August 15th, 2010

St Petersburg Russia. Two Tower Cranes were blown over in windstorms noted as "hurricane's". Considering how often I see the translation to hurricane I wonder if big winds or heavy storm simply translates that way. In both cases the operators were in the cranes and injured. In one the female operator was hospitalized with a brain injury and she suffered a broken leg. Link

The picture of the downed crane appears to be a bottom slewing crane with the machinery at the base, and it's on rails. The failure is structural and in the in the mast. As you look at, what strikes me is that it would appear that the crane was still in operation. The machine deck is opposite of the jib, but it's blow over backwards. The assumption for me is that since the tower doesn't look twisted, it was facing the wind instead of away from the wind. Sometimes operators assume that this is OK because you are getting hit with a crosswind that catches the surface of the jib. But this doesn't take into account the whole picture. Tower cranes weather vane with the jib down wind also because they lean back into the wind when they do so. Imagine walking in heavy winds and leaning backwards instead of forwards to drive through the wind. If your crane is in operation during heavy winds, you are asking it to not only deal with the winds, but lean backwards at the same time. On many cranes the jibs also have positive lift when the jib is unloaded so you also might be losing a portion of the weight of the jib that normally holds it down due to the wind exposure on the bottom surface.

Don't be a hero in the wind. Most tower cranes are to be shutdown by 70 KPH or 42 MPH. Some are sooner. Adhere to it. You may be able to be the guy that runs into the 50's (MPH) for a career, but you only endanger yourself, and everyone else around your crane. There is no warning in structural failure. It will be immediate and unforgiving.  Shutdown the crane, find out what the weather is likely to be doing from a reliable service (In US eg. NOAA, Weather Net) and if it's not looking good and going to get worse, why would you stay in the crane? The climb is not that difficult.

крах башенный кран, аварии башенного крана