pressure reading affected by valve? 1

[mfrimu]

Hello,

I have a small project and require some help. The setu is an espresso machine with a water pump, by-pass valve (to adjust output pressure), a pressure gauge and another one way valve that opens around 5 bar. See the diagram:

http://207.134.5.9/pics/pressure-diagram2.gif

When I adjust the by-pass valve and use a pressure gauge B just after the valve I get a reading of 10 bar. What I need to know is the pressure at A but I can't get a pressure gauge there. My question is, doest the one-way valve that opens around 5 bar affect pressure readings at A and B or would they be the same. The flow is minimal (1 ounce per 30 sec) so I used a sealed chamer in the diagram but in reality there is some flow out of this chamber say about 1 ounce per 30 seconds, so the one-way valve remains open.

The one-way valve is a spring with a rubber ball at the end. Would this spring change the pressure reading at B versus A???

Thanks,

Michael

 

[btrueblood]

Yes, the one-way valve can throttle the flow, giving lower pressures downstream. If the one-way valve has a perfect, leak-tight seal, then:
(Pressure A) <= (pressure B) - 5 bar