Proportional Hydraulic Valve Help Needed...

[Bluenoser337]

Having a problem with a single acting cylinder that lowers by gravity (has a checkvalve to hold it in position when stopped). The cylinder won't raise as fast as it used to even though the PLC is sending the same signal to the Proportional Control card (BOSCH 811 405 063). There is a pilot spool and main spool. Not sure where to measure the zero for adjusting, but no setting on the pot will give the desired result. The cylinder was removed and checked twice. The pump and checkvalve are new. The hydraulics guy says the flow and volume through the valve are fine, but does that mean the valve and prop card are working correctly? I am reading 10 volts on the main spool position (LVDT) feedback when full speed is requested and zero when stopped but I'm not sure this is correct. The filters are clear. Don't know what to check next. ANY assistance would be greatly appreciated!!!!

 

[Bluenoser337]

Forgot to mention...the speed of raising gets worse (slower) as the 8 hour shift progresses and the oil heats up.

 

[EdDanzer]

Check your pump flow before the valve and after the valve. Check your hose and fittings for restrictions or obstructions. A suction hose collapsing or a smashed pressure hose can have this effect. Also check to see if there is a suction or return filter problem.

 

[automatic2]

You've given a usefull clue. The system is getting worse over the shift as it heats up. Begin in the morning, when things are cool. If you have an infrared temp gun things will be easy. Otherwise you'll want access to all your components. As the system runs, go through and measure temps. A touch of hand is sufficient. Your guilty component will heat up the quickest, or with the most acute rise.