Directional valve with counterbalace valve ?

[hodinhtran]

Good day sir.
I have the two stage directional valve (upper stage valve is float type. Lower stage valve is tandem type). I use this valve (consist of upper and lower stage) with fix displacement pump for liftting load without counterbalace valve (or brake valve). So Motor overruned and load go down fast. Can I insert some valves (I don稚 know excatly what kind of valve) between the upper stage and lower stage to have the directional valve with function counterbalace valve for prevent load from falling down fast. Thank for your help.

 

[Craig Clayton]

When I worked on fork lifts there is a flow control valve on the bottom of the mast. The carriage can go up as fast as the spool movement allows but when you move the spool to lower the load it will only descend as fast as the flow control will allow. Install this concept in your system.
Craig Clayton

 

[beenthere]

Surplus Center has flow control valves. Here is a link, and they are a forum sponsor.

Surplus Center

 

[J_J]

This is one of the valves that beenthere mentioned. It has free flow of 20GPM's, and a reverse flow of 4.5 GPM. Would that be enough to slow it down to your satisfaction?

Surplus Center - HYD FLOW RESTRICTOR VALVE

Maybe a needle valve in line.

This type will get expensive, but are variable.

http://www.surpluscenter.com/item.asp?item=9-064-38&catname=hydraulic

 

[AKKAMAAN]

That was my immediate idea too, a one way adjustable flow restrictor...
Just remember that drop speed will depend on load weight...No load weight and it might be very slow down....

Also,I did not really figure what valve setup ("upper and lower stage"??) you have for the hydraulic motor.....If you have a 3 position valve (with float in neutral, and power both up and down), you can "push" down, to increase speed when there is no load weight. If so, make sure the motor can handle pressure on both port at the same time. That would be bad for the shaft seal, if there is no case drain on the motor...

 

[oldnslo]

You can install a counterbalance stack module between your two stage valve and its sub-plate. Sun Hydraulics is the leading manufacturer of these valve stacks.

These will allow you to operate at full speed and still prevent free-fall.

Roy

 

[Leejohn]

Roy look at my profile and see if you might know me.