Storage Tank-First Pipe Support Span

[LurmClaxton]

Hi folks, first post.....so go easy

I have a general question regarding the span between storage tank nozzles and the first piping support for feed and suction lines. I have seen examples where pipe supports are chocked solid within a few feet of the tank and also the other extreme where there isn't a support for maybe 10-15m.

In my view neither is good practice (for different reasons). Does anyone have any views/comments/thoughts/fears etc on this. Also does anyone know of any guidance references in API/ASME/BS/EN etc.

Thanks in anticipation

Lurmy

 

[IFRs]

The piping network must be designed to minimize forces and moments applied to the tank nozzle. If the tank is going to settle, you will need a good span to the first support. If the pipe network undergoes thermal expansion you may need to have the tank foundation coupled to the first pipe support foundation so they will experience identical settlement, and then you might need to anchor the pipe right next to the tank so the pipe support absorbs all forces and moments. Etc. I don't think there is a simple or common design, there is so much variation in conditions. But the goal is to keep forces and moments from getting to the tank in large magnitudes. My (humblest) opinion only...

 

[LittleInch]

I fully agree with IFRs. Tank nozzles are notorious for having very low limits on forces they will accept in x,y,z and torsion. These come from the tank designer. You then really need to review your piping design using a pipe stress program to give you accurate figures on the stress imposed on the nozzle, especially where large temperature variations can occur. Don't forget about the empty pipe in summer mode as this can give you large expansion loads and also the Hydrotest case which gives largest vertical loads. There are many pipe hanger special supports including spring supports which can compensate for settlement and movement. Try and avoid anchors if you can as they cause problems elsewhere, but you do sometimes need them close to the tank to limit loads on the nozzle.

As said above, there are so many variations that a general rule is not possible, but in many occasions the key to reducing loads and stresses on the nozzle is to have flexibility in your piping design. You sometimes find that putting a valve bolted onto the tank takes up a large percent of the nozzles capacity so sometimes valves need to be moved further away.

My motto: Learn something new every day

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