The hydrocyclone is a facility dedicated to the treatment of water mixed with hydrocarbons and is an advanced development. It is one of the major equipment in the treatment of produced water and usually implemented as appendices separators, desalter.

The hydrocyclone consists of a series of liners installed in vessel and supported by tube sheets.
The produced water is introduced into the hydrocyclone with a tangential inlet which increases rotation in the head of the hydrocyclone leading the formation of a free swirling flow. Progressing along the liners, the fluid rotation is accelerated by a gradual reduction in diameter liners rotation.

Within the liquid, an important field of centrifugal acceleration is created which induces a three-phase separation with dense particle like sand, which are plated against walls and driven toward the tip end with the water flow, and the droplets oil less dense than water, which are pushed into the axis of the liner where an oil cord is engendered.

The major advantage of hydrocyclones for the deoiling water compared to conventional treatment is the decrease of weight and bulk. The main use is offshore either on platforms or FPSO with more insensitivity to the ship’s movements.

Two possible operating modes depending on the operating conditions:
- Use of the pressure of the upstream capacity (P> 4.5 bar) to create the vortex separator;
- Recovery pump if the pressure is too low, with a recirculation between the outlet of the hydrocyclone and pump suction.

Flow establishes the number of liners in capacity.