L**40 rear hydaulic pressure

[dfkrug]

I would also like to see the 3-pt circuit checked at relief, but that
won't be easy. First you have to find a test port for the guage or
a place in the PB or supply plumbing that can accept a tee. I agree
that a tee in a hardline connection is hard to do.

Then you have to provide a limiting load to the 3-pt, and that 3-pt
on the Kub is very powerful. I have used chains between the upper
arms and the drawbar frame before. Be careful.

 

[J_J]

I did mess with the safety valve and had the pressure reduced but it made no difference to the pressure at the rear remote. The safety valve is a closed system anyway and has nothing to do with pressures in the rest of the system.

Now that you messed with the safety valve, it may not be a safety anymore. They show using an external pressure supply to set the safety valve. The safety is designed to go off by something causing the cyl to compress the fluid to a high pressure. Since they used an external pump to test and set the pressure, that tells me that the pump can not pump up that kind of pressure. You should still not be able to develop that kind of pressure.

What was the pressure when you only maxed out the 3pt, and where was the gage plugged in?

Why can you not operate the 3pt if you are only feathering the FEL valve, the pump flow is still flowing to the rear.

If you feather the FEL, and max out the 3pt, what pressure do you read?

 

[Leejohn]

JJ you ask this(What was the pressure when you only maxed out the 3pt, and where was the gage plugged in?)
The only way the 3pt can be maxed out is by weight or tied down, the feel back lever well not let you unless you readjust to do so.
You wanted to know this (Why can you not operate the 3pt if you are only feathering the FEL valve, the pump flow is still flowing to the rear.) You can on spool 1 but not spool 2. Spool 2 work ports go to the tank. I just tried that this afternoon.

 

[Chilly807]

Now that you messed with the safety valve, it may not be a safety anymore. They show using an external pressure supply to set the safety valve. The safety is designed to go off by something causing the cyl to compress the fluid to a high pressure. Since they used an external pump to test and set the pressure, that tells me that the pump can not pump up that kind of pressure. You should still not be able to develop that kind of pressure.

What was the pressure when you only maxed out the 3pt, and where was the gage plugged in?

Why can you not operate the 3pt if you are only feathering the FEL valve, the pump flow is still flowing to the rear.

If you feather the FEL, and max out the 3pt, what pressure do you read?

The reason they use an external pump is to have a controllable pressure source that won't damage the tractor if you make a mistake. They say to use an injector test pump, which is easily capable of 5000 psi or more.

To develop that kind of pressure with the tractor hydraulic pump would require two things. First, the relief valve would have to be either defeated or maxed, most don't have that much pressure capacity in the adjustment, and second, the 3 point lift would have to be either chained down or deadheaded by fiddling with the feedback linkage. Easy way to break something.

Sean

 

[kuboman]

The reason they use an external pump is to have a controllable pressure source that won't damage the tractor if you make a mistake. They say to use an injector test pump, which is easily capable of 5000 psi or more.

To develop that kind of pressure with the tractor hydraulic pump would require two things. First, the relief valve would have to be either defeated or maxed, most don't have that much pressure capacity in the adjustment, and second, the 3 point lift would have to be either chained down or deadheaded by fiddling with the feedback linkage. Easy way to break something.

Sean

The safety was returned to the exact setting it had from the factory. It should be fine.

 

[J_J]

Maybe the hyd pump in your machine is different and has a higher psi rating. Different part number, etc

How did you reset the safety valve with out an external hyd supply with the high pressure capability. You did say the 3pt read the same as the FEL, correct.

So the remote valve is the only place, where you get the 3200 psi.

 

[kuboman]

Update:thumbsup: Just because I lacked any better ideas or things to try I removed the relief and the check valve from the loader valve. Everything looked as it should of course. Put it all back together and decided to try things again.:mur::mur:
RR pressure was down to 2900psi and as I cycled the remote a few times plus the loader they both equalized at about 2600psi. So .....somebody here said maybe it will fix it self.:confused2: Could a stuck or partially stuck check valve do this. I always thought they worked or didn't. Or was there some debris in the RR I put on got stuck somewhere and cause the relief to partially malfunction. I don't know. Or is it possible for a pressure gauge to malfunction?
Weird but what ever happened where ever seems to have corrected itself for the moment.

 

[J_J]

I said that, and things do fix them selves. Back in the 60 through the 80's, flying in the P2 and P3 aircraft, a black box would fail in flight and we would send it to the electronics shop to be fixed, and it would come back as no malfunction. We did all the diagnostics on the equipment before sending, and it was bad in our opinion.

I also did a tour in the electronics shop as repair technician, and we would get the same type equipment, check it out and if broke , we would fix it and send it back to supply. We often sent things back with a note, calling it operator error, no malfunction. Sometimes we would pull the black box out of the built in plugs, and re-seat the unit and it would start working.

Yes, you could say that some things do fix themselves, even people.

 

[kuboman]

I said that, and things do fix them selves. Back in the 60 through the 80's, flying in the P2 and P3 aircraft, a black box would fail in flight and we would send it to the electronics shop to be fixed, and it would come back as no malfunction. We did all the diagnostics on the equipment before sending, and it was bad in our opinion.

I also did a tour in the electronics shop as repair technician, and we would get the same type equipment, check it out and if broke , we would fix it and send it back to supply. We often sent things back with a note, calling it operator error, no malfunction. Sometimes we would pull the black box out of the built in plugs, and re-seat the unit and it would start working.

Yes, you could say that some things do fix themselves, even people.

Still wish I knew for sure what it was. I am going to take the 2 gauges to a shop that can retest them. Just to make sure they are not faulty. I had them tested when I got them made up but who knows.
Anyway, tickled that it is the way you would expect it to be at the moment.

 

[Leejohn]

Well my L4240 still reads 2700psi when the RM are dead headed and the min. I go up with the boom it goes over 3000psi. I think I know why, When going up with the boom oil is going to the piston side and rod side is going to spool 1 then into the PB port that is being deadheaded at the RM valve. Now the larger piston in the cyl is compressing the smaller piston of the rod end, then we have more psi because the oil is shut off to the RV.

Now does that 1 and 1 = 2 ?????? Note the loader should still have 2700psi it is open to the RV.

 

[J_J]

Would you call that pressure intensification. I had asked about that earlier.

 

[Chilly807]

Would you call that pressure intensification. I had asked about that earlier.

JJ,

I'm not 100% sure what the exact definition of pressure intensification is, but I thought it was the result of passing fluid already under pressure through another "stage" or pumping element to further increase the existing pressure.

An example would be a multi-stage compressor or a series of water pumps.

It might be worth digging around the net to find an actual definition of intensification as it is used hydraulically.

Just as an aside, I thought the technical term for what Lee is describing is "10 pounds of sh*t in a five pound bag" :laughing:, meaning that the displaced volume is being forced into too small a space.

That is one of the reasons I had avoided using a cross-over relief valve on my rear blade cylinder, unless you can dump the excess to the tank it has nowhere to go and the pressure will still increase.

Sean

 

[J_J]

Somewhere I saw a demonstration of intensification, using only one cyl. They only installed a 10,000 pressure gage in the rod end of a cyl, and applied pressure 3000 psi to the base end, and the gage read way above the rated cyl pressure. I believe there was an accident involved.

I believe a meter out situation can cause pressure intensification by restricting the out flow in a cyl.

Here is a video to demonstrate this.

Pressure intensification caused by meter-out flow control

 

[dfkrug]

I believe a meter out situation can cause pressure intensification by restricting the out flow in a cyl.

Here is a video to demonstrate this.

That's an interesting simulation video. It shows how the pressure
rises in the rod side of the cylinder when out flow is restricted. I
experimented a bit with that when I was testing flow restrictors in one
of my hydraulic thumbs.

This is a dynamic case, however, and that pressure will drop to zero
when the piston reaches the end of its travel. The OP has tested
his AUX pressures in the static state with no cylinders, a "deadheaded"
case.

 

[oldnslo]

Pressure intensification via single rod cylinders.

Example: 2 1/2" bore x 1 3/8" rod

2 1/2" bore = 4.9 square inch area
1 3/8" rod = 1.48 square inch area

4.9 - 1.48 = 3.42 square inch area which is the rod end area of the cylinder.

Using equation of Force = area x pressure.

2000 PSI x 4.9 = 9800 lbs of force.

9800/3.42 = 2865.5 PSI on the rod end if that port is blocked..

This does NOT allow for the weight of the loader but it does represent cylinder intensification.

Hope this makes sense.

Roy

Hey Kubo, can't explain what or how but yes reliefs can fail. Typically they are designed to fail open though. Glad things are working and do NOT check it again


Without having the valve casting in front of me I can't even speculate how the RV would fail on the RR and not the FEL.

 

[kuboman]

Hey Kubo, can't explain what or how but yes reliefs can fail. Typically they are designed to fail open though. Glad things are working and do NOT check it again


Without having the valve casting in front of me I can't even speculate how the RV would fail on the RR and not the FEL.

I may just throw the gauges in the dumpster and remain ignorant. Life seems simpler that way.:laughing::laughing:

 

[Leejohn]

4shorts
I checked all the pages you posted and if you wouldn't mind would you scan page 8-M15 of the manual and post it.
I can't do it, my printed went belly up. That page shows the up system and what is going on can be seen on that page.

Thanks, Lee

 

[J_J]

kuboman,

I would suggest mounting one of those gages before the FEL, to monitor and trouble shoot the hyd system.

You could cut your pressure line and do something like this for a pressure gage extension. Just use a tee at the union and run a line up to where you can see the gage while operating the tractor.

 

[dolphins65]

Get the dealer/agent to fix the bloody thing. Too dangerous to F#^* about with girls'n'boys. Face it ,ya dunno what ya duin'...

 

[4shorts]

4shorts
I checked all the pages you posted and if you wouldn't mind would you scan page 8-M15 of the manual and post it.
I can't do it, my printed went belly up. That page shows the up system and what is going on can be seen on that page.

Thanks, Lee

Hey Lee. Sorry I missed your post. I only just noticed it. Do you still need that scan? Sorry about that.

Paul