Backhoe Jinma HW03 Backhoe return filter.

[RonMar]

I added a small 7GPM return line filter to my jinma backhoe. The size of this filter allows for easy placement inside the control cabinet below the valve using the existing return line hose cut in two. I placed a metal strap across the cabinet to support the filter, but the whole thing comes out of the way pretty easilly if you need to work on the valve. The 10MM return hose is a slightly loose fit on a 3/8" hosebarb as predicted.

The one thing I didn't expect when I fired it up was the ammount of backpressure. It pegged and damaged the little 0-30 PSI gauge I put on it Everything was cold at around 40F and this was the cartrige I had used a bit on the tractor, so I am not sure of it's ammount of blockage. Surplus center rates this filter assembly at 7GPM. The spec on my pump says 10ML/Rev and a 2000 RPM maximum. At 2000 RPM, that should be 20,000 ML or 5.28 GPM maximum, so this filter should have enough flow. The pressure did start to drop after a little operating of the hoe as the fluid warmed. I put on a clean cartridge and another gauge and it was running at 12 PSI at around 1000 RPM. I ran out of daylight and didn't have enought time to warm it up and really work it this evening. I will give it a workout tomorrow.

 

[GuglioLS]

Ron,

Nice addition to your BH. Over the years, I've seen many posts asking how to do this. Your install pictures should help out a bunch. Maybe give the filter & housing part #'s?

I'm surprised that the 30 psi gauge pegged then blew. There must be some sort of restriction somewhere down stream in the return circuit. It might be worth temporally installing the gauge on the output side of the filter to check that out. Otherwise you might get a 60 psi gauge to keep from blowing another one for when it really gets cold.

Nice & easy worthwhile addition to your BH.

Larry

 

[RonMar]

Thanks Larry
The filter is this one from Surplus Center. Surplus Center Item Detail

The bypass is incorporated in the filter so it is a simple 3/8" filter boss.

It uses this filter cartridge.
Surplus Center Item Detail

I ran out of daylight this evening, so I will warm things up good tomorrow and experiment with the pressure. Hopefully it is just a temperature thing and not another issue, like misreading my pump label specs or poor math skills calculating my available flow

Another thing that surprised me this evening, was how tough the line was to cut. I have cut steel braded line quite a few times, and this singe braid line was no slouch.

 

[RonMar]

Ok, back to the drawing board... DO NOT DO THIS MODIFICATION AS PICTURED ABOVE! There is a flaw in operation with the filter installed this way using the stock return line. I started out this afternoon warming up the hoe fluid to get a warm fluid filter backpressure reading after last nights cold readings. While warming the hoe up by digging out a couple small stumps, I blew out the "O" ring seal on the filter cartridge. Now maybe I didn't get this new cartridge on very tight last night, but I have never had this happen before. I put the seal right back in the cartrige groove and replaced the cartridge on the boss and took the tractor back to the garage to dig into this issue.

The excessive pressure I experienced last night was NOT due to the cold. Nor does it appear to be from the filter. The first thing I did was confirm flow out of the pump, timed into a bucket, and it was within 1/4GPM of the 10ML/revolution volume on the pump label. I then removed the filter and put a plain "T" in the line with a pressure gauge. This resulted in NO change in pressure. At 1800 engine/pump RPM, that return line has 40-50 PSI on it where the "T" is placed about 8" downstream from the valve. I think the reason for this is the banjo fitting at the tank return port. The ID where the line enters the banjo is 1/4". This is the smallest crosssection point I could find in the return line. I put a plain piece of 3/8 hose off the "T" back to the resovoir filler spout and this dropped the pressure back to below 20 PSI at 1800 RPM.

This pressure in itself is not really a problem as Surplus Center says the filter and boss are rated for 200 PSI. The problem is that this pressure is not static. During operation the return line pressure spikes depending on what combination of valve movements are performed. I do not yet know how high the pressure spikes, but it was high enough to prang the 60PSI gauge I put on it... A large spike could have been what popped out the cartridge seal.

The pressure is spiking because of the return line restrictions, so I need to configure a larger calibre return line, particularly downstream from the filter so these surges don't build excessive pressure in the filter due to downstream restrictions.

Red55, Ed, I still think this filter cartridge will work fine and I still plan on using it. I used it as a maintenance filter intermittently on my tractor with very similar pump volume all summer with no pressure issues. I also could not attribute any pressure to it today as I had the same pressure with it in the circuit as I had with just the "T" in the line feeding the gauge. When you said you had ordered the filter, I guess I got a little rushed to get the info out and was not expecting this overall pressure problem in the return line. Give me a few days to work out a lower restriction path from the filter to the resovoir and I will let you know what parts you need to install it.

 

[Red55]

Ron- Sorry to hear that you're running into a problem. I won't even have time to get to this modification until Jan (downtime for mach any way). I did notice on my hoe (JG-6) ordered with jinma 284 that I don't have the room you do- where you installed the filter. I also noticed that my return line is bigger that the other lines (same size as supply to gear pump above pto) This return hose goes to the banjo bolt to the tank Has 602-1601-16.8MPa Q/(HG4) JG1-M numbers on it. When I assemblied the bh I took this fitting apart to access the inside of the hydraulic tank that was covered in gunk and rust. Had filled the tank with diesel and let sit a day or two but not much of the rust came out got most of the rust out using a lint free shop towel tywrap to one of those huge 36" tywraps kinda messy but effective I have also changed the 303 fluid twice. You mention about it getting down to 40 degrees last night. Read (from taz) about two bh he had to repair from water getting into the pressure relief adjustment screws and then freezing. One of the screws had a rubber cap on it(from china). I rtv-ed both screw tops where the water would get in and used a black pipe plastic cap (from shipping to protected the nipple) to cover the top of the larger screw. I'm trying to learn as much as I can -never dreamed of even owning my own machine 8 months ago.
Good luck -ED

 

[Bob Rooks]

Ron,
That's why I went with the 1" filter & housing bushed down. You will get pressure & volume spikes while operating the hoe. The return oil from the cylinders retracting combined with some by-pass oil will (I think) exceed your filter's capacity momentarily. My return line is 3/4" all the way to the reservoir. I have back pressure readings of 2-3 psig at operating temp, and 10-15 psig when cold, and operating spikes of ~45 psig.

JFWIW

 

[RonMar]

Bob
I took pressure readings before and after I took out the filter today and saw no real difference between the filter and a plain "T" in the line. I used this filter on the tractor with basically the same pump flow and it worked fine there, so I think it will work OK. I think the biggest problem is that line necking down to 1/4" in that banjo at the end, and the bit of restriction at the elbow I used comming out of the "T"(probably close to 1/4" ID there also). Just bypassing that banjo with a straight 3/8" line cut the pressure in half. The flow from the valve outlet port decreases while you are extending a cylinder then tries to go back to normal when you stop. Line friction and that restriction at the end are what I believe cause the spikes as the oil tries to accelerate in that small line back to rated flow. I think if I open up the outlet of the filter to 1/2" line, getting rid of the restrictive elbow on the filter outlet and downstream, that will leave the most restricted part of the line ahead of the filter and this should drastically reduce the spikes at the filter. That is tomorrow mornings project.

Happy Thanksgiving.

 

[Hardpan]

Hi Fellow Tractorites!

Here's how I handled installing a return filter on my 2005 284. (Later installed on my 2007 254)
(The 284 burned and I replaced it with a 2007 254.)
I had so many problems with the Jinma backhoe that I have replaced it with the Korean LITW backhoe.
I relocated the tank inlet as low as possible, as the original high mount inlet appeared to contribute to fluid foaming.
The suction strainer was replaced with a quality screw-in model. I punched a hole in the tank filler tube just below the
tank top to raise the fluid level and to stop spewing fluid out of the fill cap vent hole.
I added a sight glass thermometer unit to the side of the tank (not shown in pics).
After I upgraded to the LITW backhoe I retained the modified Jinma tank, relocated it, added a Hayden hydraulic cooler
with a thermostatically controlled electric fan. It's mounted in front of the radiator.

The first two pictures are with the tank set up on the 284 for the Jinma backhoe.
The last picture shows the tank as it is set up on the new 254 with the LITW.

I've put about 200 hours on the LITW with this setup, and is it ever sweet!

I hope this makes sense, as I'm falling asleep writing this waiting for wifey to fiinish her pie baking for tomorrow's festivities...

A Big Happy Thanksgiving to all!

Hardpan

 

[RonMar]

I tried a 1/2" line this morning comming from the "T" to the resovoir and the static pressure was around 5PSI on the return line at 1800 RPM with the fluid cold. The highest spike I saw was around 20PSI, so this is much better than with the stock 3/8"/10MM down to 1/4" return line. I will fit the filter again tomorrow and retest the pressure.

Gotta go eat some Turkey now Hope everyone has a good one.

 

[Wayne County Hose]

Just a thought, but maybe they designed that amount of backpressure. Usually return lines are 1.5X pressure line. They may have a line that small for a reason. I don't know why, just thinking out loud. I think I would run that filter in parallel with the banjo fitting. You will still get hydraulic oil filtering, just not as much as a series circuit, but your circuit will still operate as designed. You could then also place an inline valve made to close at about 30 psi or so, this way the filter is protected.