Valve manufacturers and oil and gas sector operators can now rely on the explosive-decompression (ED) resistance of larger section 'O' rings, following James Walker's outstanding Norsok M-710 successes with its FR25/90 grade fluoroelastomer.
  The DNV-witnessed test programme, carried out in a dedicated ED test facility at James Walker Technology Centre, has given a top rating of 0000 defects — zero defects in all four samples — to 6.99mm section 'O' rings.
  The rings were subjected to rapid gas decompression from 150bar to ambient in 240 seconds — ten cycles in ten days — with a mixture of carbon dioxide and methane at 100°C, as required by Norsok M-710 test procedures.
  None of the seals exhibited any splits, blisters or tears when cut sections were closely examined under x20 magnification.
  Explained James Walker's global marketing director for oil and gas operations, Trevor Clarke: "The larger the seal, the more difficult it is to achieve ED resistance.
  "Previous Norsok tests with 5.33mm section 'O' rings proved that our FR25/90 combines an exceptional resistance to sour (H2S) gas with excellent ED qualities.
   "The latest results with this 90 IRHD fluoroelastomer show that larger seals — designed for long-term high integrity operation — can readily outperform those moulded in materials that have been specifically designed for ED resistance alone."
  James Walker does not optimise elastomers purely for ED resistance, as this can degrade other properties that are considered necessary for efficient sealing.  Instead, its philosophy is to develop ED resistant materials with excellent sealing characteristics such as low compression set, good elongation at break, and conformability for sealing against difficult surface finishes.
    FR25/90 is widely used for ED-resistant seals in the oil and gas sector: downhole, at wellheads and in upstream pipelines.
  Its low-temperature capability extends down to -50°C, dependent on application conditions, seal type and groove design. This enables FR25/90 to work in colder environments and/or at higher pressures than James Walker's other Norsok M-710 qualified elastomers.
   "With FR25/90 and FR58/90 fluoroelastomers, and Elast-O-Lion® 101 hydrogenated nitrile, all qualified to Norsok M-710, we are extending our world-leadership in ED-resistant fluid sealing products," stated Trevor Clarke.

Photo caption for above: An ED resistant seal (left) will survive rapid gas decompression, when others can fail (right).