Interpreting-P N ID Diagram

8/13/2019 Interpreting-P N ID Diagram

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Interpreting Piping and Instrumentation Diagrams [Part 1 of 5]

Part 1 Introduction

Engineers love to draw. Not necessarily in an artistic sense of te word! altoug

"eauty is! as tey say! in te eye of te "eolder. #s for me! well! I$ve never "een

accused of aving a particular gift in te arts! or potograpy for tat matter %see

"io mug sot ta&en in my natural a"itat'! "ut I ave done a few process drawings

in my (5) years as a process engineer. I guess tat$s earned me my vice! *P of

Engineering and +ecnology Development to "e precise.

,i tere. I$m -o" oo& and I$m glad to ave you along for my premier entry ere

on Enected.com were we e/plore te interpretation of Piping and

Instrumentation Diagrams! or P0IDs for tose in te &now. +is is a topic tat can

"enefit process! proect and design engineers! "usiness developers! operators!

safety! maintenance and even management. 2ow! tat a lot of fol&s3

,owever! consider tis all of te mem"ers listed a"ove will eiter come across

P0IDs intermittently or ave to wor& wit tem as a core aspect of teir o". #nd if

I still ave your attention ten! yes! you too sould ave a solid understanding of

ow to read tem3

,ey you iding te "ac&4don$t "e "asful. ou say tat you are two! tree4five

years out of scool and still not sure you really ave a good andle on P0IDs6

ou$re not alone. ,aving wor&ed for many companies and provided services to a

variety of industries over te years! I find it curious ow P0IDs are often poorly

understood "y tose wo sould &now tem "etter. In some cases! tey e/ude tis

aura of intimidating! comple/ documents tat only E gee&s %and te li&e' really

&now ow to read.

I "elieve tis is simply due to a deart of formal training. 7ol&s are ust e/pected topic& it up 8on te fly9. :iven te varia"ility in career direction our "ac&grounds in

te "est engineering field afford us! tis wor&s well for some "ut leaves oters

playing catc;up later on.


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tat not muc as canged in a few tousand years. I suppose tat$s true. ,ey! if

it isn$t "ro&e! wy fi/ it6

Enoug of my "antering! let$s get started already. I loo& forward to a ealtye/cange. Part ( will dig into P0IDs +e 7undamentals. I$ll include a few e/ample

drawings tat we can use as we venture fort down tat pat of process

&nowledge.

If you want to get a ead start! download tem ere.


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2e will tal& more a"out te lead seets %sometimes referred to as legend seets'

in Part C


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-uttons used to control motors and devices! "e tey pus"utton! toggle! or some

oter type.

Jotors and drives many motors are single speed! non;reversing "ut tere are

oter &inds tat ave varia"le speed drives! and can operate in "ot directions.

Aimit and point devices including devices tat only reveal a discrete state! e.g.! if

a tan& is at a certain level %point level'! or a valve or actuator is in a particular

position %a limit switc'

+at$s it4ust &idding.

Piping %of course3'. #ll te pipes! tu"es and even overflows in te plant. Not ust

te main process pipes inerent to te particular process! "ut even te utilities

%steam! air! fuel! etc.'.

*irtual devices on computer control screens %often as grapical representations

real;world o"ects' tat are used to interact wit te plant from te control

room@panel. +is includes tings li&e 8clic&a"le9 "uttons used to start@stop

e?uipment! operate valves! adust controller settings! setpoint sliders and dials!

evaluate alarms! etc. omputer functions and software 8lin&s9 are generally

limited "ecause it is difficult to convey complete control meaning using ust

sym"ols. ,owever! it doesn$t matter if te process is running on a ome;"rew

E/cel *-# proect wit Dic&;and;Kane grapics or a state;of;te;art ,oneywell Dutput %I@>'

Despite maor advances in computer tecnology and communications protocols!

many instruments still transmit teir signals using a trusty analog signal %via a Q;

(Fma! (Q*'. 7or switced devices! te input is typically a switc tat simply

provides a voltage input.

2ile it is not a common practice to sow te type of signal a particular device

sends to and@or receives from te control system %collectively referred to as te

I@>'! in my company I li&e to employ simple triangular sym"ols along te

interconnecting lines to elp illustrate te I@> flow %if you will' on a P0ID. +is isillustrated using te sym"ols sown in te figure "elow.

+e important point to remem"er wen you see tese sym"ols is tat te I@> flow

is always from te control computer$s perspective. +us! all outputs %D>! #>'

come out of a output module and go to some field device. onversely! all inputs

%DI! #I' are signals from field devices tat flow into some input module.


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>ter types of I@> tat may re?uire specialied transducer cards or networ&

protocols are sometimes used. 7or e/ample! te + signal is a common type of

signal tat a termocouple employs. ou may ave also eard of =+D temperature

sensors. +ere are a myriad of transmission protocols used today and as process

engineers! we don$t need to get caugt up in tat. -ut it is elpful to understand

te flow of I@> in a plant and using tese sym"ols is a ceap! easy way of sowingtat wit no penalty on te comple/ity of te drawing3

#ll of te I@> sym"ols invaria"ly lin& to te software line type %descri"ed "elow'! as

tis is used to illustrate software processing witin a computer or PA. ou don$t

&now wat is ta&ing place ust "y loo&ing at a line! "ut you can "e sure tat

watever it is! te 7unctional ontrol Description is te place to loo& to find out.

Aine


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"rief. Kust &now tat wen you see a software line! it means computers are at wor&

lin&ing te devices in some meaningful way tat relates to te system controls.

omputing 7unctions

+ese sym"ols descri"e te types of functions tat run inside a computer

program. # pro"lem wit applying tese sym"ols is tat tey do not really provide

solid insigts into ow te plant is controlled in comple/ instances. 7or tis reason!

most P0IDs will ma&e limited use of computing function sym"ols.

ou can safely ignore tese and not miss out on muc "ecause te functional

control description is really intended to descri"e control details tat tese sym"ols

try to illustrate.

*alve


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onnection +ypes

=egarding connections! te sym"ology sown in te figure "elow is standard. >ne

point I will ma&e is tat in plastic piping systems %P*! P* and #-


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+is &ind of stuff is defined in a Jaterial and Aine


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In tis particular e/ample! an I@P %current to pneumatic' transducer is necessary so

tat te valve can "e positioned to any desired opening point wit ust an

electrical signal. +is is te most common transducer function used in many

plants te oters listed are comparatively rare.


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-rea&time3

>! so now you ave a solid feel for wat P0IDs are! te purposes tey serve! teir

limitations and supporting document re?uirements and now a pretty solid andle

on te sym"ology used. Despite all te ground we covered in tis part! we aven$t

really ad a cance to go troug a few e/amples.

Everyone &nows tat wen it comes to learning new information! application it is

&ey. +e old adage 8use it or lose it9 applies. I still aim to get to some e/amples

"ut for now! ust ta&e a well deserved "rea& and let tis stuff sin& it. -esides! I$m

sure tey need to go "uy a couple more ard drives for Parts Q and 5.

-e sure to drop me any comments you ave so tat I can tailor te remaining

parts.

,ang in tere! we are almost done. our on te "ac& side of te race and eading

towards te finis line. +an&s for oining me3

Part Q odes! +ags and Aa"els


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2ile P0IDs are representations of te process to te casual o"server! teir

underlying structure more closely resem"les a relational data"ase. In fact! for

tose of you familiar wit today$s common computer aided drafting pac&ages! you

may realie tat a #D drawing is really a data"ase of o"ects assem"led in astructured manner. Even if you reuse te same o"ect over and over in a drawing!

te #D system &eeps trac& of it wit a uni?ue identifier. +is is very similar to a

process plant in tat! well for starters! we apply tags to &eep trac& of e?uipment!

piping! valves! devices! etc.Ttings tat we reuse over and over again in any

given process design.


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>perational +wea&sTimprovements often come from te operations fol&s. In my

e/perience! some of te "est improvements to a plant don$t come from te

eggead engineers sitting in teir cu"icles! "ut from te fol&s in te plant dealing

wit te macine eac and every day. It is in teir interest to ma&e it wor& "etter!

safer and ceaper.

apacity@Production angesToften! a particular unit operation needs to "e

e/panded to meet new production re?uirements or canges in feedstoc& or

product re?uirements tat sift te process design needs. I$ve seen instances

were complete new trains ave to "e added to a system.

P


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#nd of course tan&s and vessels are tagged +;1! +;(! +;C %or *;1! *;(! *;C'.

ould do tis in my sleep4

#nd so on4Aife is good. Aater on! toug less common e?uipment starts gettingadded! and tis starts to stress te 8intuitive9 nature of te system.

7or e/ample! a centrifuge is initially tagged ;1 "ut now tey need to add a

conveyor "ut is ta&en so tey decide to call te conveyor >;1. Now tey tin&!

well! we will ust revise te centrifuge tag to E;1. risis avoided4-ut wait! later

tey need to add a cemical feed pac&age and want to tag tat 7;1. >! tat$s

cool "ut ten a "unc of cross flow filter modules is added tey decide to 8steal9

te 7 la"el for tose and cange te cemical feed to E! no wait4can$t do tat!

E is ta&en "y te centrifuge. $s. ue te

Kac&son 5 song # - ! simple as 1 ( C3

# -etter +ag Num"ering


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at isa.org'. +o facilitate a ierarcical organiation of e?uipment! e?uipment tags

sould ten incorporate area designation.

# small or simple proect may ave only one area. onversely! larger more

comple/ proects may ave multiple areas. +e assignment of areas is at te

discretion of te process engineer and can "e su"ective. +e only general rule

tat I li&e to employ is tat common e?uipment tat serves multiple areas! e.g.!

utility and infrastructure system "e placed into a 8ommon =esources9 area rater

tan "e made a part of any oter process area. >nce areas ave "een designated

for a particular proect type! engineers sould strive to maintain common areadesignations on future! similar proects. 7or e/ample! te areas sown in te figure

a"ove may "e defined on te lead seet for a fictitious proect.

E?uipment +ypes! E+

E?uipment can "e identified "ased on its type using a numeric system suc as te

simple one sown "elow. In cases were e?uipment as multiple functions! user

discretion is advised in selecting te most suita"le type code.


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+is is te consecutive num"ering of li&e e?uipment in a particular area. +e

se?uence "egins wit F1. #ll e?uipment is to a ave its own se?uence num"er.

+e use of alpa"etic or oter tag suffi/es is to "e avoided.

E/ample E?uipment +ags

Lsing te system outlined a"ove! a four;digit system emerges tat may not "e

instantly recognia"le in terms of wat te specific e?uipment is %or were'! "ut it

will eventually "ecome very familiar to tose wo are intimate wit te plant. #

few e/amples using te area num"ers defined a"ove are provided "elowB

11F1 +e first pump in te tan& farm area.

1SF1 +e first tan& in te tan& farm area.

1QF5 +e fift mi/er in te tan& farm area.

(F1 # vendor pac&age in te +rain 1 area.

+e e?uipment tag num"er sould "e prominently displayed near te sym"ol used

for te e?uipment. 7or e/ample! te tag num"er for a centrifuge migt appear as

follows on a P0ID.

Aastly! all maor e?uipment sould "e named and provided general specifications

in a la"el placed along te drawing "order. # couple e/amples for a pump andtan& follow.


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It is up to your company to decide on te final formatting! location %some

companies li&e to put certain e?uipment la"els near te top of te "order'! andwic particular specifications sould "e included along wit eac maor

e?uipment la"el. +e system presented ere is fairly simple and "roadly

applica"le. Irrespective of tese details! I igly recommend tat every piece of

maor e?uipment receive a la"el wit a similar level of detail.

Instrument Aoop Num"ers

# "enefit of using four digit e?uipment num"ering system suc as te one

presented a"ove is tat te tags lend temselves toward application in defining


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associated instrument loops. +is ma&es grouping e?uipment and associated

instrumentation devices more logical.

+in& "ac& to our friends at :it=Dun Process! Inc. +eir tagging system consistedof tags li&e P;1! #:;1! E;(! etc. +ese tags are not amena"le for use in defining

instrument loops. ,owever! a four digit system does neatly tuc& into instrument

"u""les and wen you tin& a"out it! most instruments and devices serve or are

primarily associated wit a piece of e?uipment. #nd even wen tat is not te

case! tey can readily "orrow from te e?uipment type code 89 in cases were!

for instance! a pressure gauge on an air eader serving te entire area must "e

defined.

onsidering te a"ove points! te following instrument and device tagging systemis "ut one effective way to tag instruments and devicesB

2ere

PV device type prefi/ %as per I


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# suffi/ is provided to accommodate instances were many devices of te same

type are associated wit a given piece of e?uipment. 7or e/ample! a vessel may

ave many lines connected to it! eac aving its own actuated valve. +o resolve

tese instances so tat eac device as its own uni?ue loop num"er! tere are two

suffi/ tag metods tat can "e employed!

If a piece of e?uipment as redundant devices associated wit it! an alpa"etic

suffi/ may "e appended to te loop num"er! e.g.! 7*11F1#! 7*11F1-! 7*11F1!

etc. %NoteB =edundant means serving te same purpose as anoter device in a

"ac&up fasion.'

If a piece of e?uipment as multiple items of te same type! eac of wic wit

different functions %not redundant' ten a numeric system sould "e employed!

e.g.! 7*11F1;1! 7*11F1;(! etc.

E/ample Aoop +ags

-ased on te a"ove discussion! some e/ample loop tags are provided "elow. If

needed! te reader can visit a more toug discussion in Part C regarding

instrument a""reviations. %NoteB In te e/amples provided! I use te e/ample #rea

Num"ers presented as e/amples a"ove.'

PI11F1 # pressure indicator on te discarge of te first pump in te tan& farm

area.

A+1SF1 # level transmitter on te first tan& in te tan& farm area.

I+1QF5 # current transmitter %for te motor' on te fift agitator in te tan& farm

area.

#E1SF1# >ne of at least two redundant analyers on te first tan& in te tan&

farm. ,ence! one would e/pect to see #E1SF1-! #E1SF14 as indicated.

V*1SF1;1 #n actuated valve on te first tan& in te tan& farm area. +e suffi/ ;1

implies tere are oter valves associated wit tan& 1SF1 "ut in an alternate

service %i.e.! not redundant'. 7or e/ample! V*1SF1;1 may "e on te inlet to te

tan&! wile V*1SF1;( may "e on te outlet.

Aine Num"ers


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employs drawing num"er instead of e?uipment num"er "ut I generally prefer te

metod given "elow.'

V9T


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Aine specifications cover all te details related to te piping system used to andle

te fluid for te line. +is sould include all details regarding material of

construction! valves and trim! gas&ets! fittings! +@P limits! and muc more. +is is

"eyond te scope of tis series "ut is suc a critical component of plant design

tat I migt e/pand on tis in a future post.

,and *alves

,and valves re?uire a consistent and clear tagging system for reference in

operating procedures. +ere are a num"er of tecni?ues tat can "e used! "ut one

tat I generally prefer is as follows.

In te e/ample provided at left! one can discern valve sie! spec and tag num"er.

+is migt "e more information tan you want to include on some P0IDs. In cases

were you ust want to sow te valve tag and allow te spec and sie to "ederived implicitly from te line tag! te following metod is one optionB

8*9 DO


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2rap;Lp

7urter to te content in tis part! DFF( includes a few more e/amples of common

tags and codes applied in P0IDs! suc as insulation! interconnecting arrows! etc.+ese are important parts "ut are pretty self;evident. #side from tat! most

companies ave very specific ways and means on tese items so I won$t cover

tem in dept ere.

2ell! I started tis out "y saying it was going to "e fun and simple and I ope you

leave tis series feeling li&e I made some solid points tat will "e of value to you

going forward. In a follow;up to tis series! I will put togeter a complementary

video were I ta&e a few typical P0IDs %li&e te ones I$ve attaced ere' and

discuss all of tese aspects in wat I ope to "e a muc more engaging manner.ou will ten "e a"le to get a muc "etter feel for seeing and earing tis

information.

Now venture fort wit your new &nowledge and apply it for good.


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+ese videos don$t cover te second lead and oter items tat I want to cover. I

plan to cover tose in an appended post.

7ol&s! tan&s for anging toug wit me on tis e/tended ourney. I put youtroug it "ecause it$s important stuff and! in all onesty! I still love tal&ing a"out

it. #ristotle said 8Pleasure in te o" puts perfection in te wor&.9

; -o"

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Interpreting-P N ID Diagram