FULL PIPE SPOOL (SUCTION SPOOL) WITH RING REINFORCED EXPANSION JOINT FOR 96.5 BARG PRESSURE (TESTED AT 144.75 BARG)

For installation on a former jack-up drilling rig, repurposed as an offshore production facility with 12 well slots in offshore Gabon, Belman designed and manufactured a separate ring reinforced, double Bellow Tied Expansion Joint and a full pipe spool (suction spool) incorporating a Tied Expansion Joint. All this will be installed at the suction and discharge connections of the pipeline pumps.

CLIENT ISSUE
The client operates a former jack-up drilling rig, which has been repurposed into an offshore production facility where the produced oil is transported via a long pipeline to an FPSO (Floating Production, Storage and Offloading unit) for processing and storage prior to offloading to oil tankers. For the repurposed facility the client required several high-pressure Expansion Joints to accommodate the movement generated by the pipeline pumps. Specifically, the Expansion Joints needed to absorb displacements with minimal resistance at the suction and discharge connections of the pipeline pumps. The client was looking for durable and flexible solutions capable of withstanding the demanding operating conditions at the installation point, which included a pressure of 96.5 barg and temperature range of -15/+120°C as well as a harsh marine environment with salt-laden air. To meet these requirements, the client turned to Belman for assistance.

Greener initiatives in the Oil & Gas sector

The oil and gas industry has intensified its focus on greener initiatives, for example by this client repurposing existing production assets to extend their economic lifespan. This approach shortens the time to first oil while significantly reducing field development investment and the carbon footprint. Conversion projects of this nature often demonstrate excellent HSE results. Some repurposed jack-up drilling rigs can process and, in some cases, store hydrocarbons from wells rather than being used solely for drilling operations.

BELMAN SOLUTION

Full pipe spool (suction spool) with Ring Reinforced Expansion Joints + a separate Tied Expansion Joint – both for 96.5 barg pressure

Through close dialogue with the client, Belman identified the optimal solution for the application. To ensure efficient accommodation of movements under the demanding operating conditions, several design options were evaluated. Based on detailed analysis and continuous collaboration with the client, Belman ultimately proposed an optimised and improved solution. Multiple designs and solutions were discussed and assessed, including a Pressure Balanced Expansion Joint design. However, the client concluded that a separate double Bellow Tied Expansion Joint as well as a single Bellow Tied Expansion Joint welded into a full pipe spool represented the most suitable solution. Following the selection, the client verified and confirmed all pipeline and pump dimensions as well as the submitted design, enabling Belman to finalise the detailed engineering, particularly for the full pipe spool incorporating a ring reinforced Expansion Joint. Belman further supported the client by optimising cost and performance through a careful selection of materials. While some selected materials offered cost-efficient solutions with limited corrosion resistance, a specialised coating system was applied, which was chosen specifically to withstand the corrosive marine environment at the installation point.

The two flexible solutions supplied were:

The separate Tied Expansion Joint with double Bellows and ring reinforcement
The Tied Expansion Joint was designed with double Bellows to absorb axial, lateral and angular movements in combination. Tie rods were strategically positioned to control movement absorption and restrain pressure thrust. Due to the high operating pressure of 96.5 barg, the Bellows were ring reinforced to ensure pressure integrity while maintaining the flexibility. The Bellows were manufactured from Inconel 625, a material widely used in the oil and gas sector due to its excellent corrosion resistance. The flanges and the middle pipe were manufactured from A350 gr. LF2 CL1 and A106 Gr. B, materials well-suited for high-pressure applications, and were protected with a special coating system. As the separate Expansion Joint needed to work under the same pressure as the full pipe spool, it was also pressure-tested at 144.75 barg.

A full pipe spool with a Ring Reinforced Expansion Joint

As per client specifications and in close agreement with the client, the flanges and weldolet fitting were manufactured from the material A350 LF2, while the reducer, T-piece, pipe cap and elbow were made from the material A420 gr. WPL6. The pipe material was A333 gr. 6, with all materials selected for their suitability in high-pressure and corrosive environments. The Bellows were made from Inconel 625, with the ring reinforcement made from 1.4571 (AISI 316Ti), materials commonly selected for oil and gas applications. Due to the high-pressure requirement, all spool components were designed with thick wall sections. To maintain flexibility for effective movement absorption, the Bellows were manufactured from several multi-ply thin layers of Inconel 625 Bellow material and supported by ring reinforcement, thereby ensuring pressure integrity, flexibility and reliable long-term operation.

For quality control an inspector checked the coating, performed a pressure test and conducted the laser alignment.

How can Expansion Joints be designed for high pressure?

Expansion Joints for high-pressure applications must be carefully engineered to safely withstand internal pressure while accommodating required movements. High pressure generates significant pressure thrust that can place heavy loads on piping systems and connected equipment. To manage these forces, Expansion Joints are designed with specific geometries and structural features that balance or restrain pressure thrust. The Bellows construction is optimised to reduce stress and ensure sufficient fatigue life under cyclic operation. Material thickness selection versus design features plays a key role. Thick-walled components in the Expansion Joint are often selected such as flanges, middle pipes, tie rods etc. The Bellow is a bit trickier, as it needs to be flexible – and the thicker the layers, the stiffer the Bellow. To optimise both pressure integrity and flexibility, a solution that incorporates ring reinforcement on the Bellows is often chosen to help it withstand the pressure. When correctly engineered, Expansion Joints can contribute to safe and long-lasting high-pressure piping systems.
Key design elements for High-pressure Expansion Joints:

• Pressure control using pressure-balanced, hinged, gimbal or tied designs
• Optimised bellows geometry and the combination of thin Bellow layers and ring reinforcement
• Reinforcements and control units to limit loads on anchors and equipment
• High-strength and thick-walled materials suitable for high pressure and in many situations also cold/elevated temperatures, corrosive media etc.

To minimise welding and time for quality control incl. any third-party checks, Belman implemented a special method for fixing the end reinforcing ring: namely, a ring around the Bellow tangent in the top with holes. This uses a perforated ring instead of the standard gussets. This solution provides a more uniform stress distribution into the pipe, whereas gussets introduce local stress concentrations in the pipe wall due to load transfer through relatively small contact areas. The perforations allow access for weld inspection and facilitate quality control during pressure testing.

Belman Design was involved

Belman Design is a piping design entity under the Belman Group umbrella. It supported the client on 3D models of a suggested full pipe spool they wanted to design and install. Based on client specifications and an isometric snippet from the client, Belman Design created a complete 3D model in Autodesk Inventor and produced final production drawings, which were used directly to manufacture the separate Expansion Joint and the full spool pipe. Read more about Belman Design’s work here: Belman Design

Belman – long-standing experience in high-pressure, flexible solutions for the oil and gas industry

With 30+ years’ experience in the design and manufacture of customised Expansion Joints, Belman has established a strong track record in Expansion Joints for the oil and gas sector. Throughout the years we have supplied numerous remarkable designs, including a 30-tonne Expansion Joint with a special manhole for an FCCU application, a ring reinforced Expansion Joint capable of withstanding 82 barg pressure on an oil field and universal Expansion Joints for cryogenic temperatures on a LNG vessel, among many others.