LW-6 pressure relief valve

   / LW-6 pressure relief valve #1  

jezorek

Bronze Member
Joined
Apr 2, 2007
Messages
50
Location
NJ
Tractor
Ford 1910 w/1710 FEL
Can anyone tell me how to increase the setting on the pressure relief valve? I believe the factory setting is only about 1000PSI as I received it
 
   / LW-6 pressure relief valve #2  
Got a diagram to post?

Also.. you need to make sure before you up relief pressure that you will not damage other components in the system.. You really need a hyd gauge if/when you start dinking with hyd relief settings.

Many valve types can be either shimmed/unshimmed or changed with screw type adjustments.. as you are adjusting spring pressure on the relief valve.

Post more info about what you are trying to do.

Soundguy
 
   / LW-6 pressure relief valve
  • Thread Starter
#3  
I am running this BH with a 11 gal/min Prince PTO pump. I had to install a flow control valve to tame down the movement. This is a pressure relieved flow control with a 1500 PSI factory setting from Prince.
Since the pressure relief valve on the control valve bank is relieving, I assume that it is set below 1500 PSI. The digging chacteristics of the BH would indicate that the reliefe pressure is too low. The overall quality of the LW-6 leads me to believe that no quality control is done at the factory. As recieved, most of the functions worked backwards. I have no reason to believe that the relief setting was addressed.
 
   / LW-6 pressure relief valve #4  
It was probably addressed, just not with the fluid you are most likley using:) the chinese fluids are typically thicker so the reliefe is set lower so that enough of hte thicker fluid can pass to adequately control the peak pressure

IRT the pressure, sound guy is right on. You need a gauge to make sure you don't overdo it. There is a lot of history of excessive pressure hurting operators and damaging/DESTROYING equipment. Regardless of what the relief came set for on the Prince flow control valve, what is the backhoe system pressure supposed to be set for as per the Chinese Manufacturer?

As Soundguy mentioned, the setpoint will either be with a shim/flatwasher under a spring or with a screw adjustment that sets the spring tension on the relief valve. These are usually located near where the supply line meets the valve block so any overloaded spool will cause the valve to lift and dump the inlet flow into a gallery that bypasses the rest of the valves.
 
   / LW-6 pressure relief valve #5  
jezorek said:
I am running this BH with a 11 gal/min Prince PTO pump.
You have the wrong Prince pump to begin with. Should have an HC-7A (7 gpm). Works like a charm.
If you still have the Chinese oil in there, flush it out and put in AW32 HYDRAULIC OIL not AW32 machine oil (big difference).

It's quite possible that the flow control valve relief and the stack valve relief can't handle the volume and pressure simultaneously so they both lift. The 11 gpm pump is almost more than twice the requirement.
 
   / LW-6 pressure relief valve #6  
Just lower the tractor RPM and you will get lower flow.
I have a YW-6 using it on a 3510 Branson. I am running it off of the tractor hydraulics and it works great at 1400RPM. I plummed a relief valve between pressure and return lines for added safety. I ajusted it to unload at 2250psi.
Sometimes the hoe seems to have limited power and then I back out of the dig a little and it picks up a full bucket. I think it is working OK, it is me that is asking for too much.
My right/left swing seems to be wimpy though. But those cylinders are small.
 
   / LW-6 pressure relief valve
  • Thread Starter
#7  
Gents,

Thanks for you prompt input. I will put a pressure gauge into the system as recommended. It would be most convenient to tee into the outlet of the flow control valve. Sound OK?
I realize that the 11 gpm put is over size but that's what I had on hand. A flow control valve was cheaper than a new pump. While heat build up may be a concern with this set up, typical useage is under 30 minutes.
From RonMar's explaination, I believe my pressure relief valve is the screw adjustment type. It is located at the inlet of the control block. I presume that screwing in will raise the pressure. There are no instructions for doing so in the manual and there is no system pressure spec. I will post a picture of the control block for conformation in a couple of days.
It is interesting to note that the spares kit that came with BH had about a dozen cylinder seals as well as spare O rings for the face sealed fittings. I hope this is not an omen of things to come
 
   / LW-6 pressure relief valve #8  
I have the same concerns with my LW-7. It is also a weak digger and I believe it to be in the pressure relief. I use the Kama 554 tractor remotes. The TPH and FEL seem to have plenty of power but the BH is lacking. I think I will try reading the pressure an resetting it to just under the tractor relief pressure.
 
   / LW-6 pressure relief valve #9  
The Chinese LW hoes are the cheapest ones out there. I have yet
to see or try one, but I would like to.

You have to be especially careful with relief pressure settings when
running a PTO pump, as the pump usually does not have its own
relief. I think all hoe buyers (esp PTO pump users) should get a
3000psi guage ($10) and test their pressures. The factory may not
test them. If set too high, you can bend cylinders. Any well-built
hoe should be able to handle 2500psi. IMO. If using tractor hydraulics,
the tractor's system relief valve protects you. Often new hoes of
any brand have the reliefs set too low and your hoe is weak as a
result.

As for where to place your guage, you do not need to get a "T"
adapter. You can just remove a hose and stick the guage on the
end and operate that circuit.
 
   / LW-6 pressure relief valve
  • Thread Starter
#10  
dfkrug- On the LW-6 I have, removing a hose from a cylinder to place in a pressure gauge is difficult. The cylinders have bajo fittings. At the control block the lower hose on a valve is a banjo fitting while the upper hose is a right angle face seal fitting. As I mentioned in an earier post in this thread, in order to get the motions going the correct way on some functions my only recourse was to make extentions on the control block so I could swap the hoses. Due to the right and fitting I had to use this adapter so the banjo fitting would clear the right angle fitting. To complicate matters, the thread on the banjo bolt is 17 mm x 1.5. A 1.50 metric thread is 16.9 threads per inch. American lathes do not cut 17 threads per inch. Since the banjo bolts only hold the parts together and don't act as a seal, I was able to cut loose 16 TPI and get away with the fit. I'll try and post some phots of these adapters and the control block. I would like someone to confirm what I think is the pressure relief valve.
 
 
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