Help with BH technical jargon

[wirenut]

Just acquired a Jinma LW-8 self contained (had pto pump/reservoir) backhoe at a good price. The pump works, but it appears that the relief valve is popping at to low pressure. I say this because when curling the bucket in soft dirt, it stalls and you can hear the relief valve opening.
I will be installing a gauge and checking pressures, but I don't know what the cylinders are rated for or the factory setting on the relief valve. I do have some specs, but don't understand exactly what they mean. They read as follows:

*valve standard pressure=2320 psi
*valve over-loading protection=1015 psi

Can anyone explain the difference in the two specs?
Does anyone know what pressure the cylinders are designed for?

thanks for any input.

 

[wirenut]

Any comments?

 

[LD1]

Cant really comment on what those pressures mean.

It appears the valves normal pressure would be 2320psi, but the second one is worded like the relief valve. I have no Idea why it would be set so low. The minimum you normally find for a PSI rating on cylinders is usually 2500psi. And that is usually with a good bit of saftey factor built in. Same for hoses. So I dont see any reason why it would not be just fine @ 2320PSI. If every looks sound and food fittings (no black iron or water pipe fittings on there).

You really do need to but a guage on it and go from there:thumbsup:

 

[leonz]

They may have committed a typographical erroe reversing the numbers.

I am more worried about the way you are digging with the Hoe as the deeper
you dip with the bucket the more quickly the relief valve wil release which is what you want to have happen anyway.

When you use the bucket simply dig a shallower pass each time.


A cyclinders pressure rating is related to the square area of the piston exposed to the available system pressure.

 

[LD1]

A cyclinders pressure rating is related to the square area of the piston exposed to the available system pressure.

That is the correct way to calculate the force of the cylinder. But I do believe he is asking about how much pressure (psi) they can handle. IE: 2500psi, 3000psi, etc.

 

[wirenut]

They may have committed a typographical erroe reversing the numbers.

I am more worried about the way you are digging with the Hoe as the deeper
you dip with the bucket the more quickly the relief valve wil release which is what you want to have happen anyway.

When you use the bucket simply dig a shallower pass each time.


A cyclinders pressure rating is related to the square area of the piston exposed to the available system pressure.

I have no digging technique, not yet anyway, this was my first scoop after hooking it up. I was just seeing what it would do. Yes, I was asking about the allowable pressure on the cylinders. Something has to be not working right, as it is almost useless. I could have broken out this dirt with a shovel and it stalled out the bucket curl. I will be installing a gauge, just hoped to get what proper operating pressures should be.
Thanks for the replies.

 

[dboacres]

My Woods 7500BH requires a minimum 5 gpm and 2100 psi to operate efficently. Your hoses should be SAE 100 R1 spec which means 2500 PSI working pressure. The 2300 psi is a common releif valve pressure. The 1015?

 

[dboacres]

A good digging technic, is to keep your left hand on the boom control. When the bucket or dipper stick arm start to stall, pull back a little on the boom control, slightly raising it and taking the pressure off the bucket and/or dipper stick. My boom control has a float position but I find it easier to raise the boom myself. Practice , practice, practice.

 

[hayden]

Yes, the numbers make no sense as written. The relief pressure would normally be at the outer limit of the working pressure - just the opposite of what you are seeing.

That said, it may be that this particular BH is intended to have a working pressure lower than the valve ratings. This could happen if the BH is structurally incapable of handling the full possible load that the valves can handle.

A gauge is clearly the starting point to see if you are even reaching 1015 PSI. If not then you can fix that problem first and see how things perform. If you conclude you need more than 1015 PSI, first check the hose ratings to be sure they can go higher. They might only be rated for 1200 PSI or something like that. Then I'd take the pressure up slowly and carefully, but do so understanding that you might severely damage the BH structure, burst cylinders, and generally create a hazardous situation for yourself and others around you.

 

[wirenut]

My Woods 7500BH requires a minimum 5 gpm and 2100 psi to operate efficently. Your hoses should be SAE 100 R1 spec which means 2500 PSI working pressure. The 2300 psi is a common releif valve pressure. The 1015?

I installed a pressure gauge (no small feat with these weird fittings) today, and relief pressure was ~1800 psi. I bumped it up to ~2300 psi. The pto pump is rated at 7 gpm @ 2000 rpm.
thanks for the reply.