of the bacterial enzymes are able to cause sweet coagulation of

milk products which destroys the product. The majority of these enzymes are produced by

Gram negative Pseudomonas bacteria developing mainly in cold raw milk stored for

excessive time in milk cooling tanks, road tankers or milk silos. This problem will be

aggravated if the milk has been contaminated because of unhygienic conditions or lack of


cleaning-in-place (CIP). The vast majority of enzymes will be destroyed by UHT treatment,

but a few may still be active in the final product.

1.4. Molds

Molds belong to the fungi group of micro-organisms which are widely distributed in nature

among plants, animals and human beings. Molds normally grow anaerobically, and their

optimum growth temperature is between 68°F and 86°F. Molds can grow in substrates with

pH 2-8.5, but many species prefer an acid environment. The most common species in milk do

not survive pasteurization conditions, and the presence of mold in pasteurized products is

therefore a sign of re-infection. The penicillium family is one of the most common types of

molds. Their powerful protein splitting properties make them the chief agent in ripening of,

for instance, blue cheese.

1.4.1. Yeast

Yeast also belong to the fungi group of micro-organisms. They vary greatly in size.

Saccharomyces cerivisiae, used for brewing of beer, has a diameter of 2-8 micron, but other

species may be as large as 100 micron. Yeast has the ability to grow both in the presence and

absence of oxygen. The optimum temperature is between 68°F and 86°F. Optimum pH

values are 4.5-5.0, but yeast will grow in the pH range of 3-7.5. From a dairy point of view,

yeast are generally undesirable organisms. They ferment milk and cream, and cause defects

in cheese and butter. In the brewing, baking and distillation industries, on the other hand,

they are very valuable organisms.

1.5. Bacteria Phages

Bacteria phages belong to the group of micro-organisms called viruses. Viruses have no

metabolism of their own and therefore cannot grow on a nutrient substrate. Viruses infect

living cells in plants and animals. Bacteria phages (also known as phages) infect bacteria and

are consequently a problem in all dairy processes where bacteria cultures are used. They are

very small in size — 0.02-0.06 microns — and can only be seen with an electron microscope.

Bacteria phages grow at temperatures between 50°F and 113°F. They are killed by exposure

to 145-190°F for 30 minutes and tolerate pH values in the range of 3-11.


1.6. Toxicity

Micro-organisms which are harmful to man or animals are called pathogens. They can cause

death or severe illness by the secretion of toxins either directly into contaminated foodstuffs,

which are subsequently eaten, or by transfer to an animal host offering ideal conditions for

reproduction and further generation of toxins. Some toxins are inactivated by heat treatment

at 140°F for one hour.

1.6.1. Process Classification

A number of different expressions are commonly used in the food industry in relation to food

preservation. This section will, in brief terms, describe the most common terms used.

1.7. Pasteurization

Most commercial liquid food products undergo some form of heat treatment and

pasteurization is the most common. As it is usually bacterial growth that causes food to

deteriorate, pasteurization preserves the freshness of the food product. There are basically

two ranges of pasteurization:

• Low-temperature pasteurization. For milk, this is based on heating the product to 162-

169°F and holding at that temperature for at least 15-20 seconds (or equivalent)

The pasteurization may vary from country to country according to national legislation. A

common requirement in all countries, however, is that the heat treatment must guarantee the

destruction of unwanted micro-organisms and all pathogenic bacteria. The shelf life of

pasteurized milk is limited (typically 5-7 days), and primarily depends on raw milk quality

and storage temperature. During low-temperature pasteurization the phosphates enzyme is

destroyed, while the peroxides enzyme is preserved. This serves as a measure to control the

process and distinguish it from high temperature pasteurization.

• High-temperature pasteurization. This is based on heating the product to 185°F or higher

for a few seconds (or equivalent) (Fig. 1.1). The aim is to kill the entire population of

bacteria which are pathogenic for both man and animals, and almost all other bacteria as

well. By careful monitoring of the process parameters, a product with excellent quality can

be obtained with minimum heat damage. The shelf life can be extended to several weeks in

the cooling chain.


During high-temperature pasteurization, both the phosphates and the peroxides enzymes are

destroyed, and this serves as a measure to confirm that the process has actually taken places

specified.

Figure 1.1: Temperature profiles for pasteurization processes

1.8. Extended Shelf Life/ Ultra pasteurization

The term “extended shelf life,” or “ESL,” is being applied more and more frequently. There

is no single general definition of ESL. Basically, what it means is the capability to extend the

shelf life of a product beyond its traditional well-known and generally accepted shelf life

without causing any significant degradation in product quality.

A typical temperature/time combination for high-temperature pasteurization of ESL milk is

257-266°F for 2-4 seconds.


1.9. UHT Treatment

UHT — or Ultra High Temperature — treatment is based on the fact that higher temperatures

permit a much shorter processing time. With proper time and temperature combination it is

possible to achieve commercial sterility with only limited, undesirable, chemical changes in

the product. In terms of nutritive value, flavor and appearance, the quality of the product is

more vulnerable to the duration of the treatment than to the temperature applied. In the UHT

process, the milk is typically heated to 279-302°F and held at that temperature for just a few

seconds before it is rapidly cooled down to room temperature (Fig. 1.2).

Fig1.2. Temperature profiles for direct infusion, high heat infusion & indirect UHT process.


After the product has been cooled it is led to an aseptic filling machine in a closed piping

system — either directly or by way of an aseptic storage tank. The product obtained in this

way has a shelf life at room temperature of several months. The quality of the final product

depends on the raw material quality but also to a large extent, on the type of heat treatment

system applied. This is the case for UHT milk and for a wide range of long-life food products

like sauces, salad dressings, mayonnaise and soups, as well as for juices and soft drinks. In

order to combat the Heat Resistant Spores (HRS) APV has developed the patented so-called

High Heat Infusion system. It enables heat treatment temperatures as high as 302°F without

adversely affecting the product quality and still maintaining acceptable running times in the

order of 24 hours between cleaning.

Products with very high viscosity are more difficult to handle in a UHT system, and APV has

developed a special patented version of the infusion system to handle high viscosity products.

This so-called Instant Infusion system is based on very short but controllable and well

defined retention time in the infusion chamber.

1.10. Sterilization

Sterilization is another type of heating process used for products to increase keeping quality

without refrigeration. The heat treatment takes place after the product is packed. The

package, with its content, is heated to approx. 248°F and held at that temperature for 10 to 20

minutes, after which it is cooled to room temperature. Because of the lengthy heat treatment

at a relatively high temperature, this process reduces the nutritive value of the product, and it

is also liable to change its color and flavor considerably.(Fig 1.3)


Fig 1.3. Temperature profiles for conventional in-container sterilization

1.11. EU Classification

In Europe, the EU milk Hygiene Directive (92/46) suggests that “limits and methods to

enable a distinction to be made between different types of heat treated milk” may be

established (Article 20). The proposed parameters, limits and methods may be summarized as

shown in Table 2. By this method the hygienic requirements concerning food safety can be

satisfied taking into consideration the keeping qualities over varying length of time. This

method also makes it possible to establish a new definition of different types of fluid milk

products in a way that is independent of the technology of the heat treatment and the filling.


It should be noted that the chemical criteria in Table 2 are the recommendation given by IDF

and EU to the legislators, but the general perception is that this proposal will be followed.

Table 1.2. Present legislation according to EU directive 92/46

“IDF & EU suggestions for Dual Chemical Criteria”


1.12. Process Evaluation

All UHT processes are designed to achieve commercial sterility. This calls for application of

heat to the product and a chemical sterility or other treatment that renders the equipment,

final packaging containers and product free of viable micro-organisms able to reproduce in

food under normal conditions of storage and distribution. In addition, it is necessary to

inactivate toxins and enzymes present, and to limit chemical and physical changes in the

product. In very general terms it is useful to have in mind that an increase in temperature of

50°F increases the sterilizing effect 10-fold whereas the chemical effect only increases

approximately 3-fold. In this section we will define some of the more commonly used terms

and how they can be used for process evaluation.

1.13. The Logarithmic Reduction of Spores and

Sterilizing Efficiency

When micro-organisms and/or spores are exposed to heat treatment not all of them are killed

at once. However, in a given period of time a certain number is killed while the remainder

survives. If the surviving micro-organisms are once more exposed to the temperature

treatment for the same period of time an equal proportion of them will be killed. On this basis

the lethal effect of sterilization can be mathematically expressed as a logarithmic function:

K · t = log N/Nt

where N = number of micro-organisms/spores originally present

Nt = number of micro-organisms/ spores present after a given time of treatment (t)

K = constant

t = time of treatment

A logarithmic function can never reach zero, which means that sterility defined as the

absence of living bacterial spores in an unlimited volume of product is impossible to achieve.

Therefore, the more workable concept of “sterilizing effect” or “sterilizing efficiency” is

commonly used. The sterilizing effect is expressed as the number of decimal reductions

achieved in a process. A sterilizing effect of 9 indicates that out of 109 bacterial spores fed

into the process, only 1 (100) will survive. Spores of Bacillus subtitles or Bacillus


stearo thermo philus are normally used as test organisms to determine the efficiency of UHT

systems, because they form fairly heat resistant spores.

1.14. Terms and Expressions to Characterize Heat Treatment

Processes

Q10 value. The sterilizing effect of heat sterilization increases rapidly with the increase in

temperature as described above. This also applies to chemical reactions which take place as a

consequence of an increase in temperature. The Q10 value has been introduced as an

expression of this increase in speed of reactions and specifies how many times the speed of a

reaction increases when the temperature is raised by 50°F. Q10 for flavor changes is in the

order of 2 to 3, which means that a temperature increase of 50°F doubles or triples the speed

of the chemical reactions. A Q10 value calculated for killing bacterial spores would range

from 8 to 30, depending on the sensitivity of a particular strain to the heat treatment. D-

Value. This is also called the decimal reduction time and is defined as the time required to

reduce the number of microorganisms to one-tenth of the original value, i.e. corresponding to

a reduction of 90%. Z-Value. This is defined as the temperature change which gives a 10-fold

change in the D-value. F0 Value. This is defined as the total integrated lethal effect and is

expressed in terms of minutes at a selected reference temperature of 250°F. F0 can be

calculated as follows:

F0 = 10(T - 250.1) /z · t/60, where

T = processing temperature (°F)

z = Z-value (°F)

t = processing time (seconds)

F0 = 1 after the product has been heated to 250°F for one minute. To obtain commercially

sterile milk from good quality raw milk, for example, an F0 value minimum of 5 to 6 is

required.

B* and C* Values. In the case of milk treatment, some countries are using the following

terms:

• Bacteriological effect:

B* (known as B star)


• Chemical effect

C* (known as C star)

B* is based on the assumption that commercial sterility is achieved at 275°F for 10.1 seconds

with a corresponding Z-value of 51°F; this reference process is giving a B* value of 1.0,

representing a reduction of thermo phallic spore count of 109 per unit (log 9 reduction). The

B* value for a process is calculated similarly to the F0 value:

B* = 10 ( T - 275 ) / 51 · t/10.1, where:

T = processing temperature (°F)

t = processing time (seconds)

The C* value is based on the conditions for a 3 percent destruction of thiamine (vitamin B1);

this is equivalent to 275°F for 30.5 seconds with a Z-value of 89°F. Consequently the C*

value can be calculated as follows:

C* = 10 ( T - 275 ) /89 · t/30.5

Fig. 4 shows that a UHT process is deemed to be satisfactory with regard to keeping quality

and organoleptic quality of the product when B* is > 1 and C* is < 1.

The B* and C* calculations may be used for designing UHT plants for milk and other heat

sensitive products. The B* and C* values also include the bacteriological and chemical

effects of the heating up and cooling down times, and are therefore important

in designing a plant with minimum chemical change and maximum sterilizing effect. The

more severe the heat treatment is, the higher the C* value. For different UHT plants the C*

value corresponding to a sterilizing effect of B* = 1 will vary greatly. A C* value of

below 1 is generally accepted for an average design UHT plant. Improved designs will have

C* values significantly lower than 1. The APV Steam Infusion Sterilizer has a C* value of

0.15.

1.15. Residence Time

Particular attention must be paid to the residence time in a holding cell or tube and the actual

dimensioning will depend on several factors such as turbulent versus laminar flow, foaming,

air content and steam bubbles. Since there is a tendency to operate at reduced residence time

in order to minimize the chemical degradation (C* value < 1), it becomes increasingly

important to know the exact residence time. The APV infusion system has been designed

with a special pump mounted directly below the infusion chamber, which ensures a sufficient


over-pressure in the holding tube in order to have a single phase flow free from air and steam

bubbles. This principle enables APV to define and monitor the holding time and temperature

precisely and makes it the only direct steam heating system which allows true validation of

flow and temperature at the

point of heat transfer. The concept is illustrated in Fig. 1.4

Fig. 1.4 Holding Tube


1.16. Chemical and Bacteriological Changes at

High Temperatures

Heating milk and other food products to high temperatures results in a range of complex

chemical reactions causing changes in color (browning), development of off-flavors and

formation of sediments. These unwanted reactions are largely avoided through heat treatment

at a higher temperature for a very short time. It is important to seek the optimum

time/temperature combination which provides sufficient kill effect on spores but at the same

time, limits the heat damage in order to comply with market requirements for the final

product. Even though the time/temperature combination is decisive for the final quality of the

product attention also has to be paid to the actual heating profile since various reactions take

place at different temperatures. This is illustrated in Fig. 1.5 in which type a deposit is a

voluminous protein-rich deposit, whereas type B deposit is a mineral-rich deposit primarily

developing at high temperatures. In particular type a deposit — which originates from protein

denaturation — must be minimized since it is harmful to the product quality.

Fig 1.5. Deposit in UHT Plants

CHAPTER # 2

PT 100

Chapter # 2 PT 100

2.1. Introduction

The PT100 RTD Evaluation Board allows the user to evaluate Microchip’s solution to

accurately measure temperature using RTD. When biasing RTDs to measure temperature,

self-heat due to power dissipation has to be considered. RTD resistance availability typically

ranges from 100Ω to 5,000Ω. In order to measure the output voltage across the RTD over a

wide temperature range, the biasing current has to be relatively high. This higher current

causes more power dissipation through heat and skews the temperature reading. Microchp’s

solution to this challenge is to use an MCP6S26 Programmable Gain Amplifier (PGA) to

increase the sensor dynamic output range and increase measurement resolution while

significantly reducing the biasing current magnitude.

This board consists of a surface mount RTD to measure the PCB temperature. In addition,

the user can connect and measure an external leaded RTD (2, 3 or 4-Wire) and configure the

corresponding jumper to remotely measure temperature. The multiple input channel PGA

adds gain programmability into the analog circuit. The multiple input channels are used to

switch between RTDs and the gain is used to increase the sensor dynamic range. The PGA

output is connected to a differential amplifier circuit which allows the user to scale the sensor

output. The differential output is digitized using an MCP3301 12-bit differential analog-to-

digital converter. The data is transmitted to the PC using the USB interface. A Microsoft

Excel-based Graphical User Interface (GUI) is used to obtain and display the data in real-

time.

2.2. Features

The PT100 RTD Evaluation Board has the following features:

• A surface mount PT100 RTD

• External (2, 3 or 4-wire) RTD connector

• Gain and input channel programmability using MCP6S26 PGA

• MCP3301 12-Bit + sign ADC

• MCP41010 10 kΩ Digital Potentiometer

• PIC18F2550 PICmicro® Microcontroller

Chapter # 2 PT 100

• USB interface to PC

• Microsoft Excel-Based GUI

2.3. Getting Started

This section describes how to quickly configure the PT100 RTD Evaluation Board. A

Simplified block diagram of the configuration is provided in Figure 2.1.

Figure 2.1. PT 100 RTD Evaluation Board Simplified Block Diagram

Chapter # 2 PT 100

2.4. Hardware Setup

1. Connect the USB cable to PC.

2. To measure PCB temperature, connect JP1 to Local RTD position and JP2 to RTD

position.

Figure 2.2. Simplified PT 100 RTD Evaluation Board Schematic

Chapter # 2 PT 100

2.5. Software Setup

1. Once the USB connection is secure, open the 00096R1.xls file and select Enable Macro

the Excel macro will execute and the status display will indicate hardware identification, as

shown in Figure 2.3.

Figure 2.3: Microsoft Excel-Based GUI

Chapter # 2 PT 100

2. Select Enable/Disable for CH0 or CH1 (Channel 0 and Channel 1, respectively).

3. Select PGA gain, ADC sampling rate and sampling buffer size for the strip chart display.

4. Click start to start acquisition, stop to stop acquisition. Reset to Clear buffer.

5. Adjust the digital potentiometer positions to select the differential amplifier gain and trim

the current sources for the local and external RTDs.

2.6. Evaluation Board

The PT100 RTD Evaluation Board uses surface mount RTD to measure temperature. An

external 2, 3 or 4-wire PT100 RTD can also be connected to measure temperature in remote

locations. The RTDs are biased using a constant current source. In order to reduce self-heat

due to power dissipation, the current magnitude is relatively low. The small voltage across

the RTD is amplified using the MCP6S26 PGA. The PGA allows the user to digitally

program the amplifier gain and increase the sensor output range. The output of the PGA is

scaled using a differential amplifier. The differential amplifier drives a 12-Bit + sign

differential ADC, MCP3301. The digital data is read using PIC18F2550 and transmitted to

PC using a USB interface.

2.6.1. The Constant Current Source

The constant current source uses a reference voltage, one amplifier and a PNP transistor, as

shown in Figure 2.4.

Figure 2.4. Constant Current Source

Chapter # 2 PT 100

The amplifier maintains constant voltage at the transistor emitter terminal. Therefore, the

emitter and collector currents are constant. The collector current biases the RTD. The biasing

current can be fine tuned by adjusting the 10 kΩ digital potentiometer using the GUI. A

100Ω, 0.1% resistor is available for system calibration at 0°C (RTD resistance at 0°C is

100Ω). This resistor can be jumped using JP1. When connecting an external PT100 RTD,

connect JP2 to External Position.

Figure 2.5. External RTD Connections

Chapter # 2 PT 100

2.6.2. RTD Signal Chain

The PGA is used to amplify the small voltage across the RTD. The reference input pin of the

PGA is connected to the RTD negative terminal and Channel 0 and Channel 1 are connected

to the positive terminals of each RTD. This allows only the voltage across the sensor to be

amplified. The PGA has a gain error of ±1% (max.) for gains greater than 1 V/V. Refer to the

datasheet (DS21685) for details. The RTD negative terminal and the PGA output are

connected to the differential amplifier. The differential amplifier scales the PGA output. The

difference amplifier gain is shown in Equation.

Equation: Difference Amplifier Gain

The GUI uses a Microsoft Excel-based macro to open the USB port and communicate with

the PIC18F2550. When the file is opened, the macro checks hardware status. The status

display indicates hardware status as shown in Figure 2.6.

Figure 2.6: Hardware Status

Chapter # 2 PT 100

When start is clicked, the macro double checks hardware availability before starting the

acquisition. All user options such as Sampling time, Strip chart buffer size, Digi. Pot

Positions, or PGA Chn/Gain setup can be changed during acquisition.

2.7. Types of PT 100

TF101 temperature sensors use DIN 43 760 platinum resistance temperature detectors

(RTD). For precise temperature measurement the Platinum Resistance Thermometer offers

the best overall advantages in repeatability and stability over a long period. High accuracy

allows replacement

1.TF101N

-50°C...+550°C

Platinum resistance temperature sensor on ceramic substrate intended for installation into any

housing depending to user’s requirements. Very small and quick sensor, only suitable for

further treatment. Notice: do not cut the sensor leads. Thermal response time refer to

manufacturer data: T0,9 in the air 10 s, in water <1 s

2. TF101K

-50°C.. .+200°C

Platinum resistance temperature sensor on ceramic substrate protected by a heat-shrinkable

sleeve and with PTFE isolated stranded wire. The TF101K version can be installed in motor

or transformer windings. When build-in into windings do not pressure the sensor element.

Precautions should be taken to protect sensor and extension leads against push and pull

Chapter # 2 PT 100

forces. Thermal response time T0,9 in the air 100s, in water 19 s.

3. TF 101U2

-30°C...+105°C

Sensors TF101U2 are encapsulated in a stainless-steel-shell V4A. They are suitable for

measuring temperatures in fluids, under isolations, at surfaces or for inside or outside

applications. The protection class is IP 66. The version with PVC-isolated cable (3 x 0,25

mm2 in one cable) can be easily wired. The maximum ambient temperature is 105 °C.

-50°C...+200°C

4. TF101G3

-50°C...+200°C

Platinum resistance temperature sensor on ceramic substrate built into a M6 brass threaded

bush, especially suitable for being screwed into metal, e.g. for monitoring temperature of

heat sinks or heating plates. Please note that there will be a measuring error due to the design,

Chapter # 2 PT 100

as the sensor can loose heat via the connection strand.Cable length: 2000 mm Weight: 21 g.

(Dimensions see Dimension illustrations)

5. TF101ZG2

-50°C...+200°C

Platinum resistance temperature sensor built into steel tube V4A, 1/2 inch, suitable for

installation in pipes. Thermal response time T0,9 in the air 255 s, in water 45 s. Suitable for

transmission in 2- or 3-wire technique. Weight 120 g (Dimensions see Dimension

illustrations) Order numbers: 110 mm insertion depth T223137

Chapter # 2 PT 100

2.8. Technical Data

Nominal resistance

Temperature coefficient

Class B, DIN 43 760

Test voltage

Extension leads

Shrink sleeve

Measuring range

100 Ω at 0 °C

3,85 x 10 –3/K (see table)

Δϑ = ± (0,3 + 0,005 ϑ) [°C]

2,5 kV AC (not TF101N)

PTFE; silver-plated stranded copper wire 0,14 mm2

Kynar

-50°C…+170 °C permanent

200 °C max. 170 h

2.9. Cabling

ZIEHL thermostats of TR series are generally insensitive to interference in the sensor line.

Occasionally, however, undesirable switching is unavoidable, especially when temperature is

near the switching point. For this reason it is highly recommended that cables are not laid

parallel to power current lines over long distances. When appropriate, cables should be

screened or twisted together.

2.9.1. Line-resistance

With RTD sensors the resistance of the connecting cable should be considered, otherwise

Chapter # 2 PT 100

there is an measuring error. The resistance must be compensated. The resistance of a

connecting cable can be calculated as follows:

R [Ω] = 2 x l/(k x A), l = cable length [m],

k = conductivity [S x m/mm2] e.g. Cu = 56,

A = cross sectional area [mm2]

For example copper-wire: I = 50 m, cross sectional area 1 mm2: R = 2 x 50/(56 x 1) = 1,79

Ω, Resulting error = 1,79 Ω/0,385 Ω x K = 4,6 K.

2.9.2. Line Compensation

2-Wire Technique

With 2-wire connection the line resistance is compensated for by a potentiometer in the

thermostat, by programming (e.g. TR122D, TR600) or via wiring an external resistor. The

advantage of the possibly simpler and more economical running of just two wires is

counteracted

by the disadvantage of the manual compensation required in the case of longer wiring.

Differences in resistance caused by temperature changes cannot be compensated.

Chapter # 2 PT 100

3-Wire Technique

With 3-wire connection, a third wire (sense) connected to the sensor registers the drop in

voltage in one line. For compensation of line resistance it is assumed that the voltage drop in

the second line is identical (i.e. the same wire and same wire temperature). Compensation is

then performed automatically. Possible changes of resistance in the line due to temperature

changes are also compensated for.

4-wire technique

With 4-wire connection, impressed current flows via two wires to the sensor. Via a two

sensor line the drop in voltage is measured directly at the sensor. Possible differences in the

sensor connection wiring can be disregarded. A disadvantage is the higher costs involved in

running 4 wires.

Chapter # 2 PT 100

Combination of 2- and 3-wire technique

When connecting 2-wire-sensors to units with 3-wire input, the line resistance can be

compensated by connecting a compensation resistor (Rk) between ground and sense input.

Rk must have the same value as the resistance of the line. The sensor then has to be

connected to the + and the sense- input. Rk must be lower than the permitted resistance for 1

line of the 3-wire-input. Units requiring 3-wire configurations can also be operated by 2-wire

sensors. The sensor input is simply shortened. The line resistance need not be compensated.

3-wire sensors can be used as 2-wire sensors, simply by omitting one wire. 2-wire sensors

can be branched at any desired position in a 3 or 4-wire connection system. In this case

though, the line resistance of the two wires from the branching point to the sensor is not

compensated. ZIEHL thermostats, series TR are designed for use with 2 or 3-wire

connection.

2.10. Measuring Junction Location

A Pt100 measures across the entire length of the wire. The temperature reading is therefore

the average for the wire length. It is important to remember this if you are measuring surface

temperatures and the like with a spring-loaded probe.

Chapter # 2 PT 100

Figure 2.7. Length of the wire

2.11. Wiring of PT 100 Sensors

Pt100 sensors can have two, three or four wires. Pentronic recommends the four-wire version

from the sensor to the measuring circuit for maximum accuracy. Four-wire versions are

generally supplied as standard. If the instrumentation has inputs for two or three wires, the

sensor is wired as shown below.

2.11.1. Two-wire connection

Two-wire connections make life easy for the technician but at the expense of a much greater

likelihood of measuring errors arising when long extension leads are used. The problem

results from the resistance of the lead being added straight into the measured value. At 20°C,

the resistance of a 10-m, 2 x 0.25 mm2 copper lead is 1.4 ohms. In terms of temperature, this

translates into a measuring error of 3.6 °C. It is possible to eliminate the error through

calibration, but every time the ambient temperature around the lead changes, the resistance

Chapter # 2 PT 100

will also change, producing a new error. A Pt1000 film detector would reduce the magnitude

of the error to a tenth. If this is acceptable still there would then be a greater risk of self

heating.

2.11.2. Three-wire connection

A three-wire connection will eliminate most of the effect of the lead resistance on the

measured value, although this is conditional on all three wires having the same resistance.

This is almost impossible to achieve in practice. In fact only two wires have to have equal

resistances but as two of them are colour coded red you cannot easily know which is the

critical one. This is the reason we say all three wires should hav equal resistances.

Wires often come from different drawing mills and can therefore have a resistance

that differs by 5–10%.

One or more strands may be missing in one of the leads. Pentronic has encountered

leads in which two of the seven strands were missing - a difference of 28% in the lead

resistance.

Connections, switches and the like can introduce different resistances.

In extreme cases, there may be a combination of these factors at play. For example: a ten-

meter length of three-wire lead that has a resistance difference across the wires of 10% will

give a reading error of 0.18°C. However, a three-wire lead will solve the problem of the

effect of the temperature range on the wires.

2.11.3. Four-wire connection

All instruments designed for optimum measuring accuracy have four-wire connections. The

current and the signal are separated into two circuits, which render the unbalance in the

resistances of the wires insignificant. This is true provided that the difference is not of an

excessive magnitude - up to 100 ohms is often acceptable with modern instruments. The

four-wire system was previously confined to laboratory use but is now used in process

equipment, eg, indicators and controllers.

CHAPTER # 3

SOLENOID

VALVE

Chapter # 3 Solenoid Valve

3.1. Introduction:

A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to

a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic

field when an electric current is passed through it. Solenoids are important because they can

create controlled magnetic fields and can be used as electromagnets. The term solenoid refers

specifically to a coil designed to produce a uniform magnetic field in a volume of space

(where some experiment might be carried out).

In engineering, the term solenoid may also refer to a variety of transducer devices that

convert energy into linear motion. The term is also often used to refer to a solenoid valve,

which is an integrated device containing an electromechanical solenoid which actuates either

a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that

internally uses an electromechanical solenoid to operate an electrical switch; for example, an

automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid

figure 3.1.

Figure 3.1 Solenoid Coil


http://en.wikipedia.org/wiki/File:Solenoid-1.png

3.2. Magnetic field of an infinite solenoid inside

Figure 3.2 Solenoid inside with 3 loops

A solenoid with 3 Ampèrian loops: a, b and c.

In short: the magnetic field inside an infinitely long solenoid is homogeneous and its strength

does not depend on the distance from the axis, nor on the solenoid cross-sectional area. This

is a derivation of the magnetic flux density around a solenoid that is long enough so that

fringe effects can be ignored. In the diagram to the right, we immediately know that the flux

density vector points in the positive z direction inside the solenoid, and in the negative z

direction outside the solenoid. We see this by applying the right hand grip rule for the field

around a wire. If we wrap our right hand around a wire with the thumb pointing in the

direction of the current, the curl of the fingers shows how the field behaves. Since we are

dealing with a long solenoid, all of the components of the magnetic field not pointing

upwards cancel out by symmetry. Outside, a similar cancellation occurs, and the field is only

pointing downwards.

Now consider the imaginary loop c that is located inside the solenoid. By Ampère's law, we

know that the line integral of B (the magnetic flux density vector) around this loop is zero,

since it encloses no electrical currents (it can be also assumed that the circuital electric field


http://en.wikipedia.org/wiki/File:Solenoid_with_3_loops_(1).png

passing through the loop is constant under such conditions: a constant or constantly changing

current through the solenoid). We have shown above that the field is pointing upwards inside

the solenoid, so the horizontal portions of loop c do not contribute anything to the integral.

Thus the integral of the up side 1 is equal to the integral of the down side 2. Since we can

arbitrarily change the dimensions of the loop and get the same result, the only physical

explanation is that the integrands are actually equal, that is, the magnetic field inside the

solenoid is radially uniform. Note, though, that nothing prohibits it from varying

longitudinally, which in fact it does.

3.3. Outside

Figure 3.3 Solenoid outside

Magnetic field created by a solenoid (cross-sectional view) described using field lines. A

similar argument can be applied to the loop a to conclude that the field outside the solenoid is

radially uniform or constant. This last result, which holds strictly true only near the centre of

the solenoid where the field lines are parallel to its length, is important in as much as it shows

that the flux density outside is practically zero since the radii of the field outside the solenoid

will tend to infinity.


http://en.wikipedia.org/wiki/File:VFPt_Solenoid_correct2.svg

An intuitive argument can also be used to show that the flux density outside the solenoid is

actually zero. Magnetic field lines only exist as loops, they cannot diverge from or converge

to a point like electric field lines can (see Gauss's law for magnetism). The magnetic field

lines follow the longitudinal path of the solenoid inside, so they must go in the opposite

direction outside of the solenoid so that the lines can form a loop. However, the volume

outside the solenoid is much greater than the volume inside, so the density of magnetic field

lines outside is greatly reduced. Now recall that the field outside is constant. In order for the

total number of field lines to be conserved, the field outside must go to zero as the solenoid

gets longer.

Of course, if the solenoid is constructed as a wire spiral (as often done in practice), then it

emanates an outside field the same way as a single wire, due to the current flowing overall

down the length of the solenoid.

3.4. Quantitative Description

Now we can consider the imaginary loop b. Take the line integral of B around the loop of

height l. The horizontal components vanish, and the field outside is practically zero, so

Ampère's Law gives us:

where is the magnetic constant, the number of turns, the current. From this we get:

This equation is for a solenoid with no core. The inclusion of a ferromagnetic core, such as

iron, increases the magnitude of the magnetic flux density in the solenoid. This is expressed


by the formula

where μeff is the effective or apparent permeability of the core, which is a function of the

geometric properties of the core and its relative permeability. This equation is often used

incorrectly due to the lack of understanding of the difference between relative and effective

permeability, which can in fact differ by many orders of magnitude. For an open magnetic

structure, the relationship between the effective permeability and relative permeability is

given as follows:

where k is the demagnetization factor of the core.

3.5. Magnetic Field and Vector Potential For Finite

Continuous Solenoid

Figure 3.4. Magnetic Field Continuous Solenoid

http://en.wikipedia.org/wiki/File:Finite_Length_Solenoid_field_radius_1_length_1.jpg


Magnetic field line and density created by a solenoid with surface current density A finite

solenoid is a solenoid with finite length. Continuous means that the solenoid is not formed by

discrete coils but by a sheet of conductive material. We assume the current is uniformly

distributed on the surface of it, and it has surface current density K. In cylindrical

coordinates:

The magnetic field can be found by vector potential. The vector potential for a finite

solenoid with radius a, length L in cylindrical coordinates is is[citation needed]:

where

The , , and are complete elliptic integral of first, second, and third

kind.


By using

the magnetic flux density is:

3.6. Inductance of a solenoid

See also: Inductance with physical symmetry

As shown above, the magnetic flux density within the coil is practically constant and is

given by

where μ0 is the magnetic constant, the number of turns, the current and the length of the

coil. Ignoring end effects, the total magnetic flux through the coil is obtained by multiplying

the flux density by the cross-section area :

When this is combined with the definition of inductance,


it follows that the inductance of a solenoid is given by:

A table of inductance for short solenoids of various diameter to length ratios has been

calculated by Dellinger, Whitmore, and Ould.[3]

This, and the inductance of more complicated shapes, can be derived from Maxwell's

equations. For rigid air-core coils, inductance is a function of coil geometry and number of

turns, and is independent of current.

Similar analysis applies to a solenoid with a magnetic core, but only if the length of the coil

is much greater than the product of the relative permeability of the magnetic core and the

diameter. That limits the simple analysis to low-permeability cores, or extremely long thin

solenoids. The presence of a core can be taken into account in the above equations by

replacing the magnetic constant μ0 with μ or μ0μr, where μ represents permeability and μr

relative permeability. Note that since the permeability of ferromagnetic materials changes

with applied magnetic flux, the inductance of a coil with a ferromagnetic core will generally

vary with current.

3.7. Electromechanical Solenoids

A 1920 explanation of a commercial solenoid used as an electromechanical actuator

Electromechanical solenoids consist of an electromagnetically inductive coil, wound around

a movable steel or iron slug (termed the armature). The coil is shaped such that the armature

can be moved in and out of the center, altering the coil's inductance and thereby becoming an

electromagnet. The armature is used to provide a mechanical force to some mechanism (such

as controlling a pneumatic valve). Although typically weak over anything but very short

distances, solenoids may be controlled directly by a controller circuit, and thus have very low

reaction times.


The force applied to the armature is proportional to the change in inductance of the coil with

respect to the change in position of the armature, and the current flowing through the coil

(see Faraday's law of induction). The force applied to the armature will always move the

armature in a direction that increases the coil's inductance.

Electromechanical solenoids are commonly seen in electronic paintball markers, pinball

machines, dot matrix printers and fuel injectors.

3.8. Rotary Solenoid

The rotary solenoid is an electromechanical device used to rotate a ratcheting mechanism

when power is applied. These were used in the 1950s for rotary snap-switch automation in

electromechanical controls. Repeated actuation of the rotary solenoid advances the snap-

switch forward one position. Two rotary actuators on opposite ends of the rotary snap-switch

shaft, can advance or reverse the switch position.

The rotary solenoid has a similar appearance to a linear solenoid, except that the core is

mounted in the center of a large flat disk, with two or three inclined grooves cut into the

underside of the disk. These grooves align with slots on the solenoid body, with ball bearings

in the grooves.

When the solenoid is activated, the core is drawn into the coil, and the disk rotates on the ball

bearings in the grooves as it moves towards the coil body. When power is removed, a spring

on the disk rotates it back to its starting position, also pulling the core out of the coil.

The rotary solenoid was invented in 1944 by George H. Leland, of Dayton, Ohio, to provide

a more reliable and shock/vibration tolerant release mechanism for air-dropped bombs.

Previously used linear (axial) solenoids were prone to inadvertent releases. U.S. Patent

number 2,496,880 describes the electromagnet and inclined raceways that are the basis of the

invention. Leland's engineer, Earl W. Kerman, was instrumental in developing a compatible

bomb release shackle that incorporated the rotary solenoid. Bomb shackles of this type are


found in a B-29 aircraft fuselage on display at the National Museum of the USAF in Dayton,

Ohio. Solenoids of this variety continue to be used in countless modern applications, and are

still manufactured under Leland's original brand "Ledex", now owned by Johnson Electric.

3.8.1. Rotary Voice Coil

This is a rotational version of a solenoid. Typically the fixed magnet is on the outside, and

the coil part moves in an arc controlled by the current flow through the coils. Rotary voice

coils are widely employed in devices such as disk drives.

3.8.2. Pneumatic Solenoid Valves

A pneumatic solenoid valve is a switch for routing air to any pneumatic device, usually an

actuator, allowing a relatively small signal to control a large device. It is also the interface

between electronic controllers and pneumatic systems.

3.8.3. Hydraulic Solenoid Valves

Hydraulic solenoid valves are in general similar to pneumatic solenoid valves except that

they control the flow of hydraulic fluid (oil), often at around 3000 psi (210 bar, 21 MPa, 21

MN/m²). Hydraulic machinery uses solenoids to control the flow of oil to rams or actuators.

Solenoid-controlled valves are often used in irrigation systems, where a relatively weak

solenoid opens and closes a small pilot valve, which in turn activates the main valve by

applying fluid pressure to a piston or diaphragm that is mechanically coupled to the main

valve. Solenoids are also in everyday household items such as washing machines to control

the flow and amount of water into the drum.

Transmission solenoids control fluid flow through an automatic transmission and are

typically installed in the transmission valve body.


3.8.4. Automobile Starter Solenoid

Main article: Starter solenoid

In a car or truck, the starter solenoid is part of an automobile starting system. The starter

solenoid receives a large electric current from the car battery and a small electric current

from the ignition switch. When the ignition switch is turned on (i.e. when the key is turned to

start the car), the small electric current forces the starter solenoid to close a pair of heavy

contacts, thus relaying the large electric current to the starter motor.

Starter solenoids can also be built into the starter itself, often visible on the outside of the

starter. If a starter solenoid receives insufficient power from the battery, it will fail to start the

motor, and may produce a rapid 'clicking' or 'clacking' sound. This can be caused by a low or

dead battery, by corroded or loose connections in the cable, or by a broken or damaged

positive (red) cable from the battery. Any of these will result in some power to the solenoid,

but not enough to hold the heavy contacts closed, so the starter motor itself never spins, and

the engine does not start.

3.9. Switching Functions & Symbols

Most solenoid valves operate on a digital principle. They therefore possess two distinct tates,

which are (1) - when the coil is activated by an electrical current, and (2) - when the valve is

resting (without electricity). Valve functions are defined from the resting position. The direct

acting or pilot operated solenoid valves may have two functions:

3.9.1. Normally Closed (NC)

A solenoid valve is normally closed (abbreviated - NC) if there is no flow across the valve in


its resting position (with no current on the solenoid contacts).

3.1. Symbol: Normally Closed

3.10. Latching or Bi-stable

We manufacture solenoid valves designed for applications where reduced energy

consumption is the determining factor. For these applications a short electrical impulse

enables the solenoid valve to be opened or closed, and thanks to the residual effects of a

permanent magnet this is sufficient for maintaining the valve in a particular working position

with no electrical energy consumption. A short impulse of inverted polarity ensures the

valve’s return to its previous position. Electrical power consumption and heating are almost

negligible.

3.10.1. Number of Ways

The solenoid valves have two ports (one inlet, one outlet) and only one orifice (seat) allowing

fluid control. These solenoid valves have three ports (one inlet, one outlet and one exhaust)

and two orifices (seats) allowing fluid control. Typical application: to operate a single acting

cylinder

b. 1 port inlet fluid P

2 port outlet fluid A1, A2

Typical application: to select or divert flow

c. 2 port inlet fluid P1, P2

1 port outlet fluid A

Typical application: to mix two fluids


3.11. Electric Position Indicator

for piloted angle seat valves The electric position indicator with 2 micro switches monitors

the OPEN & CLOSED positions of the piloted angle seat valves of the 845xx and 847xx

series. The limit switches wired in series with a terminal block are screwed onto supports and

can be adjusted independently of each other with threaded spindles. Switches, operating

mechanism and terminal block are protected by a transparent cover on the plastic bottom

section of the case, which can be turned to any direction. This position indicator can also be

retrofitted to unmodified piloted angle seat valves of the above-mentioned series. The

operating spindle is connected to the valve spindle frictionally and axially without any slack.

This indicator can be ordered for retrofitting under Catalogue number 1257000 Figure 3.5.

Figure : 3.5. Electric Indicator

3.11.1. Features

- Reproducible switching point accuracy

- Long mechanical and electrical service life

- Readily retrofitted

- Simple, accurate adjustment of switching point

- With LED indicator


3.12. Dust Collector Valves & Blow Tubes

Valves for dust filter cleaning with through-type blow tube 2/2-way valve Buschjost has

enhanced the existing dust filter cleaning range with a valve with blow tube. This variant

offers easy, cost-effective installation and other significant benefits.

3.12.1. Features

- Higher peak pressures produced by radial flow

- Spacing from 75 mm (between pipe centres)

- No welding or adjustment necessary

- Simple, economical connection of valve to irregularly shaped tanks

- Available pipe lengths: 70 to 200 mm

- High-grade aluminium tube

3.12.2. Dust Collector Cleaning

The 82960 series solenoid system with bayonet connection is easily mounted – just push

down and turn. The internal components of the pilot system are captive. The plastic encased

solenoid can be turned to 3 different positions, 120° apart, without using tools. The factory

fitted silencer prevents annoying noise and stops ingress of foreign matter into the valve. The

solenoid design of the pilot offers maximum security against frost.

The volume above the diaphragm is minimized for extremely fast opening with optimized

peak pressures. The similarly ideal closing time ensures low air consumption. All of the

dynamically loaded valve elements are designed for a long lifetime.

CHAPTER # 4

LINE HEAT

SYSTEM

Chapter # 4 Line Heat System

4.1. Introduction

The growth of UHT milk has been remarkable, increasing worldwide in the past 20 years

especially in Europe, Asia, and South America. Surprisingly, shelf-stable milk consumption

in the U.S. is very low compared to other regions in the world (Burton 1988; Kissell 2004).

UHT-processed fluid milk is very popular in other parts of the world; however, the U.S.

population has been slow to accept it because of the "cooked" flavor in the UHT milk, their

familiarity with fresh milk (Dairy Biz Archive 2000), and the higher cost of UHT milk

(Kissell 2004).

A number of studies have determined sensory properties of various milk samples including

plain milk (Claassen and Lawless 1992; Frost et al. 2001; Francis et al. 2005), chocolate milk

(Thompson et al. 2004), powdered milk (Kamath et al. 1999; Drake et al. 2003) and

processed milks that are not specific to UHT milk (Chapman et al. 2001; Fromm and Boor

2004; Clare et al. 2005). In addition, lexicons for milk alternatives, such as soymilk, have

been published (Torres-Penaranda and Reitmeier 2001; Day N' Kouka et al. 2004; Chambers

et al. 2006; Keast and Lau 2006).

Descriptive sensory terms for ultra-pasteurized milk were developed by Chapman et

al. ( 2001) and were primarily described as "cooked aroma" and "cooked flavor". Clare et al.

(2005) used cooked/ caramelized, sweet aromatic/cake mix, fatty/ stale, sweet taste, bitter

taste, astringent, and color intensity to differentiate UHT from microwave-treated milks.

Fromm and Boor (2004) characterized sensory shelf-life attributes for pasteurized fluid milk.

Attributes related to milk flavor defects describing as hay/grain, sour/fermented, baby

formula, nutty, rancid, and metallic were key sensory attributes associated with pasteurized

fluid milk throughout shelf-life. These results showed that excluding bacterial contaminants

from milk is essential to extend shelf-life of milk products.

Processing variables have been shown to affect sensory properties of preserved milk.

Clare et al. (2005) found that UHT milk had more caramelized and fatty/stale flavor, more

brown color, and more astringency than microwave processed milk probably because of the

higher heat treatment. Keast and Lau (2006) found regional differences in sensory quality of

soymilk with those from Asia (Hong Kong, Malaysia and Singapore) being sweeter, less

salty, darker in color, and stronger in beany flavor than soymilks. Although previous


researchers have investigated the sensory properties of processed milks, none have shown

complete information for explaining the sensory characteristics of UHT milk or have

considered the differences of UHT milk properties based on country of origin. Although

there are many potential reasons that UHT milk is more accepted in countries other than the

U.S., it is possible that differences in regional milk source or processing requirements from

country to country could result in sensory differences that would have an impact on

acceptance. If the sensory properties of UHT milk from different countries can be grouped

and differentiated from those in the U.S., it may be possible to determine sensory properties

of UHT milk that can be modified to improve U.S. UHT milk.

The objectives of this study were to 1) determine the sensory properties of a wide

range of commercial UHT milk samples from various countries representing different

regions of the world, to 2) compare flavor and texture differences among samples from

various countries to determine if regional differences are a major influence on sensory

properties of UHT milk, and to 3) compare UHT to control pasteurized and sterilized

milk samples.

4.2. Milk Samples

Thirty-seven low-fat, 2% reduced-fat, and whole UHT and sterilized milk samples

were used in this study. The samples were purchased from seven countries on four continents

to represent a variety of shelf-stable milks. Samples were based on origin, fat content, and

availability. Table 1 shows the product description, origin, type of milk, heat processing, and

product abbreviation that were used for the study. Samples were obtained from France

(n = 2), Italy (n = 11), Japan (n = 1), Korea (n = 2), Peru (n = 3), Thailand (n = 13), and the

U.S. (n = 5). Fresh pasteurized whole and 2% reduced-fat milk samples were purchased from

a local retail grocery store in Manhattan, Kansas (Dillons, A Kroger subsidiary) and used as a

control. Samples had similar expiration date to avoid extraneous factors, such as sample age,

that might affect the flavor and texture of each sample.

UHT and sterilized samples were purchased in tetra-packed cartons, plastic bottles, or

tin cans depending on each country and were held at room temperature after purchasing until

the day prior to testing. At that time they were moved to a refrigerator (TS-49 commercial


refrigerator, True Manufacturing Co, St Louis, MO, USA) for storage at 1ºC.

4.3. Sample Preparation

Seventy-five mL portions of milk were poured into six 8 oz Styrofoam cups (H8S,

James River Corp, Easton, PA, USA), labeled with 3-digit random numbers for the first

serving. An additional 25 mL of milk was served to each of the panelists as a second serving

to maintain temperature during testing. Samples were tempered at room temperature for

thirteen minutes until the serving temperature of 6-7ºC was reached. During tempering,

sample cups were covered with clean dark paper to avoid light oxidation. Sample cups were

covered with plastic lids before serving to the panelists.

4.3.1 Panelists

Five highly trained panelists from the Sensory Analysis Center, Kansas State

University (Manhattan, KS) participated in the study. Each panelist had completed 120 h

of training in sensory evaluation of foods; had a minimum of 2000 h of testing experience on

a variety of food products including fresh milk, UHT milk, soy milk, yogurt, ice cream, and

cheese. Other researchers have used trained panelists to describe the flavor (Talavera-

Bianchi, Chambers, and Chambers, 2008) and texture characteristics of dairy products (Yates

and Drake, 2007; Karagul-Yuceer, Isleten, and Uysal-Pala, 2007).

4.4. Descriptive Orientation Sessions

The panelists used attributes, definitions and references from previous studies of milk

(Bassette et al. 1986; Tuorila 1986; Claassen and Lawless 1992; Chapman et al. 2001; Frost

et al. 2001; Frandsen et al. 2003; Francis et al. 2005) as initial guidelines for this study.

Three 1 ½ h orientation sessions were conducted to help the panel reacquaint themselves

with the flavor and texture of milk, to develop the attributes and references

4.5. Line Separation

GEA offers the possibility to combine the traditional UHT process with an automatic

separator to be integrated into the heating process. The In-line Separation avoids a

double heat treatment of the product and achieves in this way high product quality.

He combined function of the buffer tank as well as the additional, separate heater


provided for start and shutdown operations of the separator allow the continuous

operation of the separator during the UHT process. By use of the buffer tank, the

UHT heating can be maintained without interruption during the automated solids

discharge of the separator. The In-Line Separation is integrated in the automatic

process control of the UHT Plant so that the process steps in a thermal heating plant

such as sterilization, cooling, production, production stop and CIP are completely

automated.

Fig 4.1 Line Separation

for UHT milk, and to rate the intensities of the control milk samples. Because of the limited

amount of international samples, panelists were initially given six locally purchased UHT

and ultra-pasteurized milk samples to begin the lexicon development. During orientation

sessions, the procedures for attribute determination and vocabulary description were adapted

from flavor profile analysis (Caul 1957; Keane 1992) and other studies for developing flavor

and texture lexicons (Drake et al., 2007; Lee and Chambers 2007; Talavera-Bianchi,

Chambers, and Chambers, 2008; Hongsoongnern and Chambers, 2008a,b). A discussion of

milk samples was held until the panel came to agreement on attribute description of UHT

milk. The panel changed some attribute definitions and references after orientation sessions.

They deleted attributes that they did not find in UHT, pasteurized or sterilized milk samples

and added new attribute terms they found in samples they had not previously tasted. The final


attributes, definitions, and references used to describe sensory properties of UHT,

pasteurized.

4.6. Determining Sensory Properties

Thirty-seven UHT and sterilized milk samples were evaluated using profile techniques

during thirteen 1 ½ h sessions to determine sensory properties of the milk samples for texture

and flavor characteristics. Attribute intensities were scored on a 15- point numerical scale

with 0.5 increments, where 0 represents "not detectable" and 15 represents "extremely

strong". The panel evaluated texture attributes for each sample followed by the flavor

evaluation. After all panelists individually provided intensity scores for all the attributes

found in the milk sample, the panel leader then led a discussion to arrive at an agreement of

consensus scores for each product. Panelists were provided new samples to maintain

temperature as they discussed the samples to reach consensus on the attributes and

intensities. Panelists ate a bite of carrot, an unsalted top saltine crackers (Nabisco, East

Hanover, NJ, USA), and purified water between each sample to cleanse the palate.

4.7 Experimental Design and Statistical Analysis

A completely randomized design was used for the sample presentation. A maximum of three

samples were tested in each 1½ h session. Multivariate statistical analyses were used to

explain the relationships among the sensory terms of UHT, pasteurized, and sterilized milk

samples. Principal components analysis (PCA) was conducted using SYSTAT program

(Version 10.2, 2005, SYSTAT Software, Inc, San Jose, CA). The covariance matrix was used

for extraction and the varimax procedure was used for rotation. Attributes where all scores

were the same for all samples and attributes present in 5 or fewer samples were removed

before the analysis. PCA plots of the major principal components were made to show

differences and similarities among UHT, pasteurized, and sterilized milks. Hierarchical

cluster trees based on sensory properties were obtained from hierarchical cluster analysis

(Ward's method) using the SYSTAT program version 10.2(2005, SYSTAT Software, Inc,

San Jose, CA). Attributes added to previous lexicons to better describe the texture and flavor

of in some samples.

Dairy notes (overall dairy, dairy fat and dairy sweet) and fat feel were negatively correlated

with chalky texture and processed flavor. Overall dairy showed little linear or curvilinear


relationship to cooked and brown flavors when examined either by correlation or plots. That

indicates that brown and cooked notes may be modified independently of dairy impact. Malty

flavor appeared in only a few samples, but when it did it seemed to have some positive

relationships to brown, cooked, fat feel, and dairy fat.

Three major clusters of UHT, pasteurized, and sterilized milk samples were found, but they

did not group on the basis of either country or fat content. There were more similarities of

milks from the same manufacturer than milks from the same country or milks with the same

fat content. This suggests that manufacturing process may have affected the sensory

properties of UHT milks much more than did country of origin or fat content, disproving our

theory that the base milk may be a major factor in U.S. consumers dislike of UHT milk,

while consumers in other countries find it acceptable. Cluster 1 consisted of milk samples

from most countries included in this study, except for Peru and the U.S., with the different

manufacturers. The milks in this cluster were highest in dairy fat, dairy sweet, overall dairy

flavor, and fat feel and had little or no chalky or processed flavor. The two pasteurized

control milk samples also appeared in this cluster. Although other clusters contained whole

milk samples, this cluster consisted only of whole milk, which may indicate that in order to

have the highest dairy notes and fat feel with little or no processing effect, the UHT milk

should be made from whole milk. Cluster 2 consisted of samples from six of the seven

countries included in this study, all the various fat levels, and various manufacturers. These

samples typically were moderate to high in dairy notes (dairy fat, dairy sweet, and overall

dairy) and fat feel, and had low levels of chalky and processed notes. This cluster included

most of the samples from Parmalat and most of the U.S. samples. A subcluster in that group

contained samples that generally were highest in cooked, but without the processed note

found in some other samples. All the products in that subcluster were malty; something

unique to that group. Products in that subcluster came from Italy, Thailand, and Peru,

including 2 samples (a whole and a low-fat) from the same manufacturer in Thailand. One of

the sub-clusters included most of the U.S. milk samples (four out of seven) and half of the

Parmalat samples, including Parmalat samples from both Italy and the U.S. This group of

milk had higher processed notes and scored in the middle of all samples for cooked and

brown. Those products had moderate to higher levels of dairy notes and no maltiness was

found in them. The third subcluster in that group was comprised of samples from Italy,


France, Korea, and Peru. Sensory properties in that subcluster fell in the midrange of most

products. Cluster 3 consisted of about one-third of the Thai samples (including 2 pairs of

products from the same brands in Thailand), two Italian samples, and 1 U.S. sample from the

same manufacturer as one of the Italian samples. These products had the highest levels of

processed, cooked, brown and some of the highest chalky scores of all products tested. This

groups contained samples with the lowest levels of dairy sweet and dairy fat. The two

sterilized milk samples from Thailand were in this cluster which should not be surprising

given their high level of processing. The attributes in this cluster and the fact that the

sterilized milks are in this cluster suggest processing, rather than country or fat content,

related issues associated with the milks in this group.

Figure 4.2. Principal Component Analysis

CHAPTER # 5

TEMPERATURE

CONTROLLER

Chapter # 5 Temperature Controller

5.1. Basics of Temperature Control

This summary is concerned with temperature control, but the principles outlined apply

equally to the control of any process variable (pressure, humidity, level, flow, etc.). A

process control loop consists of a sensor to measure the process variable, a controller and an

actuator device e.g.. Contactor, fuel valve or thyristor drive, but we will take the particular

case where the variable is temperature. A temperature controlled system is composed of four

essential elements which all affect its performance:

1) The load the material or object that needs to be maintained at a (or work) particular

temperature; the load may be steady, i.e. one object at a constant temperature for a long

period, or variable/cyclic which is common in an industrial process.

2) The heat source the device(s), usually a heater of some kind, which provides heat to the

load; some applications may need cooling in which case a compressor may be switched;

however we will assume a ‘hot’ system for the purposes of these notes

3) The sensor measuring the temperature of the load and feeding this information back to the

controller

4) The controller a device which controls the heat flow to the ‘load’ by adjusting power

output from the ‘heat source’ according to the information received from the ‘sensor’. The

‘controller’ will compare the temperature measured by the ‘sensor’ with the desired ‘load’

temperature ( the Set- Point ) and increase heater power if the sensed temperature is too low,

or decrease power if the sensed temperature is too high. The heat source, the sensor and the

controller form the classic control loop mentioned above, and together act upon the load.

5.2. Practical Considerations

In practice there are several obstacles to perfect temperature control - one of these is cost, as

high precision temperature control requires highly sensitive measuring instruments and

frequent re-calibration to tell just how good the control is. Trying to attain the last fraction of

a degree of accuracy can be very expensive, so in most situations it is best to be realistic; a

sandwich toaster doesn’t need the same control as a crystal growing oven. The main

measures of accuracy are the size of temperature swing in the load (thermal bandwidth) and

the stability of its mean (average) temperature. These are affected by many factors :


A) Thermal Lag the time delay for a temperature change in one part of the system to show up

in other parts of the system; this varies considerably with the operating temperature, ambient

conditions, mass & conductivity of the load etc.

B) Temperature the variations in temperature between different physical Gradients parts of

the system at any given instant.

C) Sensor placement of the sensor in relation to the heat source and Location the load.

D) Controller these contribute to the inherent accuracy of the controller Sensitivity & and

determine its suitability for any application.

E) Heat Balance for temperature control to be possible, there must be more heat available

from the heat source than is actually required to maintain the desired temperature and replace

losses.

5.3. Types of Control

Having established the basic requirements for a temperature control system, we can

see that the load temperature (or process temperature) is compared by the controller with the

required value or set-point, set by the user. The controller automatically adjusts the power to

the heat source to achieve no error between process temperature and set-point. The type of

control action affects the performance achieved. There are two main types, On/Off and PID

control, with additional special cases of Auto-tune and Fuzzy logic.

A) On/Off Control this is the simplest form of control and is the least expensive; it takes little

account of thermal time constants and simply switches the heater off or on as the process

temperature passes through the set-point. This will usually result in continual oscillation

around the set-point (hunting) due to the switching hysteresis. It is used where high accuracy

isn’t needed, or for an over or under temperature alarm.

B) PID Control Proportional plus Integral plus Derivative control is typically used in high

accuracy situations – basic proportioning control means that the controller ‘recognizes’ the

size of the deviation from the set-point and adjusts the power output accordingly. This

prevents oscillation around the set-point, and the integral and derivative parameters add extra

accuracy, with little or no offset or overshoot when they are correctly tuned. The P, I and D


parameters can usually be adjusted (or ‘tuned’) by the user to give the optimum control for

the particular conditions of their system.

C) Auto-Tune in this type of control, the controller has onboard logic which will enable it to

automatically select the optimum values for the Proportioning, Integral and Derivative

parameters; it does this by monitoring the rate of temperature rise of the system and the

subsequent response to heat input. The operator doesn’t normally need to alter any settings

on the controller.

D) Fuzzy Logic the controller automatically and gradually decreases or increases the internal

set-point until the process stabilizes at the desired operating temperature; this results in the

elimination of overshoot/ undershoot.

5.4. More about Control Theory

With On/Off Control, the controlled element (heater, valve etc.) can only be on or off, there

is no halfway house and the size of the corrective action is unrelated to the temperature

deviation. This leads to the oscillation described above. Some controllers have an adjustable

differential, which changes the width of the dead zone between switching off and on. A

narrower differential will give smaller temperature swings, but will increase cycling rates and

cause increased wear on mechanical relays, heater elements etc. Thus, differential needs to be

adjusted to give the lowest cycling rate that gives an acceptable temperature bandwidth.

In proportioning control, the control action can be varied between 0 and 100% of the

available response, being tailored to the size of the temperature deviation measured by the

sensor. This is particularly helpful where, for example, a work cycle involves the addition of

large amounts of cold material, which cool the system down so that it needs rapid heat-up. A

large injection of heat would lead to huge overshoot without some form of proportioning

action.

The width of the proportioning band should be set to just exceed the limits of any normal

high or low temperature excursions in the system. If the proportional band is too narrow,

oscillations resembling on/off control will occur; if too wide, control will be stable but

sluggish, probably with an offset at equilibrium. Most controllers feature ‘manual reset’

which corrects the offset by biasing the proportional band up/down so that the band is in the

correct place once tuned.


An offset in the control temperature can be compensated by incorporating an Integral

parameter, which positions the proportional band for the correct power output to achieve

equilibrium at set-point. (PI control). A further addition of the Derivative function (to give

PID control) can provide anticipatory control and a fast reaction to disturbances. This is a

derivative of the error between actual temperature and set point temperature with respect to

time; it is typically set to a value approx. 15% of the I value.

5.5. Power Control

1) Rapid cycle time gives better control and prolongs heater life, but shortens output relay

life (though a solid state relay avoids this problem)

2) Proportioning band should be adjusted so that oscillations just cease; a wide band gives

stable control but increases offset from desired set point.

3) A properly adjusted Integral parameter eliminates offset; if too fast, oscillation will

develop, too slow will give poor response.

4) Too much Derivative will cause oscillations, too little will result in overshoot. you

basically have proportional control). Adjust this step-wise until offset is eliminated with

minimal oscillation around the set-point. Then adjust the Derivative parameter so that any

outside disturbances to the system are corrected rapidly but without oscillations. When

dealing with temperature control systems, it is important to consider the possible effects of a

malfunction in any part of the system any one of many possible malfunctions could cause a

dangerous situation if the heating is left permanently switched on. This could be a fault in the

sensor, controller, connecting wiring or other outside interference.

5.6. Outputs

The controller output has to be interfaced to the heat source (or other actuating device) and

this is done by various methods, the choice of which depends on the type of process and

equipment being used;

A) Relay O/P used in on/off or time proportioning modes to switch contactors etc.;

electromechanical relays are inexpensive, small, usually housed within the controller, but can

have limited life if cycled rapidly - where more rapid switching is needed a solid state relay

is recommended.


B) SSR O/P this is a switching device which contains 2 SCR’s (silicon (Solid State Relay)

controlled rectifiers) or a single triac complete with a zero voltage crossover or

synchronizing drive circuit; it usually takes the form of a potted assembly having no moving

parts to wear out, and can be either ac or dc input type.

C) Analogue where continuously variable control is needed, a OUTPUT linear DC voltage or

current output can be used; 4- 20mA,

0-5V, 0-10V, 1-5V are all standard outputs and are used for e.g. control valve actuators,

thyristor drives etc. which vary the power to the load. The output relays of temperature

controllers are capable of switching currents typically 8, 16 or 20 Amps depending on the

model of controller. Most heater loads however, are typically more than the controller's relay

can handle. For these applications solid state relays or Thyristor power controllers depending

on the type of load and the type of control required, need to be incorporated within the

control system.

5.7. Solid State Relays

These devices work in exactly the same way as mechanical relays but have no moving parts.

The input to these devices are either typically 3 to 32VDC or 90 to 280VAC and will switch

loads up to 90 Amps. The advantage of SSRs over mechanical devices are; no moving parts

to wear out, fast response, handles high inrush currents and no contact bounce.

5.7.1. Thyristor Power Controllers

Thyristor is the generic name for a SCR or Triac. These devices are used for very Large loads

up to 1000 Amps and generally include other functions such as current limiting, soft start,

fusing etc. This is the most basic and cheapest method to provide variable electrical output

power for the control of temperature. This is achieved by triggering the device on and off in

multiples of complete mains cycles. This type of control is suitable for loads whose load

resistance does not change very much with temperature.

5.8. Phase Angle

This type of control is a more precise method of switching. The device conducts for only part

of the AC supply cycle. Therefore if low power is required the device conducts for a small


portion of the AC cycle, similarly if half power is required the device is not triggered to

conduct until it is 50% of the way through half of a mains cycle. This type of triggering is

ideal for low inertia heaters such as lamps and air heater show in figure 5.1.

Figure 5.1. Phase Angle

Wt= Total power R = heater resistance

VP = phase voltage IP = phase current

VL = line voltage IL = line current

Single Phase, Line And Neutral Or Line And Line

Wt = VL x IL or VL

2/R

Three Phase, Three Wire, DELTA Configuration


Wt = 1.73VL x IL or 3 x VL

2/R

Where IL = 1.73 x IP

Three Phase, Three Wire, STAR Configuration

Wt= 1.73VL x IL or 3 x VL 2/R

Where VL = 1.73 x VP

Three Phase, Four Wire, STAR Configuration

Wt = 3 x VL x IL or 3 x VL 2/R

Where VL = VP and IL = IP

The Proportional-Integral-Derivative (PID) algorithm As the name suggests, the PID

algorithm consists of three basic modes, the Proportional mode, the Integral and the


Derivative modes. When utilizing this algorithm it is necessary to decide which modes are to

be used (P, I or D?) and then specify the parameters (or settings) for each mode used.

Generally, three basic algorithms are used P, PI or PID. A Proportional algorithm the

mathematical representation is,

The proportional mode adjusts the output signal in direct proportion to the controller input

(which is the error signal, e). The adjustable parameter to be specified is the controller gain,

kc. This is not to be confused with the process gain, kp. The larger kc the more the controller

output will change for a given error. For instance, with a gain of 1 an error of 10% of scale

will change the controller output by 10% of scale. Many instrument manufacturers use

Proportional Band (PB) instead of kc.1 The time domain expression also indicates that the

controller requires calibration around the steady-state operating point. This is indicated by

the constant term mvss. This represents the 'steady-state' signal for the mv and is used to

ensure that at zero error the cv is at set point. In the Laplace domain this term disappears,

because of the ‘deviation variable’ representation.

A proportional controller reduces error but does not eliminate it (unless the process has

naturally integrating properties), i.e. an offset between the actual and desired value will

normally exist.

A proportional integral algorithm the mathematical representation is,

The additional integral mode (often referred to as reset) corrects for any offset (error) that

may occur between the desired value (set point) and the process output automatically over

time2. The adjustable parameter to be specified is the integral time (Ti) of the controller.

Reset is often used to describe the integral mode. Reset is the time it takes for the integral

action to produce the same change in mv as the P modes initial (static) change. Consider the

following figure,


Figure 5.2. The response of a PI algorithm to a step in error

The output immediately steps due to the P mode. The magnitude of the step up is Kce . The

integral mode then causes the mv to ‘ramp’. Over the period 'time 0 to time TI' the mv again

increases by Kce. Integral wind-up When a controller that possesses integral action receives

an error signal for significant periods of time the integral term of the controller will increase

at a rate governed by the integral time of the controller. This will eventually cause the

manipulated variable to reach 100 % (or 0 %) of its scale, i.e. its maximum or minimum

limits. This is known as integral wind-up. A sustained error can occur due to a number of

scenarios, one of the more common being control system ‘override’. Override occurs when

another controller takes over control of a particular loop, e.g. because of safety reasons. The

original controller is not switched off, so it still receives an error signal, which through time,

‘winds-up’ the integral component unless something is done to stop this occurring. There are

many techniques that may be used to stop this happening. One method is known as ‘external

reset feedback’ (Luyben, 1990). Here, the signal of the control valve is also sent to the

controller. The controller possess logic that enables it to integrate the error when its signal is

going to the control value, but breaks the loop if the override controller is manipulating the


valve. A Proportional Integral Derivative algorithm the mathematical representation is,

Derivative action (also called rate or pre-act) anticipates where the process is heading by

looking at the time rate of change of the controlled variable (its derivative). TD is the ‘rate

time’ and this characterizes the derivative action (with units of minutes). In theory derivative

action should always improve dynamic response and it does in many loops. In others,

however, the problem of noisy signals makes the use of derivative action undesirable

(differentiating noisy signals can translate into excessive mv movement). Derivative action

depends on the slope of the error, unlike P and I. If the error is constant derivative action has

no effect.

Use Matlab / Simulink to explore the effect a step change in error has on the various modes

of an ideal PID control algorithm. Assume that kc = 1, Ti = 10 mins and TD = 5mins.

PID algorithms can be different Not all manufactures produce PID’s that conform to the ideal

'textbook' structure. So before commencing tuning it is important to know the configuration

of the PID algorithm! The majority of ‘text-book’ tuning rules are only valid for the ideal

architecture. If the algorithm is different then the controller parameters suggested by a

particular tuning methodology will have to be altered.

5.9. Final Remarks

The notes have reviewed PID control, discussed the modes of the various control algorithms,

the different structures of algorithms that exist and standard tuning rules. The tuning rules

reviewed include, Ziegler-Nichols, Cohen- Coon, and direct synthesis. Remember:the

tuning rules are only valid for the 'ideal' PID control structure and any prediction of control

law settings should be adjusted if an alternative PID implementation is used. The tuning rules

are only valid for self-regulating processes (i.e open loop stable processes such as those that

may be described by the 1st order plus dead-time description).

Luckily most process systems are self-regulating the exception to the rule being level

systems.

CHAPTER # 6

JOMO

CONTROLLER

Chapter # 6 Jomo Controller

6.1. Introduction

As long as 130 years ago, Sir William Siemens made the suggestion that the change of

electrical resistance of metals as a result of changes in temperature could be utilized for the

measurement of temperature itself. The material to be used should be a noble metal:

platinum, since platinum shows characteristics that are not shared by other metals. In 1886

Siemens continued to develop the platinum resistance thermometer, and, by taking

appropriate precautions, constructed a precision resistance thermometer that was suitable for

measuring high temperatures. Since then, platinum resistance thermometers have been used

as indispensable devices for measuring temperature as a physical variable. These days,

specially adapted designs make it possible to cover a multitude of applications over the

temperature range from –200 to +850 °C. Platinum thermometers can thus be used not only

in industrial measurement technology, but in sectors such as HVAC engineering, household

equipment, medical and electrical engineering, as well as in automobile technology. Wire

wound platinum temperature sensors on a glass or ceramic core as well as platinum chip

sensors made in thin-film technology are incorporated as the temperature-sensitive heart of

the resistance thermometer. Temperature-dependent resistance Platinum temperature sensors

use the effect of the temperature-dependence of the electrical resistance of the noble metal

platinum. Since the electrical resistance increases with rising temperature, we speak of a

positive temperature coefficient (often abbreviated to PTC) for such temperature sensors.

In order to use this effect for measuring temperature, the metal must vary its electrical

resistance with temperature in a reproducible manner. The characteristic properties of the

metal must not change during operation, as this would result in measurement errors. The

temperature coefficient should, as far as possible, be independent of temperature, pressure

and chemical influences. Standardized platinum temperature sensors For more than 130

years, platinum has been the basic material of choice for temperature- dependent sensors. It

has the advantage that it is highly resistant to corrosion, is relatively easy to work (especially

in wire manufacture), is available in a very pure state and exhibits good reproducibility of its

electrical properties. In order to maintain the features noted above and to ensure


interchangeability, these characteristics are defined in the internationally valid standard IEC

751 (translated in Germany as the DIN EN 60 751).

This standard specifies the electrical resistance as a function of temperature (table of

reference values), permissible tolerances (as tolerance classes), the characteristic curves and

usable temperature range. The characteristic curves are calculated using certain coefficients,

whereby the calculation distinguishes between the temperature ranges from –200 to 0 °C and

from 0 to 850 °C. The range –200 to 0 °C is covered by a third-order polynomial:

R(t) = R0 (1+ A x t + B x t2+Cx(t–100°C) x t3)

A second-order polynomial is applied for the range 0 to 850 °C

R(t) = R0 (1+Axt+Bxt2)

with the coefficients

A = 3.9083x10–3°C–1

B = –5.775x10–7°C–2

C = –4.183x10–12°C–4

The term R0 is referred to as the nominal value, and represents the resistance at 0 °C.

According to EN 60 751, the nominal value is 100.000_ at 0 °C. It is therefore referred to as

a Pt 100 temperature sensor. Temperature sensors with higher nominal values are also

available on the market, such as Pt 500 and Pt 1000. They have greater sensitivity, since the

slope of the characteristic is directly proportional to R0, the nominal value. Their advantage

thus lies in the fact that their resistance has a larger change with temperature show in figure

6.1.

Figure 6.1. Jomo Characteristics


The resistance change in the temperature range up to 100 °C is approximately: 0,4_/ °C for

Pt 100 temperature sensors 2,0_/ °C for Pt 500 temperature sensors and 4,0_/ °C for Pt 1000

temperature sensors.

As an additional parameter, the standard defines a mean temperature coefficient between 0

°C and 100 °C. It represents the average change in resistance, referred to the nominal value at

0 °C:

R0 and R100 are the resistance values for the temperatures 0 °C and 100 °C respectively.

Calculating the temperature from the resistance For the use as a thermometer, the resistance

of the temperature sensor is used to calculate the corresponding temperature. The formulae

cited above define the variation in electrical resistance as a function of temperature. For

temperatures above 0 °C, a closed form of the representation of the characteristic according

to EN 60 751 can be derived to determine the temperature.

R = resistance, measured in _

t = temperature, calculated in °C

R0, A, B = parameters as per EN 60 751

6.2. Tolerance Limits

The standard distinguishes between two tolerance classes

Class A: _t = _ (0.15 + 0.002xltl)

Class B: _t = _ (0.30 + 0.005xltl)

t = temperature, in °C (without math. sign)

The calculation of the tolerance limit _R in_ at a temperature of t > 0 °C is given by:

_R = R0 (A+2xBxt) x_t

For t < 0 °C it is:

_R = R0 (A+2 x B x t – 300°Cxt2+4xCxt3) x_t

Tolerance Class A applies for temperatures

from –200 to +600 °C.


Tolerance Class B applies for the entire defined range from –200 to +850 °C. Extended

tolerance classes the two tolerance classes specified in the standard are frequently inadequate

for certain applications. JUMO has defined a further division of the tolerance classes, based

on the standardized tolerances, in order to cover the widest possible range of applications

throughout the market.

In addition to the definition equations for the temperature-dependent deviations, the range of

validity has also been defined. Because of the inexactly linear relationship between the

resistance and temperature, measurements must be made at various temperatures to

determine the deviations from the standard

curve 3 (for t >0 °C) or 4 (for t < 0 °C)

respectively. For series manufacture of temperature sensors, tests are generally made only at

0 °C and 100 °C. So it is not possible to make a precise determination of the individual

characteristic of a temperature sensor. Since, on the one hand, it is not possible to make the

measurement uncertainty endlessly small and, on the other hand, the characteristic curve is

subject to variations caused by production tolerances, the range of validity of the narrower

tolerance classes must be restricted compared with the measuring range of the temperature

sensor. Another conclusion from this situation is that the temperature classes cannot be

narrowed without limit.

Figure 6.2. Torelance Band as a Function of the temperature


6.3. Temperature Limiter

The Jumo TB/TW is a freely programmable limiter / monitor. The universal measuring input

is freely programmable for RTD temperature probes, thermocouples as well as current and

voltage signals. TB/TWs are used to monitor thermal processes in the system for a set limit

value. If this value is exceeded, the installed relay switches the system to an operational safe

status and the LED "K1" changes from green to red. If the system reaches the "Good" range

again, the "Reset" key must be unlocked manually with a respective tool for the TB.

However, the TW automatically resets without external influence. For an adjustable

temperature, the DC 24V/20mA binary output can put out a pre-alarm prior to reaching the

limit value additionally displayed by the LED "KV".

TB/TW are installed on a top hat rail and wired via screw terminals with a cable cross section

of 2.5mm max. A setup program is provided for configuration show in figure 6.3.

Figure 6.3. TB/TW

6.4. Applications

Monitoring and limiting temperatures, pressure and other process variables, e.g. Protection of

burner control systems. Monitoring of heating elements. Protection of thermal oil systems.

Protection of boiler plants.


6.5. Brief Description

The instrument is used for the conductive measurement/control of electrolytic conductivity,

resistivity or the TDS value. In addition, the Jumo Aquis 500 CR also offers the possibility of

showing the measured conductivity according to a customer-specific table. Conductive two-

electrode cells as well as four-electrode cells can be connected to the instrument.

Temperature serves as the second input variable, measured by a Pt100/1000 probe.

expending on the measured variable, it is therefore possible to implement specific, automatic

temperature compensation. The instrument is operated using keys and a large LC graphics

display on which the measurements are clearly legible. The plain-text presentation of the

parameters makes it easier for the user to configure the instrument, and also helps in

programming it correctly. Thanks to its modular design, the instrument can be perfectly

matched to the particular application requirement. Up to four outputs are available (see the

block diagram for the functions). Typical areas of application Universally applicable in water

and wastewater engineering, service/process water and wastewater, drinking water and

well/surface water, pure and high-purity water as well as for pharmaceutical water (e.g. as

per USP, Ph.Eur., WFI), water quality measurements, TDS measurements (ppm or mg/l)

show in block diagram figure 6.4 Brief Description.

Figure 6.4. Block Diagram Brief Description


6.6. Functional Description

The instrument is designed for use on site. A rugged housing protects the electronics and the

electrical connections from corrosive environmental conditions (IP67). As an alternative, the

instrument can also be installed in a control panel, and is then protected to IP65 on the front.

The electrical connection is made by easy-to-fit pluggable screw terminals. Transmitter Two-

electrode cells (standard) as well as four electrode cells can be used for measurement. Two-

electrode cells can be connected, in the usual increments for cell constants (K=0.01; 0.1; 1.0;

3.0 and 10.0). Thanks to the widely adjustable relative cell constant, it is also possible to

connect sensors with different cell constants (e.g. K=0.2). In the case of the 4-electrode cells,

the values K=0.5 and 1.0 have been predefined for the cell constant. Here too, the instrument

can be matched to sensors with different cell constants (e.g. K=0.4). The instrument can

perform automatic temperature compensation, by acquiring the temperature of the sample

solution. Operation For easy programming and operation, all parameters are arranged in

clearly structured levels and shown in plain text. Operation is protected by a code word. This

facilitates individual adaptation of the operation, since parameters can be generally enabled

or specifically assigned to the protected area. As an alternative to configuration from the

keys, the instrument can also be configured through the convenient setup program for PC

(option).

6.7. Binary input

The following functions can be activated through the binary input: - Activate key inhibit

When this function has been activated, operation from the keys is no longer possible. -

Activate hold mode after activating this function, the outputs (analog and relay) adopt the

states that have previously been defined. - Alarm suppression (controller alarm only)

This function temporarily deactivates the alarm generation via the relay (has to be configured

accordingly). Linking the corresponding terminals by means of a floating contact (e. g. relay)

will activate the pre-defined function. Control functions the relays can have functions

assigned that are configured via parameters. The control function is freely programmable as

P, PI, PD or PID action.


6.8. Analog Outputs

Up to two analog outputs are available, configurable as analog process value output or

continuous controller. The “analog process value output” function can be assigned to the

principle measurement variable or to the temperature. The “continuous controller” function

can only be assigned to the principle measurement variable. Both functions can be combined.

With the analog process value output, the range start and end values are freely selectable.

The response of the outputs to over/ under range, hold and calibration is freely

programmable. Simulation Function the analog process value outputs can be freely set in the

manual (“Hand”) mode show in figure 6.5 Jumo Digital Meter.

Figure 6.5. Jumo Digital Meter.

6.9. Instrument Description Transmitter

The transmitter CTI-920 has been designed for use on site. A sturdy housing of glass fibre-

reinforced polyamide protects the electronics and the electrical connections from corrosive

environmental conditions (Protection IP65). A 3-wire transmitter for conductivity and a 2-

wire transmitter for temperature (output signals 4—20mA) are provided as standard.

Optionally, the conductivity can be output via an integrated 31/2 digit LCD digital display.


The standard signals can be processed by suitable indicator/ control units or directly on a

PLC. Temperature compensation (TC) Depending on the instrument version which was

ordered, the instrument can be operated without, with single or 4-fold temperature

compensation. The strong dependency of the conductivity on the temperature of the medium

usually necessitates a compensation of the temperature dependent variation. The version

without TC can be used for measurements with stable temperature conditions in which

measurement inaccuracies can be tolerated. In addition, instruments without TC can be

connected to evaluation units in which TC is performed in the software, for example (PLC or

similar) is also included in versions without TC. For most applications the version with a

single TC is sufficient. A scaled potentiometer enables the adjustment of the temperature

coefficient in the range 0 — 3%/°C. The version with a 4-fold TC permits a very comfortable

process control. Depending on the medium or the medium temperature up to 4 preset

temperature coefficients can be selected (selection e.g. via PLC, depending on process

development, medium or temperature). The temperature coefficients can also be set via 4

scaled potentiometers in the range 0 — 3 %/°C. Measuring cell The cell consists of a

hermetically sealed PVDF body inside which the two measurement coils are arranged. Holes

in the measuring cell enable the measurement medium to flow through. The cell is

temperature and pressure-stable to a high degree. For temperature measurement and

compensation, the cell is fitted with a fast-response temperature sensor (Pt100). For

applications which have to comply with the highest standards of hygiene, connection type

Varivent is available which also features a cell with a special style (see detailed diagram of

process connection -90).

The measurement principle means that there is an inevitable isolation between the

measurement medium and the current output show in figure 6.6 measuring cell.


Figure 6.6 measuring cell.

6.10. Schematic Arrangement of the Standard Cell

(1) PVDF body

(2) T-shaped through-flow channel

(3 ) liquid loop

(4 ) measurement medium

uht plant

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