Troubleshooting Air Valve Failures

[Gamecock30]

We have been having an issue with a particular solenoid air valve failing only during machine start-up. This occurs whether the machine is down 5 minutes or 5 days. The valves fail in groups of 3-10 only upon start-up. When the machine is running these valves outlast the other brands we use. This has been a problem for years and nobody has answers. Any ideas would be greatly appreciated!

FYI the machines are for glass molding.

 

[eromlignod]

Direct solenoid or poppet/pilot spool?

Don
Kansas City

 

[MikeHalloran]

My WAG:

The valves have intermittent duty coils, and the startup sequence leaves them on for too long, burning the weakest.

OR

The startup sequence cycles them too often, and the inrush current overheats them.

OR

Honestly, it could be anything else. One way to isolate problems like this is to look at the machine through a child's eyes. Try to explain to someone, even literally a child, what _should_ be going on, record that, and walk through it slowly, measuring what is _actually_ going on, and taking nothing for granted.

Okay, it would be easier with a lab full of fancy instrumentation, but get as close as you can with what you can scrounge up or improvise, and you might get lucky.





Mike Halloran
Pembroke Pines, FL, USA

 

[jpietrowiak]

Have you checked the voltage or power source being used for the valves at power up. Is it high low? Does the power go through another relay/contactor. Are these contacts going bad that for some reason draws the power down. There are many different things. But if there is more then one thing failing. Power is one thing common among them all.

Good luck

Jamey

http://www.machinetoolhelp.com

 

[MiketheEngineer]

Water, moisture or oil that blows out after a few cycles??

 

[Gamecock30]

These are pilot operated poppet valves with a sealed solenoid. There doesn't seem to be any solenoid burnout. The common denominators are synthetic air line lubrication and electrical power. We are going to try to rule out the lubrication first as this may cause the seals on the spool to swell. We were not looking into this as a cause initially due to the short time the machine can be down to generate failures, but when the machine is done we lose the kinetic forces that could overcome any swelling in the seals, does this make any sense to anyone? I appreciate all the responses and help!!

 

[SincoTC]

Does one brand of valve's solenoid have a built-in diode to prevent back-EMF from spiking contacts or controllers upstream and the the other brand doesn't?

 

[limey1]

Not only should you verify that the air lube is correct. Is it actually present? (Trust, then verify). Is the air dried?

 

[EdDanzer]

Are these AC or DC coils? Do you have an air filter and water trap before the lubricator? Have you checked the air pressure at the valve inlet?

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[gerhardl]

To me this indicates a mechanical failure more than an electrical one.

Suspicions to check in priority:

1. Oil lubrication (total check, all points as stated above, compatibillity of oil type to all sealings in solenoid). Not excessive oil, none or as little as possible. To much oil is a common problem.

2. Dirt and water. Smudge and water filters to be installed, if not present, on low-point before solenoid valves, even if all parties swear the air is clean (this is in 80% of all cases not true enough)

3. Trotteling of devices or dimensions in and out? Dust or smudge covered silencers not giving sufficient delta P in and out?

4. Air pressure above allowable or possibly higher when starting than by normal running? Measure at solenoid point! In case solenoid to weak?

5. Electrical a) Correct voltage (sufficient force) reaching solenoid? Measure!

6. Electrical b) Pilot plunger sticking by permanent magnetism by wrongly selected material combination?

1 and 2 will cover about 60-80% of all failure causes.

 

[MiketheEngineer]

For what its worth - try putting them on a separate isolated circuit and power them up after starting the machine.

You may be getting some electrical spikes that are messing things up...

 

[hydtools]

It would be helpful to know the mode(s) of failure. What fails? How do you know the valve(s) have failed? What do the valves no longer do?

Ted