The steel Y-Piece is a key functional and structural element of the festooned pipeline system, allowing leak proof passage of the fresh water flow and supporting the variable loads from the interconnecting buoyant pipe elements, also ensuring that the loads are safely transferred to the anchor line. An integral part of the design solution is the HDPE stub end to the steel Y-piece joint, accommodating the variable elastic modulus and associated creep effects of the HDPE pipe elements.

The overall design objective for AES was to support the variable external loads, both static (long term variable) and dynamically induced loads, and provide a mechanical leak-tight connection between the steel Y Piece and HDPE pipe, accounting for the life time variation in the HDPE pipe elastic properties.

AES finalized a designed solution for the Y-Piece steel body to form the nodal points of the festooned offshore pipeline and also to serve a number of critical functions in the suspended pipeline. These key functions are listed as follows:

1.     Anchoring Function

2.     Connection Function

3.     Load Transfer Function

4.     Dynamic Performance

5.     Install ability

6.     Remote Intervention

7.     Proven Technologies

AES studied, analyzed and delivered a solution with the consideration of fabrication alternatives to meet the demand of 134 pipe elements to be completed in a short lead time.

Pushing available manufacturing capabilities to bend 1.6m in diameter and 6.5m long pipe element, AES found that the Y-Piece body could be produced by induction bending of a single continuous pipe, a solution that meets ABS Subsea Pipeline Systems and ASME 31.4 “Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids code requirements.

A special Manufacturing Procedure Specification (MPS) and Inspection plan for the induction bended Y-Piece design solution has been developed by AES along with ABS certification to perform the quality control on every single piece.