I've got a boom lift, when I'm near the end of the cylinder travel the hydraulic system kind of pulses, or vibrates. It's both a sound and something I can feel. It's not really extreme, but it's a little creepy when I'm up in the air. Once the cylinder reaches end of travel it does the usual bypass squealing noise without the vibration. Any idea what causes this?
Pulsing near end of cylinder travel
- Thread starter BeezFun
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Tx Jim
New Member
Have you checked the oil in level in the reservoir lately?
jinman
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- Feb 23, 2001
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- Texas - Wise County - Sunset
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- NHTC45D, NH LB75B, Ford Jubilee
The oil level could cause some problems, but you'd think it would show up at the end of the cylinder travel when you go into bypass. I think you may have wear inside the cylinder at the 'most used' portion. I'd bet that lift was used a lot at a height exactly where you are getting the shaky operation. The internal seal is probably leaking some due to wear on the cylinder walls at that point. New seals may cure the problem because they will take a new set better and be more flexible. Can you operate the lift from the ground? If so, I'd run it up to the point where it gets shaky and then shut off the engine/pump to see if you get the boom to drop a bit. Because you have pilot operated check valves, any movement will be because of internal cylinder leakage.
Yes, it's right up to the top and there are no leaks, so it never loses any.
This is at the very bottom of the cylinder stroke for the upper boom, so this is a frequently used point because it's the position required to lower the boom to get out, or to stow the boom.
Yes
Thanks I'll try that experiment. My real concern about this is whether this vibration represents the same kind of potential problem you have with water hammer, which creates extremely high pressures that the system is not designed to take. I don't really mind it vibrating this little bit, but I don't want to be doing additional damage by sending pressure spikes through the system.
I solved the problem, the cage leveling hydraulic system needed to be bled. This lift has a sensor under the cage so that as the boom raises and lowers the cage stays level. When the boom was at the extreme lowest point, the cage was in the extreme angle trying to keep itself level and there must have been air in the system. I followed the bleeding procedure in shop manual and that solved the problem.
Tx Jim
New Member
Glad you got it repaired. It's amazing the amount of useful information that's located in an operators manual.
