Backhoe blowing hoses

[pinus]

Thanks for the info Wrenchturner...would this be the relief cartridges the manual refers to? I'll try to scan a illustration tomorrow and post it.

It is some tough digging but it has seen this type of digging without any problems before. Its the rough, red, and rocky Ozarks!

 

[J_J]

Even if the BH relief was sticking closed, the tractor PRV would relieve the pressure. for the supply hose. If the cyl hoses are blowing, there are extra forces at work here.

If the relief was stuck open, you would not have any or very little pressure.

Disregard the first part of this post.

 

[wvpolekat]

Even if the BH relief was sticking closed, the tractor PRV would relieve the pressure. for the supply hose. If the cyl hoses are blowing, there are extra forces at work here.

If the relief was stuck open, you would not have any or very little pressure.

The backhoe has an external pto pump/reservoir.

So, the tractor PRV is not in the picture.

 

[J_J]

I have to retract my last post as the BH uses an independent hyd system. It is not part of the tractor hydraulics. The BH has it's own relief valve.

 

[638]

Are you using single braid hose rather than double braid? Is it blowing off the fittings, or out the side wall? Do the hoses have the correct fittings for that type of hose. Are you using reusable fittings? etc. A awful lot of questions should have been asked before most of the responses were given!

 

[955Lincoln]

I'm curious if your ambient temperature was below normal when these hoses were blowing? Do you recall what weight the motor oil was? What viscosity hydraulic fluid did you put in? Others have asked, this is important troubleshooting information.

 

[mmurphy]

I have to agree with mace canute, find it hard to believe the viscosity being that much difference especially after all ready being out digging.
I also question if you have QD (like I believe some one else said) hooked to tank return. If so, just waiting for problems there.

 

[Wayne County Hose]

My best guess is the OP had some old hoses, got into some tough digging and worked them past their useful life for that application. What taxes hoses more than anything is pressure changes and spikes. This causes hoses to flex violently. I'm also going to guess that most of these hoses blew close to the crimp fitting. If the change in fluid viscosity caused this then every cold piece of equipment on the planet would blow hoses when they are cold.

 

[Mace Canute]

Guys, I really appreciate the feedback and points made. I should have provided some specs first. Here are some of the details in the manual:

Operating Pressure: 2150 psi
Bucket Digging Force: 2875 lbs.
Dipperstick Digging Force: 1744 lbs.
Oil: 10W40 engine oil with API "SD" classification in Northern climates, SAE 40W in Southern Climates. (I'm in southern Missouri)

I stopped at a local logging equipment shop today to have a new supply hose made. They seemed to think it was a stuck pressure valve...not sure if that is stuck shut or stuck open. Looking at the illustrations in my manual it shows what they call relief cartridges which are non-repairable except for seals...is this what they are speaking of.

Don't mind switching the fluid and filter back as discussed. At least I understand how to do this!

SAE 40 motor oil is the roughly the equivalent of an ISO 150 hydraulic oil.

Since Missouri's spring and fall average temps are about 55 F and summer averages around 75 F (winter average about 32F), a high viscosity oil like ISO 150 is probably not called for. From the chart below which shows the operating temperatures of the oil itself, not ambient temperatures, an ISO 46 or 68 hydraulic oil should work well.

As others have pointed out, the causes for the blown hoses are very likely to be either a faulty pressure relief valve or the hoses themselves not being up to withstanding the stress. Wayne County Hose makes a compelling case for failed hoses. I'm 60/40 either way on which one it could be. You might be able to take the PR valve apart, at least partially, and have a look-see at it for obvious damage or anything that looks hinky. Maybe some foreign material in the fluid got into it and is jamming it? Hopefully you get it sorted out without a lot of $$$.

 

[wdchyd]

Bad batch of hose? Badly made hoses?

I agree.....shy of hooking up pressure guages to check status of PRV, I'd suspect the hoses also.......maybe the hoses were yanked under pressure (routing..??).....best to check crimp specs and inspect to make sure these hoses were pushed in all the way before crimp....(seen that too)