Is it OK for the system to go to relief all the time?

gsdavis1 · Nov 22, 2010

I am trying to add power steering to my tractor. The pump is producing around 2000psi. The power steering valve is rated for 1000psi. I was told to get a Priority Flow Divider with an internal relief and use that for the power steering valve.

My questions are

1. Is it OK for the system to go through the relief valve all the time.

2. Will the relief in the Priority Flow Divider change the psi in the Excess Flow circuit.

Thanks
Greg

J_J · Nov 23, 2010

A hydraulic valve with relief open will generate a lot of heat. In the steering mode, I don't believe the valve is relieving all the time, only when you turn the wheel and hit the stops. The components of the steering system should match the pressure ratings of the pump.

The relief valve on the valve below, is set for 1500 psi, and will relieve when the steering load causes the pressure to go above 1500 psi.

https://www.surpluscenter.com/item.asp?item=9-4158-15&catname=hydraulic

gsdavis1 · Nov 23, 2010

Thanks for the response. But I am still a little unsure about how the relief works.

IF the valve is open center, does the relief valve only activate if the load on the circuit requires more psi that relief is set for.

Also, does the relief vavle in the Priority Valve Diverter affect the Excess Flow port.

gsdavis1 · Nov 23, 2010

Maybe this will explain it more.

My tractor's pump (for the three point lift) is producing 2000psi and about 3.5gpm.

I want to add a loader and power steering.

I was going to add the loader like shown in the picture below.

The power steering has me stumped though. Almost all the power steering valves that are available in the used market are rated for 1500psi or less. Even the ones for cars and forklifts.

J_J · Nov 23, 2010

The pump does not produce pressure, until you block some or all of the fluid. When a cyl is receiving fluid via the valve, little pressure is produced until the cyl meets some resistance, and with power steering, it is the wheels that the cyl is pushing. If you go all the way left or right, the pressure will build up and the relief valve will relieve. Similar to the power steering in you car or truck. That whiny sound when you have the wheel turned all the way.

Pumps are designed to produce volume, and the case of the pump, and the components in the system have to be able to handle the pressure generated by the resisting forces. The reliefs are designed to protect the components. If you totally block the flow, something has to give, and that will be the weakest part in the system.

gsdavis1 · Nov 23, 2010

Thanks JJ. So how would you intall a loader and power steering on my machine.

I really am not a hydraulic expert...as you can tell ( I am just a Baptist pastor who loves to get his hands greasy now and then.)

Would you hook the loader up as pictured and then a Priority Diverter Valve after that for the steering? I would prefer that the relief for the loader and rear hitch lift be more toward the 2000psi range.

J_J · Nov 24, 2010

Build your own tractor power steering systems and components

https://www.surpluscenter.com/item.asp?item=9-4158-2&catname=hydraulic

Your main pump would go through the divider valve, the priority flow would go to the steering, and has adjustable relief. This one comes set to 1500 psi, but can be adjusted. The fluid not used by the PS, would go to the loader valve. If you have a 2 GPM priority for steering, and your supply is 10 GPM's. then 8 GPM will go to the loader. The loader should have it's own relief valve.

The priority valves are selected by the GPM's that you want the steering cyl to operate.

There are plenty of PS kits on the market.

AKKAMAAN · Nov 24, 2010

I would absolut recommend/make sure there is a main pressure relief valve ,protecting pump, before flow hits the flow divider.
Rule of thumb and OSHA??, first valve after a fixed displacement pump must be the main pressure relief valve.
And using the main tractor pump, I suppose this setup will be "powered beyond" the 3p assembly, so that should take care of the main PRV ...

gsdavis1 · Nov 24, 2010

So I assume that the Excess Port is not affected by the relief valve in the priority divider?

J_J · Nov 24, 2010

According to this, no. So, if using a valve downstream from the excess flow, a relief valve is necessary. If this hyd flow was being split between a PS and FEL, then the FEL valve should have system relief for the rest of the circuit. .

https://www.surpluscenter.com/Instruct/I9-4158-2.pdf