(API 614) Piping vs Tubing for Lube Oil/Seal Gas Systems

[Rha257]

Hello everyone,

I would like to know why is tubing should not be used for sizes above 1 inch for lube oil and seal gas systems as per API 614?

I have also come across many client specs prohibiting the use of tubing even for sizes less than 1 inch. These specs insist that piping is only permitted and in the rare case where tubing can be accepted only alloy 825/625 are permitted regardless of process gas composition.

Is tubing weaker than piping? What is the problem of utilizing tubing larger than 1 inch? Is it a matter of strength?

Also, what does external loading mean in the context of tubing?

Thanks in advance.

 

[mk3223]

The tubing is typically connected using compression type of fitting. And, it may be difficult to make it totally tight without leak for larger Lue Oil tubing system, such as 1" tubing size. Instead, the seal welding piping is preferred for the application.

Regard to using the high alloy 825/625 tubing, it's based on the material requirement based on the process as well as the environmental requirements.