Piping Pressure Minimum Thickness Calculations with Unknown Design Temp/Pressure

[RedFlagEng]

Hi All,

I'm trying to calculate pressure minimum thickness calculations for existing process piping and I'm unable to find design pressure or temperature for the area. B31.3 does seem to help with this and API570 only includes unknown materials as an option. Is there a code that suggests what to do if missing design temp/pressure. I have specific material, size, schedule. I'm looking for suggestions on assumptions I could use or other areas that would be most appropriate to gather the data. Design pressure seemed to be the more difficult value to determine across a batch of piping. Which option would get more accurate results or do you think I should just find some process engineers to get data from?
[ul]
[li]Design Temperature[/li]

Utilize design temperatures from the equipment at the start of the pipe segment or​

Utilize the most extreme operation conditions expected, referencing process historian data, and then add 20-30 degrees Celsius as an assumption for ambient conditions​

[li]Design Pressure [/li]

If there is a pressure relief device present to protect the line, DP=1.1*set pressure or​

Highest design pressure of the equipment connected to the pipe segment​

[/ul]

Any advice would be appreciated!

Thanks!
RFE

 

[MJCronin]

Are there PIDs available or have they been thrown out by the previous maintenance department ?

Is there a process chemical engineer available that understands the process and can give reasonable estimates of temperature and pressure ?

Are there equipment datasheets for components like pumps and heat exchangers ? ... This will give you a starting point ?

If the equipment is running, you can do pretty well with a heat gun ..... There are probably no local pressure gauges in operation.

MJCronin
Sr. Process Engineer

 

[RVAmeche]

Those are two pretty important parts...

If you don't know them at all I would take the worst case vessel MAWP/relief set pressure/pump head/whatever and multiply it by some factor. Same for temperature.

Then state these assumptions very loudly and clearly in the calc and determine thickness.

 

[LittleInch]

Well for starters look at:

Flange ratings
Connector ratings
Any design data / nameplate on any connected equipment

Choose the lowest pressure / temp data

If you have operating data then search for highest and lowest levels of P&T

Material size and schedule should give you the ability to back calculate MAX pressure for that pipe / component, but this could be a lot higher than the lowest pressure and temp from the above items.

But you've answered your own question here "do you think I should just find some process engineers to get data from" errr YES



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

 

[RedFlagEng]

Thanks Everyone!

I'll hunt down the process engineers for support and if I can't get anywhere utilize the worst case vessel or relief as a starting point