Hi! This is my first post, but I've been lurking for a little while. Since this is something that plagues me constantly at work, I figured it would at least be worth asking about: My job often requires me to connect attachments at the end of the stick of an excavator (usually around the 20 ton range of CAT, Deere, and Komatsu). These attachments have a hydraulic motor on top (between the attachment and the yoke that is pinned to the bucket pin hole at the end of the stick). This allows the attachment to rotate 360 degrees. This may seem like a simple problem to have, but I really have no peers to approach for help, so thats why I come here. The problem occurs when I go to connect that hydraulic motor to the bucket curl circuit (where the steel lines terminate at the knuckle of the stick and boom) and more specifically, the problem is that I often get sprayed by pressurized (albeit not very high) oil when I disconnect the bucket curl rubber lines. Allow me to include a typical scenario, if it will help: I knuckle in the stick to get the fittings as low as possible. Let's say we're talking about the flat faced split flange fittings you would see on a Komatsu PC210, for example. I always turn the key back on, making sure the red lever near the door is in the 'operate' position, and move the joysticks all around, while the engine is off. This usually relieves enough pressure to make a noticeable change in how the stick/boom rest on the ground, just from the shear weight of those parts. When I feel that I have done my best to relieve the pressure from the bucket curl circuit (and relieved the tank pressure if there is a relief button/valve), I begin carefullly loosening the bolts that hold the clamps to the steel line. Usually, I'll undo the outermost half of the clamp system, then carefully loose the innermost clamp slowly. Sometimes, if there is pressure in the line, it will cause the oil to shoot outward from the stick. Other times, the pressure will be enough to blow out the o-ring while I'm loosening the fitting, and it seems to be unavoidable. Can anyone advise me (possibly some people that routinely install and disconnect attachments on excavators) on how to minimize pressurized oil spray in ways that I may not be seeing? Any help would be greatly appreciated!
On a 200 class machine that you are regularly disconnecting the lines, I would install some Stucchi couplers. You should be able to adapt from your flange fitting to a pipe or sae thread and install the couplers. They screw together even under pressure and won't spray you with oil. Every one of our machines has them on the AUX lines. I had the same issues with our EX700 but only had to deal with it a few times a year when I re-installed the stick after hauling it. I installed block off plates on the flanges that were cross drilled and added a bleeder valve to them. That way I could just bleed the lines into a bucket before I unbolted the plates. I got pretty good at judging how to position the bkt cyl when I removed the stick, only got wet a few times.
Are you attaching them permanently to the machines or the same attachment on lots of different machines?
We only put the attachment on for a few weeks at a time and it could be on any excavator from a Komatsu 210 to a Cat 330. Most of the time, its on a customer's hoe, so what I have to work with is just how they come from the factory, as far as bucket curl plumbing goes.
What I do is, have the bucket a few inches off the ground, hanging in the "neutral position". What I mean by that is about where the bucket will hang without the back pin in it. If you get it right, you can just about pull the back pin by hand, since it has no weight on it. Take out the back pin, then pull the cylinder in, but not all the way, stop an inch or so from bottomed out. Tie the rod end to the stick, then when you disconnect the hoses, there's nothing trying to move the cylinder rod. There should be nearly no pressure in the lines. When I'm putting the bucket back on, I put the main pin in, then lift the bucket a few inches off the ground. You don't have to fight to get the cylinder eye in the right place, just put the eye a few inches above the bucket eye and put your foot on the teeth and push down till it lines up.