10_twomanipulated

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©2006 Fisher-Rosemount Systems, Inc.

Slide 10 - 1

Process Control

Control Using Two Manipulated Input

Control Using Two Control Using Two

Manipulated Inputs Manipulated Inputs




Slide 10 - 2

Process Control


Control Using Two Manipulated Parameters Control Using Two Manipulated Parameters Control Using Two Manipulated Parameters

Æ Under specifiedproblem that hasmultiple solutions for

unlimited operation.

Æ Extra degree of freedom is used toachieve uniquesolution that satisfiedspecific controlobjective.

Æ Most commontechniques are: split range, valve position,and ratio control

Controller Process

SP

One(1) Controlled

Parameter

Two(2) ManipulatedParameters

FY




Slide 10 - 3

Process Control


Basis – Split Range Basis Basis – – Split Range Split Range Æ In some cases,

two or moreinputs to the

process are usedas one input.

Æ The inputs to theprocess are

maintained in afixed relationshipas determined bya splitter stationcharacterizationand stationsetpoint.

FY111

Process

AT111

AC111




Slide 10 - 4

Process Control


IP104A

IP104B

PT104

FY104

PIC104

Steam Header Example Steam Header Example Steam Header Example

400# Header

1475# Header

Boiler

Turbo

Generator




Slide 10 - 5

Process Control


ValvePosition

(% of Span)

PIC104 Output (% of Span)1000

0

100

Valve 104A

Valve 104B

Split Range Output (FY104) - Capacity Split Range Output (FY104) Split Range Output (FY104) - - Capacity Capacity




Slide 10 - 6

Process Control


Calculating Splitter SP Ranges Calculating Splitter SP Ranges Calculating Splitter SP Ranges Æ A 1% change in controller

output to the splitter should

have the same impact on

control parameter whenoperating with either valve.

Æ When manipulating the same

or similar material e.g. steam

flow to header, then the range

may be calculated based on

valve rating.

Æ Tests may be performed to

determine impact of each valve

on the controlled parameter.

Example: Steam flow to Header, splitter

interfacing directly to PRV’s, no overlap

Valve 1 rating = 50kph

Valve2 rating = 150kph

Desired Splitter Span valve 1 =

100*(50/(150+50)) = 25%

SP range for valve 1 = 0-25%

SP range for valve 2 = 25-100%




Slide 10 - 7

Process Control


IP

104A IP104B TT104

FY104

TIC104

COOLERHEATER

Example - Split Range Control Example Example - - Split Range Control Split Range Control Æ Temperature

control using

cooling andheating

Æ Valves aresequenced in afixedrelationship tothetemperaturecontroller output




Slide 10 - 8

Process Control


ValvePosition

(% of Span)

TIC104 Output (% of Span)1000

0

100

Cooling (IP104B)

Heating (IP104A)

Split Range Output (FY104) Split Range Output (FY104) Split Range Output (FY104)




Slide 10 - 9

Process Control


Testing Process to Determine

Splitter SP Ranges

Testing Process to Determine Testing Process to Determine

Splitter SP Ranges Splitter SP Ranges Æ With the process at

steady state and AO’sin Auto mode,determine themagnitude of change

in the controlledparameter for a 1percent change in eachvalve.

Æ Calculate the splitter SP span and range for

each output based onthe observed response

Time

Cooling

Heating 1%

1%

1.1degF 2.2degF

Desired Splitter Span cooling valve =

100*(2.2/(1.1+2.2)) = 66%

SP range for cooling valve = 0-66%

SP range for heating valve = 66-100%

ControlledTemperature

Example: Temperature controlled using heating

and cooling valves




Slide 10 - 10

Process Control


Split Range Control in DeltaV Split Range Control in DeltaV Split Range Control in DeltaV

Æ Splitter bock is used

to implement splitrange control.

Æ Split range control

is most oftenimplemented using

AO blocks for direct

interface to valves.




Slide 10 - 11

Process Control


Splitter Block Calculation Splitter Block Calculation Splitter Block Calculation




Slide 10 - 12

Process Control


SP

0 100

0

100

0

100

0

100

100

100

0

0

OUT_1

OUT_2

LOCK_VAL “holds ”

LOCK_VAL “is zero ”

OUT_ARRAY

0 100 0 100

IN_ARRAY

0 100 0 100

OUT_ARRAY

100 0 0 100

IN_ARRAY

0 40 35 100

OUT_ARRAY

0 100 0 100

IN_ARRAY

0 40 35 100

Splitter Block Splitter Block Splitter Block




Slide 10 - 13

Process Control


IN_ARRAY Parameter IN_ARRAY Parameter IN_ARRAY Parameter Æ The SP range

associated with eachoutput is defined byIN_ARRAY.

Æ SP range of outputsmay be defined tooverlap

Æ The SP upper end of range must be greater that lower end of rangefor each output

SP rangeassociated

with OUT1

SP rangeassociated

with OUT2




Slide 10 - 14

Process Control


OUT_ARRAY Parameter OUT_ARRAY Parameter OUT_ARRAY Parameter Æ When SP is outside

defined range, thenthe value at the endof range is used to

determine the output.

Æ LOCKVALdetermines if OUT1value is held if SP isgreater that the upper end of range definedfor OUT1.

Æ No restrictions areplaced on the output

range.

OUT1 Range for

associated SP range




Slide 10 - 15

Process Control


Example - Neutralizer Example Example - - Neutralizer Neutralizer

Neutralizer

Discharge

Reagent

AIC105

AT105

IP105B

FY105

IP105A

Coarse

Valve

Fine

Valve




Slide 10 - 16

Process Control


Split Range Output – Valve Sequencing Split Range Output Split Range Output – – Valve Sequencing Valve Sequencing

ValvePosition

(% of Span)

AIC105 Output (% of Span)1000

0

100

Fine Valve (IP105B)

Coarse Valve (IP105A)

HYSTVAL




Slide 10 - 17

Process Control


Split-range Control Workshop Split Split - - range Control Workshop range Control Workshop

IP104A

IP104B TT104

FY104

TIC104

COOLERHEATER




Slide 10 - 18

Process Control


Split-range Control Workshop Split Split - - range Control Workshop range Control Workshop Æ Step 1. Open the EXAMPLE_G module and go to on-line

operation in Control Studio. Change the mode of theSplitter block to Auto.

Æ Step 2. Change the splitter SP (setpoint) over the following range- 0, 25, 50, 75, 100 - and observe the change in thevalves and process outlet temperature.

Æ Step 3. Change the splitter SP (setpoint) to 50 and wait until the

temperature settles to a fixed value.

Æ Step 4. Make a step change in the FEED_TEMP disturbance andmanually adjust the splitter setpoint to get theOUT_TEMP back to its initial value.

Æ Step 5. Change the splitter mode to Cascade, change thetemperature control setpoint and observe the response.




Slide 10 - 19

Process Control


EXAMPLE_G – Split Range EXAMPLE_G EXAMPLE_G – – Split Range Split Range




Slide 10 - 20

Process Control


Valve Position Control Valve Position Control Valve Position Control

IP106A

AT106

AIC

106

Process

Æ PID control isimplemented using theactuator with finer

resolution or fastestimpact on controlledparameter

Æ The actuator withcoarse resolution or

slower impact on thecontrolled parameter isadjusted by an I-onlycontroller to maintain thelong term output of the

PID controller at a giventarget

pH Example

Fine Valve

A/O

ZC106

IP106B

Coarse

Valve

I-Only

Controller

SP=

Target

ValvePosition

Time

pH

Fine Valve

Coarse ValveTarget Valve

Position




Slide 10 - 21

Process Control


Example -Boiler BTU Demand Example Example - - Boiler BTU Demand Boiler BTU Demand

ZC109

FT

109A

IP109B

FIC109

FT

109B

IP109A

FY109

Low BTU – Waste Fuel

HI BTU Fuel Boiler

BTU Demand




Slide 10 - 22

Process Control


Example –Reformer Air Demand Example Example – – Reformer Air Demand Reformer Air Demand

ZC110

FIC110

FT110

SC110

Air

Machine

SecondaryReformer

Total Air Demand

IP110



©2006 Fisher-Rosemount Systems, Inc.Slide 10 - 23

Process Control


Valve Position Control in DeltaV Valve Position Control in DeltaV Valve Position Control in DeltaV Æ The OUT of

the PID usedfor control iswired to IN on

the PID blockused for I-Onlyregulation of slower

responding or coarseresolution.

PID configured for I-

Only control




Process Control


Configuring PID for I-Only Control Configuring PID for I Configuring PID for I - - Only Control Only Control Æ The STRUCTURE

parameter should beconfigured for “I actionon Error, D action on

PV”Æ The GAIN should be

set to 1 to allow normaltuning of RESET (eventhough proportionalaction is not

implemented.

Æ RESET should be setsignificantly slower than that the product of the PID gain and reset

time used for controle.g. 5X slower




Process Control


Valve Position Control Workshop Valve Position Control Workshop Valve Position Control Workshop

ZC110

FIC110

FT110

Small

Valve

Big Valve




Process Control


Valve Position Control Workshop Valve Position Control Workshop Valve Position Control Workshop Æ Step 1. Open the EXAMPLE_H module and go to on-line

operation in Control Studio. Change the mode of the flowcontroller to Auto.

Æ Step 2. Change the flow control SP (setpoint) over the followingrange – 40, 50, 60 - and observe the change in the two

outputs.

Æ Why Is the small valve maintained at 50%?

Æ Step 3. Change the SP of the valve position controller andobserve the response.




Process Control


Example H – Valve Position Control Example H Example H – – Valve Position Control Valve Position Control




Process Control


Basis – Ratio Control Basis Basis – – Ratio Control Ratio Control

Æ To fully automate a large process, itis often necessary to provide

coordinated adjustment of multipleloops.

Æ The technique of ratioing controlloops is an effective way to providethis coordination.

Æ Ratio station is used to specify ratioand to calculate setpoint of thedependent loop.

Æ Ratioing based on the independent

loop setpoint provides a noise freeremote setpoint but will be incorrect if the independent loop can not maintain its setpoint

FC2

FT2

FC1

RC2

Input = SP or PV

of independentloop

SP

SP= (Ratio * Indep Loop Input )

FT1




Process Control


Example – Reactor Feed Ratio Control Example Example – – Reactor Feed Ratio Control Reactor Feed Ratio Control Æ Catalyst flow

must bemaintained in

correctproportion tothe feed flow for correct reactor operation and

final product.

Æ Ratio controlautomaticallyprovides the

correctproportion of catalyst to feed.

FC8

FT8

RC9

SC9 Reactor

Feed

Catalyst




Process Control


Automatic Ratio Adjustment Automatic Ratio Adjustment Automatic Ratio Adjustment

Æ A process output that

indicates the impact of

the ratio of processinputs may be

maintained at target by

using feedback to

adjust the ratio targetÆ To the feedback

control, the ratio station

and associated flow

loops are considered tobe part of the process

FC1

FT1

FC1

FT1

RC2 AC1

AT

1




Process Control


Example – Slaker Control Example Example – – Slaker Control Slaker Control

Æ Effective Alkali.EA, is

maintained attarget thoughthe adjustmentof lime to greenliquor flow ratio.

Æ As green liquor feed isincreased, thenlime flow isautomaticallyincrease in a

proportion tomaintain thetarget EA.

Conductivity

FC

7

FT7

RC8

SC8

AC9

AT9

Green

Liquor

Lime




Process Control


Ratio Control in DeltaV Ratio Control in DeltaV Ratio Control in DeltaV

Æ The Ratio block is

used to implement

ratio control.

Æ IN_1 may be a

flow measurement

(wild flow) or

setpoint of another

loop

Æ The true ratio is

calculated base on

IN_1 and IN and

reflected in theratio block PV.




Process Control


Ratio Block Function Ratio Block Function Ratio Block Function




Process Control


Ratio Control Workshop Ratio Control Workshop Ratio Control Workshop

Static Mixer

AC1-1

Main Flow

AT1-1

FC

1-2

FT1-2

Blend Flow

FC1-2

FT1-2

RC1-2

% Solids




Process Control


Ratio Control Workshop Ratio Control Workshop Ratio Control Workshop Æ Step 1. Open the EXAMPLE_I_CNT module and go to on-line operation

in Control Studio. Change the mode of the Ratio block to Auto.

Æ Step 2. Change the Ratio SP (setpoint) over the following range – 0.3,

0.5, 0.8 - and observe the change in the blend flow and theprocess outlet concentration. Set the Ratio SP to 0.5 percent

and wait for the concentration to settle to a steady value.

Æ Step 3. Make a step change in the FEED and observe the way the ratio

changes the dependent loop. Did the concentration change?

Æ Step 4. Change the ratio block to Cascade mode. Change the setpoint

of the analytical loop to 40% and observe the impact on the ratio

setpoint. Does the measured concentration reach setpoint?

Æ Step 5. Open the EXAMPLE_I_PROC module and examine the process

simulation used in this workshop.

Æ Question: What are the advantages of structuring the process simulation as a

separate module? What are the disadvantages of this approach?




Process Control


EXAMPLE_I_CNT EXAMPLE_I_CNT EXAMPLE_I_CNT




Process Control


EXAMPLE_I_PROC EXAMPLE_I_PROC EXAMPLE_I_PROC




Process Control


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