New generation of OmniSeal PTFE Lip Seals for seat-to-body sealing of Cryogenic TMBVs to exceed LNG Industry leakage rate standards

Trunnion Mounted Ball Valves (TMBV) are used extensively in cryogenic service and LNG industry represents the higher potential for the manufacturers. These applications are governed by several industry and IOC standards: BS6364, ISO 28921-2, Total GS EP PVV 150 and Shell SPE MESC SPE 77-300.  

BS 6364 is the most commonly use standards for valve cryogenic test in the LNG industry but it is also the oldest as it was not revised since 1984. That explains why the max leakage rate has the higher leakage rate. IOC’s and Shell in particular, have given more stringent values in line with the technology progress of the valve industry.

In order to help Cryogenic TMBV manufacturers to upgrade the leakage performance of their valves at -162°C, Saint-Gobain has developed a new generation of PTFE lip seal that meets and even surpass leakage requirement of Shell MESC SPE 77-300. This allows Cryogenic TMBV manufacturers to bring confidence to an industry where safety is the first criteria.

Therefore, we have completed an internal R&D project to develop and pre-validate new single piston seat seal in full accordance with Shell MESC SPE 77-300 test protocol on our bespoke test rig :

• Pressure up to 420 bar He
• Temperature from -196°C up to +150°C
• 2 mockup: 3" and 8"

Based on input from major Cryogenic TMBV manufacturers, decision was made to set up our leak rate target for seat seal at 25% of Shell MESC SPE 77-300 which gives 75% for leakage through seat insert.

Our new Cryogenic Single Piston Effect seat seal outperforms all existing Lip Seals available and even surpass the requirement of Shell MESC SPE 77-300.

This new generation of design brings the performance of Lip Seal to the next level with remarkable benefits to manufacturers of Cryogenic Trunnion Mounted Ball Valves:

• Ranging from -196°C to +150°C
• Up to class #2500 (420 bar)
• Able to cope with 0.4mm misalignment of valve trim
• Low friction that allows over-pressure body cavity relief in SPE configuration.
• Roughness of hardware sealing surface Ra 0.2-0.4μm
• No need to modify the hardware / valve seat concept. No additional parts required.