operate process control

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GRADE 4 TRAINING MODULE 4 1 0

SKILL:

INSTRUMENTATION

OPERATE PROCESS CONTROL

INSTRUMENTATION

SUPPLY

OUTPUT

RANGE ROD

FEEDBACK BELLOWS

EXTERNAL

ZERO ADJUSTMENT

REDUCING TUBE

NOZZLE

FLEXURE STRAP

FORCE BAR

HIGH PRESSURE

CO-NI ALLOY

DIAPHRAGM SEAL

-FULCRUM-

FLEXURE

RELAY

TWIN DIAPHRAGM

CAPSULE

LOW PRESSURE

CAPSULE BACK-UP

PLATE

RANGE WHEEL

-FULCRUM-

FLAPPER

Santos


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Acknowledgement

Some of th e in forma t ion fou nd in th is m odu le ha s been extra c ted

from Horizontal Training Module 10, and modif ied to suit relevantcompeten cies for produ ct ion opera t ors .

Ch a n ge Au th or ity: Moom b a Tra in in g Dep a r tm en t

Typ es et b y: Tech n ica l Services , Sa n tos Ltd

Pr in ted b y: Cop y Room , Sa n tos Ltd

Sa n tos Ltd Decem b er 1 9 9 4

A.C.N. 00 7 55 0 92 3 File No: MODULE P4 10


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CONTENTS

MODULE INSTRUCTIONS 1

TRAINING OBJ ECTIVES 2

INTRODUCTION 3

1. PRESSURE 4

Pres s u re Ga u ge 4

Regu la tors 5

Proces s Tra n s m it ters 6

Pres s u re Tra n s m it ters 6

Pres s u re Switch 7

Ch a rt Recorder 8Sen s ors a n d Tra n s du cers 8

Rem ote Term in a l Un its 10

QUESTIONS 1 TO 4 11

2. FLOW 12

Orifice Pla te 12

An n u ba rs 14

Differen t ia l Pres s u re Tra n s m it ter 15

Dia ph ra gm Meter 16

Ch a rt Recorder Differen t ia l Pen Zero Ch eck 18Rota m eter 20

Tu rbin e Meter 21

Ta rget Flowm eter 22

QUESTIONS 5 TO 6 23

3. LEVEL 24

Level Ga u ge 24

Va r ia b le Dis p la cem en t 25

Differen t ia l Pres s u re 26

Fis h er Level/ Mu lt itrol 27

QUESTIONS 7 TO 9 29

4. TEMPERATURE 30

Filled Th erm a l Sys tem s 30

Bi-Meta llic 31

Th erm ocou p le 32

Res is ta n ce Th erm a l Detector (RTD) 33

QUESTIONS 10 TO 12 34

TRAINING TASK 1 35

COMPETENCY TEST RECORD 37


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MODULE INSTRUCTIONS

You m u s t r ead th is m odu le u n i t . It wi l l normal ly be s upported by an

ins truc t iona l presen ta t ion or tutor ial whiche ver i s appropria te . Where

app l icab le the re a re t r a in ing t a s ks to comp le te an d qu es t ions to a ns wer .

P rac t is e t r a in ing t a s ks an d an s wer the qu es t ions in the modu le . Seek he lp

whenever necessary .

Compet ency Tes t i ng

Tra in ing t a s ks an d th e an s wers to any ques t ion m ay be inc luded in th e

competen cy tes t . Oral an d wr i t ten tes ts ma y a lso be in clu ded where

app ropr ia te . A competen cy tes t record sh eet located a t th e back of th e bookle t

l i s ts the appropr ia te competency tes ts .

Competen cy tes t ing is a n ess ent ia l com ponen t of t ra in ing . It g ives th e t ra inee

th e confiden ce to safe ly car r y ou t a t as k an d th e Su pervisor confiden ce in t h e

t ra inees a b i li ty to car ry ou t th e ta sk competen t ly.

The s a t is fac tory com plet ion of th is m odu le , an d wh ere app licable an y

as socia ted t r a in ing task s , will lead t owards a t ta in ing Grade 4 .

Icon Descr ipt ionsIcon s ymbo ls th roughou t the m odu le ind ica te wha t you s h ou ld do .

Yo u m u s t r e a d a n d u n d e r s t a n d t h e t e xt .

You m u s t an s wer the ques t ions .

WARNING in dicates poten tial dan ger to you rs elf or oth ers .

CAUTION in dicates p otent ia l dam age to th e equ ipm ent .

You m u s t d o the t ra in ing tas k or ac t ivity .

You m u s t complete the competen cy tes t .Competency

Training

Task

Warn ing

Caut ion

!Ques t ions

?Read


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TRAINING OBJECTIVES

On su ccess fu l com plet ion of th is m odu le th e t ra inee wi ll be ab le to :

Un d e rs t a n d a n d op er a te p roce ss c on t r ol in s t ru m e n t a t ion .

Chal lengeIf you th ink you ha ve a l ready a chieved th is m odu les object ives you sh ould s ee

you r s u pervis o r , a s you m ay be ab le to a t t emp t th e comp e tency t es t n ow.

Othe r Reso urce s G ra d e 2 Tr a in in g Mod u l e 2 1 7 B a s ic In s t r u m e n t a t ion .

G r a d e 4 Tr a in i n g Mo d u le 4 1 1 P n e u m a t ic C on t r o l S ys t e m s .

Safe t y Sym bol sThe following Safety Symbols have been used to indicate personal safety

requ iremen ts when car ry ing ou t Tra in ing Tas ks . If th ere is an y dou bt as to

the m ean ing o f thes e s ymb o ls , p leas e a s k the a rea s u pervis o r .

Hard hat must be worn Safety boots must be worn

Eye protection must be worn Two way radio will be required

Ear protection must be worn Beware of moving parts around

pump jack

Gloves must be worn Protective clothing must be worn


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INTRODUCTION

The fun ct ion of ins t ru m enta t ion in t h e o il an d gas ind u s t ry is to provide an

accu ra te meas u remen t a nd con t ro l o f the p roces s .

Th is is don e in t wo ways:

Loca l con trol.

Rem ote con trol.

The fou r ba s ic elemen ts o f meas u remen t a r e :

Pres s u re.

Flow.

Level.

Tem p era tu re.

S p e c i a l No t e

In forma t ion can be gained from th e man u factu rers m an u als for par t icu lar

m odels or type of equ ipmen t. Th e in ten tion is n ot to en cou ra ge fiddlin g, bu t

to give a bet ter u nd ers ta nd in g of h ow th ings work so as to ena ble an opera t or

to ma ke th e cor rec t an alys is of opera t ing problems , then ca l l u pon th e

app ropr ia te techn ician to rec t ify th e problem, m ak ing for an ea s ier and m ore

efficien t opera tion.


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1 . PRESS URE

Comm on u n i t s o f p res s u re a re :

p s i Pou n d s p er s qu a r e in ch

Pa Pa s ca ls

k Pa Kilop a s ca ls

MPa Mega p a s ca ls

In H2O In ch es of wa ter

m m H2O Millim et res of wa ter .

P res s u re chan ges th e s h ape o f a m eas u r ing e lemen t p ropor t iona l to the

p res s u re exer ted .

CROSS SECTIONBOURDON TUBE

INCREASE

BOURDON TUBE

PIVOT

QUADRANT &PINION

PRESSURE INLET

Figure 1 Bourdon tube pressure gauge

Pressure GaugeThe m os t comm on m ethod o f meas u r ing p res s u re is by th e u s e o f a Bourdon

Tu be type pressu re gau ge. Th e Bou rdon Tub e is of e llip t ica l cross sec t ion a n d

is form ed in to a C sh ape wi th on e end secu red to th e in le t conn ect in g s tem,

while the o the r en d i s conn ec ted by a l ink to a qu adra n t an d p in ion

m e c h a n i s m .


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Pres s u re is a pp l ied to the in le t s t em an d in to the Bourdon Tube wh ich t ends

to s t ra ight en with th e increa se in pres su re . With th is movem ent th e free end

of the Bourdon Tu be m oves the qu adra n t thu s m oving the po in te r .

This type of gau ge is te rmed a com pou nd gau ge. Mos t press u re gauges ar ecal ibra ted to read O a t a tm osph er ic press u re . Th is i s refer red to a s Gau ge

Press u re.

Pressu re gau ges ar e norm al ly se lec ted so as to read 5 0-60% of th e scale un der

norm al opera t ing condi t ion . Under n o c ir c u m s t a n c e s m u s t t h e ga u ge b e

s u b jec t to p res s u re g rea te r th an 100% of s ca le, a s th i s cou ld lead to th e

Bou rden Tube ru p tu r ing an d th e gauge b lowing ou t .

RegulatorsAn imp or tan t pa r t o f the p neu ma t ic con t ro l s ys tem i s th e a i r o r gas s u pp ly

regu la to r wh ich ma in ta ins a s t eady s u pp ly o f p res s u re to a s s ocia ted

i n s t r u m e n t s .

OUTLET PRESSURE SCREW

FORCE SPRING

DIAPHRAGM

OUTLET

DAMPING SPRINGVALVE SEAT

VALVE PLATE

INLET

VENT PORT

INLET

PRESSURE

REGULATED

PRESSURE CHAMBER

Figure 2 Regulator

Op e r a t i o n (v e n t e d t y p e s h o w n a b o v e )

Air o r gas en te r s th e r egu la to r an d th e ou tpu t p res s u re is con t ro lled by the

d iaph ragm. One s ide o f the d iaph ra gm is loaded by the ou t l et p res s u re and

th e o ther i s loaded b y the force spr ing . This force is a d jus ted by th e out le t

press u re screw. Th e force spr ing pu sh es the d iap h ragm an d valve to th e open

pos it ion an d a i r flows in to the cham ber . When the p res s u re in th e cham ber

yields en ou gh force to coun ter th e spr ing force, th e valve will close a n d red u ce

th e a ir flow. Thu s the press u re in th e ch am ber is propor t iona l to th e spr ing

force.

In p rac t i ce the re i s a cons ta n t a i r d ra in on th e ou tpu t an d th e va lve will

rema in open t o som e degree . It is good pract ice to ad jus t the regula tor a t th e

average outp u t a i r flow so tha t a rea sona ble to leran ce (14 0 k Pa) is availab le

for an y flow of air . Th e volu m e capa city of th e regulat or will dep en d u pon t h e

size of the valve.


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In t h e even t of th e out pu t l in e being closed off, excess pr ess u re will be vented

th rou gh the ven t ing po r t .

Process Transmit ters

Proces s t r an s m it t e r s a r e in s ta l led nea r th e po in t o f p roces s m eas u remen t a ndthe t r a ns mi t t e r s ends a s igna l to a r emote con t ro lle r .

The t r a ns mi t t e r conver t s th e p roces s cond i t ion to a 2 0 -100 kP a p res s u re

s igna l. It is ca l ibra ted so tha t it con ver ts for exam ple th e opera t ing press u re

in s ide a sepa ra t or to a low pressu re a i r s igna l to a contr o ller .

Process t ra ns mit ters can be u sed for any type of process m eas u remen t (eg.

flow, level, p res su re , an d temp eratu re).

GAS OUTLET

PRESSURETRANSMITTER

PRESSURECONTROLVALVE

LIQUIDOUTLET

SEPARATOR CONTROL ROOM

PRESSURECONTROLLER

Figure 3 Pressure control system using a pressure transmitter

Pres sure Transm it te rsA pres s u re t r ans mi t t e r is an in s t ru men t wh ich s ens es p res s u re and conver t s

it in to a pn eu m at ic or elec t r ica l s igna l. This s ignal is th en u sed for ind icat ion

or con t ro l. The m os t comm on ou tpu t s igna ls u s ed a re 20 -100 kPa fo r a

p n e u m a t ic t r a n s m i t t er an d 4-20 m A (m ill iam ps ) for an electr ic tra n sm itter . A

pres s u re t r an s m it t e r cons is t s o f two ma jo r pa r t s - a s ens o r a s s embly an d an

amplifier.

Pn e u m a t ic Tra n s m i t t e r s

Th e press u re bein g m easu red is app l ied to a bel lows caps u le . Th e outp u t

s igna l is p ropor t iona l to tha t p res s u re an d i s t r ans mi t t ed to a pneu ma t ic

recorder .


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Ele c t r ic Tra n s m i t t e r s

Th e s e t r a n s m it t e rs m e a s u r e g a u g e p r es s u r e a n d t r a n s m it i t a s a 4 - 2 0 m A

signa l. The out pu t cur r ent i s propor t iona l to the pressu re appl ied to a bel lows

caps u le with in th e in s t ru men t . The s igna l is t r an s m it t ed to a r eco rde r ,

indicator , or controller .

Pres sure Swi tc hA pres s u re s witch i s an in s t ru men t wh ich i s u s ed to s witch a con ta c t in a n

elec t r ica l c ircu it a t a cer ta in pressu re . Pressu re var ia t ions are sens ed by a

bel lows , d iap hr agm or p is ton s ens or wh ich opera tes a m icro switch . For

examp le a h igh p ressu re switch is one wh ich opera t es with a r i s in g press u re .

A low pressu re swi tch is one which opera tes wi th th e press u re fa l lin g .

Drawing to com e

Figure 4 High pressure switch

Drawing to com e

Figure 5 Low pressure switch


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Chart Rec orderThe p res s u re e lemen t in th e r eco rde r opera tes in the s a me way as th e

Bou rdon Tu be in th e p res s u re gau ge. As p res s u re is ap p lied to the p res s u re

elemen t it tend s to t ry to s t ra ighten . A ser ies of l ink ages , conn ected to the

e lemen t , m ove the pen ac ros s th e r ecorde r cha r t .

PRESSURESENSING

ELEMENTNAMEPLATE

LINK

PENARM

Figure 6 Diagram of a chart recorder

Sen so rs and Transduc ersA sen sor i s a device which conver ts a qua nt i ty or energy in t o an e lec t r ica l

ou tpu t s igna l . With a s ens o r the ou tpu t mu s t be conver ted in to a s t and ard

ins t ru men t s ys tem va lu e wh ich can then be u t ilis ed by othe r in s t ru men ts in

the s ys tem.

A t ra ns du cer is a device which con ver ts en ergy from on e form to a noth er . In

te rms o f e lec t r ica l meas u r ing s ys tems , a t r an s du cer p roduces a n e lec t r ica l

outp u t s igna l in res pons e to a sp ecific ph ys ica l phen omen on.

It i s a d evice which is ma de u p of a s ens or an d a m odifica t ion or condi t ioning

comp onen t wh ich conver t s th e s ens o r s igna l in to a r ead i ly u s eab le ou tpu t

value . A typical t ra ns du cer configura t ion comp r ises a sens in g e lemen t ,

followed by at leas t one or two am plification s t ages a n d n oise fi lters as sh own

in F igure 7 .

Given th at th e m ajor ity of contro l lers in u se in field work are pn eu ma t ic (ie.

th ey work on ins t r u m ent a i r or gas ), the processes th a t th ey contro l are n ot a llpress u re or gas processes . Th erefore it is n ecessa ry to conver t s igna ls

re lay ing ch an ges in contro lled var iab le or remote contro l s ign als to pn eum at ic

s igna ls . This is ach ieved us ing a su itab le t ra ns du cer or sen s ing e lemen t .


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-

+

SENSING

ELEMENT

POWERSUPPLY

AMPLIFIER AMPLIFIER

NOISE FILTERS TRANSDUCEROUTPUT

TRANSDUCER

Figure 7 A transducer

An examp le of a typ ical t ran sdu cer , which is u sed widely in th e fie ld , i s th e

elec t r ica l cu r ren t to pressu re conver ter or I to P conver ter . Th is ins t r u m ent i s

used extensively for telemetry control of well chokes and in compressor

s ta t ions where th e e lec t r ica l s igna l from an SPEC 200 contro ller i s conver ted

to pressu re to opera te , via p ressu re re lay or bellows , a pn eu m at ic con tro ller .

Var ious o th er t ran sdu cers inc lud e a liqu id fi lled temp eratu re sens ing bu lb

an d cap i llary l ine con n ected to a s p i ra l e lemen t a nd l ink ed to a contro ller by

a l ink age us ed for examp le to contro l tem perat u re . Or a d i fferent ia l be llows

mea su r ing flow, the ou tpu t of which is am pl ified by a pres su re re lay an d

conn ected to th e press u re e lemen t (Bourdon tu be) in a cont ro ller u sed for flow

contro l downs t ream of a conta ctor .

T el e m e t r y S y s t e m s

Telemetry is the reprodu ct ion , a t a convenient locat ion , of m easu remen ts

ma de a t a rem ote locat ion . Telemetry ma kes i t poss ib le for a grou p of in s t ru men ts to be loca ted in a cen t r a l pos i t ion on a p lan t a nd to enab le a

s ingle opera tor to m oni tor con di t ions with in var ious pa r ts of th e p lan t .

In genera l a te lem etry sys tem cons is ts of:

A m e a s u r in g in s t r u m e n t fo r th e p r o ce s s (e g. p r es s u r e or flu i d flo w).

A s ign a l co n d it io n in g d evic e w h ic h c on v er t s t h e m e a s u r e m e n t in t o a

t r an s m it t ab le fo rm.

A t r a n sm is sion lin e.

A r e ce ivin g d e vic e wh i ch c o n ve r t s t h e in c o m in g s ign a l t o a u s e a b l eindicat ion .

Operators s hou ld refer to the Grad e 5 t ra in ing modu le which covers th e

su bject of da ta te lemetry in m ore deta i l.


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Rem ote Terminal Uni t sRTUs ar e ins ta l led a t convenient p oin t s for a nu m ber of gas wells or a sa te ll ite

s ta t ion . Th e ins t ru m ent read in gs for th a t group of wells are then b rough t

ba ck to the RTU via un dergroun d cables . Th e data f rom th e RTU is th en

tra ns m it ted v ia ra d io lin ks to th e Moomb a ins ta l la t ion . Th e RTU is a p as s iveda ta ga th e re r . It does no t t r ans mi t even t s a s th ey occu r , o r r ead ings a s th ey

cha nge, bu t only on reques t from th e Mas er S ta t ion a t Moom ba . The RTUs

are p er iodical ly scan ned , in ter rogated (a t leas t once per 30 seconds ) by the

ma s te r s t a t ion an d s o th e in forma t ion ava ilab le a t Moomba r emains cu r ren t to

the l a s t 30 s econds .

The h a rdware equ ipmen t a t Moomba compr i s es a m a in fr am e compu te r

sys tem to co llec t a ll the f ie ld d ata , ma nipu la te it in to m ean in gfu l readings ,

(eg . compu te flow from press u re a nd tem perat u re), an d d isp lay i t for th e field

controller .


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QUESTIONS 1 TO 4

1 . Na m e 3 c om m o n u n it s of p r es s u r e.

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

2 . Wh a t i s th e m o s t co m m on m e th o d of loc a l p r es s u r e m e a s u r e m en t ?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

3 . Wh a t is t h e m os t co m m on o u t p u t r a n ge of a p n e u m a t ic p re s s u r e

t r ans mi t t e r ?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

4 . Wh a t i s th e m o s t co m m o n o u t p u t r a n ge of a n e le ct r on i c t r a n s m it t er ?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Ques t ions

?


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2. FLOW

Measu rem en t of flowin g liquids a n d gas es is ess en tial for efficien t opera tion of

th e sa te llite . Th ese mea su rem ents ar e in dicated , recorded , to ta l ized and u sed

for control.

F low measurement i s accomplished by:

Dis p la cem en t :

- Pos i t ive d isp lacemen t meters .

- Mete r ing pu mp s .

Differ en t ia l Pr es su r e:

- Orifice pla te.

- Annubar .

- Flow n ozzle.

- P ito t tu be .

- Var iable ar ea (Rotam eter).

Velocit y Flow Met er s :

- Magnetic.

- Turbine .

- Ultra-sonic.

Orifice PlateTh e orifice plate is on e of th e oldes t form s of fluid flow mea su rem en t, an d i t

effectively m eas u res t h e velocity of th e fluid th rou gh a t u be of accu ra tely

kn own cross sectiona l ar ea. The orifice plate develops a differen tial pres su re

across th e p la te by p lac ing a sm al ler d iameter r es t r ic t ion in th e p ipelin e .

1/2 I.D. OF PIPE VENT HOLE

DRAIN HOLE

ORIFICE

CONCENTRIC ECCENTRIC SEGM ENTAL

Figure 8 Types of orifice plate


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CONTROLLER OUTPUTPRESSURE TO CONTROLVALVE

SUPPLYGAS/AIR

VENTNOZZLE

FLAPPER

PIVOTLIQUID FILL

HIGH PRESSUREBELLOWS

LOW PRESSUREBELLOWS

ORIFICE PLATE

FLOWCONTROLLER

Figure 9 Flow control pilot

There is a press u re drop across th e or ifice p la te as flu id f lows t hr ough it .

P res s u re on th e u ps t r eam o r in le t s ide o f the p la te is h igher tha n p res s u re on

th e down s trea m or out le t s ide . Th e in le t s ide pressu re is conn ected to a h igh

pres s u re be llows cha mb er , an d th e ou t le t s ide p res s u re s u r rou nd s a low

press u re bellows . As flow increa ses th rough t he or i fice , the press u re drop

a l s o inc reas es . Ups t r eam p res s u re r emains the s ame , bu t downs t r eampress u re is lower . Th e bellows con ta ins a f lu id , an d as th e pressu re drop

increa ses , th e h igh pr essu re bellows compr esses a n d th e low press u re bellows

e x p a n d s .

The h igh press u re bel lows is l in ked to th e flap per , so th a t a s th e bel lows

compres ses , th e flap per m oves toward th e vent n ozzle an d v ice versa .

0

10

20

30

40

PRESSURE-INCHE

SOFWATER

DIFFERENTIAL

PRESSURE

MERCURY

FLOW

PIPE

Figure 10 Differential pressure across an orifice


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PIPE

ORIFICE

ORIFICE PLATEDATA (mm)

PIPE FLANGE

FLOW

PRESSURECONNECTIONS

CHAMFERSIDE FACESDOWNSTREAM

Figure 11 Orifice restriction plate

AnnubarsTh e an n u bar i s a velocity sens or for the m easu remen t of flow throu gh a p ipe .

It p rodu ces a d ifferent ia l pressu re propor t iona l to the velocity . It h as an

ad van tage over the or i fice p la te in th a t i t resu lts in less p ressu re loss . Th edifferent ia l press u re is m easu red b y a s econ da ry device for record ing ,

integrating or control .

The u ps t r eam s am pl ing po r t s ac t a s impa c t po r t s an d th ey deve lop an imp ac t

p res s u re ac ros s th e who le p ipe line wh ich i s then averaged in the ou tpu t tu be .

HIGH PRESSURE SIDELOW PRESSURE SIDE

Figure 12 The annubar


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The d owns t r eam por t s am ples a t low p res s u re d u e to pa r t i a l evacu a t ion

(as pira tion) by the flowin g fluids . The ma in advan ta ge is ease of ins t al lat ion.

The m ain d is ad van tages a re tha t a nn u bar s r equ ir e a c lean en vironm en t in

which to opera te cor rec t ly an d in d ir ty area s requ ire regular c leaning of th e

por t s .

Different ial Pressure TransmitterThis k ind o f t r an s m it t e r is genera l ly u s ed to meas u re the p res s u re d rop ac ros s

o r ifice p la te s , an nu bar s an d o the r p r imary meas u r ing devices . The ou tp u t o f

th e t ra ns mit ter wi ll go to an indicator , recorder or a contro ller (seconda ry

device). Th e seconda ry device will read a c tu al press u re d i fference a nd can be

u sed to ca lcu la te the flow. Th e d ia l of th e seconda ry device ma y be gradu ated

to sh ow actu al flow.

SUPPLY

OUTPUT

RANGE ROD

FEEDBACK BELLOWS

EXTERNALZERO ADJUSTMENT

REDUCING TUBE

NOZZLE

FLEXURE STRAP

FORCE BAR

HIGH PRESSURE

CO-NI ALLOYDIAPHRAGM SEAL

-FULCRUM-

FLEXURE

RELAY

TWIN DIAPHRAGMCAPSULE

LOW PRESSURE

CAPSULE BACK-UPPLATE

RANGE WHEEL-FULCRUM-

FLAPPER

Figure 13 Diagram of a differential pressure transmitter


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1 6 Module 4 1 0

Read

Diaphragm MeterA d iaphragm m ete r is genera lly moun ted on a ch a r t r eco rder an d m eas u res

the p res s u re d rop ac ros s or ifice p la te s , an d an nu bar s . The p res s u re r ead ing

obta ined f rom th e recorder i s th en u sed in a ca lcu la t ion t o es tab l ish a f low.

Th e d iaph ragm m eter is a t ta ched to the rear of th e recorder . The m ovemen t of the d iaph ra gm is t r an s m it t ed th rou gh to the pen a rm as s embly by a flexu re

s t r ip / dr ive lever .

TO PEN ARMSASSEMBLY

SUPPLYGAS/AIR

VENTNOZZLE

FLAPPER

PIVOTLIQUID FILL

HIGH PRESSUREBELLOWS

LOW PRESSUREBELLOWS

ORIFICE PLATE

FLOWCONTROLLER

Figure 14 A diaphragm meter

LOW PRESSUREHIGH PRESSURE

Figure 15 A diaphragm meter

CAUTION

E xtrem e care m ust be taken when z ero ing the Rec order. Inco rrec t

proce dures wi ll re s u l t in o ver -pres sur ing o f th e un i t caus ing permanen t

damage to the d iaphragm ass em bly .Warning

Caut ion

!


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Module 4 1 0 1 7

Read

Drawing to come

Figure 16 Diaphragm meter attached to rear of a chart recorder


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1 8 Module 4 1 0

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Chart Recorder Differential Pen Zero Check

3 -w a y Ma n i fo ld

To ch eck zero:

1 . Op en 3 .

2 . Clos e 1 or 2.

To pu t ba ck on l ine :

1 . Op en 1 or 2 .

2 . Clos e 3 .

3 WAY MANIFOLD

LIQUIDS KNOCK OUT BOTTLES

TO RECORDER

STATIC PRESSURE

LOW SIDE

GAS FLOW

HIGH SIDE

GASKET

ORIFICE FLANGESORIFICEPLATE

312

BLEED VALVE

LINE VALVES (1 & 2)

VENT

Figure 17 3-way manifold


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Module 4 1 0 1 9

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5 -w a y Ma n i fo ld

To ch eck zero:

1 . C los e 3 (if op e n ).

2 . Op en 4 a n d 5 .3 . Clos e 1 or 2 .

To pu t ba ck on l in e :

1 . Op en 1 or 2 .

2 . Clos e 4 a n d 5 .

3 . Op en 3 .

5 WAY MANIFOLD

LIQUIDS KNOCK OUT BOTTLES

TO RECORDER

STATIC PRESSURE

LOW SIDE

GAS FLOW

HIGH SIDE

GASKET

ORIFICE FLANGESORIFICEPLATE

3

5

2

EQUALIZER VALVES

BLEED VALVE

LINE VALVESVENT

1

4

Figure 18 5-way manifold

CAUTION

Care m ust be taken to e nsure tha t th e d iaphragm m ete r be l lows are no t

damaged .

WarningCaut ion

!


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2 0 Module 4 1 0

Read

R o t a m e t e rTh e var iab le area m eter , which is often ca l led a ro tam eter , cons is ts of a

ver t ica l tapered tu be th rough wh ich th e flu id flow being m easu red pa sses in

an u pward d i rec t ion . A ro tor i s conta in ed with in th e tap ered tub e . Th is ro tor

is m ade o f me te r ia l more dens e tha n the f lu id be ing meas u red .

As th e flow moves up t hr ough th e tapered tu be , it ra ises th e ro tor u nt il th e

u pward flu id force balan ces the ma ss of th e rotor . The ar ea th rough which

the f lu id pa s s es ha s a u tomat ica lly been ad jus ted to accomm oda te tha t flow

ra te .

Th is ins t ru m ent m easu res flow of pu rge gas to the flare .

OUTLET

INLET

DIRECTIONOR FLOW

ROTOR

TAPERED TUBE

Figure 19 Diagram of a rotameter


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Module 4 1 0 2 1

Read

Turbine Met erFigure 20 sh ows a n exploded d iagram of a tu rb ine m eter . It cons is ts of a s tee l

tu be with a ro tor or tu rb ine mou nt ed in s ide it be tween 2 bear ings . As th e

force of th e flow in creases it tu rn s th e tu rb ine fas ter . Th e ro ta t ions of th e

tu rb ine can be m eas u red e lec t ronically an d conver ted in t o a flow.

IN

OUT

UNIDIRECTIONAL

BIDIRECTIONAL

Figure 20 Turbine meter


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2 2 Module 4 1 0

Read

Target Flowm et erFigure 21 sh ows a sch ema t ic d iagram of a ta rget flowm eter . It i s fixed in th e

pipe of th e flu id to be meas u red . As th e flow pas ses i t deflec ts th e target .

Th is deflec t ion is m easu red e i ther pn eu ma t ica l ly or e lec t ronically an d

converted into a flow.

20-100 kPa(3-15 psi)

FLOW

Figure 21 Target flowmeter


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Module 4 1 0 2 3

Read

QUESTIONS 5 TO 6

5 . Wh a t a r e flow m e a s u r e m e n t s u s e d for ?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

6 . H ow is a d iffe r en t ia l p r e s s u r e p ro d u c ed ?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Ques t ions

?


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2 4 Module 4 1 0

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3 . LEVEL

Sate l lites conta in m an y tan ks , vesse ls and res ervoirs . Th eir fu nct ion is to

s to re or p roces s h ydroca rbons . Accura te m eas u remen t o f the con ten t s o f

th ese conta iners is v ita l . In it ia lly , level m easu remen t ap pear s to presen t as imple problem, however a closer look soon reveals a variety of problems that

m u s t b e reso lved . The cont ents ma y be cor ros ive; th ey ma y tend to so l id i fy ;

th ey ma y tend to vapour ize; or th ey ma y create o th er d i fficu l t ies .

Th e com mon meth ods em ployed for au toma t ic cont inu ous liqu id level

meas u remen t a r e a s follows :

Floa t a n d ca b le.

Dis p la cem en t (b u oya n cy).

Hea d (p res s u re). Con d u cta n ce.

Weigh t .

Le ve l GaugeThe s implest form of level measurement is the f loat and pulley level gauge

foun d on a tmos ph er ic t anks .

The pr incipal components are :

A flo a t , u s u a lly ru n n i n g b e t we en t w o gu i d e wir e s , o n t h e liq u id s u r fa c e . A s c a le , u s u a lly re a d in g 0 -1 0 0 %, a t ta c h e d to th e s id e of t h e t a n k .

A p o in t e r , r u n n i n g a g a in s t t h e s c a le , c on n e ct e d t o t h e flo a t b y a c a b le .

PULLEY

INDICATOR

CABLE

FLOAT

TANK

SCALE

100%

0%

INDICATOR

TANK

PULLEY

Figure 22 Tank level gauge

CAUTION

The sca le wi l l be reversed co mpared to n ormal i e . 0% top o f tank sca le10 0% bot tom o f tank sca le .

Warning

Caut ion

!


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Module 4 1 0 2 5

Read

Variable Displace m en tMany vesse ls by vir tu e of th e ir opera t ing press u res require a d i fferent type of

level gau gin g device . Var iab le d isp lacem ent t ype level in s t ru m ents are u sed to

ind icate a nd contro l a nu mb er of levels . The a c tu at ion of low an d h igh level

a larm s is a lso a fu n ct ion of th is t ype of level ins t ru m enta t ion .

An in s t ru men t of th is type cons is ts of a ch am ber fit ted ex terna lly to a vesse l

or tower . The cha m ber is conn ected to th e vesse l by m ean s of u pper an d

lower reference legs . Internals of the chamber consis t of a cylindrical displacer

wh ich is s u s pended from an a rm which i s a t t ached to a tu be . Movemen t o f

th e d isp lacer th rough th e r ise an d fa l l in level i s t ran s fer red to the tu be . A

rotary mot ion of th e tu be is u sed to opera te pn eu m at ic or e lec t ronic s igna l

t r a n s m i t t e r s .

0

2

4PIN

DISPLACER

RISINGLEVEL

ZEROLEVEL

BEAM

FULCRUM

TUBE CLAMPED AT END

GAUGE GLASS

VARIABLE DISPLACER TYPE LEVEL SENSOR

Figure 23 Variable displacement level gauge


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2 6 Module 4 1 0

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Differential PressureTh is type of sen s ing can m easu re a h igher ran ge of levels th an th e var iab le

disp lacement type .

The differential pressure (p) cells used for level measurement are very s imilarto the type us ed for flow mea su remen t .

For th e p cel l to fu n ct ion correc t ly , th ere m u s t b e no vapou r in th e liqu id leg

an d n o liqu id in th e vap our leg, as e ith er wil l lead to in accu racies .

MINIMUM LEVEL

MAXIMUM LEVEL

CONSTANTHEAD LEG

HILO

DIFFERENTIALPRESSURETRANSMITTER

Figure 24 Differential pressure level gauge

With b o th d i s p lace r tub e an d th e p cel l, b lockages can occu r in t he reference

legs lead in g to ina ccura te meas u rem ent . To overcome th is problem th ere is arem ote elemen t type p cell . Th e elem en ts a re bolted directly to the vessel .

Process flu id ac ts on on e s ide , whi le on t he o ther s ide , a specia l liqu id ac ts on

the p r imary d iaph ragm in th e p cell . See Figu re 25 .


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Module 4 1 0 2 7

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PRIMARY DIAPHRAGM

PROCESS DIAPHRAGM

SEAL ELEMENT HISEAL ELEMENT LO

LIQUID FILL

Figure 25 Remote sensor differential pressure level gauge

Fishe r Leve l / Mul t i t ro l

The F ish er Level/ Mult it ro l is a comm on level cont ro l sys tem foun d wi th in th e

plant bu t on e th at i s la rgely m isu n ders tood. Refer F igure 26 . Cha n ges in th e

float level var y th e ou tpu t of th e Leveltrol which goes t o th e Multi trol located

im med iate ly beneath it . The Mult i t rol ou tp u t opera tes th e cont ro l va lve .

Between t he ou tpu t of th e Levelt ro l an d th e Mu lt it ro l are the h igh an d low

level a larm press u re switches .

CAUTION

The ze ro adjus tm ent o f the Leve l t ro l m ust n o t be touch ed .

Th e outp u t will ch an ge relat ive to th e level in th e vess el . Th is cha n ge willresu lt in a ch an ge in level as well as a ch an ge in th e poin t a t wh ich th e h igh

an d low level a larm s occu r .

By m an u al ly ad jus t ing th e outp u t ad jus tm ent on th e Mu lt it ro l, a cha nge in

th e out pu t to th e contr ol valve, relat ive to th e in pu t from th e Leveltrol , will

occur . Th is will resu lt in a ch an ge in th e opera ting level bu t will n ot effect th e

high a nd low level a larm s s e t t ings .

Warning

Caut ion

!


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2 8 Module 4 1 0

Read

LEVELTROL

MULTITROL

LEVEL COLUMN

SUPPLYPRESSURE

ZERO ADJUSTMENT

OUTSIDE PRESSURE

ALARMPRESSURESWITCHES

OUTPUT ADJUSTMENT

OUTSIDE PRESSURE

CONTROLVALVE

Figure 26 Fisher Level/Multitrol

LT

H/C

LCV

H/C

LCDV

H2O

LC

H/C

LSHH

LCV

H2O

PC

LCV

LC

LC

H2O

LC

LSHH

LT

INLET

SEPARATOR

GAS

H/C

H/C

H2O

35mm MBL

INTERFACE

H/C

50%

FC

H2O

FC

H2O

P

AS

75%

85%

R

50%

D

FC

SET 10% BELOW

PSV SET POINT

INLET

GASFC

R

0-12 MPR

LEGEND

PCLCLCVLSHHLCDVLT

PROCESS CONTROLLEVEL CONTROLLEVEL CONTROL VALVELEVEL SWITCH HIGH HIGHLEVEL CONTROL DUMP VALVELEVEL TRANSMITTER

INLET SEPARATOR LIQUIDS CONTROL

Water / H/C Interface Control

1. Water is dumped via LCV H2O controlled by LC H2O whichmay be snap acting or throttling control of the interface.

2. If interface increases in level above 75% signal, LC dumpwill throttle LCDV.

3. If LT H/C level increases above 75%, signal LSHH will snapopen a 2/3 way valve in LC dump output and apply 100%signal to LCDV which will fully open (if not already openedfully by LC dump).

H/C / Gas Interface Control

1. H/C level control is to maintain the interface at 50% LT H/Csignal.

2. An increase of H/C level above 75% LT H/C signal will snapopen LCDV.

3. A further increase of H/C level to 85% LT H/C signal willthrottle the innlet gas level control valve.

4. A further increase of H/C level to LSHH will trip closed the

inlet gas level control valve.

Figure 27 Instrumentation diagram showing inlet separator liquids control


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Module 4 1 0 2 9

Read

QUESTIONS 7 TO 9

7 . Na m e 5 m e t h od s of liq u id le ve l m e a s u r e m e n t .

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

8 . Wha t me th od fo r loca l d is p lay o f open t a nk l eve l wou ld you u s e?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

9 . For wh ich app l ica t ions wou ld you u s e va r iab le d is p lacemen t leve l

m e a s u r in g in s t r u m e n t s ?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Ques t ions

?


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3 0 Module 4 1 0

Read

4 . TEMPERATURE

Tempera tu re meas u remen ts a r e impor tan t in p roces s con t ro l both a s d i r ec t

in dicat ions of sys tem or produ ct s ta te an d as in direct ind icat ions of su ch

factors as react ion ra tes , en ergy flow, tu rb ine efficien cy an d lu br icant qu al ity .

P res en t t em pera tu re s ca les ha ve been u s ed fo r abou t 200 yea r s . The ea r l ie s t

in s t ru men ts were bas ed on th e the rma l expan s ions o f gas es an d l iqu ids .

Su ch filled s ys tems are s t i ll employed frequ ent ly for d i rec t temp eratu re

meas u remen t , a l though m an y othe r types a re ava ilab le .

Types of temperature sensors are :

Filled t her ma l s ys tem s .

Bi-Meta llic.

Th erm ocou ples .

Re s is t a n c e Te m p er a t u r e D et ec tor s (RTD ).

Fi ll ed The rm al Sys te m sTh is type of sys tem cons is ts of a ca pi llary tube wh ich ha s a bu lb a t one en d

an d a Bou rdon Tub e a t th e o ther . It is fil led e ith er with a liqu id or gas th a t

ha s a l inea r expan s ion r a te with a r is e in t em pera tu re . When the bu lb is

hea ted th e liqu id o r gas expan ds a nd a c t s on the Bourdon Tu be the s am e as a

p res s u re gau ge .

LIQUID

BULB

ELEVATED TEMPERATURE

CAPILLARY

AMBIENT TEMPERATURE

BOURDON

SCALE CALIBRATED INDEGREES TEMPERATURE

AMBIENT TEMPERATURE

Figure 28 Filled thermal system


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Module 4 1 0 3 1

Read

Bi-MetallicWhen two m eta ls ha vin g d i fferent expa ns ion ra tes ar e bonded together an d

hea ted , they will bend . Th i s phen omenon i s u s ed to meas u re t emp era tu re . A

s imple form of b i -m eta l therm ometer i s th e sp i ra l . When hea ted i t exer ts a

ro tary force on th e poin ter which indicates on a temp eratu re sca le . Th is typeis comm only u sed wi th in th e hydrocarbon in du s t ry , as i t is very robu s t , fa i r ly

accu ra t e , and re la t ive ly inexpen s ive . Mos t of th e d ia l gau ges foun d in a

sa telli te ar e of th is type. Th e sens ing elemen t is genera lly screwed int o a

th erm owell, which p ro tru des in to the p ipe or vesse l . This a l lows th e

tempera tu re gauge to be chan ged withou t dep res s u r ing th e p ipe or ves s e l .

LOW EXPANSION METAL

HIGH EXPANSION METAL

POINTER SCALE

SPINDLEATTACHEDTO COIL

DEFLECTIONWHEN HEATED

BI-METALARRANGEDIN HELICALCOIL

Figure 29 Basic Bi-Metal Thermometer Bi-Metallic Thermometer


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3 2 Module 4 1 0

Read

Thermocoupl eTh is is us ed extens ively in tem pera tu re m easu rem ent . A th erm ocou ple is

made by twis ting two pieces of wire made from diss imilar metals , eg. copper

an d i ron , togeth er .

When th is ju nct ion is hea ted i t p rodu ces a m i lli vo ltage which is m easu red

an d ind icated on a tem perat u re ind icator . The voltage is propor t ion al to th e

tem perat u re d ifference between th e hot ju nct ion an d th e cold jun ct ion .

MEASURING DEVICE

HOT JUNCTION

THERMOCOUPLET1

COLD JUNCTIONT2

Figure 30 Diagram of a Thermocouple


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Module 4 1 0 3 3

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Resi s tanc e The rm al Det ec to r (RTD)This type of th erma l meas u r ing device is m ad e u p of a wire which ch an ges i t s

r e s is t an ce with a chan ge in t em pera tu re . Th i s chan ge in r e s i s t an ce is

meas u red by an e lec t ron ic c ir cu i t wh ich then ind ica tes th e co r res pond ing

tempera tu re . See F igu re 31 .

OUTER SHEATHSENSINGELEMENT

MEASURING DEVICE

Figure 31 Resistance thermal detector (RTD)


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3 4 Module 4 1 0

Read

QUESTIONS 10 TO 12

1 0 . Wh a t i s a t h e r m o we ll?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

11 . Des c r ibe the compon en ts o f a bas ic the rmocou p le.

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

12. To wha t is th e milli vo ltage ou tpu t from a th erm ocou ple propor t iona l?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Ques t ions

?


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Module 4 1 0 3 5

Read

TRAINING TASK 1

Attend a t r a in ing s es s ion with the In s t ru men t Techn ic ian in your a rea an d

then an s wer the ques t ions on p roces s con t ro l in s t ru men ta t ion .Training

Task


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3 6 Module 4 1 0

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Module 4 1 0 3 7

ReadCompetency

PROCESS CONTROL INSTRUMENTATION

Com pet e ncy Tes t Record

Na m e: _______________________________________

Loca t ion : ____________________________________

Da te Su p ervis or

Com p eten cy Pa s s ed Sign a tu re

An s wer t h e q u es t ion s r ela t ed t o e a ch

section of th is m odu le. Th ere is a

tota l of 12 .

An s wer q u es t ion s a b ou t th is m od u le

pu t to you ora l ly by your su perv isor .

Tr a in in g Ta s k 1 - At te n d a tr a in in g

s es s ion with the In s t ru men t Techn ic ian

in y ou r a r e a a n d t h e n a n s w er t h e

ques t ions on p roces s con t ro l

i n s t r u m e n t a t i o n .

TRAINING MODULE COMPLETION

Su pervisor s S ign atu re

a n d Na m e St a m p : _________________________________ Da te: _______________

En te re d to Tra in in g Rec or d s : ______________________ Da te : _______________


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3 8 Module 4 1 0

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Proc es s Con trol Ins trum en tat ion

ALTERATION SHEET

An y a ltera t ions , a ddi t ions or delet ions th at in you r opin ion would contr ibu te

towards improving th i s modu le can be m ade on th i s page. Comm ents m ay be

in th e form of a comp lete wr ite-up of th e su bject or ju s t s u bject h eadings .

P lease re tu rn a ph otocopy of th is page to th e Train ing Depar tm ent , Moomba .

operate process control

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