Deployment Loads of Large Systems to Deep Waters by Aramid Umbilical Cable

The cable loads during lifting and lowering of a deep-sea system through the various depths need to be assessed for safe and reliable operation in the high seas. The accurate estimation of these loads during lifting and lowering would reduce the risk to equipment and operations waiting period at the site and increase the safety level, weather window, and operation duration.During trials at sea, a deep-sea vehicle was lifted and lowered from a ship by a subsea umbilical cable. The loads on the umbilical cable at the ship end were the resultant of the deep-sea vehicle, umbilical cable, ship motion, and environmental condition.The lifting and lowering loads during various depths were calculated from DNV-RP-H103, Modelling, and Analysis of Marine Operations [1], and Non-linear finite element analysis software - Orcaflex modelling and analysis [2].The subsea lifting and lowering [3] consist of the following phases Liftoff from the deck and shifting object near water zone, Lowering through the wave zone, Further lowering down to the seabed, Touchdown on the seabed, Crawling or locomotion on the seabed (optional) Lifting from the seabed, Further lifting up to sea surface, Lifting through the wave zone and Liftoff from wave zone and placement on deck.This paper examines the loads acting at various depths by, Calculating by DNV code and Orcaflex analysis software. The hydrodynamic coefficients for vehicle, cable, are taken from the DNV code. The details and properties of vehicle (deep-sea structure), cable, ship, and environmental conditions are modelled in Orcaflex software for analysis.