EDITOR ’ S CHOICE INNOVATIVE DESIGN
OLIVER VALVES
A completely new seal design was the only answer !
The Fife LNG plant at Mossmorran , operated by SHELL , can provide a challenging environment for any highpressure valve , but when a need arose for a number of ANSI class 300 DBB valves with a high operating temperature range , few manufacturers could meet the requirements .
The requirement for ANSI 300 class , 2 ” DBB valves suitable for a temperature range from -50 ° C up to + 350 ° C would force the designers at Oliver Twinsafe to completely rethink the sealing technology used in their double block and bleed ball valves .
An additional layer of complexity , on top of this already challenging application , came with the requirement to meet the demanding MESC 77 / 300 design validation test that includes fugitive emission testing
The actual ball sealing was readily achieved as Oliver Twinsafe already manufactures a wide range of metal seated valves , dispensing with any elastomeric seals completely . But even here special attention was needed in relation to the ball and seat materials , especially the tungsten carbide coating required to ensure long service life . For zero and low through seat leakage requirements , such as this application , porosity control of the Tungsten Carbide coating is of paramount importance . Other sealing sites throughout the valve would prove more challenging , especially the dynamic sealing requirements for the operating stem used to rotate the ball .
Industry standard stem seals , for more challenging applications usually made from Graphite , PTFE or PEEK , see a rapid degradation in their mechanical and physical properties at temperatures above 180 ° C . Searching for seals that can function across the required temperature range , Oliver ’ s R & D team turned to one of the world ’ s leading elastomer manufacturers who suggested a high-performance specialist polymer solution usually associated with jet engine technology .
Although now armed with a suitable material , turning this into an effect seal still remained elusive . The Oliver Twinsafe designers and R & D team worked through many traditional configurations , with limited success ; the only answer was to design a completely new stem seal arrangement in house .
The decades of knowhow in the Oliver team and a rigorous testing led development process , eventually came up with , a now patented , stem seal design that delivered fugitive emission leak rate B across the full temperature range required also passing the MESC 77 / 300 design validation test .
A combination of experience , innovative design , class leading R & D , and the drive to meet the most challenging applications makes Oliver Twinsafe one of the world ’ s leading valve manufacturers .
For further information contact Richard Featherstone at rfeatherstone @ valves . co . uk or simply call us on + 44 ( 0 ) 1565 632636 . Or visit us at www . valves . co . uk / twinsafe .
For further information , please visit www . valves . co . uk / twinsafe
16 PECM Issue 55