Abstract

Atlantic Richfield Indonesia, Inc. (ARII) operates a monopod well platform in 97 feet of water depth in the Java Sea. As a result of its dynamic characteristic, operating sea states of three to six foot wave heights were causing horizontal deck motion of up to 12 inches. This is three times more than static deflection. This level of movement causes severe motion sickness for operators remaining on the deck for more than a few minutes.

The design, installation and operation of such water filled liquid damper system was completed and the Tuned Liquid Damper (TLD) was tuned to the natural frequency of the monopod. The system is similar to systems which are used in Australia to dampen the motion of telecommunication towers. In this system, energy is absorbed by the sloshing action of the water contained in the tank.

Careful tuning of the size of the tank and mass of water, and optimally placed baffles within the tank result in the peak motion being reduced markedly compared with the undamped system. Measurement of deck motions before and after the installation of this TLD were made by Bandung Institute of Technology (ITB). Reduced deck motions were clearly demonstrated by these measurements.