how quick exhaust valves work? 

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thanks for the information sir, helpful for my channel.

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+gijs volker Thank you for your comment and letting me know that it helped you.

+mekanizmalar my paint val gun was shooting like 5 meter i block port 2 so ther was no pressure now i shoot like 40m

+gijs volker Wow 8 fold increase!

For opening emergency doors you should use a different circuit. The quick exhaust valve I am talking in here has a different purpose. For example you want the cylinder piston forward at slower speed but return to starting point much faster.

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Incorrect, you will still need the 3 port sov to exhaust the pressure at port 1 on the QEV, if you use a 2 port sov you will lock in the pressure and the cylinder wont return. Unless you backed off the upstream self relieving regulator to a pressure whereby the spring can overcome it. But in my honest opinion, stick with a 3/2. Cheers

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Pressure relief valve is used in hydraulic circuits. When a piston stalls in mid stroke, pressure rise in the cylinder pipes or hoses, This is not desirable. When pressure is above some preset value, relief valve sends portion of oil to the tank and reduces the pressure to desirable level. However keeping hydraulic pump running in this stalled condition causes hydraulic oil temperature to rise. The quick exhaust valves usually used in pneumatic circuits, to increase response time of a cylinder to pressure change. For exampled, if a piston is pushed forward to do a job and you want to piston to return initial condition as soon as possible. Rather then releasing pressurized air through tubes, than from valve and then silencer, quick exhaust valve immediately releases the air to the atmosphere. However quick exhaust valves usually creates more noise in the system.

A pressure relief valve opens at a set pressure to protect the circuit/system. Does not have to be hydraulic only, my air compressor has a relief valve to protect the tank if shut of switch fails. en.wikipedia.org/wiki/Relief_valve