REPLACING PTO PUMP

[J_J]

The extra valve and hose could mount on the lift arms. Your PTO hoses would plug into the input of the electric valve, and your implement hoses plug into the valve output. Now, you have reverse just by throwing a toggle switch.

 

[J_J]

I don't think any fluid is being sucked through the tram pump, unless the wheels are turning. If you are just sitting there using an implement like the mini-hoe for several hours, very little of that fluid is filtered. According to the hydraulic news letters, Those fine particles are what causes most of the wear. It acts like an abrasive.

One other neat solution I have thought of is this. A small oil pump and a 1 micron filter assembly to clean the tank every day or week, or by the hour. Just like the roaster on TV, set it and forget it. If you put a pressure gauge on the pump assembly when new, you will notice a difference between a clean filter and a dirty or clogged one over time. The 1 micron filters cost around about $45.00 if I remember correctly.

 

[Bob999]

<font color="red"> When changing your filter, put a 1 micron in instead, run a few light duty tasks totaling an hour or so, then go back to a 10 micron. In all reality even 10 micron is pretty fine [1/10th the thickness of a sheet of paper; </font>

My understanding is that the variable displacement pump is quite susceptible to damage from foreign matter in the oil and that is the reason that PT has placed a filter on the intake side of that pump. By comparison the gear pumps used for the steering circuit and the PTO circuit are much less susceptible to damage.

I further understand that placing a filter on the intake side of a pump is inherently a compromise between the potential for damage from cavitation in the pump if the filter becomes dirty or clogged with the result that flow is restricted and the potential for damage if dirty oil is introduced into the pump. The requirement to change the filter every 50 hours is an attempt to ensure that the filter will not become sufficiently loaded to restrict flow and cause cavitation which will quickly destroy the variable displacement pump.

So if my understanding is correct there could be significant risk in using a 1 micron filter in the circuit, even for a short period of time.

 

[J_J]

I don't think you can suck large quantity of hyd fluid through a filter that fine. In most cases, the fluid is pushed through at low pressure. I don't think it would work on the output of the hyd pumps, but I am just not sure.

 

[Bob999]

<font color="red"> I don't think any fluid is being sucked through the tram pump, unless the wheels are turning. </font>

My understanding is different. The variable displacement pump includes two pumps--the charge pump and the main variable displacement pump. When the treadle is in the neutral position the variable displacement pump has zero displacement and does not pump any fluid. However, the charge pump is always pumping fluid.

This subject came up some months ago in discussions about the hydraulic oil cooler and a poster noted that if you started up the tractor and let it idle that the oil would pass through the hydraulic cooler and that it would gradually warm up.

 

[J_J]

After reading several articles, I found this. If the tram pump is a swash plate type pump, the article says that if the swash plate is perpendicular to the axis of rotation, no fluid will flow. I believe that the purpose of the charge pump is to make sure that the swash plate cavity is full of oil at all times.

My conclusion is this, at a full stop, no fluid flows through the filter or tram pump, however, the other gear pumps are always running and will develop heat, and that is why the hyd oil cooler is warm.

 

[Bob999]

<font color="red">My conclusion is this, at a full stop, no fluid flows through the filter or tram pump, however, the other gear pumps are always running and will develop heat, and that is why the hyd oil cooler is warm.
</font>
Certainly the PTO and steering/lift pumps are running and developing heat. I also share your understanding that the purpose of the charge pump is to assure that there is a pressurize supply of fluid for the variable displacement pump.

However, I believe that the hydraulic oil cooler is in the Variable displacement/drive circuit and that the PTO circuit and steering/lift circuits are separate with the result that flow in the cooler must come from the charge pump.

 

[J_J]

I don't have a hydraulic schematic in front of me now, but you could be right. However consider this, all fluid flows back to the tank eventually, and then is recirculated through out the system. All pumps use the same fluid and get hot and are therefore cooled by the hydraulic cooler.

 

[Spiffy]

Mounting the valves on the lift arms; now that's thinking outside of the box - literally! /forums/images/graemlins/cool.gif

I'm still thinking under the hood since my aux pump feeds both front and rear; of course, if I never get around to mounting anything besides the BH back there it doesn't matter. Hmmmmmm, must think about that some more! /forums/images/graemlins/smile.gif

 

[Spiffy]

<font color="blue"> I don't have a hydraulic schematic in front of me now, but you could be right. However consider this, all fluid flows back to the tank eventually, and then is recirculated through out the system. All pumps use the same fluid and get hot and are therefore cooled by the hydraulic cooler. </font>

Perhap this is what you guys are getting at, but what about a fine filter right before the cooler? I'd still want to monitor the pressure -before and after to determine feasability, and during to determine filter life. I picked up a 5000psi glycerin filled gauge for under $20 the other day.

 

[SnowRidge]

As I understand it, the tram pump operates on a closed circuit and pumps oil only when the machine is moving, but the circuit isn't 'oil tight,' and some oil is 'lost' through the pump's case drain. The charge pump is working constantly, as long as the engine is running. The oil lost by the tram circuit internally is replenished by the charge pump. Any oil not used to replenish the tram pump circuit and that lost from the tram pump's case drain goes back to the tank by way of the oil cooler. While the engine is running, oil is being circulated through the filter, the charge pump, and the oil cooler at all times. The charge pump and the tram pump are both inside the same housing, for those reading this that don't own PTs themselves.

Spiffy, I suspect a fine filter anywhere between the tram pump housing and the return port of the tank would be likely to blow seals, probably somewhere inside the tram pump housing. I recently read an article that said plugged filters on case drains can cause serious damage in hydraulic systems. I think a fine filter would look just like a plugged filter in this case.

 

[Bob999]

<font color="red"> However consider this, all fluid flows back to the tank eventually, and then is recirculated through out the system. All pumps use the same fluid and get hot and are therefore cooled by the hydraulic cooler. </font>

I share your understanding that the tank is common to all systems--It is the source and return point for each of the three separate systems on most PT units--tram or variable displacement pump circuit, PTO circuit, and steering/lift circuit.

However, my understanding is that the flow through the hydraulic cooler originates from the charge/variable displacement pump. Thus fluid pumped by the PTO pump goes back to the tank without passing through the cooling coil. Similarly fluid pumped by the steering/lift pump goes back to the tank without passing through the cooling coil.

 

[BobRip]

Having a fine filter in parallel with the coarse filter would give some flow through the fine filter. Fluids do not just flow through the path of least resistance, they flow through the other paths as well, just more flows through the low resistance path. It is just like two resistors in parallel. The lower resistor value carries more current (fluid), but the higher resistance resistor carries some. I don't know what the ratio would be.

Bob Rip

 

[Bob999]

<font color="red"> Perhap this is what you guys are getting at, but what about a fine filter right before the cooler? I'd still want to monitor the pressure -before and after to determine feasability, and during to determine filter life. I picked up a 5000psi glycerin filled gauge for under $20 the other day.
</font>

I think that the pressure in the cooler is quite low--first because the charge pump pressure output is relatively low pressure and second because there is an unrestricted line from the cooler to the tank. However if you were to put a 1 micron filter in the circuit pressure could build up as the filter loaded up.

There are special cleanup filter units made to refine the fluid in hydraulic systems. My understanding is that they typically use a 3 micron filter element and have a separate motor/pump and use hoses to take fluid from and return it to the reservoir. These systems are used when the tractor is not operating. Ones I have seen cost several hundred dollars.

 

[J_J]

I have already plumbed quick disconnects to several circuits on my 1445. I just plug in the gauge when I need to read the pressure. I don't think the pressure will be any higher than 3000 psi. I think that the relief valves are set at 2750.

 

[J_J]

I received my PTO pump the other day, and installed it Only took about 20 min to take the old pump off, two bolts and two hyd connectors. Two bolts to install the pump, and new o-rings on the connecting plugs and hooked everything back up. I still have to lower the engine assembly back down and bolt it down. I haven't made up my mind about using 10W40 motor oil or synthetic motor, or synthetic hyd oil.

 

[J_J]

Old pump dissembled.