3 replies to this topic

[VISHAL KHADKE]

What is meant by "Process Critical" and " Stress Critical Lines"?

[gvdlans]

What is meant by "Process Critical" and " Stress Critical Lines"?

Did you ask a more experienced collegue? If not, why?

In my experience, a process critical line is a term used in a design/engineering project. It is a line where the isometric drawing needs to be approved by the process engineer.
Examples are:
- lead line/tail end of Pressure Safety Valves (PSVs) (since process engineer needs to verify pressure drop meets PSV requirements)
- suction lines of compressors (since process engineer needs to verify that no liquid can build-up here
- suction lines of pumps (since process engineer needs to verify the NPSH available for the pump)
- etc.

A stress critical line is a line where the isometric needs to be approved by the stress engineer.

[VISHAL KHADKE]

Dear gvdlans,
Thank you very much for your very good explaination. For this answer I tried to search on the net but could not get satisfactory answer esp. for process crical lines so I posted it on this forum. Now it is very clear and now a suitable criteria can be worked out for critical analysis of the pipelines as suggested by you.
Regards,
VISHAL

What is meant by "Process Critical" and " Stress Critical Lines"?

Did you ask a more experienced collegue? If not, why?

In my experience, a process critical line is a term used in a design/engineering project. It is a line where the isometric drawing needs to be approved by the process engineer.
Examples are:
- lead line/tail end of Pressure Safety Valves (PSVs) (since process engineer needs to verify pressure drop meets PSV requirements)
- suction lines of compressors (since process engineer needs to verify that no liquid can build-up here
- suction lines of pumps (since process engineer needs to verify the NPSH available for the pump)
- etc.

A stress critical line is a line where the isometric needs to be approved by the stress engineer.

[Himanshu Sharma]

Dear Vishal

I would like to answer your question in two parts.

First 'Stress Critical Line': Normally two phase line or especially Slug Flow Line ,where the stress loading comes in trough and crest (as per slug movement) .Structure on which these line are resting are low frequency so the frequency of Piping should be high enough so as to avoid resonance.Typical values are above 6-8Hz.A process engineer need not worry about this as his job is over by providing a Simple note in P&ID such as "Expected Slug Flow line,take special care to prevent vibrations"

Second Process Critical Line: Adding my two cents to beautiful explanation by 'gvdlans'...These circuits are typically low pressure circuits,where you first provide Diam of the line as per assumed length and after routing is done ,check the actual length from isometrics.

Adding some more to it...

1.Recycle Gas Compressor Circuit
2.Regenerant Vaporizer Circuit
3.Reactor Inlet Piping in case of low pressure Hydrotreating ractors