unloader valve

[charland]

I am designing what can best be described as a carwash system. There is a high pressure pressure pump (positive displacement, piston) and a variety of things feeding off the pump (spray bars, spray wands) and there is no way of knowing what the volumetric requirement would be depending on what is being used and what is turned off.

I think the systems I'm looking at use an unloader valve to allow any unused volume to flow back to the inlet of the pump. This confuses me because I thought an unloader valve opened up completely once the pressure setting had been met and therefore pressure to the other spray wands would be lost. I need something that will safely bleed off any extra volume while maintaining my set pressure.

any clarification on the operation of an unloader valve would be greatly appreciated

Thanks Charlie Harland

 

[BigInch]

It opens then closes again when system pressures go below the set pressure.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[charland]

OK, so if I have a 4gpm pump at 1000 psi, can I use 2 gpm at 1000 psi and have the other 2 gpm going through the bypass circuit? Or will I lose all pressure once the unloader valve opens?

 

[BigInch]

It should hold at set pressure as long as your pump can supply the volume you're using at that set pressure.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain