This is a good point in the discussion to bring up valves. A desander skid or system may have valves to isolate the skid (inlet and outlet water lines), manifold valves for instruments, sample valves, and general utility valves – but the most important valves are those that handle concentrated slurry. These will generally be the valve(s) between the desander and secondary accumulator, and valve(s) discharging slurry from the secondary accumulator. The header graphic (from Everlasting Valve Company) shows actuated valves in both of these locations.

The discussion below pertains to these two operation-critical valve locations.

General Design

• DO NOT BUY CHEAP VALVES. Don’t let a poorly selected valve ruin the operation of your skid.
• The valve flow path diameter must not be smaller than cyclone insert apex diameter.
• The valve flow path diameter may not be indicative from valve nominal size. Check valve drawing to ensure you are using full port valve and diameter is sufficient.

Valves for Handling Slurry Must be of Suitable Design and Material

• Slab Gate: available at all ANSI ratings, can be rebuilt in-situ, slab and seat should be 410SS with hard face (WC, nitride, or Stellite®)
• Slurry Knife Gate: from mining industry, best type but limited rating, typically 300# max design, do not use any polymer internals
• Rotating Disc: Available in wide variety of pressure rating and body materials, self-lapping (maintains tight seal), excellent in sever slurry use, full port flow – the recommended valve for desander slurry use
• Not Recommended: Needle, globe, and general service (metallic) ball

The next article will discuss secondary accumulator sizing and use.

References

1. Rawlins, C.H., and Wang, I. I., “Design and Installation of a Sand Separation and Handling System for a Gulf of Mexico Oil Production Facility,” SPE Production and Facilities, paper 72999, Vol. 16, No. 3, 2001, pp. 134-140.