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Check valve question .....

Check valve question .....

(OP)
I got my flow valve in Friday and the control boards. I changed all my spool type valves to poppet type to minimize leakage and thus my load lowering.

Now I have a question about my check valves.

On air systems I have built, the check valves I used would not allow flow until the pressure on the low side had risen to the greater than the pressure on the high side.

Looking at the construction of check valves, I am not sure this is true?

It looks like as long as the low side pressure overcomes the spring, it will lift the poppet. If this is true then the flow would go from the low side to the high side causing the load to drop??????

Again, I admit I just don't know enough. Maybe this is not the case. But if it is, maybe since I am using this ( at least the top one ) as a load check then maybe some type of check valve that will not open till the low pressure is greater than the high pressure???? Maybe a pilot to close and hook the pilot to the high side? I did find a few but the hold/flow ratio was 2:1 ... not good either as I would then need twice the pressure on the low side to open the valve.

Can you guys straighten me out again!!!!!!!

Again, the flow circuit is attached.

Thanks .... Mike

Thanks ..... Mike

RE: Check valve question .....

Some check valves work on spring force, some work on pressure differential.

In your case, the check valve will not open until the upstream pressure is more than the down stream pressure + the spring pressure.

While the cylinder load is higher, the check will stay closed. Increasing upstream pressure will eventually cause the valve open, but the pressure will be higher than down stream. Oil will flow across the check and into the cylinder.

Decreasing upstream pressure will cause the valve to close, the cylinder will stop.

RE: Check valve question .....

xtal, dont worry, flow will never go from low pressure to high pressure through anything, remember flow is from high to low pressure. check valves are designed to never let flow go in the reverse direction.

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