If I have piping coming from CPP area governed by ASME B31.1 to Refinery OSBL rack and then ISBL - what should be the allowed deflection between two supports in steam piping for piping span fixation ?

B31.1 asks for 2.5 mm between supports, where outside B31.1 it can be 10 mm as per our standard fog general purpose.

Unless we keep a good slope like 1/200, in refinery application -it can to zero to 1/500 for steam piping sometimes in rack - is the piping not prone to condensate accumulation and prone to damage due to condensate driven water hammer ?

reg,
sam

I try to keep the saggment not over 0.1'' as B31.1, but if the line sloped, when the plant is not operated, as long as the saggment does not create low point I consider drain will eventually collected to drain pot(or so). Then, water hammer would not be caused by condensate at the plant start-up.

Of course, there could be lack of drain pot or mis-installation etc. but that's another things to consider I guess.

FYI, my current project steam piping slope is 1/100.

Condensate accumulation is a complex coordination between pressure drop, heat loss, line speed, and yes, pipe geometry, including pocket size. As such, we're better off relying on end-user requirements, which is based on real world findings.