No!!!!
I have seen two Grove All Terraine cranes tip over, and a third that tipped off a dock into 50 feet of salt water. And a 50 ton truck crane tip over in a parking lot.
The first three accidents caused by over extending the crane capacity by first, picking a heavy load, then booming down. The salt water version was amplified by picking a load off a dock, then a combination of lowering the boom and swinging over the water. It's a funny feeling looking down into murky salt water, seeing a yellow glow, and knowing a 50 ton capacity crane is on the bottom. The operator was extremely lucky: One of the ground crew was an excellent swimmer, he dove off the dock, swam down into the cab, and pulled the operator out. Otherwise we would have had a drowning. We had to bring in a 300 ton barge mounted crane to retrive the 50 tonner from the drink. Loaded it directly on to a barge, then it went to a scrap yard.
Before using a crane, the operator must fully understand the capacity vs. the boom angle, the boom extension, and the distance of the load from the center pin, or swivel center, of the crane. For instance, a 50 ton crane has that capacity with the boom upright, retracted, and the outriggers extended fully and no rubber on the ground. Start squirting out that boom, or dropping the boom angle, and the capacity is rapidly reduced. The boom weight of hydraulic cranes can get you into trouble real fast, it is a much different animal from a cable stayed lattice boom crane.
I watched, from a distance, a operator turn over the 50 ton truck crane in a parking lot. He extended the boom straight out in front, flat out, so he had access to grease fittings. He did not have the outriggers out. Then this wise fool decided to swing the boom so he could lower the head of the boom closer to the ground. Got about a 30 degree angle to the right of the centerline of the truck chassis and she tipped over on the side. Took a 100 ton crane to upright it, plus a lot of bucks to get it back in operating condition.
Less than a month ago, in this area, a large all terraine crane tipped over frontwards. Crushed the cab and killed the operator. Booming down a heavy load caused this one.
In summary, have an experienced hand at the crane controls that fully understands what he is doing. I have been around a lot of crane usage, up to 300 ton cranes. A crane accident is very fast, no one has time to react, and they are extremely deadly. My rule when observing a crane pick was to be a distance at least the boom length away from the crane.
[This message has been edited by John Ricks (edited 04-04-2003).]