11 replies to this topic

[Diep Thanh]

Dear experts,

I need your help please!

Currently I have studied P&ID preparation with miscellaneous piping arrangement. The point is that I can not understand the purpose of piping components indicated in P&ID ( such as gate valve, spectacle blind, etc). Take my figure as an example, could you please interpret what is the purpose of them and why we have a piping arrangement like that?

Please be noted that my service is hydrocarbon liquid and 

SO stands for temporary steam out connection

OWS stands for drain to Oily Water Sewer

DOS stands for Dry Oil Sewer.

Thank you for your time!!!

 

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[fallah]

Hi,

 

At first, you should learn how a P&ID is prepared and developed; then you would understand the functionality of each component in every P&ID you will face to...

[Diep Thanh]

Hi Mr. Fallah,

As you mentioned, only preparers can understand the reason why that piping components are indicated there in P&IDs, right?

[farid.k]

Dear experts,

I need your help please!

Currently I have studied P&ID preparation with miscellaneous piping arrangement. The point is that I can not understand the purpose of piping components indicated in P&ID ( such as gate valve, spectacle blind, etc). Take my figure as an example, could you please interpret what is the purpose of them and why we have a piping arrangement like that?

Please be noted that my service is hydrocarbon liquid and 

SO stands for temporary steam out connection

OWS stands for drain to Oily Water Sewer

DOS stands for Dry Oil Sewer.

Thank you for your time!!!

It depends on the plant practice.

Different plant will have different practice. For example, OWS service, other plant has that service too and the configuration of the PID would be same but not 100%. Such as what I have seen in other refinery, they don’t have specticle blind. But for your case, maybe the contractor that do the engineering want to make it as it is required by client to put the specticle blind, or might be due the the valve is passing or maybe that piping has not been use anymore. So the P&ID will indicate what you need. The best person to be consulted why it has been captured in P&ID as so is the process engineer that produce the P&ID. Normally, they will make it and follow as per existing configuration. And typical process engineer normally will know how to read the P&ID and why it look so for example by-pass and isolation valve at control valve, high point vent, low point drain, check valve at pump discharge, strainer before the pump etc.

[shan]

Top piping 3/4" valves for high vents

Bottom 3/4" valves for low drains

Spectacle blinds for the safe guard of accidental drain valve opening

 

P&ID is a graphic communication between engineers.  There are general rules to develop P&ID, although some company specifications or project requirements may be involved.  It will be a disaster to a process engineer if he is unable to understand P&IDs developed by the other engineers or his P&IDs are unable to be understand by all other process engineers.

Edited by shan, 03 June 2015 - 08:40 AM.

[farid.k]

Top piping 3/4" valves for high vents

Bottom 3/4" valves for low drains

Spectacle blinds for the safe guard of accidental drain valve opening

 

P&ID is a graphic communication between engineers.  There are general rules to develop P&ID, although some company specifications or project requirements may be involved.  It will be a disaster to a process engineer if he is unable to understand P&IDs developed by the other engineers or his P&IDs are unable to be understand by all other process engineers.

not really disaster for fresh process engineer. very experienced process engineer don't know how to "read" P&ID, yes, big disaster.

Edited by farid.k, 03 June 2015 - 09:12 AM.

[shan]

Well, if you are a CEO or a senior engineering VP, you do not have to read P&ID either.  There are always some exceptions, if you extend any statement to the extreme.

Edited by shan, 03 June 2015 - 11:18 AM.

[Diep Thanh]

Thank you for your explanation, experts!!

As mentioned, P&IDs shall be generated and developed  based on "GENERAL RULES", then they are reflected some " COMPANY SPECIFICATION"/ "PROJECT REQUIREMENTS". I believe that, for process engineer, they don't need to care about the details of the last two ones ( company specifications, project requirements). For example, the "PROJECT REQUIREMENTS" says " If system of ANSI class 900# or above, double block valves shall be provided". OK, process guys will do "OK, I will incorporate in my P&IDs and I don't need to explain why they are indicate here, in my PIDs". That's no problem, isn't it?. Any details arising in P&IDs development,only preparers know the reason why they are indicated in their P&ID. Therefore, for project requirements/ company specifications and arising in engineering are not the critical points!!!

However, the point is that "GENERAL RULES". I believe that process engineers who take care P&ID have to explain why you indicated this valve here, that spectacle blind there. For example, I have one flow control valve with 2 gate valves, one drain valve, and one globe by pass valve. Process Engineers are able to explain like this: " In case of maintenance, the control valve may be taken off when the two gate valves are closed, the drain valve will be used to drain the fluid remaining in the control valve. The globe valve is used for by-pass since it is the best to control the flow-rate". That's good explanation, isn't it?

Therefore, I believe that any "GENERAL RULES" has its own explanation. Even though your company has engineering standard, you can not tell Client like" That's my company standards, I just followed them". That's unacceptable! That's why, the point is that how fresh process engineers can understand the "general rules" and are able to explain to Client? Or they have to wait to a chance to learn more experience when encountering a lot of real projects?

Thank you guys for your time!!

Edited by Diep Thanh, 03 June 2015 - 09:01 PM.

[paulhorth]

Diep,

In general, the details shown on PIDs are specified in design documents called Philosophies, such as the Isolation Philosophy, Vent & Drain Philosophy, Control Philosophy etc. These documents are written by the contractor's process engineers and reviewed and approved by the Client. They will be different from one client to another and also will depend on the type of plant. The Isolation Philosophy defines where to apply spectacle blinds, double-block-and-bleeds, removable spoolpieces and so on. You should locate a copy of this document for the project you are working on.

To comment on your sketch, I am surprised to see spectacle blinds on the 3/4 inch drains, first because this is rather small for such a fitting, and second because the drains discharge directly to a tundish, so breaking the flange to swing the blind results in the tail pipe dropping off! A simple plug would be better.

A Spectacle blind is used where the downstream end of the pipe is attached to a vessel or other unit, it provides visible evidence that the line has been isolated.

 

Paul

Edited by paulhorth, 06 June 2015 - 12:33 PM.

[Zubair Exclaim]

what is the service .. is this related to Aromaics .... cryogenics or some toxic stuff ... them these additional spectical blinds may be justifable... but still  for a quarter inch connection seems hard to swallow

[bmsharad]

ISA has some standards re P&ID symbols. Other than that, a legend-symbol drawing usually accompanies each set of P&ID. These explain meaning of symbols

[titim]

hi all

please wich book is good for process specially for refining (PID).

Edited by titim, 21 August 2015 - 11:48 AM.