Cavitation

[dig-dug-dan]

Can anyone recommend a hydraulics expert, kind of guy who can look at a system to find faults etc?

Mate of mine has two or three red rhino 5020 crushers, they all suffer the same problem. Run for a few minutes, look in the hydraulic tank and it looks like a pint of beer!

He is based down in eastsussex/ Kent area, but he is prepared to take the machine to someone if that helps.

Red rhino have been no help whatsoever, other than to swap two pipes over which made no difference

[htb]

Cavitation or air leak?

[monkeybusiness]

Air leak between the tank and the pump more than likely. Is there a filter before the pump? Check the seals if so. 

[dig-dug-dan]

5 minutes ago, monkeybusiness said:

Air leak between the tank and the pump more than likely. Is there a filter before the pump? Check the seals if so. 

Could be, or someone else says revs too high for the pump?

[monkeybusiness]

9 minutes ago, dig-dug-dan said:

Could be, or someone else says revs too high for the pump?

I had cavitation with a pto hydraulic pump running a big winch and had to up the delivery hose to 1.5 inch diameter - no issues since. It didn’t require a particularly high flow of oil, but the bore and length of hose was enough to limit delivery. 

[dig-dug-dan]

20 minutes ago, monkeybusiness said:

I had cavitation with a pto hydraulic pump running a big winch and had to up the delivery hose to 1.5 inch diameter - no issues since. It didn’t require a particularly high flow of oil, but the bore and length of hose was enough to limit delivery. 

mmm. thats interesting! so is it a simple case of a bigger hose from tank to pump? how will that work with the fittings that screw into each?

[monkeybusiness]

4 minutes ago, dig-dug-dan said:

mmm. thats interesting! so is it a simple case of a bigger hose from tank to pump? how will that work with the fittings that screw into each?

I’m not saying that will definitely fix your issue... Are there any restrictions/joints/quick release couplings etc in that hose run? Focus on those first (go up a fitting size where possible). My example had QR fittings which were more than likely the pinch-point, but we went bigger right through (which was expensive!). 

If there is a suction filter make sure it is clear and capable of handling the flow. Also check that any internal tank strainer isn’t blocked (often only accessible after fully draining the oil). I’m guessing these machines work in a dusty/gritty environment - what’s the tank breather situation? Can course particles find their way into the oil (potentially blocking the in-tank strainer before finding their way into the rest of the system)? 

Is there plenty of oil in the hydraulic tank (providing a decent ‘head’ for the pump)?

I’d still check for upstream air leaks first though.  

[openspaceman]

1 hour ago, monkeybusiness said:

Air leak between the tank and the pump more than likely. Is there a filter before the pump? Check the seals if so. 

Yes and I don't think cavitation would end up with air in the oil, it's when a vacuum bubble is pulled and then collapses.

 

I've seen this where the tank is shallow and oil is sucked in in the same way air gets pulled through the bath plug, and that was several inches of vortex.

 

Also does the oil return above or below the level in the tank?

Edited September 30, 2019 by openspaceman

[dig-dug-dan]

34 minutes ago, monkeybusiness said:

I’m not saying that will definitely fix your issue... Are there any restrictions/joints/quick release couplings etc in that hose run? Focus on those first (go up a fitting size where possible). My example had QR fittings which were more than likely the pinch-point, but we went bigger right through (which was expensive!). 

If there is a suction filter make sure it is clear and capable of handling the flow. Also check that any internal tank strainer isn’t blocked (often only accessible after fully draining the oil). I’m guessing these machines work in a dusty/gritty environment - what’s the tank breather situation? Can course particles find their way into the oil (potentially blocking the in-tank strainer before finding their way into the rest of the system)? 

Is there plenty of oil in the hydraulic tank (providing a decent ‘head’ for the pump)?

I’d still check for upstream air leaks first though.  

Yes, it does work in dusty conditions. I will have to ask him further, as I know my machines inside out, not up with these red rhinos.

[dig-dug-dan]

20 minutes ago, openspaceman said:

Yes and I don't think cavitation would end up with air in the oil, it's when a vacuum bubble is pulled and then collapses.

 

I've seen this where the tank is shallow and oil is sucked in in the same way air gets pulled through the bath plug, and that was several inches of vortex.

 

Also does the oil return above or below the level in the tank?

I will have to check with him!