Solenoid Air Valve and Solenoid Vacuum Valve

May I know whether they are the same thing?
Can I use a regular Solenoid air valve to gate vacuum?

The MAC valves we use are rated for both pressure and vacuum. However, if you're using a valve with an air-actuated pilot, you would need to supply external pressure for it--vacuum won't operate the pilot.

To elaborate: Many valves are actually two valves in one. Since the solenoid is relatively small, it actuates a tiny valve called the pilot. Pressure from the pilot is what actually shifts the main valve. (Think of it like a small relay driving a contactor.) So even if the main valve is rated for vacuum, you still need pressure for the pilot to work correctly. With some valves you can specify either an internal or external pilot; internal means it uses whatever is fed to the main valve.

Tofo said:

May I know whether they are the same thing?
Can I use a regular Solenoid air valve to gate vacuum?

Click to expand...

Kolyur is right on the money. I know Ross Valve also makes some vacuum rated valves as well. Depending on the size needed that have a new 'Dale' series which is a smaller manifold type and also larger line mounted valves.

Numatics and SMC might also but I've only ever used those for non-vac applications.

Haven't had much luck with SMC for vacuum operation.
ASCO works well, they have vacuum rated valves also. However I have used some of their standard oil/air valves to 10-5 Torr.
It really depends on:
1. valve size
2. pressure on inlet of valve
3. vacuum on outlet of valve
4. how fast you want to flow through valve when open (CV)

yes you can, however when it has a membrane inside it needs pressure to operate and that is loss of pressure,

A little information about the application and the specific valve will be helpful.

I don't recommend diaphragm type solenoid valves in vacuum unless you're in the barely vacuum range, above 300 torr (Thats atmosphere down to -8 psig for us Yankee Luddites )

That said, you can sometimes get away with using a diaphragm type valve on clean vacuum at lower pressures if you mount the valve upside down so that gravity is working with you to move the membrane away from the valve body orifice.

I wouldn't do it... But...

A couple of decades back I was asked to take a look at small table top vacuum lab furnace. It would pump fast down to about 75 to 50 torr and then slow to a crawl. It would not go lower than about 500 millitorr no matter how long you let it run. The roughing valve was a diaphragm type solenoid valve. Once pressure dropped low enough there wasn't enough differential pressure to lift keep the weight of the diaphragm off the orifice. I recommended that it be replaced. Customer said "OK, but what can we do now till we get the right valve?" I flipped it over upside down and pumped down to around 50 millitorr in very little time but wouldn't go much lower. IMO that was still not satisfactory, however the customer thought I was a miracle worker. Sometime later he had me back to do something else and I noticed that he had never replaced the valve.

Moral of the story: Don't be enamored by the simplicity of a solution that isn't really a solution.

If this is a high-vac application then its best to use a valve designed for high vacuum. If cost is an issue then you can get good performance from a vacuum rated ball valve with a rotary air operator attached to it and use a small 3-way/2 position solenoid operated air valve to pilot the rotary actuator.

Did you find a valve to work?
So what is a good 24V Solonoid valve to turn Vacuum On/Off?

gbradley said:

Did you find a valve to work?
So what is a good 24V Solenoid valve to turn Vacuum On/Off?

Click to expand...

It really depends on:
1. valve size
2. pressure on inlet of valve
3. vacuum on outlet of valve
4. how fast you want to flow through valve when open (CV)

kolyur said:

The MAC valves we use are rated for both pressure and vacuum. However, if you're using a valve with an air-actuated pilot, you would need to supply external pressure for it--vacuum won't operate the pilot.

To elaborate: Many valves are actually two valves in one. Since the solenoid is relatively small, it actuates a tiny valve called the pilot. Pressure from the pilot is what actually shifts the main valve. (Think of it like a small relay driving a contactor.) So even if the main valve is rated for vacuum, you still need pressure for the pilot to work correctly. With some valves you can specify either an internal or external pilot; internal means it uses whatever is fed to the main valve.

Click to expand...

Good piece of information
Thanks

Peter Paul 20 or 70 series. 20 series link.

keithkyll said:

Peter Paul 20 or 70 series. 20 series link.

Click to expand...

Wouldn't you need a three position valve to actuate a vacuum pickup?

Yes. Sorry, didn't know the application. For a vacuum pickup, I'd use a smaller model 53.