Water entrained by crude oil is salty (about 30 to 300 g/l). If salt water is not totally removed from the crude, the subsequent stabilization process causes the concentration and eventually the crystallization of salts

Salts may accumulate and cause severe problems in the downstream equipment (such as heater and exchanger plugging, pump unbalancing, reboiler corrosion, etc.).Water content (% or ppm) and salt content (mg/l or PTB) are criteria for the acceptance of crude oil by pipeline transportation companies, tanker companies and refineries.

Desalters are equipment designed to remove salt water, in order to control salt content of the crude oil, commonly within 5 - 20 PTB salt (14 -57 mg/l) by use of static or modulating electric fields that improves water coalescing and separation.