New calculation method for riser-tensioner ropes

Riser-tensioner ropes are constantly stressed ropes. Depending on the heave amplitude of the platform only short rope sections are stressed by bending cycles. For equalized utilization of ropes they will be slipped and cut-off regularly. The time interval between two slipping procedures will be determined by the number of ton-cycles, which will be calculated as product of rope load and number of heave cycles. The slipping length and the number of ton-cycles between two slipping procedures is given by manufacturers of Riser-Tensioners or by experience. The improved fatigue behavior of modern rope constructions will not be considered appropriately. In the following a calculation method will be presented which gives an optimized slipping length in dependence of geometry of Riser-Tensioner and heave amplitude as well as an optimized time interval between two slipping procedures in dependence of used rope construction.

Author(s): Briem, U.