sobre codificacion p&id

7/29/2019 Sobre Codificacion p&Id

1/11

Part 4 Codes, Tags and Labels

So you are back for more in Part 4? After all we went through

in Part 3, those still standing probably deserve a medal or something. That said, unlike

Part 3 where we really covered a lot of detailed nuts-and-bolts, this part will be a

comparative piece of cake. Kind of like the last day of school where you know you still

need to go and it might even be kind of fun, but you dont have to do any real work and

the stuff you do take home will be memories not homework. Thats the frame of mind

you need to have for Part 4, ok?

But before you take this as a cue to start shooting spitballs at your host, sit up straight

because this part is vital to your understanding and development of clean, clear, odor-

free P&IDs.

Since this series is kind of long (hey, who snorted!?), lets get the requisite recap out of

the way for those who missed the previous parts and need to circle back:

Part 1 talked about why the interpretation of P&IDs is important to everyoneinvolved in the planning, design, and construction through operation of a process

plant. Part 2 described the various functions P&IDs serve and highlighted the kinds of

information they convey, along with the support documents that are commonly

associated with them. We also talked about some of their weaknesses.

Part 3 covered the nitty-gritty aspects of instrumentation and control symbology.Along with that, we dissected tag abbreviations and how loop numbers uniquely

identify devices. Since we were on a roll, we closed out this part with all the

ancillary I/O symbols, line types, piping connections and other various sundry

items peripheral to the main theme.

Up till now, we have spent a great deal of our time focusing on the first lead sheet,

D001 Instrumentation and Valves, provided along with other drawings in thesupporting file download to this series. In this Part 4, we will turn our attention to the

remaining lead sheet, D002 Codes, Tags, and Labels.


2/11

As I have mentioned previ

have

company uses and thats O

labeling on a P&ID, only t

system that is amenable to

you will. Thats a concept

sort of prerequisite. Hang i

P&IDs Are Really Dat

observer, their underlying s

fact, for those of you famili

you may realize that a CA

structured manner. Even if

CAD system keeps track o

plant in that, well for starte

devices, etc.things that

So I am here to tell you folCAD, you are really assem

bowtie. Im serious and I w

if only from an academic s

concepts are extremely val

Some examples? Ok, beh

illustrated using CAD on

Contains collectionobjects (valves, pu

usly, D002 is an example lead sheet typical

used in the past. It may look different from

K. Its not as important how a company pref

at they do it clearly, consistently and based

future change and additions. An extensible t

hat may be a bit unfamiliar to some so I will

there, I see the finish linejust around the

abases, Wait..what?

hile P&IDs are representations of the proces

tructure more closely resembles a relational

ar with todays common computer aided dra

drawing is really a database of objects asse

you reuse the same object over and over in a

it with a unique identifier. This is very simil

rs, we apply tags to keep track of equipment,

e reuse over and over again in any given pro

s, when you design a process and develop tling a database along the way. This isnt lu

ould urge you to get familiar with relational

andpoint. Like object-oriented programming

able towards implementation in our line of

ld my exhibitslike a database, a proces

a set of P&IDs:

of similar objects with unique tags so that e

ps, instruments, etc.) can be uniquely identi

f the ones I

the ones your

rs to do

n a robust

gging system if

discuss that as a

corner!

s to the casual

atabase. In

fting packages,

bled in a

drawing, the

ar to a process

piping, valves,

cess design.

e P&IDs inacy with half a

database design,

, these abstract

ork.

plant

ven identical

ied.


3/11

Is assembled in a structured manner that lends itself to additions, deletions,changes, etc. with a granularity as coarse as whole unit areas, down to a single

valve on a pipe anywhere in the plant.

Contains lots ofmetadata in the tagging systems that can inherently provide (orlink to) much more detail such as specifications, materials of construction, data

sheets, etc.

Theres more than just the above but I will rest my case. I hope you agree that while the

tags and labels themselves are self-evident, the real power is in the underlying tagging

system used. And so youre still thinking, why must a tagging system be so robust and

extensible? I mean, come on Bob, arent you making a mountain out of mole hill?

Well, glad you asked; the answer is quite simply because most plants change over

their useful life. Change comes from a lot of different angles:

Operational Tweaksimprovements often come from the operations folks. Inmy experience, some of the best improvements to a plant dont come from theegghead engineers sitting in their cubicles, but from the folks in the plant

dealing with the machine each and every day. It is in their interest to make it

work better, safer and cheaper.

Capacity/Production Changesoften, a particular unit operation needs to beexpanded to meet new production requirements or changes in feedstock or

product requirements that shift the process design needs. Ive seen instances

where complete new trains have to be added to a system.

PSM Audit ReviewProcess Safety Management requires that processdocumentation be kept up to date and routine plant audits and Process Hazard

Review may reveal changes that should be implemented to a plant that is already

in operation. The P&IDs are the reference upon which such reviews are based

and must always be in a current As-Built state.

The key take-away from the list above is that the P&IDs serve initially as the process

definition upon which the plant is designed. But then they serve operations long after

the plant is built. This is why earlier in this series I espoused the need for engineers to

be routinely, actively engaged in ongoing operations. Not only will you learn a lot about

the plant that you yourself may have helped build, the feedback you receive will be

invaluable to maintaining a safe operation. Plus, you can implement the lessons learned

on future projects.

Now that Ive driven home the importance of a structured tagging system, lets turn

attention to the meat of this Part 4the actual tagging of equipment and devices.

Equipment Tags

Lots of companies use what appears initially to be an intuitive, simple system to tag

equipment. It later reveals itself not to be very intuitive or robust. Lets pause for

fictitious example (that bears no resemblance to my past, really).

GitRDun Process, Inc. has decided to build a new plant to produce Trimethylkabif, a

precursor to a drug that yields quick weight loss, improved memory and muscle tone


4/11

while eliminating irritable bowl, gastric reflux and attention deficit. The process folks

start out tagging equipment as follows:

Pumps are simply tagged P-1, P-2, P-3 (makes sense right?) Agitators are tagged AG-1, AG-2, AG-3, etc. Dude this is so simple! And of course tanks and vessels are tagged TK-1, TK-2, TK-3 (or V-1, V-2, V-

3). Could do this in my sleep

And so onLife is good. Later on, though less common equipment starts getting added,

and this starts to stress the intuitive nature of the system.

For example, a centrifuge is initially tagged C-1 but now they need to add a conveyor

but C is taken so they decide to call the conveyor CO-1. Now they think, well, we will

just revise the centrifuge tag to CE-1. Crisis avoidedBut wait, later they need to add a

chemical feed package and want to tag that CF-1. OK, thats cool but then a bunch of

cross flow filter modules is added they decide to steal the CF label for those and

change the chemical feed to CE, no waitcant do that, CE is taken by the centrifuge.So they bite the proverbial bullet and call the chemical feed skid CS-1 where S is

intuitive for supply. Right? Try again quiz kid. Nobody is going to see that as

intuitive. And then one day, it hits GitRDuns process engineers that their initially

conceived so-called intuitive tagging system is a heap of broken confusion and nobody

knows their CEs from their COs. Cue the Jackson 5 song A B C, simple as 1 2 3!

A Better Tag Numbering System

To avert the problems inherent in the above example, many process industries utilize a

numeric-only system for tagging equipment. This helps simplify the logical

categorization of equipment during the process design phase. Moreover, a structured tag

system is more intuitive for the development of design documentation, operating

procedures and training, and general documentation upkeep/maintenance. With that in

mind (and considering the points presented earlier in this Part), the following method isbut one example of how to tag process equipment using an extensible system.

Area Number, AN

Most sizable process plants are comprised of multiple areas. An area is a physical,

geographical, or logical grouping determined by the site. It may contain process cells,

units, equipment modules, and control modules (more details can be found at isa.org).

To facilitate a hierarchical organization of equipment, equipment tags should then

incorporate area designation.


5/11

A small or simple project may have only one area.Conversely, larger more complex projects may have multiple areas. The assignment of

areas is at the discretion of the process engineer and can be subjective. The only general

rule that I like to employ is that common equipment that serves multiple areas, e.g.,

utility and infrastructure system be placed into a Common Resources area rather than

be made a part of any other process area. Once areas have been designated for a

particular project type, engineers should strive to maintain common area designations

on future, similar projects. For example, the areas shown in the figure above may be

defined on the lead sheet for a fictitious project.

Equipment Types, ET

Equipment can be identified based on its type using a numeric system such as the

simple one shown below. In cases where equipment has multiple functions, user

discretion is advised in selecting the most suitable type code.

Sequence Number, SQ

This is the consecutive numbering of like equipment in a particular area. The sequence

begins with 01. All equipment is to a have its own sequence number. The use of

alphabetic or other tag suffixes is to be avoided.

Example Equipment Tags

Using the system outlined above, a four-digit system emerges that may not be instantly

recognizable in terms of what the specific equipment is (or where), but it will eventually


6/11

become very familiar to those who are intimate with the plant. A few examples using

the area numbers defined above are provided below:

1101 The first pump in the tank farm area. 1701 The first tank in the tank farm area. 1405 The fifth mixer in the tank farm area. 2901 A vendor package in the Train 1 area.

The equipment tag number should be prominently displayed near the symbol used for

the equipment. For example, the tag number for a centrifuge might appear as follows on

a P&ID.

Lastly, all major equipment should be named and provided general specifications in a

label placed along the drawing border. A couple examples for a pump and tank follow.


7/11

It is up to your company to decide on the final formatting, location (some companies

like to put certain equipment labels near the top of the border), and which particular

specifications should be included along with each major equipment label. The system

presented here is fairly simple and broadly applicable. Irrespective of these details, I

highly recommend that every piece of major equipment receive a label with a similar

level of detail.

Instrument Loop Numbers

A benefit of using four digit equipment numbering system such as the one presented

above is that the tags lend themselves toward application in defining associated

instrument loops. This makes grouping equipment and associated instrumentation

devices more logical.

Think back to our friends at GitRDun Process, Inc. Their tagging system consisted of

tags like P-1, AG-1, CE-2, etc. These tags are not amenable for use in defining

instrument loops. However, a four digit system does neatly tuck into instrument bubbles

and when you think about it, most instruments and devices serve or are primarily

associated with a piece of equipment. And even when that is not the case, they can

readily borrow from the equipment type code 9 in cases where, for instance, apressure gauge on an air header serving the entire area must be defined.


8/11

Considering the above points, the following instrument and device tagging system is but

one effective way to tag instruments and devices:

Where;

PX device type prefix (as per ISA 5.1) EQ the associated equipment tag (as defined above) SX duplicate or redundant device suffix (see details below)

Duplicate Suffix, SX Rules

A suffix is provided to accommodate instances were many devices of the same type are

associated with a given piece of equipment. For example, a vessel may have many linesconnected to it, each having its own actuated valve. To resolve these instances so that

each device has its own unique loop number, there are two suffix tag methods that can

be employed,

1. If a piece of equipment has redundant devices associated with it, an alphabeticsuffix may be appended to the loop number, e.g., FV1101A, FV1101B,

FV1101C, etc. (Note: Redundant means serving the same purpose as another

device in a backup fashion.)

2. If a piece of equipment has multiple items of the same type, each of which withdifferent functions (not redundant) then a numeric system should be employed,

e.g., FV1101-1, FV1101-2, etc.

Example Loop Tags

Based on the above discussion, some example loop tags are provided below. If needed,

the reader can visit a more though discussion in Part 3 regarding instrument

abbreviations. (Note: In the examples provided, I use the example Area Numbers

presented as examples above.)

PI1101 A pressure indicator on the discharge of the first pump in the tank farmarea.

LT1701 A level transmitter on the first tank in the tank farm area.


9/11

IT1405 A current transmitter (for the motor) on the fifth agitator in the tankfarm area.

AE1701A One of at least two redundant analyzers on the first tank in the tankfarm. Hence, one would expect to see AE1701B, AE1701C as indicated.

XV1701-1 An actuated valve on the first tank in the tank farm area. The suffix-1 implies there are other valves associated with tank 1701 but in an alternateservice (i.e., not redundant). For example, XV1701-1 may be on the inlet to the

tank, while XV1701-2 may be on the outlet.

Line Numbers

Similar to equipment and instrumentation, every pipe on a P&ID requires a unique tag

number so that it can be uniquely identified during design, or referenced in operating

procedures. Since most lines are also affiliated with a major piece of equipment to

which they connect, I like to employ a numbering system similar to that used for

instrument loops whereby the equipment tag is integrated into the line tag in the

following manner (Note: D002 provides an alternate method that employs drawingnumber instead of equipment number but I generally prefer the method given below.)

XSVCET:SQLS

Where;

X the nominal size of the pipe SVC the service code for the material that normally flows in the line (see

examples below for list)

ET:SVC a unique line tag that includes two parts, the equipment tag fromwhich the line originates followed by a unique sequential number

LS line specification for the pipe, including class and material type, valves etc.Service Codes, SVC

Service codes are abbreviations for the fluid the line primarily handles.


10/11

Since some lines can serve many different process fluids, the fluid used to specify the

materials for the line should go here. The list should be available on a lead sheet in a

manner similar to that provided in the example above.

Line Specifications, LS

Line specifications cover all the details related to the piping system used to handle the

fluid for the line. This should include all details regarding material of construction,

valves and trim, gaskets, fittings, T/P limits, and much more. This is beyond the scope

of this series but is such a critical component of plant design that I might expand on this

in a future post.

Hand Valves

Hand valves require a consistent and clear tagging system for reference in operating

procedures. There are a number of techniques that can be used, but one that I generallyprefer is as follows.


11/11

In the example provided at left, one can discern

valve size, spec and tag number. This might be more information than you want to

include on some P&IDs. In cases where you just want to show the valve tag and allow

the spec and size to be derived implicitly from the line tag, the following method is one

option:

V D# SQ

Where;

HV or V A literal and required part of all hand valve tags D# last two digits of P&ID drawing number SQ Sequence Number (01 to 99) V0001 The first hand valve on P&ID D100 V1205 The fifth hand valve on P&ID D102

Example Hand Valve Tags

V0001 The first hand valve on P&ID D100 V1205 The fifth hand valve on P&ID D102

Wrap-Up

Further to the content in this part, D002 includes a few more examples of common tags

and codes applied in P&IDs, such as insulation, interconnecting arrows, etc. These are

important parts but are pretty self-evident. Aside from that, most companies have very

specific ways and means on these items so I wont cover them in depth here.

Well, I started this out by saying it was going to be fun and simple and I hope you leave

this series feeling like I made some solid points that will be of value to you going

forward. In a follow-up to this series, I will put together a complementary video where Itake a few typical P&IDs (like the ones Ive attached here) and discuss all of these

aspects in what I hope to be a much more engaging manner. You will then be able to get

a much better feel for seeing and hearing this information.

Now venture forth with your new knowledge and apply it for good. Stay safe and have

fun.

And dont forget to shoot me some feedback or que

sobre codificacion p&id

Documents