How to bleed sealed bucket levelling system on bucket truck

[amanda11270]

I have an Altec AT series bucket truck, and some of the smaller hydraulic hoses are bubbled and need replaced. Most I can do easily as they all go to minor functions of the machine. However four of them are on the bucket leveling system. It appears to have the two hoses coming from the electric pump or return valving in the tower of the boom assy. They go to what looks like a manual valve assy on the top of the tower, where the hoses split between two that go to the power tilt function bucket, then to the sealed system auto leveling cylinder. My question is, are the things that look like manual valves that can be opened or closed with wrenches what I would use to bleed the air out after I change the hoses on the leveling cylinder lines (assuming its not going to bleed itself). Im sure the power tilt for the bucket will bleed itself, but the leveling I think I have to bleed my self. If you are not familiar with bucket trucks, its a small cylinder at the base of the boom, that has lines going up the boom that when the boom lifts, this small cylinders extends and levels the bucket using another cylinder at the end of the boom where the bucket is. But also this bucket can be power tilted as well. When I replace these leveling lines I think its gonna be all out of adjustment and would like to know where it is bled to adjust this.

I work as a refrigeration tech, electrician, plumber, but this is my first hoorah into hydraulics, I usually have a good idea how things work, just in the case I need a little information before proceeding, im not really messing with any of the heavy boom lift, or boom extension hoses, those are all larger sized and still in great shape. Just all these smaller 1/4 sized hoses have bubbles in them, and I would like to be proactive before they fail and start actually leaking fluid.

 

[willie59]

Welcome to HEF amanda11270. :drinkup

I've worked on a few Altec machines, not familiar with yours though and just which hoses you're replacing. However, if it's just a short length of hose, not much air will get in the system to affect bucket leveling. But if it's a good length of hose, I typically would replace the hose then crack open the hose fittings for the leveling cylinder at the bucket, operate manual leveling, and purge air from hoses in that manner. I hope this helps.

BTW, most bucket lifts like this use non-conductive hose assemblies. If that's the type of hose you're replacing, make sure you replace with equivalent and not wire braided conductive hose.

 

[amanda11270]

Thanks for the reply Willie59, I have 7 hoses total to replace. One is in the trunk of the boom about 12 inches long, its leaking badly. Two more are on the end of the boom at the bucket also about 12 inches long. The other four are all longer and go to the bucket, but they are for the leveling system and lower boom sections. They are all 1/4 size hoses. It seems to me that all the major function hoses are still in good shape, my 1/4 inch hoses had bubbles in the outer skin so im replacing them before they leak.

Do you know also, my Altec has full electric controls via toggle switches, everything has solenoid type valves that control the hydraulics. Four of the connections for my bucket control hoses are deep at the pivot point of the boom. If I lift the boom up (easier to get to these fittings), and break loose these 1/4 inch hoses, will they in anyway cause the boom lift cylinder (has larger separate 1/2 inch size hoses) to fall? I think im right about this and have been eyeing up changing these hoses for a couple days, and can probably do it by lifting the boom and supporting it with a jack at the boom base as a just in case, but I think its plumbed separate as far as I can see and these small hoses should not affect the large cylinder. I just don't want it to fall on me.

 

[willie59]

Of course I have to add a legal disclaimer and say you shouldn't do that, and that the Altec manual most likely recommends supporting the boom while it's elevated, again, for legal liability reasons. But to be real, if you fully raise the boom and disconnect those 1/4" hoses it shouldn't cause the boom to do anything as 1) they have nothing to do with the boom circuit, and 2) the boom hoist cylinder has holding valves on the cylinder. Those holding valves lock the oil in the boom hoist cylinder to prevent it from crashing to the ground (with you in the bucket) in the event that the hose/hoses that control boom hoist cylinder were to burst. Nevertheless, do keep your wits about you when working under the elevated boom.

 

[amanda11270]

Thanks for the reply, everything you said is exactly what I had figured. I planned on possibly lifting the boom just enuf to access the hoses under it, and putting a small bottle jack underneath it between the rubber stop on the lower turret arm and the boom arm as a precaution in case it does want to drift downward. I changed two real short hoses on the upper boom tonight from boom arm to the bucket tilt cylinder and they were in the leveling circuit also, and the whole boom arm didn't move at all, just the bucket tilted slightly.

Another thought I had was, I do lighting work for a local small warehouse and know the owner sorta well, I was thinking of possibly seeing if I could maybe borrow their forklift sometime after hours or weekend they are in and not working in trade for a future repair/project. Im sure Altec probably recommends something of that sort as support for the boom arm.

 

[willie59]

Sounds like you're on top of it. Keep in mind though, although a forklift would be comforting in supporting the boom for repairs, an industrial forklift does not have the holding valves on the mast cylinder like your Altec boom does. That forklift mast could not only leak down, but it could also come crashing down in the event of a mast cylinder hose failure.

 

[mitch504]

I thought forklifts had holding valves, I guess I'll start distrusting them more severely now.

 

[willie59]

Generally speaking, telehandler type forklifts have holding valves mitch, industrial type forklifts typically don't. They may have a velocity fuse on the mast cylinder, but not holding valves. Again, speaking in general.

 

[amanda11270]

I got a leaking hose replaced in what I would call the boom tower, its below the turret at the base of the boom, near the fluid tank, what a pain in the butt to get to, I had to undo a few things to get to this 12 inch long hose that was leaking right at a sharp bend in it. I also replaced the spin on filter as well. Hopefully Saturday I will have all my hoses done, im saving the ones at the upper turret under the boom for when I have enuf time to do them all in one shot.

I have another question about my truck though. Why do the hydraulics make squealing sounds in certain functions, and what I would call normal hydraulic sounds in others. Example: The bucket tilt makes a squealing sound when I use the power tilt function always, the large boom lift cylinder sounds like what I would call normal hydraulic sounds going up, but coming down it makes the more of a squealing sound. The extend and retract, never makes a squealing sound. Is this because of the holding valves?

 

[willie59]

I have another question about my truck though. Why do the hydraulics make squealing sounds in certain functions, and what I would call normal hydraulic sounds in others. Example: The bucket tilt makes a squealing sound when I use the power tilt function always, the large boom lift cylinder sounds like what I would call normal hydraulic sounds going up, but coming down it makes the more of a squealing sound. The extend and retract, never makes a squealing sound. Is this because of the holding valves?

It's likely quite normal sounds for your machine. Generally speaking, squealing sounds in hydraulic operations are generated by a restriction to flow. In the case of your bucket leveling, it's likely they have either fixed or adjustable orifice valves that will only allow the leveling to move at a determined slow speed. In simpler terms, the pump on your rig has enough output to make the large boom lift cylinder move relatively fast by moving a lot of oil. If you applied this same amount of oil output from the pump to that little bitty cylinder on the bucket leveling, the bucket would move so fast you'd think you were on a mechanical bull. The squeal from booming down is likely from the counterbalance valve (holding valve). Harder to explain that the bucket leveling with an orifice valve, but same result. The counterbalance valve is restricting oil flowing through it, much like an orifice, to prevent boom from simply "dropping" when you boom down, it's holding back pressure on the boom down circuit. For lack of a better description, imagine the counterbalance valve being a "descent speed control" valve. I hope this helps.

 

[amanda11270]

Thanks again for all the help, I did all my lines this morning, but found two more that do the extend/retract function split with steel braid showing. Im gonna order and do them next. Today I used my jack as I was cautious to break free those lines with the boom sitting on the hydraulics alone, but it wasnt necessary, the jack I mean.

The extend/retract lines I have to do with the boom fully up, as there is no access otherwise. They are the ones in the photo with white paint flaking on them, I think those are the last original ones on the machine.

 

[buteomont]

Bucket is not level, anyone know how to level it?

I have a '97 F450 w/Telsta bucket lift. The bucket is not level - it stays the same amount of out-of-level if it's up, down, or anywhere in between. I can't figure out how to adjust the hydraulic leveling cylinder though. There are some adjustments on the cylinder attached to the bucket, but I'm not sure if they will help or not and I don't want to mess it up worse than it already is. Anyone know how to level the bucket?



Thanks!

 

[amanda11270]

I have since sold my altec truck due to lack of use, I now miss it for hanging my xmas lights. However if I remember correctly the bucket levelling was a sealed system that had a way to freewheel the bucket back to level or wherever you want it. From that point it was self levelling, it scared me replacing those lines as I learned all this as I went.

 

[Imdavid]

If anyone needs parts for telsta a28d lifts, including hydraforce pressure relief valves (rv3 and rv5?)or parts for altec at200 lifts, shoot me a message. I have many parts available. I do apologize if this isn't the correct forum to say that I have things for sale, I just realize how hard it is to find certain parts for some of these lifts.

 

[Dead Silence]

If anyone needs parts for telsta a28d lifts, including hydraforce pressure relief valves (rv3 and rv5?)or parts for altec at200 lifts, shoot me a message. I have many parts available. I do apologize if this isn't the correct forum to say that I have things for sale, I just realize how hard it is to find certain parts for some of these lifts.

I have a lift truck (A-28D) with the boom sawed off and the leveling lines plumed together. I got the inner boom to move out about 2 inches and that's it. I've trjed bleeding the lines at the end of the boom. Any ideas?

 

[Naomi040507]

If anyone needs parts for telsta a28d lifts, including hydraforce pressure relief valves (rv3 and rv5?)or parts for altec at200 lifts, shoot me a message. I have many parts available. I do apologize if this isn't the correct forum to say that I have things for sale, I just realize how hard it is to find certain parts for some of these lifts.

Im actually looking for that bucket stabilizer cylinder for a28d, if you have one. The one on my had a part #c301 if it helps.

 

[ljbaker09]

I need parts for an at200 badly

 

[Pfm0482]

Telsta 28 boom when raised slowly falls

Have sevral telsta tel28 but one is giving me problems when out working you raise to hight needed and at a blink of an eye the boom has fallen and your on top or up aginst something and no signs of leaks I noticed some square blocks on cylinder with electric wires are those pressure holding valves. ..can someone help me also have 2 of these trucks for parts

 

[CHRIS74]

Do you have a bucket leveling cylinder for an A28D bucket truck

 

[David1]

Do you have a bucket leveling cylinder for an A28D bucket truck

I haven't been on the forum in quite a while, but I do have the cylinder you. If anyone need a28 or at200 parts, the best way to contact me is 614-352-6052. Thanks