Pipelay Systems’ design and build high performance, flexible lay systems capable of installing flexible flowlines and risers, umbilical and power cables.
A typical flex-lay system will be a Vertical Lay System (VLS) or a Horizontal Lay System (HLS). The VLS is a tower fitted with a top aligner, tensioner(s), worktable, clamp and dedicated A&R system and lays product vertically to the seabed with tensions of 75Te and above. The HLS is a structure that supports a tensioner(s) and an over-boarding chute with the vessel crane and deck winch doing A&R functions, lay tensions are generally below 75Te and the product is laid in an S-lay configuration.
Flex-lay systems are generally supplied with a storage device to hold the product. These are typically basket carousels or small product reels used with a standard Reel Drive System (RDS).
A VLS is designed for use over a moonpool or the port /starboard sides of a vessel. They are generally not used over the stern because of the difficulty carrying out basic operations in a typical sea state due to the amount of relative vessel movement.
The simplest VLS comprises an Aligner Module, a Tensioner and a Work Platform with clamping carried out by a temporary clamping arrangement and A&R functions handled by a suitable crane. Alternatively, the VLS can house an Aligner, Tensioner, Centraliser(s), Collar Clamp, Work Platform, Gantry Hoists, Tuggers and dedicated A&R System allowing it to be self-contained and operate independent of the vessel crane.
The VLS can be designed as a permanent installation on the vessel or as a modular construction suitable for vessels of convenience.
A typical VLS is shown below
A HLS is designed for use over the port, starboard or stern of the vessel with most used over the stern, especially for cable lay.
A basic HLS comprises a tensioner and overboarding chute with the equipment mounted directly to the deck and the crane doing all A&R functions. On the other hand, Pipelay Systems is also able to supply more complex HLS with a tensioner(s), angled support structure, chute, work platform with handling aids, clamp and dedicated A&R system.
Most HLS type systems are designed to be modular in construction for ease of installation or removal.
Both the HLS and VLS are used with a storage device to hold the product. For power cable this is a basket carousel where a large capacity of product can be stored for a single campaign, typically 5000Te to 10000Te. For flexible flowlines and risers of long lengths a basket carousel (or carousel) is used and for short lengths a Reel Drive System (RDS) is used. For long lengths of umbilical, a carousel is preferred so that the end terminations can be easily stored on the roof, while for short lengths a Reel Drive System (RDS) is often used.
Carousels can be supplied with partitions to allow multiple single products to be stored and for power cable where two types of cable are bundled and laid together. Carousels can also be provided as split units where an inner and outer segment run independently at different speeds (rpm) to match the product lay speed.
Some vessels use the basket carousel as the permanent installed feature and change the lay system between a VLS for flexible pipes and umbilicals, and an HLS for power cables, Pipelay Systems can assist with this change.