Hello Stressers!!!

In my current company, I have seen this equipment list and there is a section there where there is a requirement of zero nozzle allowable at interface to cooling tower. This equipment list is still in the FEED stage of the project. Yes, there is an expansion at the tie-in point, but this does not necessarily mean that the load will be zero at the interface point to cooling tower package. There will still be some load although not so high.

I want to know from my fellow stressers, how do you straighten out this issue to Mechanical group or Cooling Tower Vendor. They will just simply say, just add support as near as possible to cooling tower.

Anyway, just correct me if I have made any wrong statement. Please share also those who have experience the same. What I'm thinking is to do flange check at the interface but documentation wise, I think it's not ethical to ignore a requirement which is impossible to achieve. It is better to straighten out that requirement as early as possible and put some realistic values.


Cheers!!!

Correction to my post, expansion joint instead of expansion only. I forgot the word joint.

Cheers!!

A good engineering group will know not to do this and wait for it to go until everything is finalized. However, in such cases, I'll have to issue a statement such as:

"It is physically impossible provide 0 loads on any nozzle in CAESAR without ethically incorrect inputs, as they will in no way resemble reality. The practice of doing so would outright negate the purpose of the stress analysis in the first place. Failure on your part to provide criteria for allowable combined loading on the nozzle will result in stress being unable to guarantee any routing will be viable, and any such requested results will be 'for information purposes only.' Interpret the results at your own risk and liability."

After which, stress provides loads they've made a reasonable attempt to keep low, and the manufacturer has to agree to make it work.

Ideally, this agreement comes as part of the bid and quote, but I find the end user ends up having to pay extra for it, anyways, because of limited places to purchase the equipment.

Thanks Michael for your opinion. Your definitely right, vendor will always ask for extra payment in cases these things slip through from FEED to EPC without noticing this type of requirements. It's sometime disappointing to see this kind of requirement in bid and quote.


Anyway, just sharing my experience. I have seen this twice already from two different EPC company. They will just say engineering judgment will come into play.

Any other opinion is highly appreciated.

Cheers!!

Cooling tower for power plant usually made from FRP, its strength is as weak as paper.
If you just connect your piping to the tower nozzle in CAESAR II, even if you use the expansion joint, you get the failure without adding any thermal effect.
Usually process guy put expansion joint at nozzle and put more support near the nozzle instead of calculating nozzle loads, but if the submission of nozzle load is needed, I consult with vendor and get the flexibilities of tower shell and nozzle(if they are up to, lowest vendor usually not possible to do that). Usually its very low, and the nozzle load is within the value without any trying.

Thanks Caesar III for sharing. Actually, I haven't seen in detail the connection to cooling tower. I haven't performed one also a Cooling tower piping stress analysis. But maybe in FEED stage, it is better to include in the quotation that Vendor must perform detailed stress analysis during Detail Engineering (maybe they can give it to a consultant if they don't have in-house engineer to perform such analysis) and include it as part of their deliverable. Instead of simply saying zero load which is hard to document in the stress package. If this is really a weak connection, then maybe it is warranted to prove how weak is weak. Anyway, it all boils down into cost. As what Michael pointed out, if this is the case then the stress analysis will just be for information only.

Any other opinion is highly appreciated. I want to know also how other stress engineers who have real experience in this cooling tower have overcome such requirement.

Cheers!!!

At some point, we'll need to start charging the fabricators instead of the buyers for doing the engineering work for their equipment.