sort of in a pinch and need our 20T crane to get a machine off a trailer coming in. Our machine coming in will weigh around 31000 and figuring 1000 for dead loads on the block and wires. At the radius we need just to get centered up over the trailer will have about 28-29Klbs "rated" capacity in the crane. Now about the only thing we need to do is lift, pull truck out, lower, done, and machine is low value, but I am wondering if we need to dig up some counter weight to wiggle this job out or if a RT telescopic crane would typically have a little extra in it?
Depends. We talking about grove or something else. The crane won't go over at that radius. Your in the structural part of the load chart there. These kind of picks are where booms get bent. You can't get a forklift or something to take a little of the load. That's what I'd do.
Extra counterweight isn't going to help, as knepptune says, you're in the structural portion of the chart. That means you don't tip, you break when you exceed capacity. " Chart" is 85% of true capacity. Figuring 1000lbs for rigging and block, are you counting stowed jib, aux head, unused line? Is it 28 or 29k? 3' of radius can make a huge difference in a max pick, are you sure about all of it?. You have enough rigging to handle it? Not just the tie down chains from the trailer? Your operator does this every day, and isn't going to be boomed down a touch too far, when he gets a little boom deflection, and it slides on the trailer, dragging him up with it? You're thinking 32,000 total load, and only good for 28k, that would be past my personal comfort level. My comfort level stops at 10% over chart. If your good for 28k, 10% is a extra 2,800. That bumps you to 30,800, and you're 1,200 over that. You say its a low value item. What's the crane worth? What's the truck and trailer worth that's bringing it? What's your business worth? What's the guy on the tag lines life worth? If someone gets killed, you get to live with that forever, I don't want to tell someone she's now a widow. I almost lost my business 8 years ago, when a operator working for me, dumped a crane, and I thank the good lord every time I think about it, not so much about the business, but because its a miracle 4 guys didn't lose their lives that day. Accidents happen as a chain, a series of events, and when I did my personal post accident review, at any point in 5 series of things, someone had stopped, none of it would have happened. I don't go looking for reasons to go past safe, the job is dangerous enough as it is, don't go looking for trouble to save a buck. That said, and with me off of my soap box of spouting off, (sorry) Within a hour of my shop, I'd be under $1,000 to unload it, California, is probably more, but probably not $1,500.
Obviously I am thinking about it way in advance, which means I am well aware of the situation and concerns. I am already calculating a few things as worst case. The machine may weigh as little as 27,800 but other records show it as 30,700. the manual jib is removed from the crane. Yes we have several 40K "rated" straps. We do have professional structural engineers here and do plenty of math, so we are going off half cocked here, and we all intend to make it home safe. If we need to supplement the lift, thats what we have to do, but I tend to think we have enough wiggle in this. I am estimating the radius at 15ft, but actual radius needs to be 13.25ft if we are getting down to the inch, which boost capacity just over 30K. If it really came down to it, we have a few items that can be removed from the machine to get the weight into the sweet spot.
Great- just have your professional structural engineers redo the math on your 20 ton, call it a 40 ton and do what you want. If this is the old omega 20ton you asked some questions about a while back, there's no 13.25' chart. Its 10-12-15'. over 12' you use the 15' chart. That said, you say this item is coming in on a truck. Most trucks I'm familiar with are at least 8' wide, but your in california, so who knows. If its that p&h, its 9' 6" to your front bumper, plus 4' to the center of the trailer, so your just a tick under 15', 13' 6" to be exact if your bumper is on the trailer, which will be fun when the trailer comes up with the air bags when your lifting the load, dragging his trailer rails up the bumper of the crane, but what do I know, I do this everyday, have your engineers draw it out. Even if your over the side, which is structurally the weaker position (I'm not a engineer though- you better have yours check that out) the crane is 17' 7" wide to the outside of the pads, meaning 8' 9 1/2" to the center plus 4' to the center of the trailer (better hope its not a 102" trailer) you're knocking on 13' of radius, reality says your going to be 15'. The charts I'm seeing online (P&H omega 20 ton rt) are 32,000 at 12' and 26,000 at 15'. Minimum your showing for your item is 27,800 so your going to be over in the best case, not worst case. If you've got a different crane, then that changes things. I don't understand it, and maybe I'm missing some part of the general idea here. You don't know enough about what your doing, so you post here looking for advice. knepptune and I give you the advice that should be given (and really if you don't do it every day, chart should be chart), and now you and your engineers are all up on the fact, that the charts the factory boys put out in 1975, don't really mean what they said. You "feel" there's wiggle room? Your wear pads on the crane are all up to snuff, and you're sure your perfectly level so your not side loading. Those omega's don't have the best turntable to frame connection, usually that's where they let loose when they've been abused (I'm sure yours hasn't, and its in better shape than when it left the factory, so don't worry about pushing it). You're already over your capacity on best case, not worst case. If you told your boss "no problem, we can unload it", and now your really worried about doing it, fess up and tell him you can't. If you are the boss, why would you do something like this? If it really doesn't matter what happens to what your unloading, hook a chain to it and drag it off the trailer. Anyone that really knows cranes,(does it for a living), is going to tell you a 20 ton rt really isn't enough crane for unloading 32,000. And if what the guys, who do it every day, have to say about it really doesn't matter, why ask?
Be careful, Hot and toasty, Just happened today! A client, fooled the operator, told him 7 tons and it was 20+! It is a 50 ton crane by the way!
So are the manufactures' "rated" capacities just suggestions? That would be great... my 56,000lb GVW dump truck should have "wiggle" room to carry 65,000lb and my 12,000lb trailer should haul my 17,000lb Cat. I only have to move it a few miles, what could possibly go wrong. Oh, you were talking about a crane, nothing ever goes wrong with a big lift...
Hate to beat a dead horse but sometimes you have to make sure he's really dead. One other factor not mentioned here is boom length. No way your making that pick without running some boom out. Or it would be really odd. There's more chart gone. If you have very short rigging maybe you won't but picking something off a trailer with no boom out is rare. Especially on a small crane like yours. I dk about crane op but I was always way more comfortable pushing my chart in the stability part of the chart. If the crane gets light just dump the load. You overload in the structural part of the chart and you don't know when it's to much until something gives.
I do similar stuff, machinery moving and truck unloading, and in this instance I would bring an additional 15k forklift. This is kind of risky stuff and a tiny mistake may be irreversible, so better to be careful.