Alpha Thames Subsea Ltd

Operations Division at:- Fyfield Business & Research Park, Fyfield Road, Ongar, Essex, CM5 0GN

Tel: +44 (0)1277 364736 Email:



22 May 2000


An innovative new valve design from Alpha Thames Subsea is promising to bring important benefits for offshore and subsea installations. The new AB3 valve is currently undergoing prototype testing with BEL Valves of Newcastle who are confident that if the trials meet their expectations, it will have a major impact on the market.

The AB3 is a Rotary Expanding Plug valve created by the engineering design team at Alpha Thames Subsea of Upminster, UK, for use in demanding subsea and offshore situations. It is a true metal to metal sealing double block and bleed valve that is up to 25 per cent more compact and lighter in weight than a comparable standard gate valve, and eliminates the problems associated with standard taper plug valves. It has been designed to pass from being fully open to creating a complete seal after a 90-degree rotation. This is achieved with zero psi on one side of the gate and up to 10,000 psi on the other. It has, in addition, been initially designed so that it can be operated by a conventional ROV (Remotely Operated Vehicle) manipulator and without the need for special tools or gearing.

The first new valve is being manufactured from corrosion resistant materials Inconel 625, 725 and tungsten carbide. It features two diametrically opposed seal segments around a single central spool. The spool holds the segments against the flowing ports to achieve a complete metal to metal seal. A cam action enables the seal segments to be retracted towards the centre of the valve prior to being rotated through 90 degrees into the fully open position where an unrestricted full flow through-bore is created.

Unlike many valves in common use today, the AB3 does not require critical seat machining and is therefore more compact and simpler to manufacture than a plug valve or a spherical ball valve assembly. Because the valve body has a parallel bore of constant diameter, it can be cylindrically honed to achieve surface finishes of 0.4 Ám or better. Its design and the materials from which it is manufactured make it resistant to attack from abrasion and corrosion and hostile subsea environments. It has an expected design life of 20 years at full load and duty.

The first full size version of the new valve is currently being developed by BEL Valves which will subject it to an extensive programme of tests. The combined design team at Alpha Thames Subsea and BEL Valves is confident that its performance will meet all of their expectations. During the development phase opportunities for modifications that can improve the manufacturing production process will be identified.

Because some production details of the design have not been finalised, a price for the new valve has yet to be determined. Initial estimates by BEL Valves suggest, however, that its cost will be comparable to a metal seated ball valve.

When development is complete, the new product will be manufactured by BEL Valves under non-exclusive world-wide licence to Alpha Thames. Recognised as a leading valve manufacturer world-wide, BEL Valves estimates that production of the new design could take-up a significant proportion of the company's turnover within five years. If development of the AB3 continues as planned, BEL Valves hope to have the first of the new valves on the market by the middle of next year.

Alpha Thames Subsea, which is part of Kockums Holdings of Sweden, has developed the AB3 valve with BEL Valves. Based in Upminster, Essex, Alpha Thames Subsea is a project management and engineering design company with over 30 years experience in subsea systems and technology. It has established itself through an exceptional level of design expertise gained in the demanding offshore sector that is also suitable for a wide range of modern industrial applications.