Allan in NE: Relief valves!

So many thoughts and suggestions spread out over too many threads I thought I would start a new thread.

Those relief valves on the type of valve, that you have shown a picture of, will normally be direct acting relief’s and will have opening between the inlet port and a cavity connected to the tank port. This opening will have a seat ground in the tank side of the passage, and this passage will be blocked by either a ball or a poppet. This ball or poppet will be held “closed” by a spring who’s tension is set by an adjusting screw.

On the inlet side the system hydraulic pressure in opposing the spring pressure and trying to push the ball or poppet “open”. When the valve “opens” any fluid that flows through this passage is being “bypassed to tank”.

The rating stating that the relief valves were factory set on the test bench for 1500PSIG @ 10 GPM simply means that at that flow rating the pressure will maintain @ 1500 PSIG.

When you put the valve on your system of 19 –21 GPM and stall out a cylinder the relief valve must open more to bypass the additional fluid, this means that it will take more pressure to push against the spring force to create the additional opening. In fact you may find that at your system flow rate that the relief pressure may be (for example) 1585 – 1625 PSIG, so you may need to reset the relief valve if 1500 PSIG is to be the maximum value of the system.

Also note that the pressure difference need between the inlet and tank port to cause the valve to operate is around 1500 PSIG, so if you use a valve that is not intended for power beyond the back pressure on the tank cavity will assist the spring force so you will no longer have the 1500 PSIG pressure difference with the system pressure @ 1500 PSIG this will cause the relief valve loose it ability to protect the system.

I haven’t had a loader with a one-way cylinder on the bucket for many years. I guess you are satisfied with the forward gravity tilt for your operation but I was wondering if now would be a good time to consider a two-way cylinder for tilt while you are still pondering the valving?

Think the darned hydraulics are going to be a walk in the park compared to gettin' some water to this darned heater and block heater.

Been fightin' a plug in the head all afternoon that won't come out. Might have to tie into the system bypass if it doesn't give up soon. Awfully long run for those heater hoses tho.

Just had that head gone thru at the machine shop too. :>(

Allan

I know it will work.

All I need is some oil, a on/off faucet for each function and a drain just like the original setup only built in a different configuration.

I just wanted to make sure that the valves had enough "flow" to haul that much oil.

Thanks,

Allan

I couldn’t find many specs on your Cross valves, but let me say that other brands of single valve that I have information on limit the pressure on the tank port to about 500 PSI.

If you have the spec sheets on the valves I think it would be prudent to check the maximum pressure allowed on that tank port. Keeping in mind that with the hookup you are proposing, the upstream valves will have the system pressure on the tank port when a down steam is operated. And the real killer would be if you ever operated two or more valves at on time.

Ok now that I have tossed in my 2 cents worth I will get off your case and you can get on with the project.

All the sheet says is that the valves are rated to 2,000 lbs.

Don't think a guy would want to operate two of 'em at the same time. That for sure would backfeed a dump on the upstream valve or naturally kill the lift on the downstream valve.

Sure wish I could save that old rotary valve, but there just isn't any room fer it inside the cab. But, they work so darned nice. :>(

Allan

If the second valve in the series happens to be being operated at the same time, and that cylinder reaches the end of it's stroke, the relief valve in the SECOND valve in the series then has to operate, too, and with a fairly high flow pump, the pressure the pump "sees" when these 2 reliefs in series are operating will be a LOT more than if only the first valve is being operated, with a clear "return to tank" for the bypassed oil.