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Supagraf Premier is manufactured in a novel manner from reinforced exfoliated graphite ribbon to provide a length form packing that is tough and flexible with excellent resistance to extrusion at fluid pressures up to 210 bar. It is also chemically inert within the range pH 1-14, and works efficiently at temperatures from -200°C to 450°C in oxidising conditions, or to 650°C in steam and non-oxidising environments.
The packing incorporates an advanced lubricant system to avoid graphite pick-up on the valve stem. This keeps friction levels low and ensures that valve action is smooth and reliable, with minimal break-out torque.
Third party testing by the Valve Test Centre at Leeds University, UK, has shown that Supagraf Premier can maintain better than 500 ppm emission control with equal efficiency on both rising stem and quarter-turn rotary valves. Tests were completed over 12 000 cycles of valve operation with temperature cycling from ambient to 200°C and 300°C. The working fluid was helium at 40 bar pressure.
Using one type of packing for both rising stem and quarter-turn rotary valves will save on stock-holding costs for maintenance engineers and valve manufacturers who previously fitted special moulded ring sets that work best on only one type of valve.
Further work to prove sealing efficiency and longevity has been undertaken at the James Walker laboratories. Supagraf Premier survived physical endurance tests at 40 bar pressure with methane, while emission levels were kept constantly below 500 ppm. Results showed that the compressed packing rings coped exceptionally well for over 12 000 operating cycles and the valve stem remained in perfect condition.
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