PSVs on Vendor Package Equipment 1

[don1980]

All,

What is your experience in getting adequate design documentation for PSVs that are part of packaged or skid mounted equipment?

Are you successful in getting the documentation you asked for in the specifications?

Thanks,
Don

 

[zdas04]

Nope, Almost never. The problem is that the PSV is supposed to be sized based on credible scenarios, and the vendor almost never gets that information so they make stuff up. The can't help it, they have to meet your schedules and you don't provide the data, so they tend to not base sizing on the target loaction but on some generic event they are not anxious to share.

David

 

[SNORGY]

zdas04:

Yep. Pretty much sums it up.

What we do is link all the vendor packages together and then review the sizing basis on all PSVs, "ours" and "theirs". Where we see busts, we either add the correct ones in "our" piping or get them to add it in "their" piping, usually at costs borne by Client.

At the end of the day, "we" (the EPC firm) are usually responsible for the entire Pressure System Design Registration with the appropriate Regulatory Body, so the onus is ultimately on "us" to be sure that all of the PSVs are correct.



Regards,

SNORGY.

 

[dcasto]

I hate it when a standard compressor package has PSV's set at say 1650 psi beacuse the cylinders are rated at that. the bottles and coolers and PSV's are set for that. Show me where any normal everyday gas system is rated at 1650. SO, We end up either replicaing the PSV or replace (reseting is difficult because the whole thing is wrong). But, the cost savings over custom design is worth it.

 

[skearse]

Another vote for what zdas said. It's a complete PITA to get a lot of that info, and as an owner you'd think we'd have a lot more leverage on receiving it than an EPC firm may. It usually takes a lot of kicking and screaming on my part to get them to even think about site-specific scenarios. Even if that's successful, changing the design from 'non-standard' usually entails a pretty hefty change order penalty...

 

[zdas04]

I recently spec'd a compressor for a client for a specific well. I did the credible scenario analysis (that I provided to my client, not the packager) and told the packager what the credible flow rate was for their sizing. The packager started giving me the "change order" spiel and I said "you haven't spent a single Engineering or Fabrication dollar at this point, WHAT CHANGE ORDER?". He backed off and the proper PSV's were designed into the package from the beginning.

The packagers/manufacturers are not always the villain here, sometimes it is the end-user not bothering to do the analysis until the machine is on the ground.

David