Design Pressure and temperature of Piping

[usatab]

As a fresh piping designer, i have to design piping for anhydrous ammonia. the design parameters for ammonia storage vessel are:

Design pressure: 33 bar
Design temperature: -40 C/60 C

but operating conditions are:

operating Pressure: 9 bar
Operating temperature: -33 C

So, for the piping point of view should my design conditions be 33 bar and -40C or with respect to operating conditions like 1.3 times of operating pressure?

someone has elaborated document or simplified explanation that can be helpful in future please do share.
thanks in advance.

 

[LittleInch]

Your design conditions should be set out in the piping material schedule for the piping identified on the P & ID.

This is by the look of it is 33 bar at -40 to + 60.

that's a big temperature range to cope with for expansion so is going to be fun dealing with that, but if that's what the piping can see from time to time then that's what you design for.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[davefitz]

someone has already determined the design conditions are 33 bar at -40/+60 C, and unless otherwise proven, has had a valid rationale for that decision. It would be best to find out who made that decision and what it was based on prior to changing those design decisions. It could be that they know the tank is located in an area that would endanger the public ( or the workers) if the relief valve lifted and released ammonia to the environment when the pressure increases due to the change in stored fluid temperature temperature . If you were to reduce the design pressure and thus force the lifting of the relief valves you may be endangering the workers .

"Nobody expects the Spanish Inquisition!"

 

[usatab]

Dear davefitz,

i just want to clear my concept that should the design parameters of vessel and piping be same or we can select different parameters.

vessel is designed at 33 bar and -40 C/+60C. i am asking for piping parameters.

vessel is designed at high parameters because at ambient temperature (+30- +40C) ammonia will convert to gas and pressure will increase.
but thats not the case in piping.so, for piping can we reduce our design pressure keeping the design temperature same(-40 C/+60C)?

 

[LittleInch]

NO. Piping design parameters should be determined by process conditions and written as such on the P & ID.

Unless there are very good reasons why the piping is separated from the pressure source then you design to the pressure source.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[racookpe1978]

Have you talked to your boss? To YOUR senior piping engineer?