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Anti-cavitation valve


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I have a 3141 backhoe on a 3616 loader that drifts down excessively on the lift cylinder. The schematic I have doesn’t show a circuit relief valve but rather an anti-cavitation valve. I suspect this also functions as a circuit relief valve but what I need is an explanation of what an anti-cavitation valve does for this circuit.

I know that an anti-cavitation valve is supposed to make up for necessary fluid, I think, when the boom is dropped fast, but there is a restrictor in the line that I thought would prevent it from dropping too fast.

The stabilizers drift down as well but the schematic, I haven't looked at the actual valves yet, shows no circuit relief - it just depends on the system relief.

I haven't dug into it yet, just an armchair exercise so far. I did reseal the bucket cylinder, and, aside from a rolled O ring, it looked good. I have no reason to suspect the other cylinders to be in any other condition.

An education would be appreciated. Thanks.

I wasn't thinking and first posted this in the general section

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Check the anticavation valve - they are in the valve between the fittings for each valve - you will have to take the tie bolt out as it goes thru the center of the valve and there as a snap ring that holds the valve in. The orginal ones had rubber on them that would get hard and flake off - replaced them with metal style. Alot of the backhoes you had to remove the complete valve from the machine to get the te rod out.

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What is cavitation?

Cavitation occurs when the volume of hydraulic fluid demanded by any part of a hydraulic circuit exceeds the volume of fluid being supplied.

This causes the absolute pressure in that part of the circuit to fall below the vapor pressure of the hydraulic fluid. This results in the formation of vapor bubbles within the fluid, which implode when compressed.

Cavitation causes metal erosion, which damages hydraulic components and contaminates the hydraulic fluid. In extreme cases, cavitation can result in major mechanical failure of pumps and motors.

While cavitation commonly occurs in the hydraulic pump, it can occur just about anywhere within a hydraulic circuit.

In the hydraulic valve described above, the metal erosion in the body of the valve was so severe that the valve was no longer serviceable. The valve had literally been eaten away from the inside, as a result of chronic cavitation.

In this particular case the cause of the cavitation was faulty anti-cavitation valves, which are designed to prevent this type of damage from occuring.

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Hi, New Englander and PeterIH175B.

The form of cavitation that you mention, Peter, is, as you said, the cause of sometimes catastophic mechanical failure. How-wevver, there is another phenomenon that occurs in hydraulics when hydraulic fluid exits from the rod enf of a ram faster than it can be pumped into the cylinder end of the ram and which some people incorrectly call cavitation.

Many hydraulic systems had various types of valves installed in various places in the lines to prevent this from happening. Technically, these valves should be called flow restrictor or flow reducer valves as that is what they do but some folks call them anti-cavitation valves.

What you may be experiencing with your lift and stabiliser rams is either leakage past the packings on the ram pistons themselves or leakage past the control valves. The company for whom I work - when I am not on long service leave like now - has a 'yellow' 943B track loader which leaks a LOT past the control valves in the hydraulic tank. Because they are in the hydraulic tank and therefore hard to get at, the boss won't repair them. He can't get his head around the notion that repairing them would boost the machine's production capability and also keep his operators happier - which in turn would boost production even more.

Just my 0.02.

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