Generally a solids control system will have all the 4 stages separation equipment for drilling cuttings and fluids. However, not all the equipment would have to be used when drilling. Hence, it will be better to design an overflow line for the drilling fluids on the mud tank to let the drilling fluids could flow bypass the equipment will not be used in some specific process.
In generally condition, the overflow line is designed as a U type slot on one side of the mud tank top. It is starting from the sand trap compartment of the mud tank to at least the suction tank where the high pressure mud pump could suck the active drilling fluids and transfer to the rig. As per customers’ requirements, this overflow line could extend to the drilling fluids mixing tank and storage tank.
Shale shaker, de-sander, de-silter and decanter centrifuge are seen as the 4 stages of solids control equipment which can finally separate out the cuttings with size down to 2-5 microns. In some solids control system, there will also have vacuum degasser located between the shale shaker and cyclone units. This degasser is used to remove the entrapped gas in the drilling fluids like CO2. However, this degasser unit is not used very often.
When the time no need start this machine, we can close the gate on the overflow line to the degasser sucking compartment, and then the drilling fluids could flow directly to the de-sander compartment after treated by the shale shaker. Even, sometimes then no need the cyclone unit, the drilling fluids could flow into the centrifuge feeding compartment. This always happens at the beginning time of the drilling as there is not much cuttings in the drilling fluids.
By opening or closing the gate between the overflow line and each compartment of the mud tank. The mud engineer could guide the drilling fluids flow so than do a better control of the solids control system. You know, turn off the equipment will not be used temporally will save a lot when drilling, and that is also a protection on the machine.
Knowing how the overflow line works would be much helpful for us to design the drilling fluids solids control system. Once the system arrives at the drilling site, this could greatly help to increase the working efficiency.