How do pressure valves work?

[waseem19]

please provide any internet sites or articles about how does any pressure regulating device work,whether it is pressure reducing or sustaining valves,

i need the theory behind it as well as the actual physical things and motion that makes it work, how does it sustain the pressure or reduce it.

please also any sites about the terminology of valves ,, all the common names for all valves types ,it's realy confusing


please guys ,any help would be very appreciated

thanks alot

 

[valvetech]

The pressure regulating valve works by a force being applied to the spring which is the desired set point, this pushes down on the diaphragm holding the valve in an open position allowing flow through the valve. Somewhere downstream a pressure reading is taken and transfered to the underside of the diaphragm. If the force downstream is greater than the spring force that pressure pushes the diapraghm up and restricts the flow/pressure until the pressure on the upperside of the diaphragm is greater than that below the diaphragm and the valve then return to the open position.

http://www.jordanvalve.com/JORDAN1.html

Will give you an idea how this works in a sliding gate seat valve.

 

[WWTraveler]

You can down load the Crosby engineering handbook on relief & safety valves here.

http://www.andersongreenwood.com/docnet/library/enghnbk.pdf

 

[keyardee]

Assume that you are filling a closed vessel with say compressed air through a throttling valve.If you close the valve there is no flow into the vessel and consequently no pressure rise in the vessel.If you open the valve there is flow and consequent pressure rise.Assume that you have got a pressure gauge mounted on the vessel and you have posted an assistant near the valve to watch the pressure gauge and regulate the flow accordingly.
When the presseure gauge reading goes more than the desired level the assistant closes the valve regulating the flow.When the reading goes down the assistant opens the valve to allow more air into the vessel which raises the pressure inside.This cycle may repeat any number of times.So instead of having a man to monitor the gauge and act,a small device is installed in place of the throttling valve which measures and compares the pressure with the desired"set" pressure and acts accordinglly maintaining the pressure.So this is the pressure regulating valve. Any more doubts?

 

[waseem19]

keyardee, thanks very much , one more question , if i have a peak point along a pipeline ,a one way tank at that ponit to keep the pressure from dropping incase of surge event ,,

now, do i need a pressure sustaining valve downstream of that tank (peak ponit) ,and why if i need one ? isn't the tank enough to protect the pipe ?

 

[keyardee]

Hi waseem
i am unable to configure your exact requirement.you want to protect -the tank or the pipe line.If it is the tank, better try a safety valve with sufficient capacity .If it is for the pipe, connect a surge tank of required volume to minimise if not eliminate the pressure surges. What exactly you mean by the one way tank- is it a closed vessel with only one inle/outlet.If that is what you mean then this should protect your pipe line.

 

[waseem19]

i want to protect the pipe ,the tank is only there to let water to the pipe, in case of pressure drop. so the water can flow only from the tank to the pipe(check valve) ,however there is a re-filling line connected to the tank,
the tank isn't pressurised, so it got no compressed air,

i hope it's clear now.
so do i need that sustaining valve downstream

 

[keyardee]

Hi waseem19
please make out a sketch of your piping layout indicating the inlet and outlet positions and the tank.If it not possible to include the sketch in this forum kindly contact k_ramdas41@hotmail.com along with the sketch.On understanding your piping a better solution might result.