Oil-water separator level control valves require continuous maintenance, due to an environment that is more destructive than many other valve applications. Over the years, service life of a few weeks between complete rebuilds was common, but this has changed. Velocity-control technology, aimed at two root causes - the implosive force of cavitating water and the erosive effect of concentrated sand driven by high-velocity water - has solved the problem in many cases. At the Statfjord B platform in the Norwegian sector of the North Sea, the output of some wells - crude oil, gas, produced water (with a specific gravity of about 1.03), and sand - flow into a single separator tank where the constituents separate out in layers according to their specific gravities. Each well may not have enough sand production to cause an operational problem, but the combined sand production is more than enough to cause severe erosion of the level-control valve trim.
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