Jimna 284 hydraulic problem

[RonMar]

Yep, 10u is the wrong filter for the suction side. Way too restrictive, especially when the fluid is cold. There is no place to put a return line filter on the 284, at least easilly, as the final return from the 3PH valve is back thru the sidewall directly into the reservoir. Everything upstream of that point back to the pump is subject to full system pressure.

The relief/bypass may or may not open under vacume, and any type of weak spot or leak is probably allowing air to reach the pump. Or it is sucking it thru an internal pump seal. Pressure rated seals often are very poor at resisting vacume. It could also be sucking in around the filter cartridge seal...

At any rate, I think that is the wrong filter element for this application... They make coarser mesh or paper cartridges for this type installation.

 

[Bob Rooks]

Yep, 10u is the wrong filter for the suction side. Way too restrictive, especially when the fluid is cold. There is no place to put a return line filter on the 284, at least easilly, as the final return from the 3PH valve is back thru the sidewall directly into the reservoir. Everything upstream of that point back to the pump is subject to full system pressure.
Ok, did not know that.

The relief/bypass may or may not open under vacuum (Yes, it does. At approx 10" Hg), and any type of weak spot or leak is probably allowing air to reach the pump. Or it is sucking it thru an internal pump seal. Pressure rated seals often are very poor at resisting vacuum. It could also be sucking in around the filter cartridge seal...

At any rate, I think that is the wrong filter element for this application... They make coarser mesh or paper cartridges for this type installation.

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[J_J]

There is some erroneous data being passed out here. My Power-Trac which uses a VSP pump has a 10 micron suction filter, and has been using filter like this for over 30 years. The only problem with suction filters is they have to be changed to keep the fluid clean. These filters were designed to be in these systems, and have been working as advertised. We all know about the filters blocking the flow of fluid when cold or dirty, and the pump may cavitate and could damage itself. A lot of hyd system also use return filters, and that is by design, so you have to go with the flow, if it is in your system, continue to use it unless you can design a better filter system.

If he is sucking air, then it is a leak in the fittings or cracked parts.

 

[Bob Rooks]

There is some erroneous data being passed out here. My Power-Trac which uses a VSP pump has a 10 micron suction filter, and has been using filter like this for over 30 years.
The Variable Speed Peristaltic (VSP) pump is a whole different animal and not subject to the same issues as gear pumps.

The only problem with suction filters is they have to be changed to keep the fluid clean.
This is not a problem, it is routine maintenance. Suction side filters would have a vacuum gauge to show the amount of restriction.

These filters were designed to be in these systems, and have been working as advertised. We all know about the filters blocking the flow of fluid when cold or dirty, and the pump may cavitate and could damage itself. A lot of hyd system also use return filters, and that is by design, so you have to go with the flow, if it is in your system, continue to use it unless you can design a better filter system.
And this can be easily accomplished.

If he is sucking air, then it is a leak in the fittings or cracked parts.
Agreed.

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[biggerten]

If the OP had the filter head installed backwards (I'ts not clear to me whether he did or did not) the bypass wouldn't work. It seems to me that that would increase the chance of drawing air into the system.

I've had my Jinma for 5 years, and been all over the Chinese tractor boards. The consensus is to use a 150 micron filter on the suction side, a lot of these originally came with a screen in the tank that doesn't hold up well, and started to be replaced or augmented by the filterheads around the 2005 time frame.

Ron's statement about the three point return being internal is correct, that is why I figured the filter would explode if on the output side, it's NOT designed for the pressure.

 

[Bob Rooks]

If the OP had the filter head installed backwards (I'ts not clear to me whether he did or did not) the bypass wouldn't work. It seems to me that that would increase the chance of drawing air into the system.
What it would do, assuming everything else is air tight, is to draw oil in reverse flow through the filter media (in this case, pleated paper) eventually causing early failure and filling the hydraulic system with paper bits. There is no screen on the outside of the filter media, only the inside. I've looked at several. In addition, it would cause aeration from cavitation because of the relatively low velocity.

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[RonMar]

It is not erroneous data for a gear type pump. They do not respond well to suction side restrictions. In fact, there is a whole school of thought to do away with inlet side filtration alltogether, adding instead, a good return filter, filler neck filtration and air vent filtration and dessicant. If the reservoir is kept clean and dry, and any fluid added is filtered/screened, there is really no need for a suction strainer. Any particulates generated internal to the system are most likley going to come from the pump or points downstream. Those particulates are much more effectively trapped by a small micron return line filter, returning cleaned fluid to the reservoir... What does this do for you? Well in cold climates, it should extend pump life on systems that must endure cold starts, by reducing pump cavitation due to restricted flow...

The factory intank strainer on my 284 was pretty cheesy. I replaced mine with an off the shelf #100 mesh stainless model designed to be screwed into a NPT bung in the side of a reservoir. I rebuilt the original pipe with an elbow on the end and put the new strainer horizontal in the reservoir at the bottom of the pipe... I have thought about adding an internal pipe fitting to where the fluid returns to the reservoir, piping it outside to a 10u filter cartridge and then returning it back to the reservoir. Sure would be nice to have time to try all my hair brained ideas I did make a maintenance filter that connects from the aux port on my system thru a return line filter and back to the reservoir, to filter most all the fluid to 10u. but when it is in place, I cannot use the 3PH, so it only gets run occasionally, or when the BH is in place.

 

[adpl]

Thanks everybody for your input! Much appreciated! I have reached the conclusion that the cotter pin side goes towards the resivoir, it would appear that the only way the bypass would engage is with suction from the pump end (at least that is my best guess). I have found and repaired one obvious leak and that has helped a little but I am still getting heavy foaming. Any advice as to how to trace were the other air leaks are comming from (aside from the obvious dripping of fluid)? What is the consensus / best recomendation for sealing the connections......teflon plumbing style tape or some sort of liquid sealant compound?

 

[greg_g]

I've already weighed in on the type of thread sealant, but I can comment on the fluid. When advised to use AW32 hydraulic fluid in their 200 Series Jinmas, a few owners mistakenly purchased AW32 machine oil instead. Machine oil does not have the anti-foam properties that are typically found in hydraulic fluid.

//greg//

 

[J_J]

Sometimes it is difficult to detect a suction leak. Tighten everything such as fittings, clamps, etc as much as possible.