Process Engineering • Design • Fabrication

Crude Oil Dehydrators and Desalters

Electrostatic desalting is employed for both oil field and refinery applications, to facilitate the removal of inorganic chlorides and water-soluble contaminants from crude oil. In refinery applications, the removal of these water-soluble compounds prevents or minimizes damage to downstream distillation equipment. Click here to learn more.

Conventional AC Electrostatic Dehydrator/Desalter

The conventional AC (Alternating Current) electrostatic dehydration system is an efficient method to remove high salinity formation water from the crude oil stream. This process relies on establishing a high voltage AC electrical field in the oil phase of dehydrator/desalter vessels. The electrical field imposes an electrical charge on water droplets entrained in the oil stream, thus causing them to oscillate as they pass through the electrodes.

During this oscillation the droplets are stretched or elongated and then contracted during reversal of the imposing AC electrical field. During this agitation the water droplets co-mingle and coalesce into droplets of sufficient size to migrate, by gravity, back into the lower water phase of the vessel for disposal.


Several modifications are available to enhance the conventional AC electrostatic system. These modifications include:

Electrostatic AC/DC Dual Wave Dehydrator/Desalter

GasTech's Dual Wave design utilizes both alternating and direct current through multiple plates to promote enhanced water extraction and chloride level reduction.


GasTech's Dual Wave AC/DC system provides the client with the following benefits:

  • Inlet diffuser manifold
  • Anti-vortex water collector
  • Anti-vortex drains
  • Oil collection weir baffle
  • Open bottom distributor troughs
  • Dry oil collector piping
  • AC/DC Plate type electrodes
  • Sand-jetting system
  • Inverted sand troughs
  • Interface sludge draw-offs
  • Matrix packing
  • AC electrodes
  • Steam-out system
  • Electrostatic Heater/Treater

The GasTech horizontal heater-treater combines the advantages of emulsion breaking heat with electrostatic dehydration in a single vessel package.

The unique thermal section is designed with an inlet shroud for liberating both gas and free water from the emulsion. This flow path allows the free water to separate for disposal, without further heating, resulting in fuel savings for the client.

The open bottom distributor troughs provide even dispersal of the heated oil across the entire electrode section for optimum dehydration before being collected for discharge to the pipeline or storage.