Oil & Fuel Bypass oil filter for those that care

[J_J]

Although it is true, that the VSP/tram pump input filter is the only filter, it is in the correct place to filter the closed loop circuit, which should be kept extra clean. Over time, it will filter at about 10 % of the VSP pump flow. There is no set figure for the time to filter all the fluid in the reservoir. You and I could do better than that, by adding a return filter on the return lines from the PTO, and the steering/lift circuits.

If something should break down in the closed loop circuit, it will flow through the pump and wheel motors in a loop, and leakage from the wheel motors and the pump case drains will eventually get back to the tank, but that is all unfiltered oil, so all contaminants will flow to the reservoir, and wait for the input pump and filter to repeat the cycle. Therefore a return line filter would serve the purpose of filtering the particular circuit.

As far as the micron rating for the return line filter, I really don't know how they select a particular filter. I suspect it is by how much back pressure a filter would cause. Some hyd circuits do not like back pressure.

Tank strainer type filters usually have a high micron rating, and the return filters have a lower micron rating, and then the input/suction filters are in the 10 to 25 micron region, and bypass filters could be in the range of 1 to 3 micron.

You just don't want to blow up a filter by to much pressure, or or cause back pressure, or block a suction filter, which will starve the pump and cause severe damage.

 

[smartguyz]

I have installed a filter on the return line of my mower to provide additional filtration. It has worked well for me.

http://www.tractorbynet.com/forums/power-trac/146146-pictures.html#post1686972

Guys, this looks by-far like the simplest solution. For example, it doesn't introduce any additional pumps or electrical circuits, and only has one filter and an extra hose. (plus what ever bracket you fab up for it)

So... is this a good idea, and if so, then what kind of filter/housing should we use for it?

Bob999 can you tell us what you used?

During most times, my fine-cut mower is my most-used PTO-driven attachment, so this would certainly fit the bill for me.

-Rob

 

[SpringHollow]

The simple filter idea worries me because if there is no reliable bypass that can handle the pressure and flow, the can blows up if the filter ever loads.

Ken

 

[smartguyz]

The simple filter idea worries me because if there is no reliable bypass that can handle the pressure and flow, the can blows up if the filter ever loads.

Ken

That's a fair concern. So does that mean that we're back to perhaps a bypass filter, mounted to the mower, with some kind of splitter (I don't know the correct word for the hydraulic component) to divert some small amount of flow to the filter?

I guess I like it because it doesn't involve more pumps, and valves, and is simpler.

What if we went back to the original idea, of having a bypass filter system? Could it be safely plumbed into the main PTO return?

-Rob

 

[Bob999]

I would think the bypass filter is only filtering about 5 % of the total oil drawn by the pump, and on our machines, sometimes it is not drawing very much fluid from the tank. Since out system is a closed loop system, the same fluid flows in a loop and is mixed with make up fluid . The reason for the makeup fluid, is some of the fluid is cooling and lubricating the hyd wheel motors, and feeding all four wheel motors case drain lines back to the pump case, and then out to the hyd cooler and then to tank.

My understanding of the fluid flow in a PT is: the charge pump, located in the variable displacement pump, draws fluid from the tank through the filter on the suction line. The fluid from the charge pump goes to make up any fluid losses in the wheel motor circuits with the remainder flowing to the oil cooler and then back to the tank. For the larger PT that have a case drain at each wheel motor the fluid from the case drain flows back to the tank.

So my understanding is that all fluid drawn in by the charge pump flows through the suction filter. I believe that this flow is several gallons per minute at typical motor operating speeds--at least for the larger PT models.

 

[Bob999]

Guys, this looks by-far like the simplest solution. For example, it doesn't introduce any additional pumps or electrical circuits, and only has one filter and an extra hose. (plus what ever bracket you fab up for it)

So... is this a good idea, and if so, then what kind of filter/housing should we use for it?

Bob999 can you tell us what you used?

During most times, my fine-cut mower is my most-used PTO-driven attachment, so this would certainly fit the bill for me.

-Rob

I used a high pressure filter from the Surplus Center (Page 74 in the current catalog--item number 9-7293). It is $160 and comes with a 10 micon filter. Lower micron filters are available from other sources. The filter includes a bypass.

I used a high pressure filter because there is a quick connect between the filter and the tank and there is a risk that the connection could be disconnected and expose the filter to high pressure. My calculus was that this, while more expensive than a simple return line filter, was well worth the reduction in risk of a major oil dump.

 

[J_J]

I believe that most suction and return line filters have a bypass in them in case the filter clogs up, and this could be a gage, or a switch to shut the engine down.

Bob, you said the same thing I did about the fluid flow, except that your fluid from the case drains goes directly to tank. All four wheel motors collect at a common manifold and one line goes to the pump case, then the fluid from the pump case is routed back to the radiator, cooled, and sent to reservoir.

I believe this would be the simplest and cheapest filter arrangement. When not using the PTO, insert a filter into the QD's, and flip the pump on. The fluid will be low pressure, because there is no restrictions in the path of fluid flow. So just turn the PTO on while you are working at other things. If you are using the mower, plug the return line into the filter, and filter whatever comes out of the motor circuit. At 8 GPM's for the green machines, and up to 18 GPM;s for the red machines, you would be filtering a lot of fluid, more so than what you are doing now. Of course you would have a gage on the filter, or a beeper or horn. You can get the filter housing and filter for about $25.

High pressure filters are used before the component to protect the motor or whatever.

 

[smartguyz]

I believe this would be the simplest and cheapest filter arrangement. When not using the PTO, insert a filter into the QD's, and flip the pump on. The fluid will be low pressure, because there is no restrictions in the path of fluid flow. So just turn the PTO on while you are working at other things. If you are using the mower, plug the return line into the filter, and filter whatever comes out of the motor circuit. At 8 GPM's for the green machines, and up to 18 GPM;s for the red machines, you would be filtering a lot of fluid, more so than what you are doing now. Of course you would have a gage on the filter, or a beeper or horn. You can get the filter housing and filter for about $25.

High pressure filters are used before the component to protect the motor or whatever.

OK, so let's take JJ's suggestion.

If we were to buy this item: https://www.surpluscenter.com/item.asp?catname=&qty=1&item=9-7293

and a couple of hoses with quick connects, could we simply follow JJ's plan?

Am I reading this properly? It says it has a 50PSI bypass - I assume that means that there is an internal bypass on this filter where if the restriction to flow exceeds 50PSI, it simply bypasses the filter?

If so, then I guess we still need a gauge to see what the inline pressure is, but it would solve the need for a separate bypass, would it not?

It seems that this would provide a reasonable additional filtration system for around $200...

-Rob

 

[smartguyz]

Here's the specification sheet from Zinga...

I also called an spoke to a technician at Surplus Center. He said that the filter head on this item has a built-in safety bypass set to 50PSI, so that if the filter is clogged, it will automatically bypass. He also said that the "Visual Differential Pressure Indicator" is a mechanical 'pop-up' device that will pop-up when the filter is clogged and excessive pressure is required for the fluid to go through the filter - it is supposed to act as a 'change filter element' indicator.

Wow. This appears to be the ticket!

-Rob

 

[KentT]

OK, so let's take JJ's suggestion.

If we were to buy this item: https://www.surpluscenter.com/item.asp?catname=&qty=1&item=9-7293

and a couple of hoses with quick connects, could we simply follow JJ's plan?

Am I reading this properly? It says it has a 50PSI bypass - I assume that means that there is an internal bypass on this filter where if the restriction to flow exceeds 50PSI, it simply bypasses the filter?


If so, then I guess we still need a gauge to see what the inline pressure is, but it would solve the need for a separate bypass, would it not?

It seems that this would provide a reasonable additional filtration system for around $200...

-Rob

It is my understanding that what you're really concerned about on bypass valves is pressure differential. The housing, however, must be able to handle the full pressure, should you dead-head the hydraulics.

For example:

Pressure at the inlet of the filter MINUS the pressure at the outlet of the filter must be LESS THAN 50 psi, or the filter would bypass.

The system could have 2500 PSI at the inlet, but as long as it had more than 2450 PSI at the outlet, it would not bypass...