Valves for Compressed Air

Why - air is pretty soft stuff?

I'm afraid the shocks generated into the pipeline or machine would not be healthy.

So why not introduce a reservoir downstream of the valve so that the pressure builds up more slowly?

A solenoid valve that switches a 4in air line at 7 barg is a rare beast!

As a rider to that, the air flowrate passing through the small valve might not be enough to mobilise the machine in the first instance, in which case the line pressure downstream might still be low when the big valve opens. It's just something the original poster needs to bear in mind when designing the system.

Is it desireable to totally depressurize the line downstream of the shutoff valve? If not just put a small pressure regulator in a bypass line around the main shutoff and keep the down stream line pressurized to a desired pressure. If it is desired to depressurize the down stream line then vent it through a small solenoid valve that closes to repressuize the line . . . will cost you a little air . . . but could also put a solenoid in the line to the regulator to shut off air when desired to depress the line by opening vent solenoid.

Like most compressed air plants I know, there are a lot of air leaks on the equipment and we are considering closing the air when a machine is stopped in order to save energy. One way of doing that without fail is to link a solenoid valve with the machine main switch. Most equipment valves will be in the 1/2" -- 1" range, but the 4" size could be used for shutting down whole sections of the air line. So once a valve is closed the downstream side will depressurize through the air leaks. It's possible that up to 1" size, one could just open the air solenoid valve directly but for larger sizes it is ideal to start with a pilot valve.

Put pulse dampers downstream of your valves ...

http://www.pulsation-dampers.com/

http://www.pulsedampers.com/

http://www.pulsation-dampeners.com/

These may not fit your application, but they'll give you an idea of what's feasible. Google 'pulse dampers', 'pulsation dampers', etc.

Cheers! DZ

I thought manufacturers should have already devised a simple way of opening compressed air into a depressurized line using a single solenoid-operated valve with a pilot line. However from the replies so far this does not seem to be the case! Thank you all for contributing. Your suggestions have helped.

You are so right. Now he can go into Spirax sarco site and get this Control valve with positioner to open slowly.

If you just want to slowly pressurise a line on start-up then an air operated diaphragm valve in the main line (to control the flow to the machine) with a control pressure coming from a 3 port 2 way solenoid valve that is fed by air via an adjustable flow restrictor.

Adjusting the restrictor governs the speed at which the main valve opens.

(I drew a picture but I don't know how to insert it here)-(copy and paste didn't work)

You should look into a "soft start valve". We use SMC, but I am sure that all the pnuematics companies have them. They can be tied in electrically as well, to remove air from a cell whenm the gate key is removed and then upon return of gate key and "auto" situation the air pressure will indeed build up slowly for safe and less "slamming" operation

GS

Hello Sir,

Soft start valve will be suitable for your application. We offer METALWORK range of products. Visit www.metalwork.in For more details about these valves kindly get back to me.

Regards,

RAMARAJ.T

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