We’ve covered all the theory and background and models – so let’s look at the operation of a multiphase desander at varying gas void fractions (GVF) and turndown scenarios. Posts B-FSM-089 and B-FSM-090 covered capacity, turndown, and performance for hydraulic and pneumatic flows, respectively.

**Turndown Performance at 0% GVF**

The baseline scenario is shown in the graphic below. A 10” multiphase desander is operating on hydraulic (liquid only) flow. The design point is 13,000 BPD which gives a 25 psi pressure drop. At the process conditions listed the separation size is 24 microns. At 20 minutes the flow drops to 5,500 BPD which reduces the pressure drop to 5 psi (minimum operating point) and the separation size coarsens to 38 microns. The flow then returns to design point, then at 30 minutes the flow increases to 18,500 BPD (maximum operating point). The pressure drop and separation size at the high end are 50 psi and 19 microns, respectively.