Hydraulic Over Pressure Pump Protection Question

[Bean Juice]

Has anyone ever installed a bypass valve or pressure relief for the aux hydraulic circuit? I bought a new compact last spring with a back hoe. One of the hydraulic couplers to the backhoe failed and separated. This this was on the return line and the pressure blew out the valve body for the backhoe and also deadheaded the hydraulic pump which destroyed it too. The tractor had less than 10 hours on it and the dealer picked it up and repaired the whole thing under warranty. my previous tractor had a bypass valve that had a pressure blow off in case something like this ever happened. This machine doesn't have any such protection. I'm worried someone (possibly me) may go to take the backhoe off and forget to connect the hydraulic feed and return lines together and blowing the pump again. Id very much like to prevent this from happening again. Thoughts?

 

[LD1]

If sure it can be done....but the manufactures cannot predict and prevent the hundreds of "one in a million" fluke failures that "might" happen.

The bigger question is how you didn't notice the deadheading before it trashed the pump? On compact tractors, something like that is usually quite noticeable. Engine bogging, other functions slow, etc

 

[ptsg]

Most, if not all of these new/newer tractors have a main relief valve for the entire system. If that didn't work, I suspect someone connected the wrong lines to the backhoe loop and completely bypassed the main relief when it was assembled at the dealer.

If you can tell us what brand and model of tractor you have, we can confirm or deny that.

 

[mrmikey]

Most, if not all of these new/newer tractors have a main relief valve for the entire system

I had a Jinma (Chinese Tractor) and there was no pressure relief other than what was on the loader valve. I had disconnected the loader and forgot to hook up the hoses to one another and went to start the tractor. Lucky for me, the pump and tang coupling was strong enough that the engine made one attempt at turning off the starter and stopped solid with no damage...I was lucky.
After that, I put a pressure relief right after the pump pressure line came out of the pump, that way everything was protected. It took a bit of wiggling to get it in place but I figure the first incident was a warning to get my act together or the next time I wouldn't be as lucky..............Mike

 

[RickB]

If sure it can be done....but the manufactures cannot predict and prevent the hundreds of "one in a million" fluke failures that "might" happen.

The bigger question is how you didn't notice the deadheading before it trashed the pump? On compact tractors, something like that is usually quite noticeable. Engine bogging, other functions slow, etc

Most, if not all of these new/newer tractors have a main relief valve for the entire system. If that didn't work, I suspect someone connected the wrong lines to the backhoe loop and completely bypassed the main relief when it was assembled at the dealer.

If you can tell us what brand and model of tractor you have, we can confirm or deny that.

Most backhoe valves can't tolerate high pressure on the return circuit which was created when the return hose coupler disconnected. No doubt the main relief was open. That did nothing to keep the spool seals and probably the seals between the valve slices from blowing out of the backhoe valve.
Left to run over high pressure relief long enough the pump failed.
There is no fail-safe for this scenario other than more awareness on the part of the operator.
There is no doubt there were clues both small and larger that something was amiss.

 

[Bean Juice]

The tractor is a Branson 2610 with the BH100 Back hoe. It happened when I was moving a bucket load of dirt with the front loader. I was driving up a hill and didn't notice the engine straining more than I would have expected driving a load up a hill. I also only had had the tractor for 10 hours so I wasn't very familiar with how it should sound. When I got to where I was going, I noticed something was up when the front bucket wouldn't curl back after dumping. That's when I saw hydraulic oil all over the ground. Both front and rear. I seems I should be able to put a safety valve in. I Just wanted to know if any one has done it and how.

 

[oldnslo]

Bean
Does you loader valve have 6 or 7 lines connected to it? 4 would be for loader lift lower and curl dump.
If 7 then Your 2610 should have a relief valve in the loader valve and if plumbed correctly the loader should have worked just fine even with the backhoe connection unplugged.
If 6 then not sure how Branson plumbed your tractor

 

[ptsg]

The service manual for the Branson 2510 shows a main relief valve on the block that feeds the loader. The 2610 is the updated version of the 2510, so I expect it to be the same. I don't have the manual for the 2610 unfortunately.

If the backhoe was connected the right way, the system had two relief valves, the main one and the one on the loader valve. So that would've saved the pump for sure and I will go as far as saying that it would save the valve as well.

Being that it also trashed the pump along with the valve, I wonder if the backhoe wasn't connected right and basically bypassed the two relief valves and the relief valve on the backhoe valve becomes irrelevant since it has no where to send the excess pressure. Which is still the theory that makes the most sense to me.

 

[RickB]

The service manual for the Branson 2510 shows a main relief valve on the block that feeds the loader. The 2610 is the updated version of the 2510, so I expect it to be the same. I don't have the manual for the 2610 unfortunately.

If the backhoe was connected the right way, the system had two relief valves, the main one and the one on the loader valve. So that would've saved the pump for sure and I will go as far as saying that it would save the valve as well.

Being that it also trashed the pump along with the valve, I wonder if the backhoe wasn't connected right and basically bypassed the two relief valves and the relief valve on the backhoe valve becomes irrelevant since it has no where to send the excess pressure. Which is still the theory that makes the most sense to me.

Running an open center system over a properly installed and adjusted relief valve continuously can and will trash a pump in short order. I have already explained the damage to the backhoe valve. They simply do not tolerate high pressure in the return circuit. There's no mystery with that.

 

[ptsg]

Running an open center system over a properly installed and adjusted relief valve continuously can and will trash a pump in short order. I have already explained the damage to the backhoe valve. They simply do not tolerate high pressure in the return circuit. There's no mystery with that.

It would take at least a couple hours of running that way to even cause some damage to the pump. As the OP explained, he quickly found out about the issue, plus that system runs at 140 bar and the pump is rated for over 200 bar or something along those lines.

As far as the valve, it kind of hit or miss whether it can handle it or not. On my homemade backhoe, the backhoe valve is being feed through the Tank port of the drive motor valve ever since I put the machine together and it has easily over 900 hours. I do have a main relief valve right after the pump and yes, I know it's not the right way to do it but it just works anyway. So far I've had absolutely 0 issues with the cheapest valves one can buy on the market.