jinman
Rest in Peace
- Joined
- Feb 23, 2001
- Messages
- 21,008
- Location
- Texas - Wise County - Sunset
- Tractor
- NHTC45D, NH LB75B, Ford Jubilee
Jay, I believe the method of testing hydraulic system pressure and relief is to tie the lift arms down (a factory special tool may be available) and then move the position control until the relief valve opens while monitoring the pressure. Every warning I have seen relates to not keeping pressure on the arms for too long because the hydraulics may overheat. At no time have I seen any warnings about bent arms. I'll double-check this tonight in my repair manual, but I'm going to go out on a limb and say that the properly designed arms will never bend under the maximum lift pressure of the hydraulic system. That's the only way it makes sense.
Now, if you have something held by the arms and suddenly something heavy drops on the implement or arms, that's a different matter. Damage to the arms would depend on whether the relief valve was before the HPL control or after it. In the case of the NH 16LA loader and control valve, you only have relief valve protection when the joystick is out of neutral postion. Once you return the joystick to neutral, there is a fluid lock. That's why if you hit a rock or stump with a down-turned bucket, you are likely to pop a hydraulic hose. ...don't ask me how I know. /forums/images/graemlins/blush.gif
**EDIT**
Well, I guess I'm showing my age. The lift-arm tie-down method was something I found in a manual for my old Ford Jubilee. It's oh so much simpler on the new tractors. The TCs are checked using the remote hydraulic adapters (either for the loader or using the rear remotes). All you need is a pressure gage attached to a short hose and a quick-connect adapter. Pop it in and operate the remote while the tractor is running and you'll see exactly the pressure at which the relief valve lifts. /forums/images/graemlins/laugh.gif
Oh well...I'm sure this won't be the last time I'm wrong. /forums/images/graemlins/blush.gif If I'm lucky it will be the last time today. /forums/images/graemlins/laugh.gif
I still stick by my assertion that the lift arms should not bend under any pressure the tractor's hydraulic pump can apply. That's just good design.
Now, if you have something held by the arms and suddenly something heavy drops on the implement or arms, that's a different matter. Damage to the arms would depend on whether the relief valve was before the HPL control or after it. In the case of the NH 16LA loader and control valve, you only have relief valve protection when the joystick is out of neutral postion. Once you return the joystick to neutral, there is a fluid lock. That's why if you hit a rock or stump with a down-turned bucket, you are likely to pop a hydraulic hose. ...don't ask me how I know. /forums/images/graemlins/blush.gif
**EDIT**
Well, I guess I'm showing my age. The lift-arm tie-down method was something I found in a manual for my old Ford Jubilee. It's oh so much simpler on the new tractors. The TCs are checked using the remote hydraulic adapters (either for the loader or using the rear remotes). All you need is a pressure gage attached to a short hose and a quick-connect adapter. Pop it in and operate the remote while the tractor is running and you'll see exactly the pressure at which the relief valve lifts. /forums/images/graemlins/laugh.gif
Oh well...I'm sure this won't be the last time I'm wrong. /forums/images/graemlins/blush.gif If I'm lucky it will be the last time today. /forums/images/graemlins/laugh.gif
I still stick by my assertion that the lift arms should not bend under any pressure the tractor's hydraulic pump can apply. That's just good design.