In Newport we found a washer on deck below the crane and concluded we likely had a critical crane issue, so stopped using it until we understood the problem. We later found a bolt on deck as we arrived into Baltimore. It was pretty clear that something was coming apart in the crane.
James took the crane apart and found the boom extension hydraulic ram mounting bolts were all loose. Two bolts were close to falling out, and the other two had fallen out, damaging the threads on the way out under load. It’s good that we caught it before more damage was done.
The boom extension ram has welded-on tabs for bolts visible in the second picture below. The tabs don’t bolt down flush and consequently the bolts flex under load and loosen off. We tapped out and installed ¼” longer bolts. Then we put washers underneath to space up to the excessively high tabs and torqued them all down with Loctite. This issue is now resolved and it will no longer flex and self loosen.
There was a second crane issue we wanted to attend to at the same time. The up/down rope was starting to show some friction when operating without load. We suspected it was just friction in the sheaves the rope runs over inside the boom extension. Unfortunately, the sheaves can only be accessed after removing the boom extension from the crane and then removing the linear winch from the boom extension.
Removing the boom extension requires taking off the hydraulic lines driving the linear winch and then removing the four screws that attach the hydraulic extension ram mentioned above to the push block. This is same ram that had come free from the boom but we’re now looking at the other end of the ram where it attaches to the boom extension.
Here we had the opposite problem. Rather than come loose, the stainless screws were effectively welded into the aluminum housing by rust. You can see some bubbling paint in the region in the second picture below. James applied progressively more force until eventually he was using an impact wrench One hex key socket twisted (first picture below), and one screw was damaged. There was no way they were coming out.
We next tried an Easy Out. It took progressively more load until it shattered predictably with part of the easy out still in the hole (second picture below). We were able to remove the Easy Out but it’s clear that these four screws will need to be drilled out in order to lubricate the linear winch sheaves and replace the lifting rope. Neither job is urgent so we decided to order parts and return the crane to work. We’ll open it up again for this second job once we have the parts and the time.
While failing to remove the boom extension, we were able to get the extension nose casting out, which includes the nose pulley. Minor corrosion was causing the pulley to have more friction than it should. We cleaned off the corrosion and lubricated the friction surfaces which helps the up/down operation to operate freely without excessive friction. But we will need to eventually take out the linear winch to lube those parts as well. For now the crane is back to the safe and reliable operation we have come to expect from it.