BX-25 backhoe relief valve adj.

[doghouse]

Thank you JJ

 

[Tractor Seabee]

Seems to me that most all BH would have their valve relief.

Can you explain how the over load relief works, and are you talking about work ports relief. As far as I can see there is one overload relief. I thought I explained in my post.

So if the loader relief is setting the relief for the BH then the BH could never exceed the tractor pressure of 1850 psi. The Hydraulic Circuit relief valve is integral to the HST. It sets the system pressure for at the point for the BH, 3 Point, FEL, and Power Steering. The FEL has no separate relief valve or overload relief valve. The PS is a separate circuit controlled by a Priority Valve, same pressure

However the cyl could see pressure above that by mechanical force acting on the BH cyl. Each cyl work port would need a relief valve. That is what the Overload Relief does for the BH system

Can you show pictures of the relief you are talking about?

doghouse ,

Can you post the psi reading for each of the BH cyl using the retract mode until the relief goes off, if it ever does.

A good cyl will develop full relief pressure in fully retracted or extended mode.

Kubota BX25-LA240-BT601 | Backhoe Loaders Equipment Specs


Backhoe:
Backhoe type: Kubota BT601
Weight: 617 lbs [279 kg]
Digging depth: 73 inches [185 cm]
Reach from pivot: 103 inches [261 cm]
Loading height: 60 inches [152 cm]
Bucket force: 1,936 lbs [878 kg]
Dipperstick force: 1,171 lbs [531 kg]

JJ,

Not knowing the OPs level of mechanical understanding of hydraulics I tried to make it simple. If he really wants to get into this subject in depth he needs to get his own WSM first. I tried to make it simple and not confuse with issues not really related to his question. When you get the diagrams from Messicks you will see the operation. The WSM has 20 pages that describe the BH operations and zero on servicing. See more notes on your comments above. My opinion is Kubota supports their dealer shops by users have to bring these problems there rather than fixing them like you and I try to do.

On the pressures and when the main relief valve opens; on my BX if I stall out the cylinder at the end of travel or the max load, I can definitely hear the relief go off. I have not experienced developing an exterior load that sets off the Overload relief, not sure I want to see that point. If it doesn't relieve as set it could blow a piston or a hose. I had an outside overload with the FEL (which has no overload relief) and it disintegrated the cylinder piston assembly.

Ron

 

[J_J]

Regarding the relief valves on the BT601 BH, there are two relief on the BH valve itself.

The dipperstick cyl has a relief of 2498 - 2560 psi.

The swing cyl has a relief of 1991 - 2062 psi.

In order to check or change those values, you need an external hyd pump with a rating of 2560 or higher.

You will not be able to see that relief pressure when mechanical forces cause the two cyl to exceed the the set limit.

The force that the tractor hyd pump can provide, is the tractor relief valve pressure of 1778 - 1849 psi.

This pressure, can be checked and adjusted if necessary.

So if you think the BH is weak, it just might be.

While operating the BH and you hear or see the relief pressure, that cyl is performing as advertised.

This pressure developed by the BH is variable based on the force the operator is applying.

You can have a 3000 psi hyd gage plumbed into a tee in the IN port of the BH valve and see the operating pressure at any time.

 

[doghouse]

Thank You J.J

 

[glastron23]

normally on backhoes the swing cylinder spool will have a relief on both of the control valve spool hose outputs. The swing on a dual cylinder setup will normally be set at a lower pressure that pump relief, some single cylinder systems will be set higher than the pump to held with the swinging due to the lack of force that the single can produce.
the crowd cylinder will be equipped with a relief on the outer boom retract/pull in side of the cylinder(normally the base side of the cylinder) at the spool valve hose output. This is normally set higher than the pump so as when you try to crowd the boom in and it stalls then you grab the main boom and move it in it will over pressure the crowd cylinder, the relief will blow off when it exceeds the max force for the outer boom.
As far as setting the reliefs that are set higher or lower than the pump you have to remove them, set them in a test block and using a hydraulic power supply set them for the rated pressures, you can not set them on the backhoe..

 

[glastron23]

trying to load a pdf of the valves may have to get them up later..

 

[J_J]

You mean you don't believe anything I said.

I have the PDF.

You can set the relief pressure on the Backhoe using a manual hyd pump.

 

[glastron23]

http://www.kubotabooks.com/AutoInde...df&AutoIndex=ae28ea41f5f102320f32e2f24d44a4d8
page 43 shows the valve body parts#190 are the swing cylinder reliefs and part# 170 is the crowd cylinder relief