Hydraulic Valve Solenoid Fails Frequently

[zaphod1]

We have two identical hydraulic systems on a production line. One hydraulic valve coil fails daily (or even more often). The systems are the same electrically. My question is can excessive stiction in the valve or unusual forces in the mechanical system create this problem?

 

[Ron]

Yes. I'm no Sparky, but sounds like your solenoid is way undersized.

 

[gerhardl]

No.

Not if the solenoid is built for 100% time with current on, and receives correct voltage.

The solenoids should be marked or type identification give information about feeding current limitations (nominal voltage plus/minus and time allowed with current on)

If the solenoids for the two valves are identical, and the performance required relatively identical, you should have a look at the factual input to the solenoid and check out necessary protection on the feeding line and source to ensure correct voltage without peaks when solenoid current is cut in and off and during use.

My guess is that the electrical systems differ in feed current or current peaks to the solenoid.

 

[JLSeagull]

Although solenoid valves fail, something is very wrong if the failure rate is anually let alone daily.

If experiencing coil failure, consider replacing the solenoid coil with Class H, the high temperature insulation model. Solenoid coils usually comply with various standards and different temperature categories exist. Class F is a common rating with a temperature limit of 155 degree C. Class H increases the rating to 180 degree C.

If the problem relates to the frequency of cycling and valve stiction issues, consider using a solenoid valve as a pilot, operating a pneumatic supply to a pneumatically operated valve. This would not be a simple replace in kind situation and requires more work. However, I cannot imagine dealing with daily solenoid valve failure.

 

[itsmoked]

A solenoid maker's favorite company! I have some cheap light bulbs you might want to try...

You likely have one of a couple problems.
The valves are rated for operation at a certain maximum fluid temperature. If you exceed this temperature the coil's operating temperature exceeds its limits and melts.

You should check things out because this may indicate that your hydraulic system is running far to hot and the next thing to fail will be seals, pumps, rams, and the hydraulic fluid itself. Just fixing the valve/solenoid may allow worst damage to soon follow because the system now sheds half its load automatically on valve burnout.

Or, If the hydraulic fluid is not excessively hot and this is an AC solenoid any obstruction that prevent the valve armature from fully seating will cause the coil to burn out in less than two seconds. This is because AC solenoids draw 5 to 20 times their maximum current until they actually seat. If the valve is mechanically damaged or there is some debris somehow caught behind/above the armature, (like spring fragments), this would cause a random burnout.

If the coils only burnout after the system has run for an hour or more it is probably a heat issue and most likely your fluid overheating. Get a radiator put in asap. If the solenoid seems to fail entirely randomly, like five minutes after start up then it's probably a damaged valve.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zaphod1]

For further clarification- There are two machines both doing identical work on the line. Both machines are identical. This is a relatively new problem and several people from all shifts have looked into this problem. The design, from the manufacturer, is a 196 Vdc coil on a Bucher hydraulic directional valve. The power comes from a 230 volt source that is switched through a solid state relay and then rectified through a full wave bridge. (Again, identical for both machines) Over the course of trying to pinpoint the problem on the machine in question, the SSR has been changed, the rectifier has been changed, the wiring has been changed and the valve itself has been changed (not to mention the coil- on several occasions). This valve actually runs about 10 degrees C cooler than the other system. I haven’t had much exposure directly with the problem, other than to put a scope on the coil and verify that the signal very similar to the working system. Thanks for your posts.

 

[vpl]

sometimes a diagram helps ...

BTW, it looks like ItSmoked answered your original question -- yes, if there is mechanical damage to the valve, it will affect the hydraulic system. If it's failing daily, then it's time to isolate the line and open the valve up.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[msquared48]

My guts tell me to look at overheating, for whatever reason. The only thing I have heard that is different here is the location of the two solenoids.

Location, Location, Location. It's a pertinent here as in marketing.

Mike McCann
MMC Engineering

 

[itsmoked]

Hope that's a DC solenoid if you're rectifying the AC.

Then I scratch my head, as why would anyone want to use a DC one in that location?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[badservo]

Have you checked the system pressure? what does this valve control? What is the voltage at the coil for each system? Any other valves between this valve and the actuator its driving? Picture? What's the temperature of each valve? (we don't know if its 10C cooler of borderline or normal)

 

[zaphod1]

I agree, it is a strange design to say the least (196 volt DC Valve?!). During operation the temperature on the hotter valve (the one that doesn't fail) is 60 degrees C. The valve itself has been changed (probably a few times) since this started. Even though this may be an unusual design, it was working fine up until a few weeks ago and the other system still is functioning. There has been, to my knowledge, no major mechanical problem with the system. To further complicate things- the system is on a food line so the hydraulic oil is food grade (undoubtedly some type of vegetable oil) so it is not the best oil for a hydraulic application.

 

[maytag]

Rectifying AC for a DC coil is not uncommon, other manufacturers do this although this is the first 196 DC I have heard about. More common is 96 VDC. If you could post a schematic you might get some more input. Its been my experience that you would have shaft seals for the pump and the pumps themselves fail before a valve if high oil temp or inferior lubrication was the root cause.

Maytag