The horizontal screw discharging sedimentation centrifuge, commonly known as the horizontal decanter centrifuge, is an efficient centrifugal separation device. It utilizes the solid-liquid-liquid density difference and enlarges it by thousands of times with the centrifugal force field. The solid phase settles under the action of centrifugal force, achieving solid-liquid-liquid separation. The entire feeding and separation process are continuous, closed, and automatic. As a high-speed rotating centrifuge, its advantages are evident.
Advantages:
- Large adaptability to materials, capable of separating solid particles in a wide range of sizes from 0.005 to 2mm, even when the sizes are uneven.
- Automatic, continuous, long-term operation with easy maintenance and the ability to perform closed operations.
- Large single-machine production capacity, compact structure, small footprint, and compatibility with DCS control.
Similarly, its failure modes are direct, with the majority of malfunctions manifested as machine vibrations. Therefore, operators should have a basic understanding of machine vibration and dynamic balancing. The drum and screw of the centrifuge must be balanced using dynamic balancing. Some balancing issues, such as drum and screw deformation, may require professional correction due to the lack of balancing correction equipment.
During operation, some issues can be prevented, such as:
- Due to the structural limitations of the centrifuge, the rigidity of the drum and screw is not significant. Long-term positioning causes bending deformation due to self-weight, resulting in increased vibration. Machines not in use for an extended period should be test-run every half month.
- Follow the specified start-up and shutdown cleaning procedures.
- Regularly monitor machine vibrations and noise, address issues promptly, and avoid working with malfunctions.
Common Failures and Solutions for Horizontal Decanter Centrifuges
Common Failure 1: Machine Blockage
The first sign of centrifuge blockage is a prolonged time without discharging residue. Under unchanged feeding conditions, the discharged clear liquid gradually becomes cloudy, darkens, and approaches the color and state of the feed. This is accompanied by an increase in drum current, a significant decrease in drum speed, and a continuous rise in slag discharge torque. These indicators suggest the possibility of internal blockage.
In such a situation, do not press the emergency button, as the centrifuge is running at high speed without a braking device, and the emergency button cannot provide any help at this time.
First, immediately cut off the centrifuge’s feed. In most cases, the centrifuge can automatically eliminate the blockage through the pushing action of the screw. If the blockage cannot be eliminated by self-pushing, immediately reduce the drum speed or shut down the drum drive. However, do not shut down the screw motor. After the drum speed is reduced, the blocked solid residue may gradually loosen and be discharged outside the machine by the screw.
If a centrifuge is genuinely blocked, operators should inject water into the machine immediately and make every effort to restore the operation of the screw, ensuring that, as long as the screw can rotate, the centrifuge is not truly blocked and can potentially return to normal. Injecting water into the machine and restoring the screw’s operation are the preferred methods for eliminating blockages.
Common Failure 2: Abnormal Machine Vibration
Abnormal vibration in a centrifuge is a destructive force that can cause severe damage to the machine. Machine vibration can be classified as slow vibration and sudden vibration. Slow vibration mostly indicates wear and tear on the centrifuge, where external components are worn or detached, and the bearing system gradually suffers damage. Sudden vibration often indicates internal material blockage, significant damage, and detachment of internal components. In most cases, the first step is to check whether the slag system has malfunctioned, leading to an accumulation of solid residue, and whether the liquid circuit is blocked, causing liquid to spread back to the centrifuge drum.
Common Failure 3: Excessive Bearing Temperature
When experiencing high bearing temperature, first, actively check if there is an excessive addition of bearing grease, if there is excessive vibration in the centrifuge, and if there are abnormal noises in the bearing operation.
Simultaneously, observe the color of the waste grease from the bearing. Normal waste grease should be light gray. If the waste grease changes its color to black, rust yellow, or shows other abnormal colors, it suggests potential bearing damage, and it is advisable to replace the bearing in advance.
Regarding abnormal noise in the bearing area, not all noises indicate a problem with the machine. Pay special attention to distinguishing normal “gear oil layering” sharp noises. This noise is produced by a friction component lubricated with grease inside the bearing seat during normal centrifuge operation, and it emits a specific sharp sound. The characteristic is intermittent, occurring at irregular intervals. After performing 1-2 grease refilling actions, this noise temporarily disappears and reoccurs later. Judging this noise requires careful observation and continuous experience.
Common Failure 4: Manual Drum Rotation
Manual drum rotation is one of the essential methods for judging whether there is internal material accumulation and whether the drum can start smoothly when the centrifuge is stationary.
When manually rotating a normally free drum, the drum rotates very easily, and the drum can freely decelerate until it stops, with the stopping angle position being random. If the drum’s rotation is very heavy, and when manually rotated and released, the drum reverses and almost stays in the position before rotation, repeatedly rotating and the drum stopping at the same angle each time, it indicates the presence of solid residue accumulation inside the drum. Starting the drum at this point will cause severe unbalanced vibration with increased speed. In such a situation, run the screw to discharge internal materials while injecting water, and then start the centrifuge again.