A client working in Off Shore had a contract for laying a pipe with vulnerable cover on the seabed. These pipes have to be welded on each other. That is why this vertical pipelaying vessel had placed a grabber at 50 meters above sealevel. The grabber should be able to position the pipe perfectly vertical so all pipes would be welded in a straight line. Due to waves and crane movements customer was afraid that the grabber would damage the surface of the pipe. Client accepted the solution of a rubber co extrusion Practical Solution did give although customer had other solutions in their minds. The solution was a co extrusion of rubber plates. The toplayer of this plate that would get in contact with the pipe was made of a hard rubber. A hard rubber has a less friction coefficient compared to a softer rubber. You want the friction to be low. Impact forces would be taken by a softer rubber underneath the harder rubber. With hollow chambers in the soft rubber you can play with impact energy ammounts. Due to low friction the soft surface of the pipe would not be ruptured off. Due to a soft underlayment also impact energy from ship movements (when the pipe is positioned by a crane) on the pipe can be delt with. This was again a very simple and effective solution for this challenge.
The client accepted this propesition although clinet had been thinking a lot how to solve this problem. I did also suggest a waterfilled damper. This damper could also absorb forces when the pipe swings to fast towards the grabber. The damper is placed on the grabber. By sending towards a zero point with adding or removing water positioning of the pipe would not be a problem. Customer thought of positioning problems and did not want to add this simple cheap and very effective (good shock absorbing) tool.
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