JW-03 Still Broken

[cv63usafsfs]

Hey guys,
Well my Jw-03 backhoe is out of service again . After replacing a shredded O-ring in the pressure relief valve last time it stopped working, I thought I had it fixed. Nope. It started to make groaning and vibrating noises anytime I would move the boom up, side to side, or pull in any other the other cylinders all the way. Then out of no where the boom fell down while I was trying to pull it up and everything stopped working. I pulled apart the pressure relief valve and found that same o-ring had shredded again and clogged the thing up. So I cleaned it, replaced the o-ring, and added more hydraulic fluid. Tested it out today and it worked for a bit but now that groaning sound is back and its starting to get sluggish like the o-ring shredded again. Anyone have any idea what could be causing the groaning noise and for the o-ring to keep shredding?

 

[Bob Rooks]

The "groaning' noise could be the relief valve lifting off of it's seat but that's usually a screeching sound. Could be that you are using the wrong type of O-ring or the relief setting is too high. Some of these relief valves will use a hard nylon O-ring.

 

[cv63usafsfs]

Thanks for the reply! The o-rings I have been putting in appear to be the same as the one that came in it unless the last owner changed it. How would I go about changing the relief setting?

 

[Bob Rooks]

You will need a 3,000 psi gauge and some schedule 80 steel fittings first, then hopefully RonMar or Greg can complete the task. I took my pressure readings from my Prince pump which had an extra tap on the discharge side.

 

[RonMar]

You will need the gauge, and an 18MM - NPT adapter to connect the gauge to the valve block. The valve block uses an adapter in the working ports that goes from a straight metric fitting to the metric O ring face seal used on the hose ends. The metric-NPT adapter should be available at your local hydraulic shop, take one of your hose end adapters along to properly size the metric end on the NPT adapter. You may also need an intermediate adapter to get the NPT side of the adapter down to the size used on the gauge.

Put the structure down on the ground/fully suport it, and then pick a working circuit, boom up, boom down bucket curl ect. One of the outrigger circuits is probably the best as it will motentially move the structure the least if you push the lever the wrong way during the test.

Remove a hose fitting and adapter on one of these working ports at the valve and screw the metric/NPT adapter you purchased into that working port on the valve, then screw the gauge into the adapter. Put the hose you removed into a bucket. Now, with safety glasses and gloves in place, provide hydraulic power to the BH. Once powered, operate the valve that feeds the port you put the gauge into. If you move the valve the wrong way, the BH cylinder for that circuit will move, and fluid will squirt out of the hose into the bucket. If you move it the right way, nothing will move and the gauge will register pressure. Basically you are deadheading the fluid flow into the gauge, and in order to keep flowing the fluid pressure builds till the relief valve opens. The pressure registering on the gauge is the pressure that the relief valve is releasing at/regulating the pressure at. Adjust the relief valve till the pressure on the gauge reads the rated pressure for the BH.

i am not at home right now, but if I recall teh proper pressure for the HW-03 BH is 16Mpa, or 2670 PSI. I will confirm this when I get home later.

 

[erj]

The o-rings I have been putting in appear to be the same as the one that came in it unless the last owner changed it. QUOTE]
Did you get the PDF file on PRV disassembly that I emailed you in June? That had the correct sizes for the o-rings.
RonJ

 

[cv63usafsfs]

Thanks for the help guys. I will work on acquiring the parts for the gauge, and erj I will double check the o ring size. Ill let you know how I make out.

 

[cv63usafsfs]

I finally have the pressure gauge installed and working. I ran a quick test today and all the cylinders seemed to be operating below 2000psi cold, until I maxed out the cylinders and got that groaning sound, at which point the psi jumped to around 2300 - 2400. What kind of pressures should I be getting for the different cylinder operations? When I get some time later in the week Ill get full pressure readings, cold and hot, for each of the cylinders. Also, what RPM do you guys usually run it at? Thanks again for all your help!

 

[erj]

CV6-
What you are looking for is the max pressure shown when the Pressure Relief Valve activates. You should be able to get that by following RonMar's description in a previous post.

RonMar-
I don't remember the proper setting but the 2670psi mentioned in your note seems a little high. Please post proper setting.

RonJ

 

[RonMar]

CV6-
What you are looking for is the max pressure shown when the Pressure Relief Valve activates. You should be able to get that by following RonMar's description in a previous post.

RonMar-
I don't remember the proper setting but the 2670psi mentioned in your note seems a little high. Please post proper setting.

RonJ

Yes, it is a little high. I was working from memory and never got back to confirm it. 16 MPA is correct as per the manual, but that converts to 2320 PSI.

 

[RonMar]

I finally have the pressure gauge installed and working. I ran a quick test today and all the cylinders seemed to be operating below 2000psi cold, until I maxed out the cylinders and got that groaning sound, at which point the psi jumped to around 2300 - 2400. What kind of pressures should I be getting for the different cylinder operations? When I get some time later in the week Ill get full pressure readings, cold and hot, for each of the cylinders. Also, what RPM do you guys usually run it at? Thanks again for all your help!

While the cylinders are moving, you can see any pressure up to the relief pressure. That is just the pressure necessary to perform the work being done(cylinder/arm moving). The pressure you are interested in is the full relief pressure which is achieved when the cylinder stops moving(reaches an end stop or the earth stops it's travel) while the lever is held. Your description sounds prettymuch normal for pressures with the full relief operating in the 2300 PSI range. 16MPA = 2320PSI...

As for engine RPM, I run 1500-1800 typically. Any faster and the boom swing gets pretty twitchy. Those cylinders are pretty small compared to the rest of the BH and fill rather quickly even with the restricted orofices found on those working ports. They are also on a short lever arm which moves the boom quickly.

So what exactly is making noise on your BH when you fully extend/retract a cylinder? Is the noise comming from the valve block where the relief is located, or is it comming from the pump?

If it is comming from the pump, and you are game, I have a fairly easy test for you to try to see if it quiets the pump operation under full load/relief pressure. Basically you remove the rear cover of the control cabinet. Then you disconnect the banjo bolt fitting where the return line is connected to the top corner of the reservoir tank(screw bolt back into tank fitting). Pull that return line back up thru the BH frame so you have some slack available. Remove the reservoir filler cap and mesh screen filler funnel and put the return line down the filler pipe as far as possible. Then run the BH and max out the cylinders and see if it sounds any different under load...

AGAIN 16MPA = 2320 PSI, sorry for the earlier error...

 

[erj]

Just a small suggestion - secure the hose that you run down into the top of the tank just to be safe.
RonJ

 

[cv63usafsfs]

So I have good news and bad news. The good news is the vibration is gone. I isolated the noise down to the pump and were the hose from the pump connects to the valve block. Taking a closer look at the pump I noticed that when its running the output line gets pinched between the pump and the 3pt hitch, so I set the pump up upside down so that the line was no longer pinched. That did the trick.

Now the bad news. After a while of testing it by moving some dirt around, the pressure suddenly dropped. All of the cylinders maxed out at 500 psi and would barely move. Any ideas on the latest issue?

 

[jakell2010]

That doesn't address the o-ring issue,,did it shred again?

 

[Bob Rooks]

My guess: Since you don't have any filters in the hoe's hydraulic system, the pinched hose was damaged internally and bits of it stuck in the control and relief valves.

 

[RonMar]

Sounds like something stuck in the relief valve to me also, or another shredded O-ring...

What fluid are you using?

 

[cv63usafsfs]

That's what I was figured. Hopefully its just gunked up and not a shredded o-ring again. Once I find time I will take it apart yet again and see whats going on with it. Thanks again for your all your input.

 

[cv63usafsfs]

Finally got time to take it apart today. Turns out the o-ring shredded again and clogged up the rest of the valve. Any ideas on why it keeps doing this? What brand/type of o-rings do you guys use, maybe the ones I picked up are no good.

 

[Bob Rooks]

The spool could be travelling too far and catching an edge. Check and adjust the linkage or spool stops.
The O-rings should be Nitrile, Buna-N, polyurethane, or silicone. Plain rubber or neoprene don't hold up well at all in hydraulic service.

 

[cv63usafsfs]

Finally got time to take it apart today. Turns out the o-ring shredded again and clogged up the rest of the valve. Any ideas on why it keeps doing this? What brand/type of o-rings do you guys use, maybe the ones I picked up are no good.