Is this some kind of pressure relief valve?

[Hilbilly]

At the end of last winter I converted my 3PTH snowblower to hydraulic use, so I could use it on my skidsteer and drive forwards but I think the hydraulics were running too hot. So this year, in preparation for winter, I ran some pressure tests to see if I could find the heat source. One of the items of concern was the cross over relief valve. There is a 200 psi pressure drop across the valve I have now. So I've been looking at factory built implements to see if they use a similar valve and noticed that several appear to use what looks like a simple "H" connection. Can anyone tell me what this setup is and how it works?

 

[Fallon]

It should be a 1 way valve. When you spin a motor & impliment it gains a lot of momentum. When you cut power to the motor, all that momentum turns the motor into a pump. If the control valve is closed, all the fluid being pumped by that motor turned pump has nowhere to go & blows up hoses or other things. That 1 way valve let's the fluid from the out port on the motor(pump) just go back to the input until things slow down. When things are running normally high pressure on the inlet side & little pressure on the output keep the valve closed so it does nothing.

 

[Hilbilly]

Thanks Fallon.

It took me a while to understand the principle but finally got it. This valve would allow the snowblower to slowly come to a stop when the hydraulic in feed is stopped, instead of hammering to an instant stop. I like it and will install one.

 

[Fallon]

Yup. It's relatively cheap & easy if your impliment only spins 1 way.

My hydraulic post hole digger spins both ways. So the check valve wont work. The PHD is low speed & momentum so it hasn't blown out much hoses yes despite having no relief. The hoses jump hard when I stop it. I have a crossover relief valve sitting there waiting to get installed. The crossover relief opens in both directions, but only opens at a certain pressure.

1/2 NPT 3 GPM 15-3 PSI Hydraulic Cushion Valve | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

 

[aczlan]

Personally, I would want a valve that would work in both directions on a snowblower as well. That way if you get something jammed in there, you can reverse it and back it out.

Aaron Z

 

[Hilbilly]

I currently have a cross over relief valve installed on the hydraulic lines for the snowblower but the hoses still jump when the flow to the auxiliaries is stopped. I also have to remember to slow the engine down before shutting off the auxiliary. I have the cross over installed to protect the gear box on the blower, in case something gets jammed in the fan. I would like to remove the cross over valve from the system because there is a 200psi pressure drop across it and I am having some heat issues with the hydraulics on the SS. If I can devise a way to install a shear bolt on the gear box input shaft then I will likely remove the cross over and install a check valve to relieve some of the hammer when the flow is shut off.

I never thought about having the ability to reverse the blower if something jammed in it. I haven't used it on the SS enough yet to run into that issue but I know it will happen. When using the blower on the tractor there have been a number of times something got jammed in the auger or the fan and in each case the shear bolts have done their job. For tractor operation there is a shear bolt on the driveshaft which protects the gearbox and another on the auger. With the converted operation there is no shear bolt protection for the gear box input shaft and according to the salesman where I bought the materials for the conversion, that is the reason for the cross over relief valve. I would prefer a shear bolt though. I'm thinking of drilling a hole through the hydraulic motor shaft and the sprocket hub, to install a shear bolt.

 

[aczlan]

I currently have a cross over relief valve installed on the hydraulic lines for the snowblower but the hoses still jump when the flow to the auxiliaries is stopped. I also have to remember to slow the engine down before shutting off the auxiliary. I have the cross over installed to protect the gear box on the blower, in case something gets jammed in the fan. I would like to remove the cross over valve from the system because there is a 200psi pressure drop across it and I am having some heat issues with the hydraulics on the SS. If I can devise a way to install a shear bolt on the gear box input shaft then I will likely remove the cross over and install a check valve to relieve some of the hammer when the flow is shut off.

Sounds like your crossover relief valve is undersized for the flow rate that your skidsteer puts out (which would cause the hydraulic fluid to heat up and the pressure drop that you are seeing). How many GPM/PSI is your skidsteer rated for? Perhaps you need to put in a bigger crossover relief valve?
Something like this: 3/4 NPT 3 GPM 15-3 PSI Hydraulic Cushion Valve | Prince Mfg | Brands | www.surpluscenter.com ($76 bi-directional relief valve) or this: SAE 12 3 GPM Hyd Motor Relief Bypass Valve | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com ($170 one way relief valve with a coast valve to let the motor coast to a stop, does not allow the motor to be run in reverse)
Both are rated for 30GPM and up to 3000PSI.

I never thought about having the ability to reverse the blower if something jammed in it. I haven't used it on the SS enough yet to run into that issue but I know it will happen. When using the blower on the tractor there have been a number of times something got jammed in the auger or the fan and in each case the shear bolts have done their job. For tractor operation there is a shear bolt on the driveshaft which protects the gearbox and another on the auger. With the converted operation there is no shear bolt protection for the gear box input shaft and according to the salesman where I bought the materials for the conversion, that is the reason for the cross over relief valve. I would prefer a shear bolt though. I'm thinking of drilling a hole through the hydraulic motor shaft and the sprocket hub, to install a shear bolt.

IMO, your crossover relief should take the place of the shearbolt. No need to dig through the snow that way to get out a bent shearbolt and try to get things lined back up to get a new one in that way.

Aaron Z

 

[Hilbilly]

This is the one I have installed. https://www.tractorbynet.com/forums/hydraulics/404069-some-kind-pressure-relief-valve.html#post5244939

I note it states a directional control valve should be used with it but I do not have one installed.

 

[Texasmark]

It should be a 1 way valve. When you spin a motor & impliment it gains a lot of momentum. When you cut power to the motor, all that momentum turns the motor into a pump. If the control valve is closed, all the fluid being pumped by that motor turned pump has nowhere to go & blows up hoses or other things. That 1 way valve let's the fluid from the out port on the motor(pump) just go back to the input until things slow down. When things are running normally high pressure on the inlet side & little pressure on the output keep the valve closed so it does nothing.

+1. Have a similar setup on my JD 375 round baler.

 

[Hilbilly]

This is the one I have installed. https://www.tractorbynet.com/forums/hydraulics/404069-some-kind-pressure-relief-valve.html#post5244939

I note it states a directional control valve should be used with it but I do not have one installed.

My apologies. The above link is wrong. Here is the correct one. 3 GPM Cross Over Relief Valve | Princess Auto

The reason I prefer a shear bolt is that I am having heating issues with the SS and this cross over valve is producing a 200psi pressure drop. I would like to eliminate as many heat sources as possible.