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Liquid Desander – Hydraulic Capacity, Turndown, and Performance for Insert Style Units (B-FSM062)

Desander insert being installed into a pressure vessel housing

Putting together separation performance and hydraulic capacity, we can see the effect of flow rate (hydraulic capacity) turndown and performance. The flow rate (turndown) and performance are interlinked. A cyclone-based unit (desander) thus has a separation size that can be tuned to match changing condition.

We now discuss the turndown and performance for insert style (i.e. single cone design) desanders. This is for liquid only flow. The chart below plots flow rate (produced water) versus pressure drop. It also shows the separation size (D98) experienced through this range of flow rates. Data is presented for desander inserts from 4” (100mm) to 20” (500mm).

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Hydraulic Capacity (per insert)

  • These are the recommended operating ranges (per insert). If more flow needs to be treated, then multiple vessels are used in parallel.
  • 100 mm (4”): 1200-2800 BPD
  • 150 mm (6”): 1500-4100 BPD
  • 200 mm (8”): 2000-6000 BPD
  • 250 mm (10”): 6000-18000 BPD
  • 400 mm (16”): 13000-40000 BPD
  • 500 mm (20”): 27000-82000 BPD

Turndown: Maintain within ΔP Range

  • Minimum ΔP: 5 psid – Needed to form/maintain vortex
  • Maximum ΔP: 50 psid – Capped to balance wear life
  • No shear maximum like deoilers

Separation Performance (D98)

  • 100 mm (4”): 19 microns at 50 psid and 36 microns at 5 psid
  • 150 mm (6”): 23 microns at 50 psid and 43 microns at 5 psid
  • 200 mm (8”): 26 microns at 50 psid and 49 microns at 5 psid
  • 250 mm (10”): 31 microns at 50 psid and 58 microns at 5 psid
  • 400 mm (16”): 48 microns at 50 psid and 91 microns at 5 psid
  • 500 mm (20”): 60 microns at 50 psid and 115 microns at 5 psid

Residence Time

  • Average 1.3-4.2 seconds for 4”-20” desanders
  • Allow 60 seconds after full flow for stable measurement (to ensure vessel completely liquid-filled)
  • Rapid response to slugging – separation is maintained within ΔP boundaries

The next article will discuss hydraulic turndown performance due to process changes and slugging. 

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.

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