Can someone please explain the difference between pressure relief valves and back pressure regulators? They both seem to function the same way with the same internal structure but a GO (Circle Seal) PR57 adjustable relief valve cost $79 while a BR3 back pressure regulator cost $569.
Hi Glen
I'm no expert, but run into each at work. The relief valve, as I know it, is really not intended for continuos duty, more just a safety thing to prevent excess pressure in a system. Quite often RV's tend to leak after they pop once or twice. They usually don't have very good regulation, when they lift they are designed to stay open for some amount of 'blowdown', i.e. quickly reduce the pressure behind them to a value somewhat lower than the set 'cracking' pressure.
Backpressure regulators, on the other hand, are designed to vent pressure above their setpoint more or less continuously and to a much finer degree. Think plain old regulator, but on the other end of the system. In my work they are used to maintain sample system pressures just above vent header pressures to ensure continuos flow through the sample system into the somewhat varying pressure of the vent header. Did that make sense?:)
Could you use a regular RV to maintain a set pressure in a vessel or system? Probably, but at the expense of maintaining a steady pressure and probably with reduced longterm reliability.
If you've got the terminology just a bit wrong it makes sense.
Pressure relief valves do just that - relieve excess pressure from the system. To the air, to ground, somewhere, anywhere except back to the system.
Back pressure regulators, in my world, are pressure regulators which can accommodate pressure build-up and relieve that build-up _back up stream_.
We use them on dishwasher booster heaters, and most states have now made them mandatory for domestic use, along with an expansion tank.
The thing is, when your house is empty and no one is using hot water, the hot water heater still cycles to maintain temperature. Since raising the temperature of water one degree F can raise the pressure
100 PSIG, the pressure which results from heating the water needs someplace to go - ergo, the water pressure regulator supplying the house needs to be a back-pressure relieving type.The excess pressure is relieved back to the street, which in turn means that the expansion tank needs to be charged to the same level as street pressure - otherwise it can't do it's job.
The BORG carries both types of water pressure regulators and several sizes of expansion tanks. Cheers, Fred McClellan the dash plumber at mindspring dot com
I am well aware of the purpose of both valves but the thing is, the manufacturers of larger valves claim they are both the same and discuss both applications for the same valve models. They are just to big and to low pressure.
This is a water maker, not a high tolerence application. I need to keep the system between 780 and 850 PSI at 2.5 to 5 gallons a minute. The variable flow means I can't use a needle valve as the primary pressure control so I have to either use some sort of regulator on the discharge end. I also don't intent to spend $600 on one valve when the whole rest of the system will end up under $1500 including a stainles Cat 241 pump.
I realize that a BP3 will have less histerisis but a 70PSI range is a pretty big target and the GO PR57 is good for several million cycles. I am more worried about valve chatter than anything else.
Fred McClellan wrote:
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