hydraulic oil

[classictruckman]

The Holding valves or check valves are not in the valve bank they should be at or part of all the boom cylinders.
They prevent the movement of the cylinders in the event there is a loss of hydraulic pressure like a hose blowing or part of the valve bank breaking.

Make sure yourself that the holding valves are working before you go up in the bucket again, you should have a daily routine of doing a drift test to ensure the holding valves are working every morning.

 

[Toparboring]

I had a line to a tree spade blow . The thing was how fast the window to the bobcat was covered. I heard it hit the window through muffs and a full throttle bobcat. glad things are good Mark.

 

[allmark]

[ QUOTE ]
The Holding valves or check valves are not in the valve bank they should be at or part of all the boom cylinders.
They prevent the movement of the cylinders in the event there is a loss of hydraulic pressure like a hose blowing or part of the valve bank breaking.

Make sure yourself that the holding valves are working before you go up in the bucket again, you should have a daily routine of doing a drift test to ensure the holding valves are working every morning.

[/ QUOTE ]
How do you do a drift test?

 

[classictruckman]

It maybe called a different test, but around here we call it a drift test.

First you lift the booms out of the rests then shut off the engine, pull the control valves open then see how much the booms move when there is no longer any pressure in the lines. Then move the booms into different positions(like over-center) and repeat the test.

There is a certain amount of movement that is allowed, it should say in the manual that is specific to that boom.

You can do the same test to a stick crane or knuckle boom crane that has holding valves.

 

[allmark]

Thanks.

In the scenerio above with the bucket the valve may have malfunstioned opening the circuit in a similar fashion putting pressure as normal to open the holding valves. I dont know without more detail of the incident.