The Drilling fluid (mud) Mixing System Drilling fluid is very expensive, modern day operation can have as many a 7000 bbls of fluid on the rig at one time, the active system (that's the one that is being circulated there could me as many as four systems on the rig at one time?) needs to be kept in good condition, The fluid returning from the well will first be directed to the solid control system where as much of the solid as possible will be remove, it will then flow back to the active tank (pits) where sooner or later it will need to be reconditioned  built. If the fluid needs reconditioning it will be drawn from the pits using a Centrifugal pump. The centrifugal pump consists of a rotating impeller mounted inside a casing, unlike positive pressure piston pumps, e.g. "the rig mud pumps",  centrifugal pumps provide constant “head.” Consequently, the pump and associated piping system must be correctly sized and designed to deliver the required flow rate and desired head.  Fluid enters the casing at the center (the eye of the impeller). As the impeller spins, the fluid is accelerated to the circumference by the curved impeller vanes. The accelerated fluid exits the impeller and enters the pump casing where kinetic energy is converted into pressure energy. Pump Performance Curves, illustrate that the head generated by centrifugal pumps decreases very little as the flow rate is increased.  Conversely, the flow rate through mixing system is not affected much by head. However the pump should be sized to provide the correct head at the flow rate dictated by the pump rate or system designed operating pressure . Here we see  very basic lay out where the mixing pumps are piped in to the low pressure system, not there are two suction lines lines the lower being the mixing suction to the mixing pumps

The bulk surge tank are the hanging and supported by 3 hang of points, two are pin, fixed with a load cell fitted, the third the load cell connect to a gauge allowing the operator to judge the amount of chemical being added to the system

After circulating the drilling fluid around  the low pressure lines where it will pass through mixing system hoppers it is return to the holding mud pit where it is allowed to settle In the pit room the line can look very confusing, however ever pit will have the same lines leading into it and it is just a mater of working on one pit and following the lines back