Rubber expansion bellow

[siiruy]

Gents!
Need some advise on the tolerance between rubber expansion bellow and pipes.

The alignment on the pump discharge is ok but the alignment on pipe side read 4mm diferences.

so, the question is, how much allowable tolerance for the said bellow with pipe, and what standard which i could refer too?

 

[rmw]

EJMA, Expansion Joint Manufacturers Association. Get one of their manuals. It has all the information ou need.

rmw

 

[ColonelSanders83]

RMW: These are rubber expansion joint the EJMA applies to metal only according to their website

"The Expansion Joint Manufacturers Association, Inc. is an organization of established manufacturers of metal bellows type expansion joints. "

I order to evaluate the acceptability of your misalignments you need to find out who the bellows manufacturer is and get their design information and movement limits. I have attached an example for one type of rubber bellows; you need to obtain the cut sheet for your particular unit, as there is substantial variation between manufactures and types.


Always remember, free advice is worth exactly what you pay for it!

 

[rmw]

ColSanders,

I find your comments interesting in light of the fact that I first became acquainted with the EJMA standards via their use with the specification and application of fabric EJ's in the mid '90's. I interpreted the OP's request to be one of trying to understand EJ's-their applications and limitations, hence the referral to EJMA. The principals presented there are true irrespective of whether the joints are metallic, fabric or rubber and I stand by my recommendation.

rmw

 

[siiruy]

ColSander / rmw,

Thanks for the tip and advise regardless of what material or standard both of you refered to.

And since my vessel used a hug amount of bellow, metal or non metal metarial, i really need some guideline as to speed up my construction.

thanks
siiruy

 

[ColonelSanders83]

rmw: Fair enough, the EJMA specs are an excellent reference for that porpose. My experience with rubber bellows and metal bellows has simply led me to deal with them differently as far construction tolerance go.

siiruy

In thinking further on your question, I thought I would point out that when I specify the use of a metal bellows joint I have the manufacturer design it to take up a specific amount of movement with some margin. Construction misalignments cannot be taken up by the metal ballows as it was designed for movements it will see in operation in order to keep the costs down and have it work with equipment sensitive to nozzle loads.

Rubber bellows on the other had are a stock items with known displacement limits specified by the manufacturer for thier particular unit. In all of the application I have used them for, our temperatures are less then 220F and 150 psi. Thermal displacments are on the order of 0.050 in to 0.1 inch in most cases. If I get a request from the shop to bless thier construction misalignments I compare thier request + thermal growths to the manufacturers specified allowable to determine accepatability. If it comes in under I allow the misalignmnet to be installed. If it violates, I won't sign off on the alignment until they bring it under the manufacturers limits.

Just my two cents worth.

Always remember, free advice is worth exactly what you pay for it!