Currently trying to decipher 2 control valve sizing that were performed by vendor.

1. Line size is 4", then we have 4 x 2 reducer and finally 2" control valve.....Vendor has used line size of 4" for valve sizing.

2. Line size is 3", then we have 3 x 2 reducer and finally 1.5" control valve.... Vendor has used line size of 2" for valve sizing.

should we use the actual line size or reduced line size during the calculation and why? Also when it comes to above calculations which is the right one?

Thank You

 

detailed valve calculations involve line loss calculations, fluid velocity, line drain requirements, etc.
It is not uncommon to use reducers where the controlled flow is much smaller than the line size is capable of supporting.

Confirm the maximum flow conditions with the process design staff.

 

Thank you very much for your reply. Much appreciated.

 

Thank you very much for your reply. Much appreciated.

Correction for pipe geometry is built in control valve sizing equation , So use of actual line size is correct. For more details refer to Masoneilan handbook of control valve sizing , which will be available on net. I wonder reason to use 3 x 2 reducers for 1.5 in valve,
Hope this helps
JR