Coselle™
The heart of Sea NG’s technology is the “Coselle” high-pressure gas storage module. Coselle is an acronym for “coiled pipe in a carousel”.
A single Coselle consists of seventeen kilometers (~10 miles) of 168 mm (6”) diameter high-strength line pipe that has been coiled into a reel-like support structure called a carousel. Natural gas is contained in the pipe at a pressure of about 220 bar (~3,200 psig). Each Coselle can contain approximately 3.3 MMscf (~94,000 scm) of natural gas at near ambient temperature. This is an extremely large amount of gas for a single container.
Cut-away of Coselle
larger imageCoselles are stacked within the ship’s hold, and connected using a proprietary manifold and control system. These Coselle stacks are configured in different numbers in a series of ship designs offering ship capacities between 50 and 500 MMscf per ship.
The Coselle gas storage system has been fully designed and extensively tested, and has received full approval from the American Bureau of Shipping.
Advantages of the Coselle gas storage system:
Safety
Inherent safety is assured by the small cross sectional area of the pipe. Independent analysis by both DNV and ABS has concluded that even under the most severe failure modes, the resulting natural gas release can be safely vented to atmosphere with no damage to adjacent Coselles or ship structure. The carousels and cargo house are filled with inert gas to further enhance safety.
Inspection
The Coselles are coiled pipelines and can therefore be fully inspected using well proven gas pipeline inspection techniques.
Stacked Coselle
larger imageHigh Integrity
Sea NG ships have relatively few Coselles and therefore need only a simple manifold with few valves and fittings to connect them. All valves and fittings are located on the ship’s deck, facilitating maintenance and minimizing operating costs.
Pipe Availability and Cost
The standard high-frequency induction welded line pipe required for Coselle fabrication is competitively and readily available from numerous pipe mills in a number of countries worldwide. This pipe is much less expensive and more readily available than large diameter pipe typically used for pressure vessels.
Ease of Construction
Pipe welding processes are simple and well understood and pipe reeling is well proven and has been in routine use in the subsea pipeline industry for over 20 years.
