Stop me from blowing up my hydraulic pump (again)

[O6qFc27P]

There's no clear markings to indicate "pump" and "tank" ports on this loader control valve.

I'm pretty sure I know which way it goes, but I'm 100% sure about the implications of getting it wrong (an expensive mistake I made once 10+ years ago)

The left side casting has the pressure relief valve assembly/adjuster. The rightmost casting has no features other than the port at the top right.

So, which port connects to the pump? Top left or top right?

Thanks!

 

[GreensvilleJay]

I have to ask who is the mfr and what part number is cast onto the body ??
If nothing, then HOW can you be SURE it'll handle the pressure of YOUR pump ??
There's no way I'd connect without knowing the 'details'......

 

[GreensvilleJay]

I'd 'think' the pump(P = pressure) would be on the side where the pressure relief valve is, but as important is HOW do you know it's good for the PSI of your pump , rated for the GPM you need, ??

 

[O6qFc27P]

I'm not the least bit worried about the flow/pressure ratings. My hydraulic system is pretty modest, and I've used this valve with no problem in the past.

Unfortunately, it's not marked with the usual "P" and "T" markings.

I'm hoping somebody familiar with valves like this one knows how they tend to work inside. If not, I'll fiddle around with the relief spring and some compressed air until I'm confident about it.

 

[Henro]

I'm not the least bit worried about the flow/pressure ratings. My hydraulic system is pretty modest, and I've used this valve with no problem in the past.

Unfortunately, it's not marked with the usual "P" and "T" markings.

I'm hoping somebody familiar with valves like this one knows how they tend to work inside. If not, I'll fiddle around with the relief spring and some compressed air until I'm confident about it.

I am puzzled why a wrong hook up would damage your hydraulic pump. Your tractor should have a pressure relief valve in the system protecting the hydraulic circuit and limiting maximum pressure. This would be there whether or not you have a loader installed.

I would be surprised if the PRV in the loader valve was the only protection offered to the tractor's hydraulic system. Is there a chance that you tractor's PRV is not functioning properly, and that is why you had an issue in the past? I cannot see the thread title as I type this, but I think you said you had a hydraulic pump failure in the past...and you believe a wrong hook up of the loader valve could cause this again...

 

[O6qFc27P]

I am puzzled why a wrong hook up would damage your hydraulic pump. Your tractor should have a pressure relief valve in the system protecting the hydraulic circuit and limiting maximum pressure. This would be there whether or not you have a loader installed.

I would be surprised if the PRV in the loader valve was the only protection offered to the tractor's hydraulic system. Is there a chance that you tractor's PRV is not functioning properly, and that is why you had an issue in the past? I cannot see the thread title as I type this, but I think you said you had a hydraulic pump failure in the past...and you believe a wrong hook up of the loader valve could cause this again...

Yes, I've already broken the hydraulic pump once.

As far as I'm aware, the only relief valve in my gear-driven B7100 is at the 3PT hitch. I'll be tapping hydraulic flow from the bypass block visible in the background at the top left corner of my photo.

There's no over-pressure protection between the pump and that point.

 

[kubotafreak]

My guess is P port on right, T on left. Reasoning, If the relief is on the left it will only limit the pressure of what is before it.

 

[North Idaho Wolfman]

Top Left

I am puzzled why a wrong hook up would damage your hydraulic pump. Your tractor should have a pressure relief valve in the system protecting the hydraulic circuit and limiting maximum pressure. This would be there whether or not you have a loader installed.

Older model tractors put the pressure relief valve at the end of the circuit and and interruptions before that would overload the pump.

Yes it was a design flaw!

 

[North Idaho Wolfman]

Yes, I've already broken the hydraulic pump once.

As far as I'm aware, the only relief valve in my gear-driven B7100 is at the 3PT hitch. I'll be tapping hydraulic flow from the bypass block visible in the background at the top left corner of my photo.

There's no over-pressure protection between the pump and that point.

Normally on all valves the relief is located on the input side of the valve. so top left.
If you want to be 100% sure you have it right and not do damage to the pump.
connect a tee on the line from the pump with a pressure gauge, leave the stop lever engaged so the tractor won't start and crank it. If the gauge goes up when cranking it's backwards, reverse and retest.

 

[O6qFc27P]

Top Left

This is what I was expecting to hear.

connect a tee on the line from the pump with a pressure gauge, leave the stop lever engaged so the tractor won't start and crank it. If the gauge goes up when cranking it's backwards

This doesn't quite make sense to me. The in/out ports are directly connected with the valves in their default position. Pressure won't rise (and the loader will operate) regardless of which way I connect the valve...

...Until I hit the end of the cylinder stroke, at which point *something* is going to happen.

 

[O6qFc27P]

My guess is P port on right, T on left. Reasoning, If the relief is on the left it will only limit the pressure of what is before it.

Well, the pump is before it, so that's what I'd want to put the limit on...

 

[North Idaho Wolfman]

This is what I was expecting to hear.



This doesn't quite make sense to me. The in/out ports are directly connected with the valves in their default position. Pressure won't rise (and the loader will operate) regardless of which way I connect the valve...

...Until I hit the end of the cylinder stroke, at which point *something* is going to happen.

If the loader valve has a check valve build into it it will rise immediately without any flow requirements to the loader.

Now if it doesn't, then connect the pressure gauge to one of the loader lines, and bottom it out very briefly watching the gauge, if it climbs higher then the system pressure the ports are reversed.

 

[Henro]

Top Left


Older model tractors put the pressure relief valve at the end of the circuit and and interruptions before that would overload the pump.

Yes it was a design flaw!

Interesting to know. I would never have guessed...thanks for the education!

 

[O6qFc27P]

If the loader valve has a check valve build into it it will rise immediately without any flow requirements to the loader.

Now if it doesn't, then connect the pressure gauge to one of the loader lines, and bottom it out very briefly watching the gauge, if it climbs higher then the system pressure the ports are reversed.

Definitely no check valve between the in (out?) and out (in?) ports. If there were, I'd be able to figure out which one's which with little difficulty

 

[Dustyx2]

Top left. There is a chance that the relief valve is set higher than your pump is rated for. You could back it off and then by use of a pressure gauge and dead heading a cylinder you could set it back up to the recommended pressure for your tractor.

 

[O6qFc27P]

Top left. There is a chance that the relief valve is set higher than your pump is rated for. You could back it off and then by use of a pressure gauge and dead heading a cylinder you could set it back up to the recommended pressure for your tractor.

Thanks!

I've dug around in some old notes / photos from last time this came up, came to the same conclusion (top left).

I've had the valve hooked up to this tractor before, so I know the relief mechanism in the valve works (I can hear it running at the end of the cylinder's travel). I was just *super wary* about hooking it up backwards again

 

[Dave_eng]

I clearly recall that NIW has always cautioned owners of B7100 type tractors who use the hydraulic block to power a loader or other implement to be certain to use a spool valve with a built in relief valve otherwise the pump will not have the protection of the main relief valve located at the 3 pt hitch valve.

This diagram from the B7100 WSM.

Dave