Class 150 valve on Class 600 pipeline?

[Valving]

There is a pipeline and max. op. pressure is 90 (6 bar) psi.
Pipeline pressure class is class 600.
Would it be a problem to install Class 150 valve on this pipeline?
Would there be a liability problem?

 

[LittleInch]

In the circumstances you note, then there may not be a practical problem doing this, BUT, putting this valve on the pipeline now limits it's MAOP / design pressure to about 18 bar. This needs to be checked, noted and any pressure relief or pressure limiting devices on any part of the connected system needs to be reset to this presumably lower design pressure. You also need to verify that no system connected to the pipeline can exceed this pressure. Doing this is bad practice as in the future someone else may not notice that your valve is #150 and just see the other #600 fittings and assume that they are all the same.

So in essence yes, you are creating a potential liability in doing this and it doesn't sound like a good idea to me.

In any event pipelines are not rated by their fittings but have a bespoke design pressure <= the flange rating.

Your question and phrasing shows a worrying lack of knowledge about pressurised systems. If you get some of this wrong you kill people very easily. A #150 valve exposed to #600 full rated preassure will fall catastrophically.

More details would help.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[zdas04]

I've done this on systems that needed 600 ANSI rated equipment early in the reservoir life and then the reservoir pressure declined to where 150 ANSI was reasonable. First thing I did was recalculate the credible scenarios for all the PSV's with a new 18 bar setpoint. With those calculations in hand I specified replacement PSV's for every vessel on the system. After all the PSV's were replaced I installed the ANSI 150 equipment with confidence. That was nearly 20 years ago and the new set points have still not caused a problem. A couple of the vessels have been removed from the field and re-rated back to ANSI 600 levels (via a hydrotest) and the PSV's were replaced.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[LittleInch]

Zdas, As i would have expected, you did it properly, but tho OP has not given us all the info. I've seen people use the normal op pressure at the end of the line as justification for something similar, not considering all possible scenarios including shutdown and downstream pump running against a closed valve. Lower class valve broke and spilled thousands of gallons of gasoline.

If the max op pressure really is 6 bar and can't go higher then ok, with revised RV set point s etc, but this needs careful review.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Valving]

Little inch and Zdas thanks for input.
I considered all scenarios you mentioned but just wanted to write basic issue to get exact comments.
There are people very much experienced like you and always apprecicate your words and timing.

 

[SNORGY]

How big is the valve?

For the money you might save, is it worth doing all of the engineering that you would need to do to justify that what looks odd is actually correct? Or are you better off just getting the hefty valve and being done with it?