may be gravity fed or charged by centrifugal pumps to provide additional volumetric efficiency to the mud pumps. The role of mud tank for solids control Mud tanks play an important role in a solids control system. It is the base of solids control equipment, and also the carrier of drilling fluids. Solids control equipment that are all mounted on the top of mud tanks include the following: shale shaker vacuum degasser desander desilter centrifuge mud agitator Vertical slurry pump Drilling fluids flow into the shale shaker directly after it returns to the surface of the well, and the solids that are removed by the screen would be discharged out of the tank, and the drilling fluids with smaller solids would flow through the screen into mud tank for further purification. A centrifugal pump sucks the shaker-treated fluids up to the desilter or mud cleaner for further purification. And vertical slurry pump is used to pump the drilling fluids up to the centrifuge, and a mud pump would pump the drilling fluids from mud tank into the borehole after it is treated by centrifuge and the circulation system continues. The number of the mud tanks that are needed on the drilling rig depends on the depth of the well, and also the mud demands of drilling. Normally the shale shaker and vacuum degasser and desander are mounted together on the same mud tank as the first tank at the oilfield, while desilter and centrifuge on the second tank. Also, the drilling rig has other different tanks such as a reserve tank, emergency tank, etc. The classification of mud tank Mud tanks are an important part in the solids control system. Based on functions, mud tanks include metering tanks, circulating tanks, chemical tanks, aggravating tanks, precipitating tanks, storing tanks, etc. References Drilling fluid