Efficient solids control equipment like shale shakers and centrifuges are vital to drilling operations. Having these tools in place helps maintain a clean drilling fluid that reduces waste disposal costs and formation damage. However, sometimes issues with these pieces of equipment arise. Here are some tips and strategies to help troubleshoot common problems with these centrifuges.
During the rotational movement of the centrifuge, substances with different densities get separated. Dense components settle first, lighter ones later.
Simple centrifuges consist of a motor, the holder for the tubes called a rotor, and some control electronics. They often have an electromechanical timer, which switches off the motor after a specific time. Usually, these timers have cheap clockwork parts that wear out quickly. They are often difficult to repair. A tachometer can help check the speed of a centrifuge. A tachometer might not be available in remote areas, but a simple centrifuge without a digital display probably does not need one. Every measurement and check should be recorded in the maintenance log. A trained technician should be consulted to inspect the solids control centrifuges if the results are unsatisfactory.
Decanter centrifuges are the 4th stage of a rig solids control system, including shale shakers, vacuum degassers, and designers. These machines separate drilling mud into liquid and solids. They are commonly used in nuclear reprocessing to separate fission products. When a decanter centrifuge is suddenly stopped, it is often because the interlock is stuck or broken. It is a simple mechanical mechanism using a solenoid that pushes a pin through the lid’s latch. It should be checked for voltage across the solenoid and a switch transistor. Also, it is good to check that the lid hinges, lock mechanism, and bucket carrier lubrication are sufficient. Lubrication should be done as suggested in the user manual. Also, ensure the centrifuge is not spinning, and all power cables are disconnected before opening the lid.
Excessive Vibration or Noise
Disc stack centrifuges are complex equipment that requires a solid understanding of operating them. Training can help your team better identify problems that might be emerging to avoid costly repairs and improve separation efficiency. The control unit is the brain of your centrifuge. It receives settings from the control knobs like speed and time, as well as information from sensors for the actual speed, open lid, and imbalanced load. It then controls the motor, brake, and lid lock. The motor speed sensor is usually a forked photoelectric or Hall effect sensor on the rotor shaft. It has three cables: plus, minus, and the control signal, a square wave. Check the sensor and the power supply first with a multimeter.
Just like unbalanced car tires, a decanter centrifuge that’s not balanced can cause vibration and performance problems. It includes poor safety, excessive wear and tear of parts, and reduced efficiency and speed. It can be caused by improperly closed tubes, plates, or even missing lids. Ensuring all centrifuge components are properly cleaned and sealed is the best solution. Also, if the lid interlock mechanism isn’t working correctly, check the solenoid or the latch for damage and proper adjustment. Lubrication is necessary, too, especially for the lid, hinges, lock mechanism, and bucket carrier. A little grease will go a long way and should be applied periodically. Be sure to wipe off excess grease afterward.
Centrifuges separate solids from liquids using centrifugal force. The solids are flung outward by the spinning of the bowl and strike against the undersides of matching holes in the disc stack. The heavier components are displaced toward the center while the lighter ones move downward, away from the bowl. Tubes in the rotor must be evenly distributed and loaded symmetrically to avoid imbalanced centrifugal forces. They should also be suitable for their holders or buckets (not too big or too small). Modern centrifuges have a built-in timer that switches off the motor when centrifugation is done. They also have a brake activated by a resistor that bypasses the rotating motor. The resistor converts the rotary motion into electrical energy that generates heat to slow down the rotor. ReadMore…