Until recently, the typical causes of crane incidents were adverse weather, earthquakes, ship berthing procedure, and inattention to either operations or maintenance. But today’s situation has become much more complex.
First, due to increases in the number of quay cranes in operation over the past 15 years, there have been proportionate increases in the number of crane incidents. In addition, cranes have become much larger in size and are far more challenging to operate – with less visibility, controllability and slower response times due to
the greater working distances involved.
It is difficult to prevent damage caused by extreme weather conditions, such as typhoons/hurricanes or from earthquakes and tsunamis, the majority of crane incidents have a strong human component. For example, when mechanical or structural failures occur, these can often be traced back to deficiencies in human activities like crane maintenance, lack of adherence to safety standards, or even poor workmanship or design of the quay crane itself.
People also play a prominent role in collisions between vessels and quay cranes. These collisions occur when a movable part of a crane strikes a ship or when a moving vessel collides with a crane. Quay cranes are designed to lift vertical loads. While they can tolerate the horizontal loads of wind, storms and even minor tectonic shifting activity (earthquakes), they are not designed to absorb the abrupt impact from a collision with a vessel or an adjacent crane.
Even a brief impact from a vessel can significantly weaken a crane structure – even when little apparent external damage can be seen. The damage caused by a ship snagging a crane boom (in ‘boom down’ position) is especially vicious. This is due to the fact that when a vessel catches the forward tip of the crane boom, it is essentially using a lever with a long arm – thus multiplying the force. The tremendous force twists all of the main components of the structure, and in extreme cases, the crane will collapse.