External loads on piping equipment

[Janimi]

Hi guys,

my company is fabricating equipment with piping on it (pumps and max 10 m of piping) acc. to e.g. ASME B31.3.
Normally we go with an anchor point directly at the Tie-In point to have clear separation between our side and the customer side.
Often the customer asks for allowable forces and Moments on our flange connection. Internally we are limited by the acceptable nozzle loads of vessels, pumps and so on.

For me it is hard to define this loads. How do you do that? What is the weakest part is this case? The pipe support (anchor), steelwork where the pipes are connected to or the pipe itself? Or do we need to have a look on that individually? Max pipe Size is 12", normally we have max 6" and a lot of small piping , schd 10S-40S.

Can someone give a recommendation for a method to define acceptable loads?

Thanks in advance

 

[LittleInch]

The attached was in a post in the storage tank forum but look at the first tables.

http://www.piping-engineering.com/nozzle-loads-part-1.html#comment-7152

I would then do a stress check using these values as your initial input on the flange and see whether your supports, anchors and other nozzle loadings are Ok.

Often you find the "anchor" you've used is actually pretty flimsy and allows a lot of piping load to go back into the skid. Thatmight be ok, it might not - depends on your layout, flexibility, temperature range etc etc

So unless all your skids are the same then you might need to stress check each one.

As said it's just a start point - Nozzle loads on supplied equipment are either not defined or tend to be somewhat conservative.

Be prepared to have your figures challenged if you go for too low a loading.

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

 

[Janimi]

I just had a look on the same website some minutes ago and I got the feeling that this topic is not 100% clear at all.
Sure, the pipe stress engineers of the plant want to have acceptable loads so they can do their layout but I think its not that easy to define when you have a clear interface between us as supplier of the equipment and the customer.

We use very stiff anchors so I think this will not the weakest part. The strange thing is that nearly all suppliers of pipe supports just give accepatable forces but no acceptable moments. I found an excel sheet in the SHELL DEP to transform the moments and compare with the forces but this is just useful when the pipe support has a "huge" length. It is not applicable when you just have a thick pipe and a plate welded to the running pipe and screwed to the steelwork.

The other problem is that we make custom made skids so every skid and the piping on it is individual.

From my point of view it would be useful to do some mechanical calculations of the anchors including the pipe and give a huge safety factor to use the support for a whole amount of skids as standard...

 

[XL83NL]

How we normally go with this is, is by using a list of allowable forces and moment per flange size and class rating. This is the max the pipe stress engineer can go to, and the minimum the manufacturer equipment needs to meet. Now comes the question; how do you define values for that sheet .... there are some wonderful articles about this, as well as numerous topics which can be found on Google (quite often redirecting to the ever so wonderful eng-tips).

Certain equipment, like API pumps and HEX's, have their own max allowable forces & moments, if theyre desinged acc a certain API standard like API 661.

Another interesting read would be to go through the ASME conference proceeding papers;

http://proceedings.asmedigitalcolle...&f_ContentType=Proceedings&SearchSourceType=3

There are some very useful papers in their which will help you to determine some sort of allowablw nozzle load that should work for most cases, without having the need to FEA-model all types & configurations, as this would be monkish work.

 

[SmilesAtTheMoon]

The weakest point is probably the operating case nozzle loading on the pump. In order to get the allowable, you'll need to assume some ratio of moments and forces and test them. The client's pipe stress engineer should know that the vendor reported allowables are limited by the assumption of the ratios of moments and forces in that calculation. The best solution is to target a reasonably robust design for your skid and either give the installation team a way to test their particulars or be prepared to be asked if certain load profiles are ok.

 

[bimr]

Normally the manufacturer will exclude any loads because like you stated there is no method to know what loads are anticipated.

It is not unreasonable to request that the customer state the anticipated loadings.