Home Made Spacer (Spec Blind)

[chrcon]

i have come across a situation where to correct an error in piping measurements a 5.5" spacer was fabricated by a local mechine shop and installed
is there any code requirements for this spacer?
space has been installed inbetween 2 - 3" 150# RFWN flanges (length of spacer = 5.5" FTF)

 

[doct9960]

Sorry if I cannot answer your question directly, in terms of code restictions. I don't any code books handy. I will just give you something to think about...

For 3"-150# flanges, you require (4) 5/8" dia. bolts. For clamping your spacer in between those flanges, you would need approximately 9" long bolts. Have you considered if the bolts will buckle?

 

[davsy]

It may be a silly question but why not make a spool piece 5.5" long with 3" flanges on each end. Then you should not have any code questions.

 

[jte]

This isn't really any different than say a wafer check valve snugged up between flanges - at least conceptually. Check the material, wall thickness, etc. Been there, done that... Though I'd prefer a mini-spool also but sometimes that doesn't work given specific geometrical issues/interferences.

I would not suspect a buckling failure since the studs have no mechanism to go into buckling... As soon as the flange pair goes into compression (most likely on one side from bending) the nut will simply lift a bit off the back side of a flange and let the flange face carry the compressive load through the gasket. Or am I missing something here?

jt

 

[doct9960]

jte,

You are right. The bolts are always in tension, except when the flange pair goes into bending. When the flange pair bends, some of the bolts are in tension, while the others are not. Compression due to bending would be on the spacer and the gaskets. There shouldn't be any buckling of the bolts, except when the nuts are welded to the flange which would be very unlikely. Sorry for the slip of the mind.

 

[doct9960]

chrcon,

For process piping, check ASME B31.3 para 304.7.2

 

[JohnBreen]

Hello chrcon,

doct9960 hit the nail squarely on the head.

The ASME B31 Pressure Piping Codes require us to calculate to satisfy pressure design requirements unless we use a "listed component". Look at Table 326.1 for a list of Standards to which pressure containing components are manufactured. For example we can use B16.9 welding fittings in our design without qualifying them by performing calculations.

If you want to use an unlisted component you must qualfy it per the requirements of, for example ASME B31.3 para 304.7.2. I just read a thread in the "piping" forum in which a question is asked regarding using a B16.9 welding reducer and making it an unreinforced branch connection by "stubbing into it"!!! That mindless modification would create an "unlisted component" and if common sense failed completely, it would send us off to ASME B31.3 para 304.7.2 for methods for qualifying this "thing".

Regards, John.

 

[rzrbk]

Unless you have a drawing of the spacer, and proof of the material it was made of, I believe davsy had it right.

Two 3" 150# RF WN flanges welded together should give you a 5.5" spool piece, with no question about the spacer's adequacy, or keeping up with it in records.