Hi All!
I apologize if this is in the wrong forum section. I considered the accessories section, but that seemed more for actual machine accessories.
Several years ago I was given a hydraulically lifted scissor table which is an older version of Harbor Freight #69148. When last I used it, it worked fine. But it was not used for a couple of months & now won't lift. There were no oil drips under it and the reservoir was full when I removed the fill cap.
I am guessing that many people here have hydraulic equipment in their shops and may have encountered the problems my table is presenting. Hopefully you all will see where I'm going wrong with my attempted repairs.
I tried purging air with every method I could find.
In the past, the most success I've had is to: Fill the cylinder, put the fill plug in, hold the release (lowering) lever while pumping slowly about 20 times. Then I'd remove the fill plug while holding the release lever to let air escape. Then I'd repeat as needed. No luck this time.
I removed the cylinder and took it to the bench for testing. I drained the fluid to look for chips or other debris & to get a new start with fresh hydraulic oil (ISO 32). It is set up at the angle it is while in the table. (Photo Attached)
Here are my amateur's diagnostic steps:
On The Bench:
I repeated the air purge procedure. No air was expelled.
While pumping, some light pressure had to be on the ram, pushing it back into the cylinder. If no pressure was applied, the ram would not move. Very light palm pressure worked and the ram pumped up and down quite well. It would go to it's full travel distance.
When pumped up, the ram held fast & fully extended until the release lever was pressed. Then, I could push the ram back into the cylinder. The last 1/2 inch was quite hard to push.
Back In The Table:
The cylinder would not lift, even if pressure was put on the ram while pumping. (I carried it to the table vertically- ram up- so no air would mix with the oil. I also had the table propped up vertically while installing.)
If I lift the scissors by hand to fully extend the ram, the table will drop back down about 1/2 way and stay in place - even overnight.
I tried loading about 600 pounds on the table and the ram did not lower until I squeezed the release lever. Then it lowered as it should.
If I lift the table by hand and let it settle to where it stops, more pumping does not raise it further.
Back On The Bench:
I removed it from the table, took it to the bench and it would not pump up.
I removed the fluid and inspected it for debris. None was found.
I also tried draining & using ISO 68. The symptoms didn't change. (I didn't try ISO 100)
The manual is mute on which weight of oil to use.
My Summations:
A) No seals are leaking because no oil was under it after not using it for 2 months. No oil is leaking now.
B) It seems that the release system is holding because if the ram is lifted by hand, it held the 600 pounds.
C) The safety is not releasing because a manually lifted table can be loaded with weight.
D) I don't think the seal on the ram's piston is bad because a manually lifted table will stay up overnight.
My Confusion:
A) The pump is suspect because the ram won't lift, but no more air is coming out when purging.
OR...
B) I am also suspecting that I am not purging the air properly. (I even let it sit with the ram extended for a day to see if more air rose out of the system. No luck)
C) The fluid level is OK because the level is at the fill plug opening when the ram is retracted.
D) I have absolutely no idea why, while on the bench, I have to press lightly on the ram to get the pump to raise it.
Attached is a photo of what this hydraulic pump looks like. I apologize that I'm not the best of photographers!
Thank You All for any ideas you can lend to this project. I'm stumped!
Enjoy This Day!
Paul
I apologize if this is in the wrong forum section. I considered the accessories section, but that seemed more for actual machine accessories.
Several years ago I was given a hydraulically lifted scissor table which is an older version of Harbor Freight #69148. When last I used it, it worked fine. But it was not used for a couple of months & now won't lift. There were no oil drips under it and the reservoir was full when I removed the fill cap.
I am guessing that many people here have hydraulic equipment in their shops and may have encountered the problems my table is presenting. Hopefully you all will see where I'm going wrong with my attempted repairs.
I tried purging air with every method I could find.
In the past, the most success I've had is to: Fill the cylinder, put the fill plug in, hold the release (lowering) lever while pumping slowly about 20 times. Then I'd remove the fill plug while holding the release lever to let air escape. Then I'd repeat as needed. No luck this time.
I removed the cylinder and took it to the bench for testing. I drained the fluid to look for chips or other debris & to get a new start with fresh hydraulic oil (ISO 32). It is set up at the angle it is while in the table. (Photo Attached)
Here are my amateur's diagnostic steps:
On The Bench:
I repeated the air purge procedure. No air was expelled.
While pumping, some light pressure had to be on the ram, pushing it back into the cylinder. If no pressure was applied, the ram would not move. Very light palm pressure worked and the ram pumped up and down quite well. It would go to it's full travel distance.
When pumped up, the ram held fast & fully extended until the release lever was pressed. Then, I could push the ram back into the cylinder. The last 1/2 inch was quite hard to push.
Back In The Table:
The cylinder would not lift, even if pressure was put on the ram while pumping. (I carried it to the table vertically- ram up- so no air would mix with the oil. I also had the table propped up vertically while installing.)
If I lift the scissors by hand to fully extend the ram, the table will drop back down about 1/2 way and stay in place - even overnight.
I tried loading about 600 pounds on the table and the ram did not lower until I squeezed the release lever. Then it lowered as it should.
If I lift the table by hand and let it settle to where it stops, more pumping does not raise it further.
Back On The Bench:
I removed it from the table, took it to the bench and it would not pump up.
I removed the fluid and inspected it for debris. None was found.
I also tried draining & using ISO 68. The symptoms didn't change. (I didn't try ISO 100)
The manual is mute on which weight of oil to use.
My Summations:
A) No seals are leaking because no oil was under it after not using it for 2 months. No oil is leaking now.
B) It seems that the release system is holding because if the ram is lifted by hand, it held the 600 pounds.
C) The safety is not releasing because a manually lifted table can be loaded with weight.
D) I don't think the seal on the ram's piston is bad because a manually lifted table will stay up overnight.
My Confusion:
A) The pump is suspect because the ram won't lift, but no more air is coming out when purging.
OR...
B) I am also suspecting that I am not purging the air properly. (I even let it sit with the ram extended for a day to see if more air rose out of the system. No luck)
C) The fluid level is OK because the level is at the fill plug opening when the ram is retracted.
D) I have absolutely no idea why, while on the bench, I have to press lightly on the ram to get the pump to raise it.
Attached is a photo of what this hydraulic pump looks like. I apologize that I'm not the best of photographers!
Thank You All for any ideas you can lend to this project. I'm stumped!
Enjoy This Day!
Paul