need very low pressure check valve for natural gas 6" (vertical orientation)

[USAeng]

I need check valve to have very low cracking pressure and highest Cv. It is in a vertical 6" flanged pipe for natural gas. The blower we have going to a flare produces 17"wc static pressure and then gas must go through 100+ft of pipe,flame arrestors, and a few other pieces of equipment before flare. Anyone know a good one to check out? must be vertical orientation

 

[LittleInch]

Try a butterfly wafer check valve. Any nrv on a vertical leg is a problem, but you can get some pretty lightweight plates on these and maybe do without the spring or make it very low strength.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[USAeng]

Inquired about wafer style butterfly... has Cv of about 700-750 which is too low... need Cv of 1700+ according to AE