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B31.3 SIF for Reducers

B31.3 SIF for Reducers

B31.3 SIF for Reducers

Hello everyone,

I need help regarding SIF for B31.3 reducers. Normally we use 2 for this value but sometimes it cause problems in qualifying the model due to highly localised stresses.

Any tip in this regard?

Thanks for the help  

RE: B31.3 SIF for Reducers

If all else fails read the code! B31.3 does not require SIFs for reducers.


RE: B31.3 SIF for Reducers


Xhpipe is correct, B31.3 does not require an SIF for reducers.

I have some other advice for you concerning the modeling of reducers. Many people model reducers with average dia.'s and wall thicknesses. This is fine in some cases but if your reducer small end connects to a rigid element, make sure you code a small element that defines the reducer small end next to your rigid element to get the actual stress that will be occuring at that point.


Houston, Texas

RE: B31.3 SIF for Reducers

Note that CAESAR II Version 4.50 added a "reducer element".  You no longer need to code reduces using "average properties".

Reducer element in CAESAR II (4.50 or later) will attain the correct SIF, based on the active piping code.  Of the codes that CAESAR II addresses, roughly half subscribe to the B31.3 view (SIF=1.0), and the other half to the B31.1 view (SIF is computed based on equation).

Richard Ay

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