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How to Find Maximum Operating Pressure from P&ID

01/27/2011 1:14 AM

Dear bro,

Right now, I am trying to read a P&ID. I need to know how to know maximum operating pressure from P&ID. I see PSV in P&ID, set pressure 1400 psi. Look picture below.

can we said that is maximum operating pressure? then, that pressure valid for piping class D or class A? (see that picture, there is connection for piping with different class A and D).

Regard's

Thanks

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#1

Re: how to know Maximum operating pressure from P&ID

01/27/2011 3:16 AM

There should be a schedule attached to the P&ID giving the max operating temperatures and pressures for the main plant items depicted on it.

As for the piping, each line should be numbered and a separate piping schedule prepared from it giving the line size/class/materials/diameter, etc., including any trace heating or lagging.

If these details are not present, then either the P&ID needs more work, or the supporting documents need to be found, or possibly both.

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#2
In reply to #1

Re: how to know Maximum operating pressure from P&ID

01/27/2011 3:52 AM

thank for the answer.

I have all the piping data (material, size, schedule, and class) but the maximum operating pressure. Also I can calculate design pressure, but I don't know the maximum operating pressure. From the example picture, there is PSV set 1400 psig, do you know what it mean?. D and A in the picture are pipe class... piping D from equipment (separator) to PSV, and A piping from PSV to vent header. or Can I assume maximum operating pressure piping D is 1400 psi?

Regard's

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#4
In reply to #2

Re: how to know Maximum operating pressure from P&ID

01/27/2011 8:50 AM

You need to take account of maximum pressure when relieving. Normally PSVs are sized to give 10% rise over set pressure when relieving at maximum design flow.

This might be somewhat OTT in your case, as it appears to be a thermal relief valve. As this releases fluid caused by thermal expansion of contents of a vessel etc, flow is likely to be quite low. You could check by estimating maximum heat input (from sun, surroundings etc.). Don't need to allow for fire under the vessel; if fire has to be allowed for the spec should say this, and it's called a fire relief valve, typically a lot bigger than thermal relief valve.

Cheers.....Codey

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#5
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Re: how to know Maximum operating pressure from P&ID

01/27/2011 10:46 AM

OO I see..

Thank You Bro.

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#13
In reply to #2

Re: how to know Maximum operating pressure from P&ID

01/29/2011 5:48 PM

Well-run companies use the Hazop Study approach to plant management. The maximum operating pressure should be in the Report. See if it's in there.

Also, there should be a written Process Description. See if it is in there.

Another place to look would be for the Equipment Data Sheet for the vessel immediately upstream of the valve in question. Have a look in there too.

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#3

Re: How to Find Maximum Operating Pressure from P&ID

01/27/2011 8:45 AM

Hello Ikhwan,

If the relief valve is to be set at 1,400 psig, it's safe to assume that this is the maximum operating pressure of the downstream system. Maximum design pressure may be higher.

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#6
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Re: How to Find Maximum Operating Pressure from P&ID

01/27/2011 10:52 AM

Hello,,,

Thanks for the answer. Really appreciate it

So, I can assume the maximum operating pressure for piping class D (from equipment to PSV = 1400 psi?. Then for piping class A, it should be less than that.

What I should do to know maximum operating pressure for piping class A (from PSV to vent header)?

Regard's

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#7
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Re: How to Find Maximum Operating Pressure from P&ID

01/27/2011 11:17 AM

Ooops: "upstream" !!! Downstream is likely vented to atmosphere.

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#8

Re: How to Find Maximum Operating Pressure from P&ID

01/27/2011 11:07 PM

you can refer the supplier datasheet for device MIN and MAX operating system

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#9
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Re: How to Find Maximum Operating Pressure from P&ID

01/28/2011 9:13 AM

Ummm... "which" supplier do you mean, Banana ?? This is a P&ID which likely refers to equipment from many different vendors. Each may have a different min and max operating pressure spec for their equipment.

The only "supplier" that one can refer to in this case is the author of the P&ID.

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#11
In reply to #9

Re: How to Find Maximum Operating Pressure from P&ID

01/28/2011 12:43 PM

Yeah, that's right!

currently I assume different maximum operating pressure for each piping segmentation (based on pipe class, outside diameter). I assume the pressure in PSV for the piping before it (class D at the picture, red). Is that ok?

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#12
In reply to #9

Re: How to Find Maximum Operating Pressure from P&ID

01/29/2011 4:28 AM

True, in my career (process developer then process designer then construction manager, at last startup engineer) I set a small number of Design Pressure, to reduce the number crunching needed to design the piping. Referring to the maximum operating pressure you must differ between process and piping/Equipment, for me you must start with a clear knowledge of process flow diagram (which must indicate T, P, etc.) and the process itself, then you Are able to' supply All data you need, alzo those not indicated in the P&ID. The limits arising from piping/equipment Are different and is better if you ask the Suppliers.

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#10
In reply to #8

Re: How to Find Maximum Operating Pressure from P&ID

01/28/2011 12:37 PM

Usually suppliers provide design data ( design pressure, design temperature, nominal wall thickness etc)

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#14
In reply to #10

Re: How to Find Maximum Operating Pressure from P&ID

01/30/2011 9:41 PM

All the device or instrument have the MAX and MIN working pressure and temperature. So you can refer it, for the piping itself you need to refer the design specification in final documentation.

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#16
In reply to #14

Re: How to Find Maximum Operating Pressure from P&ID

02/04/2011 6:45 AM

I think is better to explain, although still approx. but this is my view of the engineering, mainly from the design of new processes and not from the design of scale-(up or down) existing plants: The process design usually fix the max and min temperature and pressure to "control the process": these are basic data. The Basic design usually fix the max and min temperature and pressure for the mechanical design of equipment, piping, instruments, etc.: these are official data to transfer to downstream engineering. An equipment or instrument or other must withstand the official values from Basic Engineering having max allowable working pressure greater than or equal of the values from basc engineering; so it is possible that: we need MAWP= 16 barg, piping have nominal pressure 16 barg, etc. but the pressure element have MAWP= 40 barg. Sorry for my poor and confused english. What do you think about ending this topic to start a new one about "safety factors in the design"?

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#15

Re: How to Find Maximum Operating Pressure from P&ID

02/02/2011 9:27 AM

do you work for the company that supplied the P&ID? or is that your customer?

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#17
In reply to #15

Re: How to Find Maximum Operating Pressure from P&ID

02/04/2011 11:27 AM

In my case I was the process developer, then process designer, then the process manager during the basic design. After that I become the technical database during the detailed engineering and the construction. This is because I was employed by a small company (although owned by Dow Agrosciences) with great attention to the defense of patents and knowledge. Now as consultant with also some project management duties I am more free to support companies only where it needs and in a more broad mean. I think that Oil and Gas or Petrochemical projects (my first job in my career) are different because the plant is more "standard", more expensive and with a big separation between the process owner, the engineering and procurement company and the customer (that usually has few technical knowledge on process and design). In our projects we are like a pioneers with pro's and con's).

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