Compact XMTs drive small bore valve extra-long stem innovation

Engineers at LB Bentley, a Severn Glocon Group company, have developed fully tested stem extensions up to 6.3 metres in length to overcome space restrictions on XMTs.

Stem Extensions

The innovation was prompted by a challenge the small bore subsea valve specialist faced for a North Sea subsea project. Through conduit gate valves and dual manual rotary gate valves needed to be positioned some distance from where they would be controlled by a Remote Operated Vehicle (ROV) outside the structure.
Stem extensions ranging from 1meter to 6.3meters in length were required, bringing significant design challenges. Material selection demanded particular attention. It involved a detailed assessment of tensile strength since the extensions needed to be robust and non-flexing, but not brittle. Ultimately mild steel was the material of choice.
The research and development team also looked in detail at existing valves’ design to identify changes required to accommodate the longer stems. Consideration was given to the interface between valve and extension, the required angle for turning and the relative indicator rod position.
Indicator rods usually move rotationally, but due to the stem length required in this project the design was modified to accommodate a linear movement. Another important feature of these valves is the indicator rod’s shear point, enabling the valve to remain operational even if the indicator rod should become inoperable.
The stem extensions themselves have a modular design, which potentially offers shorter lead times as they can be back stocked when offering stem extension on future projects.
Robert Walker, Head of Sales and Marketing for LB Bentley, says: “This breakthrough solution greatly enhances the flexibility and versatility of our small bore valves. As XMT design becomes increasingly compact, it unlocks a wider spectrum of potential locations.”
The modified valves and stem extensions have been fully approved. In-factory tests were conducted on the entire assembly, providing assurance that the set-up was functional before the valves were added to the XMT.
LB Bentley is part of the Severn Glocon Group which holds a Queen’s Award for Enterprise, International Trade and employs more than 850 people worldwide.

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