Bypass valve configuration

[Valving]

I received request from a plant , for 2 bypass valves
on bolted bonnet class 600 gate valve. (12inch)
I am used to have bypass line (and valve) for equalizing
down and up stream pressure but is 2nd line necessary for bolted bonnet valve?
I believe this is a typical solution for pressure seal valves due to
the working principle.
Any input would be appreciated.

 

[gerhardl]

You will always get a better answer giving a more detailed and specific question.

The general answer is that under specific circumstances (fluid, pressure, operation (stillstand), valve quality and construction, piping layout and valve placement etc.) it could be sensible both to have a bypass and service valves.

With a correct selection of valve construction and materials, including operator choice and dimension according to all above, it should not be necessary.