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Fast Track 1999 Process Control / Measurements Lafarge Institut Cimentier / 1

FAST TRACK

September 1999

MEASUREMENTS

nstitut Cimentier


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Fast Track Part 1/1999 / Process Control - Measurements / Institut Cimentier / 1

Measurements

WHY


Measurements

Flow (Pressure) Flow (Pressure)

Temperature Temperature

Power Power


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SLD 13:00-xx

Why measurements

Objectives:

Be able to take any given measurement for an audit

Direct other to take the measurements

Intro:

I will be looking for answers/ comments from group

therefore - don't flip ahead

Explain Objectives

Why do measurements?

Why do we need good measurements?

Measurements

As with gas laws. the important measurements to be made are in order toobtain:

1) Pressure (total, static, and/or velocity)

2) Temperature (wet-bulb and dry bulb)

3) Flow (velocity)

MEASUREMENTS


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Why do we need to MEASURE?

To obtain data used for process control

What is important when measuring?

Measurement Method

Precision

Repeatability


AirflowMeasurement Methods

Pitot Tubes (S & L)

Anemometers

Piezo metric Rings

Fan Curves

Pitot Tubes (S & L)

Anemometers

Piezo metric Rings

Fan Curves


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Why do we need measure?

GROUP ANSWER FIRST

Why do measurements? - Write answers on flip chart

What is important in measuring?

Why do we need good measurements?

* Make sure that they realize that without reliable and accurate measurements(i.e. the right numbers) all further process work will be wrong and wrong

conclusions and recommendations may be made.

Airflow measurement methods

Mention that there are various methods for determining the airflow

Ask why you would use one over the other - answer that each method has

advantages and disadvantages and that knowing what they are will determinewhat method to use at what location.

Pitot tubes most frequently used

Anemometers at fan inlets, usually when no suitable location for Pitot tubes is

available

Piezometric rings, for continuous monitoring

Fan curves for design numbers (lacks in precision)

MEASUREMENTSQuestion

?


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The Pitot Tube

Total Pressure

Velocity + Static

StaticStatic0-40

0-10

0-2

Ref

1.25


S Type Pitot Tubes

Airflow

Used in Dusty Streams

Need Calibration Factor Either Cp or Cv

Manometer connections + ve to Total Pressure

- ve to Static Pressure

Used in Dusty Streams

Need Calibration Factor Either Cp or Cv

Manometer connections + ve to Total Pressure


Measures Total

Pressure

MeasuresStatic P


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SLD 13:00-xx

The Pitot tube

Mention that there are two types of Pitot tubes:

S tube

L tube

Use in conjunction with a manometer to determine the velocity pressure,which determines the air velocity

It is the most common method used to determine airflow.

S type Pitot tubes

SHOW S PITOT TUBE

Emphasize that the S-tube is used mostly in our systems due to dirty airstreams.

The difference between Total and Static pressure is the velocity pressure.

Velocity pressure will always be positive.

S-tube has a correction factor usually c=0.85 (approximately)

Show direction of L-tube with respect to flow direction

MEASUREMENTS


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L TypePitot Tubes

Used in clean gas streams

No calibration factor (always = 1)

Same manometer connections as S

+ ve to Total Pressure


Used in clean gas streams

No calibration factor (always = 1)

Same manometer connections as S

+ ve to Total Pressure


Airflow

Measures

Static P

Measures Total

Pressure

(Vel + Static)


Pitot Tube Measurement Locations

Circular cross-section of duct Rectangular cross-section of duct Circular cross-section of duct Rectangular cross-section of duct

x

x

x

x

x

x x

x

xx

xx


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SLD 13:00-xx

L type Pitot tubes

SHOW L PITOT TUBE

Emphasize that the L-tube is used in clear airstreams only, it plugs up easily industy conditions

The difference between Total and Static pressure is the velocity pressure.

Velocity pressure will always be positive.

L-tube does not have a correction factor c = 1.

Emphasize that for both types of tubes, the connections are important.Show direction of L-tube with respect to flow direction

Pitot tube measurement locations

Ask group where they would take Pitot tube readings?

Ask group: What do you need to take a Pitot tube reading?

Size of duct (ID or area of rectangleLocation of measurement points within the duct.

-explain that different sources offer different recomm.

- more is always better

Explain that with a circular duct it is best if three sample ports at 60 degrees fromeach other is used. However it is most common to only have two sample ports at90 degrees from each other


?


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Pitot Tube Measurement Locations ina circular duct

X1 X2

X3

X4

XnD


Pitot Tube Measurement Locationsin a rectangular duct

Inside Number of

diameter t raverse points K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 K11 K12 K13 K14 K15 K16of duct in each of 3

diameters

Less

than 8 ft 8 .021 .117 .184 .345 .655 .816 .883 .979 - - - - - - - -

8 ft thru

12 ft 12 .014 .075 .114 .183 .241 .374 .626 .759 .817 .886 .925 .986 - - - -

Greater

than 12 ft 16 .010 . 055 .082 .128 . 166 .225 . 276 .391 .609 .724 .775 .834 .872 .918 . 945 . 990


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Pitot tube measurement locations in a circular duct

In order to obtain a representative average airflow, it is necessary to locate thetraverse measurement points accurately.

For a circular duct, according to AMCA (Air movement and control association), it isrecommended that the number of traverse points as indicated on the slide are basedon log-linear Pitot traverse method.

Explain that the circular points on the drawing are the sample points while theequation:

Xn= D * kn

where XN= the sample location (of point n)

D = inside diameter of the duct

kn= the factor from the table on the slide

Mention that it is important to mark the Pitot tube (often with tape) before starting.

Another important point is not to forget the nipple size.

Pitot tube measurement locations in a rectangular duct

Similar to the circular ducts, traverse points must also be determined for a rectangularduct.

MEASUREMENTS


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What data is required todetermine airflow

Pitot Tube - Cv Duct Dimension Gas Density Velocity Pressure

Pitot Tube - Cv Duct Dimension Gas Density Velocity Pressure

Remember:

where V = gas velocity

PV= velocity pressure CV= Pitot tube factor r = gas density

V CP

V

V *

*2


75% Rule

Data is GOODwhen:

75% of Pv > 0.1 x Pv max

How do you know if data is good?


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What data is required to determine ariflow

It is important to have a well calibrated S-type Pitot tube in order to have anaccurate value for CV.

Remind them that CV= 1 for an L-tube.

With this information we will know the airflow

Remind them of the velocity equation as seen in Basic Gas Laws

with the added CVfactor.

How do you know if data is good

GROUP ANSWER FIRST

How do you know if your data is good?

It is essential to be able to eliminate numbers that are not good.

Turbulence of flow can severely affect flow measurements.

The location of your flow measurements along the system are very important.

EXPERIENCE will the guide in the future.


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75% of velocity press measurements aregreater than 0.1 Pv max

A- Ideal P. Distribution

P. Max10

P. Max

B- Good P. Distribution

P. Max10

P. Max

C- Satisfactory P. Distribution

P. Max10

P. Max

P. Max10

P. Max

D- Do not use

80%

60%

P. Max10

P. Max

E- Do not use

40%

P. Max10

P. Max

F- Do not use

20%

35%

35%


Measurement Locations

Rule of Thumb - Good sampling location is

6 duct diameters downstream of a fitting

2 duct diameters upstream of a fitting

Rule of Thumb - Good sampling location is

6 duct diameters downstream of a fitting

2 duct diameters upstream of a fitting

A B

E F

C

D


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This slide is to give the students an idea of what the velocity profile can be in a

duct, as well as showing which of the profiles would seem acceptable and whichwould not.

Remind them that the picture is only in 2 dimensions and things could change if wewent across the duct at another location (this is why we suggest 3 sample ports,and insist on at least two. In many cases, unacceptable data may be OK, andvice-versa.

Measurement locations

Ask students where they would take Pitot tube measurements.

Stress the importance of sample locations.

Mention the difficulties in plants: location, temperature, material flow, etc. (tertiaryair ducts, for example.

Explain that the rule of thumb is always possible. That is when decisions must bemade and the 75% rule may be used, and other methods (anemometer or fancurves may be used)

It is important to realize that the fan curve may be used to make sure thatmeasured results are in the right ballpark.


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Inleakage

Plugging of Pitot tube

Material build-ups

Location of Measurement

Inleakage

Plugging of Pitot tube

Material build-ups

Location of Measurement

What to watch out for inPitot tube measurements?


Anemometer

5.3 m/s

Needed:

Inlet Dimension

Air Density:

temperature

air pressure

gas composition

(water vapour)

Needed:

Inlet Dimension

Air Density:

temperature

air pressure gas composition

(water vapour)


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What to watch out for in Pitot tube measurements

Remember the importance of accurate measurements.

Inleakage can drastically change results. Make sure to cover sample port as Pitottube is inserted.

Due to the dusty environment that are usually present during pressure measurementsat a plant, Pitot tubes plug easily.

Remember to use a S-tube in dusty ducts, but this can still plug.

Material build-ups can reduce the cross-sectional area of a duct and increase the gasvelocity, be sure that no significant build-ups are present at a sample location.

Again the importance of measurement location is imperative, so make sure to choosewisely.

Anemometer

Show the students a vane anemometer.

Vane anemometer

Hot wire anemometer

Both measure air velocity

Explain method Show the students the two methods of getting measurements:

1) circle method (from outside of grid, go encircles until themiddle.

2) multiple measurements (average out errors)

Remember: don't stand in front of grill

watch - partially closed dmprs create Hi/lo, so need auniform traverse

accuracy can vary as much as 20%

Question

?MEASUREMENTS


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Anemometer - which Area?

of Grill = Area2

Plane of

measurement= Area1

Area1 > Area2

therefore

V1 < V 2

Front View Full Inlet

Side view

Close-up of Grill

Open Area


Anemometer - Which Area?

Which Diameter?

Scope to what point? No problem


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Anemometer - Which area?

GROUP ANSWER FIRST

What area? Does one take the grill into account?

In general the grill is ignored due to its small wire mesh.

However if the mesh is large in diameter and the relative area is large, it must betaken into account, and adjusted for.

The determination of the area is often where the error in measurement (up to 20%)usually occurs.

Anemometer - Which area?

What area?

Want

average air flowover

area of flow

Whatever you use, be consistent.

Without flute it is very easy.

with a flute end to the duct, an approximation of the area must be taken as shown ondiagram.

Question

?MEASUREMENTS


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Piezometric Rings

Inlet Bell Piezometer

On-line pressure

analyzerprovides continuousmeasured data

Watch for:

build up on screen

dented inlet bell

On-line pressureanalyzer

provides continuousmeasured data

Watch for:

build up on screen

dented inlet bell


Estimating Flows from Fan Curves

109876543210

8

9

10

11

12

13

14

15

16

17

18

0

4

8

12

16

20

24

28

32

36

40

Volume (acfm x 1000)

StaticPres

sure(inWG)

Pow

er(BHP)

Fan Curve ( Clinker Cooler Fan)

NOT CONSIDERED A GOOD PRACTICE

BECAUSE OF SYSTEM EFFECTS

NOT CONSIDERED A GOOD PRACTICE

BECAUSE OF SYSTEM EFFECTS

FAN CURVES REPRESENT FANS

UNDER IDEAL LAB CONDITIONS

FAN CURVES REPRESENT FANS

UNDER IDEAL LAB CONDITIONS


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Piezometric rings

The piezometric ring is used as a continuously monitoring tool.

Used in clean air streams only, due to plugging.

Not used for audit purposes due to large error possibilities (although it can be usedto cross-check Pitot tube or anemometer readings.

Often used at inlets of cooler fans in cement industry.

Estimating flows from fan curves

The last method of evaluating the airflow is with static pressure measurements, anda fan curve.

System effects

May or may not be significant, but will drastically affect your results

It is good practice to use it as a check

If the differences in fan curve vs. Pitot tube or anemometer results are significantone can:

quantify the cost of system effects

MEASUREMENTS


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Which is the right method

to determine the airflow?

Pitot Tubes (S & L)

Anemometers

Piezo metric Rings

Fan Curves

Pitot Tubes (S & L)

Anemometers

Piezo metric Rings

Fan Curves


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Break

Give 10 minute break exactly (optional if time is available)

Which is the right method to determine airflow?

Ask students what the right method is.

Answer: it is still debated, but several rules are present.

1) When an ideal location with steady flow is available, Pitot tubes arerecommended.

2) Anemometers can be used at fan inlets only, when no appropriatePitot tube location is available.

3) Piezometric rings and fan curves should be used as cross-checksor last resorts only.

Experience will guide, and it is a very good practice to use two different methodsin order to verify answers as much as possible.

Question

?MEASUREMENTS


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What tools do we have tomeasure Temperature?

Thermometer

Sling thermometer

Infrared Temperature gun

Thermocouple

Pyrometers

Calorimeter

Thermometer

Sling thermometer

Infrared Temperature gun

Thermocouple

Pyrometers

Calorimeter


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What tools do we have to measure temperature?

Bring as many of these as possible.

Explain the uses and limitations of each.

1) Thermometer: low temp. only (good accuracy.

2) Sling thermometer: low temp only, dry and wet bulb temps, difficult to use in

ducts.

3) Infrared gun, poor accuracy, but used for difficult to access places as aquick guide or to determine surface temps.

4) Thermocouples: - high temp applications (can also obtain wet bulb temps byadding moist end. ( Very high use to obtain temperatures in ducts and otherenclosed areas in cement industry)

5) Pyrometers:(2-color or hot wire) = high accuracy, measures surfacetemperatures

6) Calorimeter: Clinker exit temperature by temperature change of water.

Question

?MEASUREMENTS


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Dry Bulb Temperature

The gas stream temperature

Get the thermocouple junction upstream of

the port to avoid cooling from leak air

Leak air

T/CGas flow

162


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Dry bulb temperature

The dry bulb temperature is required in most cases.

In most cement plant applications, a thermocouple is used to determine thetemperature of the stream.

Gas stream temperature is obtained by placing the thermocouple into the flow.

Remember that inleakage is a concern since it could lower the temperaturereading.

There will be areas where the flow is so small that there is not directional flow, atthis point inleakage becomes even more important to prevent.

Inleakage can be minimized by covering the port opening with your hand as theprobe is inserted.

MEASUREMENTS


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Wet Bulb Temperature

Start with wick thoroughly soaked

Evaporation will lower temp from DB temp (if

not the gas is saturated already)

When the temperature comes to equilibrium you

have the wet bulb temp

Super heated vapor

Air & H2O

130

Sat VapWet rag wick

Wrapped on T/C


Power Measurements

Types of Motors (most common)Types of Motors (most common)

Motor shaft power equations work for the above motorsMotor shaft power equations work for the above motors

1) Variable Speed

a) Variable Speed (AC)

b) SCR (DC)

1) Constant Speed

a) Induction (AC)

b) Synchronous (AC)


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Wet bulb temperature

Wet-bulb temperature readings are important but very difficult in cement plants.

In ducts, sling thermometers can not be used and thermocouples are once againthe instrument of choice.

The tip of the thermocouple must be covered in a wet rag (or other) to insure 100%moisture.

The temperature should hit stability as the wet bulb temp., but in reality, theequilibrium position is often very difficult to accurately determine, because dustclogs the rag or the water evaporates too quickly or there is too large a gapbetween the rag and the tip of the thermocouple which allows inleakage.

Practice wet bulb measurements before an audit situation where time is of theessence.

Power measurements

Ask group why we measure power?

Explain that power is the amount of energy drawn by a motor.

We must measure power because this is one of the important costs to a cementplant.

Motors fall into two categories:

Alternating Current (AC) and

Direct Current (DC)

Motors are also either constant speed or variable speed (variable speed motors aremore expensive, but they draw less power. They are used when the motors outputdemand varies greatly).

Question

?MEASUREMENTS


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Motor Shaft Power

If the motor is greater than 5 HP and operating at 90% or more of FLA:

either of the following may be used

[ ][ ]A) Hmo = [NPH]

Hmo = Motor Shaft Horsepower

NPH = Nameplate Horsepower

FLA = Full Load Amps

NPV = Nameplate Voltage

NLA = No Load Amps

Measured values the average for 3 phase

MEAS AMPS

FLAMEAS VOLTS

NPV

[ ][ ]B) Hmo = [NPH] MEAS AMPS - NLAFLA - NLA y

Equation A is within 5% for motors > 5 HP and < 90% FLA

Use average of A and B for motors < 5 HP or > 90% FLA

If Hmois less than 50% of NPH error can be 15% or more


Single Phase, Direct Current & 3Phase Motors

Hmo =[Amps] [Volts] [Power Factor] [Motor Eff]

746

Single Phase or DC Motors Single Phase or DC Motors

For DC motors

Delete Power Factor from the formula Use armature Amps and Volts

Hmo = 3 [Amps] [Volts] [Power Factor] [Motor Eff]

746

3 Phase Motors 3 Phase Motors

Use the average of the measured phase values

For variable frequency motors measure at the motor


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Motor shaft power

Explain the equations (they are straight forward).

Explain that there are potential errors involved in power calculations.

Give example (allow 2 minutes to solve), then correct.

NPH = 20 Hp

MEAS Amps = 12 Amps

FLA = 15 AmpsMEAS Volts = 25 V

Nameplate voltage = 28 V

Single phase, direct current phase motors

Single Phase, DC and 3 phase motors are measured differently. It is important tonote that all results are in Horsepower.

Give the formulas as stated.

Explain that power is a calculated number (often calculated by a monitor).

Big push from TYTP to reduce power.

Hmo= 20 Hp12 V

15 V

*25 V

28 V

Hmo= 14.3 Hp

MEASUREMENTS


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Gas Analysis

High temperature fibres

PROBE

Filter

Leak-freePump Gas Analyzer c/w Flowmeter

Length of hose for cooling

Dryer

Oxygen

COCO2SO2NOx

Stack

Exhaust Gas CircuitPreheater ExitPreheater CycloneKiln Exit


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Gas analysis

Another important measurement that is important to have is gas analysis.

These are obtained primarily by on-line gas analyzers as shown.

Explain "typical" setup

see drawing

auxiliary pump may be needed

(are a problem area for inleakage)

filters may plug

desiccant needed to be changed

REMEMBER results will be on a dry basis

It is important to realize that Consultants are often hired to obtain results:

they are often wrong

watch for "standard air" watch for dry or wet basis

cross-check (e.g. overall sulfur balance)

Portable oxygen analyzers are also common.

MEASUREMENTS


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Calibration of Equipment

Process equipment must becalibrated

Many pieces are very sensitive to

operating conditions

Poorly calibrated instruments will

lead to WRONG conclusions

Process equipment must becalibrated

Many pieces are very sensitive to

operating conditions

Poorly calibrated instruments will

lead to WRONG conclusions


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Calibration of equipmentIt is essential to stress the importance of properly calibrated equipment.

State that a full audit may be put into question if poorly calibrated equipment is used(this includes weigh feeders also).

State that there are enough difficulties in obtaining good results (such as unevenflow, dusty conditions, difficult to access areas, difficult temperatures to obtain,

clinker at kiln exit) without adding poor measurement tools.

MEASUREMENTS


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Recap

Flow (Pressure) Flow (Pressure)

Temperature Temperature

Power Power


Measurement - Completed

See you tomorrow


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SLD 13:00-xx

Recap

This afternoon we covered how to measure flow temperature and power.

Remember that the choice of the appropriate equipment is important.

Reiterate the importance of measurement location.

Calibration is important.

The measurement process is very important, prepare before measuring byknowing EVERYTHING that you wish to before starting to measure.

Measurement - completed

State that this is the end of day.

Tomorrow, they will start with fan systems

MEASUREMENTS

measurement d

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