1 reply to this topic

[Chemitofreak]

Hi,

 

Why are instruments mounted on equipment and PSV flanges rated for minimum 300# rating.

 

Thanks in advance.

[ankur2061]

Hi,

 

Why are instruments mounted on equipment and PSV flanges rated for minimum 300# rating.

 

Thanks in advance.

That is not a universal rule. Some companies follow this and some don't. The only way to logically explain this is to calculate nozzle loads (allowable forces and moments) based on connected piping / tubing for the PSV / Instrument and then decide the pound rating. However most engineering including vessel design is required to be completed before vendor data including weights for the instruments and / or PSVs is available. By over-designing for pound rating (300#) the design engineer is trying to ensure that the chances of a instrument / PSV nozzle on the vessel not able to bear the nozzle loads is minimized. This is a time saving measure in terms of allowing fabrication of equipment / vessels with higher pound rating for instruments / PSVs directly mounted on equipment / vessels. However, due diligence is required to ensure that if the process requires higher pressures than 300# the nozzle pound rating provided is able to cater to the process requirement.

 

Hope this helps.

 

Regards,

Ankur