B3030 relief valve

[Stef]

Does anyone know the shim's thickness coming fact. on a B3030 relief valve? /forums/images/graemlins/confused.gif It can be 0.1mm, 0.2mm or 0.4mm (2175 to 2320 psi). I've included a drawing of the valve with part numbers in PDF file format to show you what I'm talking about. /forums/images/graemlins/wink.gif Any thought could be helpful. Thanks

 

[Stef]

Does anyone know the shim's thickness coming fact. on a B3030 relief valve? /forums/images/graemlins/confused.gif It can be 0.1mm, 0.2mm or 0.4mm (2175 to 2320 psi). I've included a drawing of the valve with part numbers in PDF file format to show you what I'm talking about. /forums/images/graemlins/wink.gif Any thought could be helpful. Thanks

 

[KennyV]

Stef…
Relief valves use shim stock to make allowances to the fact that you can not mass produce valves/springs exact.
The relief valve is set to the correct pressure for its application by using various shim thicknesses… I don’t think you would necessarily find a dozen in a row using the same shim thickness and producing the same pressure. KennyV.
BTW are you changing your pressure?

 

[KennyV]

Stef…
Relief valves use shim stock to make allowances to the fact that you can not mass produce valves/springs exact.
The relief valve is set to the correct pressure for its application by using various shim thicknesses… I don’t think you would necessarily find a dozen in a row using the same shim thickness and producing the same pressure. KennyV.
BTW are you changing your pressure?

 

[Stef]

KennyV, thanks, you're probably right. But I wonder why the max pressure varies between 2175 to 2320 psi? (see attachment) But again, your explanation could be right about that too. Different spring, different pressure. A bit more for a B2630 (2204 to 2349 psi) because the pump turns faster (2800 rpm compared to 2600 for a B3030).

No I'm not changing the pressure. But here's the reason why I ask technical questions: I have no leak down whatsoever on my FEL and my backhoe BH75 leaks a lot so I'd like to try to fix it.
<ul type="square"> 1) I try to understand the whole hydraulic system of my B3030.
2) As I said, no leak down for my FEL LA403. It means, the cylinders and the control valve of the loader are well sealed.
3) No leak down of the 3PH and the hydraulic system of the tractor is great.
4) So it's either or both: the backhoe cylinders or the BH75's control valve. It was great when new and then it started to leak. Maybe metal chips travelled into the hydraulic system and cause some seals to malfunction. I saw my tractor on the parking lot of my dealer, the backhoe up, no sign of leak down for hours even days.
5) I'll start by testing all the cylinders individually (7 of them) to see if they leak or maintain their pressure over a definite period of time (let's say a couple of hours 2 to 4). If all the cylinders pass the pressure test then it's the control valve.
6) Look at the valve. I'd start by checking the relief valves mounted on the valve (6 of them: 2 for dipper, 2 for boom and 2 for swing). [/list]

What I don't understand yet is:
<ul type="square"> 1) Why there's no relief valve for the bucket and stabilizers? The only explanation I can see so far is: they use the max pressure the tractor can provide so the only relief valve needed is the one on the tractor. The dipper, boom and swing use lower max pressure so they need relief valves with lower settings.
2) When my BH75 leaks down, all the cylinders are affected: bucket, dipper, boom, stabilizers (swing? I don't know, it's hard to tell it cannot leak "down"). What could cause a leak down of everything and not only one cylinder? I think this is a crucial information to be able to pinpoint the problem efficiently but I don't know what to think about it yet. [/list]

The backhoe of my former BX23 had virtually no leak down. The one I own now lies on the floor in two hours so I'm pretty sure I can do something about it. I have to pinpoint the problem and solve it. Engineers, show yourselves /forums/images/graemlins/wink.gif

 

[Stef]

KennyV, thanks, you're probably right. But I wonder why the max pressure varies between 2175 to 2320 psi? (see attachment) But again, your explanation could be right about that too. Different spring, different pressure. A bit more for a B2630 (2204 to 2349 psi) because the pump turns faster (2800 rpm compared to 2600 for a B3030).

No I'm not changing the pressure. But here's the reason why I ask technical questions: I have no leak down whatsoever on my FEL and my backhoe BH75 leaks a lot so I'd like to try to fix it.
<ul type="square"> 1) I try to understand the whole hydraulic system of my B3030.
2) As I said, no leak down for my FEL LA403. It means, the cylinders and the control valve of the loader are well sealed.
3) No leak down of the 3PH and the hydraulic system of the tractor is great.
4) So it's either or both: the backhoe cylinders or the BH75's control valve. It was great when new and then it started to leak. Maybe metal chips travelled into the hydraulic system and cause some seals to malfunction. I saw my tractor on the parking lot of my dealer, the backhoe up, no sign of leak down for hours even days.
5) I'll start by testing all the cylinders individually (7 of them) to see if they leak or maintain their pressure over a definite period of time (let's say a couple of hours 2 to 4). If all the cylinders pass the pressure test then it's the control valve.
6) Look at the valve. I'd start by checking the relief valves mounted on the valve (6 of them: 2 for dipper, 2 for boom and 2 for swing). [/list]

What I don't understand yet is:
<ul type="square"> 1) Why there's no relief valve for the bucket and stabilizers? The only explanation I can see so far is: they use the max pressure the tractor can provide so the only relief valve needed is the one on the tractor. The dipper, boom and swing use lower max pressure so they need relief valves with lower settings.
2) When my BH75 leaks down, all the cylinders are affected: bucket, dipper, boom, stabilizers (swing? I don't know, it's hard to tell it cannot leak "down"). What could cause a leak down of everything and not only one cylinder? I think this is a crucial information to be able to pinpoint the problem efficiently but I don't know what to think about it yet. [/list]

The backhoe of my former BX23 had virtually no leak down. The one I own now lies on the floor in two hours so I'm pretty sure I can do something about it. I have to pinpoint the problem and solve it. Engineers, show yourselves /forums/images/graemlins/wink.gif

 

[MadReferee]

The relief valve should have nothing to do with leak down. The reason there is a relief on each work port for the dipper, boom and swing is to prevent damage to the hydraulic system if you use one of those functions past their limits in either direction. For example, trying to lift something too heavy or pushing against an immoveable object. My 1963 TD6 dozer has a relief on each work port of the lift and curl spools too.

Relief valves work when the pressure exceeds a certain point. That point is determined by a calibrated spring with shims. The relief spring will compress and open a direct path to the tank circuit. Now if you have a broken spring or maybe a very, very weak spring then it might cause leakdown. I don't think that is your problem.

 

[MadReferee]

The relief valve should have nothing to do with leak down. The reason there is a relief on each work port for the dipper, boom and swing is to prevent damage to the hydraulic system if you use one of those functions past their limits in either direction. For example, trying to lift something too heavy or pushing against an immoveable object. My 1963 TD6 dozer has a relief on each work port of the lift and curl spools too.

Relief valves work when the pressure exceeds a certain point. That point is determined by a calibrated spring with shims. The relief spring will compress and open a direct path to the tank circuit. Now if you have a broken spring or maybe a very, very weak spring then it might cause leakdown. I don't think that is your problem.

 

[KennyV]

Stef
Your logic sounds good…
Finding a leak down can be a problem. You might find a fast, like yours, using a stethoscope, either electronic or conventional. You will need to have everything around rather still and quiet, then as you near the leak you will hear it.
Multi viscosity oil can leak down where a strait weight may not. There are no real seals in many control valves, close machine tolerances usually give acceptable leak down, most leaks like you have outlined are in the control valve. Good luck and happy hunting.
Should you locate, post back with your findings…KennyV.

 

[KennyV]

Stef
Your logic sounds good…
Finding a leak down can be a problem. You might find a fast, like yours, using a stethoscope, either electronic or conventional. You will need to have everything around rather still and quiet, then as you near the leak you will hear it.
Multi viscosity oil can leak down where a strait weight may not. There are no real seals in many control valves, close machine tolerances usually give acceptable leak down, most leaks like you have outlined are in the control valve. Good luck and happy hunting.
Should you locate, post back with your findings…KennyV.