Since the discovery of the Valhall oil field in the Norwegian sector of the North Sea in 1975 with production beginning in 1982, it has supplied approximately 65,000 barrels of oil per day. Originally developed with three facilities, the complex today consists of five bridge-linked platforms for quarters, drilling, wellheads, production and water injection respectively. In addition, three wellhead platforms, Hod, Valhall Flank South and North, have been installed about 6 km each, from the Valhall complex. Due to seabed subsidence (about 25 cm per year), resulting in the water depth at site increasing by about 5 meters, as well as the call to operate more efficiently re-development of the field centre is well underway.
A new platform will be built adjacent to the existing Valhall. The new platform as well as all the existing equipment on the Valhall field will be supplied with electric power from shore through a HVDC Light transmission, with the existing gas turbines being decommissioned when the new installation starts operating in 2010, making Valhall one of the most environmental friendly fields offshore.
BP Norway’s vision for the re-development of Valhall is to provide ”Safe, Intelligent, Maintenance-Free and Remotely Operated Facilities”. Fitting in with BP Norway’s vision, UK manufacturer Midland-ACS, commissioned through their long-term Norwegian partner Haakon Ellingsen, were tasked with designing and engineering a number of different configurations of pneumatic manifold solutions incorporating specific solenoid operators for the re-developed facility.
Traditionally the control system design and configuration for a fully automated valve package would be produced by the valve or actuator manufacturer as a necessary requirement of the bid process, or a valve automation centre allied with one such manufacturer. This approach is sufficient for smaller quantity requirements but, design logistics, control of integral components outsourcing for control system packages and the critical nature of assembly requirements to ensure a high-integrity working valve package are of concern for engineering contractors specifying equipment, as well as equipment operators.
As the appointed Pneumatic Actuation Manifold provider Midland-ACS assumed responsibility for engineering, procurement co-ordination, fabrication and assembly, as well as the testing of the assembled systems. In order to add further value all of the required design work was completed by the Midland-ACS engineering team hence saving their customers resource and reducing the project lead-time considerably.Manifold Specs
To withstand the environmental conditions that would be present on the Valhall site both the ¼” and ½” NPT versions of the manifolds were elected to be made from 316 Stainless steel. With the air temperature on Valhall varying from –8.2oC to +24.5oC (100 year design), the manifolds were designed and engineered to withstand temperatures as low as -20oC and as high as +80oC at a rated maximum inlet pressure of 17 bar.
With safety being a key element in BP Norway’s vision for the redeveloped Valhall platform, Midland-ACS were required to design safety features and fail safes into each configuration of manifold. Designed and manufactured in accordance to NORSOK standards, as well as BP’s additional technical requirements to NORSOK (BPN specifications) the Air Filter Regulators and the Relief Valves were pre-set to operate at the specified system operating parameters. As part of the design a 1.25 bar differential was maintained between the required actuator working pressure and the specified relief pressure.
In order to accommodate specific solenoid operator requirements Midland-ACS work with a number of renowned solenoid manufacturers, thus allowing the manifold solution to be tailored to both valve control system construction and client solenoid specification requirements. For this re-development project they partnered up with valve manufacturer Parker and their Lucifer range of solenoids. Adhering to the EU 94/9/EC ATEX directive and EU 73/23/EEC European Union Electromagnetic Compatibility directives and the EExme and EExia approvals, the field instruments, dependent on the manifold configuration it was being attached to, were supplied in 3/2 and 5/2 forms.
Each of the manifolds were individually tagged and mounted on back plates with specific Traffolyte legend plates. As part of the overall design the need for external pipe work was reduced significantly. In removing the bulk of the external pipe work the overall integrity of the circuit was increased, as the number of potential leak paths were reduced, a highly desirable feature in exposed and difficult to access areas on oil rigs.
With the manifold panels simply requiring mounting directly onto the valve actuators cost savings could be maximised and is often the preferred option on large process valve piloting operations. This represents a significant reduction in lead-time, man hours, material cost, and weight, whilst delivering the afore mentioned improvement in integrity of design and reliability.
Each configuration of manifold was subject to a rigorous test processes in accordance to Quality Assurance standards, FMEA tool deployed to drive control plans and internal audit schedules prior to despatch. Testing included electronics, pressure and full sequence leak testing ensuring that every potential leak path is duly eliminated to ensure longevity of the system. Each configuration of manifold was then supplied with test reports and full documentation packs. One of the reasons Midland-ACS were chosen for this project was their systems reputation for reliability. By being responsible for the production of the actuator control panels they could ensure the quality of all components and materials selected for inclusion.
The expected re-development completion date of the new platform is 2010, where the Valhall field will almost certainly continue to be on stream until 2050. The field is likely to have an oil production capacity of 120 mbopd, a gas handling capacity of 143 mmscf/d with a total liquid capacity of 200 mbpd (oil and water).
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