Presure Retention Issues With 10t Bench Press

[stupoty]

Hello,

I've got a generic 10ton hydraulic press that a friend left with me, it's got some sort of issue with holding pressure, cant quite figure out what it is thats letting by in the system.

http://www.drapertools.com/product/10582/10-Tonne-Hydraulic-Bench-Press

Sometimes if you pump fast that seems to help, sometimes it stops letting by when it gets above 700-900psi.

The return valve is a silly plastic knob but it feals tight and trying to tighten it more dosn't seem to help.

I've added some more oil and repeatedly bleed it. Although i still seem to be able to release air from the bleed valve.

Any standard issues known about with thease style of press?

By the way the manual isn't very acurate and the hand pump cylinder isn't the same as the one shown their.

Stuart

 

[f350ca]

Stuart, inside the pump unit there are probably two check valves that are spring loaded ball and seat units. I've had trouble with them. The balls are simple ball bearings easy to source and replace. Get 4 of them. Use one to reform the seat. Simply drop it it and give it a good hit with a hammer and punch to reshape the seat, then toss that ball. If it still doesn't seat I've drilled the passage one size bigger to remove the old seating surface then repeated with the ball and hammer operation.

Greg

 

[RJSakowski]

An intermittent ability to hold pressure is probably caused by debris caught in the check valve seat or the pressure release valve seat. Were the seats bad, they would not hold pressure all the time. A small amount of rust or O ring shaving can cause this type of problem.

I would suggest draining, cleaning, and refilling with fresh hydraulic oil.

 

[Bill Gruby]

If id does indeed have two check valves and you swap the balls. The seats should be reshaped as already said. Don't forget those springs, one or both could be too weak, allowing the pressure to bleed off. Change them also.

"Billy G"

 

[TOOLMASTER]

never really needed one to 'hold' pressure

 

[stupoty]

never really needed one to 'hold' pressure

Sorry I might have phrased it badly , the pressure drops of as soon as the pump stroke stops and you need to pump it quite quickly to get it to build. If you pump slowly you can hear the fluid letting by and the pressure dosn't rise(it falls) as your pumping, with no movement of what your pressing.

When it's operating "normally" the pressure dosn't fall as the lever is moved back for another stroke.

I will drain it out and do some disassemble to check the valve's for damage / corrosion / guber in the fluid

When I was bleeding it the factory filled oil smelt like filtered used engine oil, it was quite clear with a hint of yellow oil colour.

figures crossed for a simple fix

Stuart

 

[stupoty]

two check valves

debris caught in the check valve seat

I think the check valves are the two fixings at the bottom , one has a large slot screw head the other a hex head like a bolt.

Going to go find a clean container for the oil

Any recommendations for oil to use ? The manuals not very specific on that.

Stuart

 

[Vladymere]

Why find a clean container for the oil? A dirty one should work also. Whatever you drain your engine oil into prior of proper disposal. You are planning to replace the fluid, aren't you?

Vlad

 

[stupoty]

Why find a clean container for the oil? A dirty one should work also. Whatever you drain your engine oil into prior of proper disposal. You are planning to replace the fluid, aren't you?

Vlad

It's new oil in their Even if it dosn't go back in the press I think it could be used elseware. The press has had very little use, the friend that left it with me had been storing it for a while as they only used it once or twice.

I've used it to press a puly off a motor shaft and I pressed one other thing that escapes my memory. A real testament to the quality and long life of cheep tools ;-)

Stuart

 

[tomw]

This is not helpful, but I read the thread title as "Issues with 10t bench press" and thought "wow, I never benched more than 315 lbs."

Ah, youth...