Three gate valves from different manufacturers have been performance tested in a test loop. Anticipated production rates on the Statfjord Satellite Fields (SSF) have been simulated. The testing was part of the pre-qualification of the Christmas tree valves for this project. The tests were performed in order to determine the expected cycle life and failure mode while operating in a sand slurry environment. The valve’s ability to hold gas liquid pressure was monitored throughout the test.

On completion of the tests, the valves were disassembled and inspected for wear and tear, and the gates subjected to a material analysis.

Information gained from the tests has proved to be very useful for the development of SSF.

Four main discoveries were made during the testing:

  • (i)

    - Grease in the valve cavity traps and accumulates sand.

  • (ii)

    - The ability to operate in a sand slurry is dependent on the geometry of the valve internals.

  • (iii)

    - Valves designed for API class II sandy service do not necessarily perform satisfactorily when test conditions are changed from those specified in API spec 14D.

  • (iv)

    - Gates with tungsten carbide coating on high alloy steel performed better than those on low alloy steel.

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