Another tipped mobile crane today. This time over in eastern Switzerland, exactly the same model as we have frequently used these past years – as was the case in the jobs I posted about recently.
Ok, I will be the first person to admit that it can be hard to get your load estimates spot on, depending upon the condition of the tree and the time of year. As I was writing about in that post I linked to above, sometimes you get it wrong. But even then, there is usually still margin for error, not that I am advocating to bank upon the fact, mind you, the aim has to be to get it right.
But this accident is way beyond anything like that… the crane was parked up on a terrace above the forested area they were removing trees out of. In the images you can see the way they were working their way backwards, which makes sense, as you are successively clearing work space for the next pick as you go, so far so good.
It is hard to tell from the images, but if I had to make a guess the tree covered in ivy in the right hand image went the wrong way, was hung below the centre of gravity, so that it tipped away from the crane, not only overloading it, but tipping it over the ledge and down into the gulley.
Incredibly, no one was hurt, there were forestry workers to either side of where the boom impacted, the driver was operating the crane with the remote… this could have ended a lot worse! Having said that, the material damage is quite considerable, the crane leaked oil into a stream, so an oil barrier had to be erected, and also – needless to say – the crane is totalled. This is not the kind of damage you are going to pay for with your pocket money.
I am not writing this in a gleeful or gloating spirit, on the contrary, I am very glad to hear that no one was hurt, and alway feel for the crew on site when something goes this badly wrong. Having said that, you cannot help but wonder what exactly did go wrong here. First and foremost, the load attached was obviously too heavy. At the risk of boring you, I cannot emphasise enough the need to document picks! Document the estimated and actual load. In writing. How else is one supposed to have a learning effect? One could well imagine how in the case above, the forestry crew were oblivious to the fact that as they were moving away from the crane they were successively chewing into its load capacity, but as the loads were not explicitly being called out and noted, this point was missed. All you need then is a tree which is heavier than the rest, not clear line of sight to the crane operator and hey presto! One tipped crane.
This is all admittedly highly speculative. The facts will certainly emerge as time goes by, but cranes do not tip by their own accord, there is almost always operator/ human error involved – a bad call, target fixation, lack of experience or somebody in a rush to get the job done. The good news is though that there are relatively easy checks and balances to put in place to decrease the likelihood of this kind of accident from happening: site briefings involving all persons on site before work starts, clear communication channels, clear designation of roles, documentation and evaluation of picks, correctly slinging the pieces – and factoring in a margin of error.
Expect the unexpected. And remember: every day you do not tip a crane is a good day.