Internal Nozzle Area

Can you use internal nozzle area to pass UG-37 area-of-replacement requirements?

Yes, you can!

Any area within the limits of reinforcement counts as area towards the UG-37 area-of-replacement requirements, including internal nozzle area. Adding an internal nozzle projection is a way some designers meet the area-of-replacement rules when they need a little extra reinforcement. 

However, make sure that the process department for your Owner/Operator is okay with using internal nozzle projection in your designs before going forward. Some specification sheets allow internal projection for inlet nozzles but not for outlet nozzles. Others do not allow internal projection at all!