Wetted Suface Area for Pig Launcher

[kunal14284]

Hi,

I am new to this forum. Can anyone please let me know wetted sufrace area formula for oil pig launcher/receiver?

Attached is the sheet in which wetted surface area calculation is shown, but i could not understand the formulas.

Thanks in advance.

Regards
Kunal

 

[don1980]

The basic guidance for wetted surface area, used world-wide, is found in API 521. Relief designers should be familiar with that. It discusses wetted surface area for the different types/orientations of vessels. Read and understand that. Then, when you have a task like this, use that knowledge appropriately for the task at hand.

I'm guessing this pig trap is fabricated according to pipe code rather than vessel code. API 521 is written for ASME Sec VIII pressure vessels. The owner can choose to protect this "segment of pipe" as though it's a vessel, but personally I wouldn't in this case. My resoning is based partially on the fact that this is pipe rather than a vessel, but it's also based on the fact that pig traps are normally empty of all liquid contents, except during those infrequent pigging operations. The decision of wheteher to treat this like a vessel should be based on a risk assessment.

The bottom line is that I think you're spending time and money on something that (a) is not required, (b) is a very low risk, and (c) can't be adequately protected by a relief valve anyway (relief valves can't prevent failure of a gas/vapor filled container exposed to fire).

 

[Chance17]

As a general practice, pipe & pipe components do not require
overpressure protection due to external Fire.
Is external Fire the purpose for wetted area calculation?

 

[kunal14284]

Thanks for the response.

Yes Wetted area is needed for heat absorption calculation.

Regards
Kunal

 

[MortenA]

sometimes pig traps are considered pipelien - sometimes as a vessel.

You could always go worst case and assume that the trap is full of liquid - and then calculate the required area. If its not too big (e.g. smaller than a D then why bother. If it larger maybe then you will have to actually think

Best regards

Morten