Thinking about building a scrapyard and what crane to use made me think…
As a rule…
(NB someone will come up with exceptions)
If the load isn’t vertically under the lifting point it either can’t be lifted or will be a dangerous lift.
Loads are normally lifted with the lifting point as close as possible vertically over their centre of gravity - the exception to this is to lift all the corners (but the lift point will still be as close as possible over the cog or special arrangements will be made - or to lift one end, support it and then lift the other - or to lift with more than one crane… the alternatives need care.
These add up to the simple fact that lifts are made safely when they are made vertically.
Loads are normally lifted only as far as necessary to clear anything they will move over and then moved before any final hoist to height is made… this keeps the centre of gravity low… this also means that if rushed a pendulum effect may occur… but a pendulum near the ground which may be lowered is a lot better than a pendulum sticking up from the ground in the form of a jib with a big weight near the top.
Guy ropes may be used to control a lifted load.
Slings and things are a specialist skill…
Mostly cranes are located, made stable and then used to lift. Many mobile cranes have stabliising legs which effectively fix them while they lift. It is safer to stabilise, lift, place, move, stabilise, lift, place and so on than to lift and travel.
Cranes need firm bases to work from.
Cranes fall over when things are done wrong - possible model scene there
Sometimes tall or long jibbed cranes buckle.
Where Cranes are used to unload trucks or cars the truck or car needs to be able to get under them or the lifting point of the crane able to get over them… obvious… but look at a lot of models… this also means space for semis to manouvre…
Use wire rope or nylon straps for rigging, not chains.
Understand the strengths and weaknesses of chokers, spreaders and tag lines, and use them when appropriate. Avoid low angles (near horizontal) in rigging. All rigging should be inspected before every lift.
Plan set-ups to avoid powerlines, and lifting over areas used by people, occupied buildings, and vehicles. Maintain as high of a vertical angle on the boom as possible, during all lifts, even if it means tearing down and setting up in a new place, or even if it requires getting a different crane…
Riding the ball costs ten grand if OSHA catches you.
Outriggersd must extend so that the entire crane is off the road wheels. No rubber touching ground during a lift.
Although a vertical drop can be accomplished 122 feet from the center pin on a crane with a 120 foot boom, by using a tagline to swing the main cable out of plumb, the wise operator will add a jib or get a bigger crane.
Modern cranes are not designed to operate near maximum rated capacity. By the time a modern crane “goes light” on one or more axis, serious damage may have already been done to the turntable, boom and outriggers.
ONE signalman communicates directly with the crane operator, taking his cues from the lift supervisor, and ONE supervisor is in charge of any given lift.
When the signalman is not instantly obeyed by the crane operator, all onsite personnel should clear the area described by a horizontal boom (plus jib) height radius from the center pin, plus 50 feet. Clutch failures aren’t as rare as you think.
Sudden stops, starts or unintentional grounding, especially when slewing, booming out, or booming in can tip the crane by momentum effects. Slow and steady movement is safest.
Simple rule for crane-watchers (aka sidewalk superintendents):
Do your watching from across the street, down the block or the rooftop restaurant of the next-door casino. If you have to raise your eyes more than 45 degrees from the horizontal to see the top of the highest point on the crane, you’re too !!! close!
Chuck (From Sin City, where there are a LOT of cranes in use)
Don’t raise the jib/boom near powerlines unless they are certified as isolated by the power company. (On UK railways there are warning signs at trackside both sides of anywhere overhead powerlines cross the track. Don’t know if you do this in the US).
Same applies on overhead electric lines. 3rd Rail has to be isolated before outriggers are put out.
Load weight plus distance is also a factor. A couple of years ago I was in on an investigation of a turnover accident of a 250 ton rubber tired road crane. They were trying to lift an object weighing only a few tons, but it was out too far. The operator thought big crane, small load and everyone is in a hurry - don’t bother taking the time for outriggers and over the crane went. Fortunately, no injuries, but most of a day’s work was lost including bringing in 2 cranes from another site to set the crane back on its wheels.
From first hand obsevation…Crane operator drops magnet, magnetizes the magnet, brings up scrap,swings 180 degrees and drops scrap by demagnetizing the magnet and swings crane back around 180 degrees to the scrap pile and repeats the above moves till the gon/truck is loaded.Its as simple as that.
The Big Blue accident is a famous incident among Wisconsinites. It occured while workers were constructing a new baseball stadium for the Milwaukee Brewers, known as Miller Park. The Stadium has retractable roof sections in a “fan” pattern, and as they were lifiting one of the ginormous roof panels the crane collapsed. It delayed the opening of the park by about a year between the investigation, clean up, and rebuilding. When the stadium first opened the Brewer’s put a memorial outside the Stadium honoring those who were killed. A very, very sad and unfortunate accident. It’s a shocking video to watch too, especially when you see it for the first time.
If you read bit between the lines, you’ll see that Item Six on my list addresses precisely this point.
Matter of fact, so does Item Seven.
Never laid one over, not yet anyway, but when I sat back into the tagline to swing the truss out the extra two feet so it could slide down into the vertical saddle, I pretty much had a 50 ton crane balanced on one corner.
The nearest outrigger shattered a two layer mat made out of four by fours and dug an 18 inch hole below that.
