Desander and Desilter in Solids Control System

Apr 11, 2013

As two indispensable equipment in the solids control system of oil & gas drilling, desander and desilter are responsible for separating the small solids in the drilling fluids that has been treated by the shale shaker and vacuum degasser. The desander takes care of the solids with diameter 45~74μm, and 15~44μm for desilter.

Normally desander is mounted on the top of the first mud tank together with shale shakers and vacuum degassers, while desilter is mounted together with centrifuges. Sometimes to save the top area of the mud tank, desander and desilter are combined together to work as high efficient mud cleaner.

Desander and desilter are consisted of hydrocyclones, high pressure flow pipes and a small shale shaer at the bottom. For desanders and desilters, only one vibration motor is used to drive the screen basket. while for high efficient it would need two motors. There would be equipped with two 10″ or 12″ iron hydrocyclones for desander just as the solids need to be separated is relatively big, and include some sands in the mud. While for desilter, it would be equiped 6 to 12 pcs 4″ hydrocyclones. which are made of wear-resisting plastic.

Working Principle of the Hydrocyclones:

For the work principle of hydrocyclones, it works like this. First the drilling fluids is sucked up to 0.25Mpa ~ 0.4Mpa by sand pump, and enters into the cones through the side inlet which is normally only 2-1/2″ in diameter. The fluids then flows spirally inside of the cone. Effected by the centrifugal force, the heavy solids in the fluids would be thrown towards the inner wall of the cones, go down to the bottem, and discharge through the sand discharge port, while the light fluids would go up and discharge through the upper oulet. The diameter of the bottom discharge port is adjustable, and with a cover of hydrocyclone.

As a wear part of desander and desilter, the lifetime of hydrocyclones is not so long as other parts. So it is neccessary to check their working condition, and replace them with new ones. As a whole set of the hydrocyclone, clamps and flang are also replaced together with the hydrocyclones.