Vacuum Relief Valve vs Check Valve?

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Vacuum Relief Valve vs Check Valve?

Postby DAD300 » Thu Dec 07, 2017 6:47 pm

I am wondering what the engineers here think about this idea.

VRV's are expensive, say $80usd or more. They open at a set pressure (for a boiler 1-5PSI) to prevent negative pressure in a boiler or steam jacket while cooling, preventing collapsing the vessel. They also chatter when in use. And you never really know if they are stuck or not.
VRV r.jpg
VRV
VRV r.jpg (1.29 KiB) Viewed 43 times


Why shouldn't I replace a VRV in a design with a Check Valve that costs $5usd? The Check Valve opens at any minimal negative pressure, preventing collapse. The cost dif and availability is crazy as every big box store has these. And you can always poke the opening to see if it is stuck!
Check Valve r.jpg
Check Valve r.jpg (37.99 KiB) Viewed 43 times

Basically, the price dif makes me ask!
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Re: Vacuum Relief Valve vs Check Valve?

Postby RedwoodHillBilly » Thu Dec 07, 2017 8:03 pm

GodDamnit, you always come up with what is an obvious solution to a problem (obvious after it's explained to me). I use a PRV/VRV like you show in your 1st pic. But when you think about it, what is the VRV part but a check valve set to about 1/2 PSI. My question is what pressure will the check valve/VRV pop off at?
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