A decanter centrifuge as a complete unit includes - a frame, housing, control panel, main motor, back drive (hydraulic or gearbox), lubrication system and a variety of sensors, solenoids, and monitors, and last but not least “the guts” or the rotating assembly (RA). The rotating assembly consists of two main components: a bowl and a scroll (screw conveyor). The centrifuge bowl is driven by an electric motor. The internal scroll, which operates at a slightly different speed than the bowl (differential speed) is driven by a radial piston hydraulic motor.
The feed is introduced thru a pipe into the RA’s feed chamber. This is the area of the centrifuge where the feed is accelerated to the speed of the scroll and the liquid exits thru nozzles located in the feed chamber. With G-force the heavier particles are accelerated and collected on the inside of the centrifuge bowl. Due to the differential speed, the solids are scraped on the inside of the bowl and transported to the solids discharge ports. The solids exit into the housing and from there, drop into a conveying system.
To keep your decanter centrifuge operating at an optimal standard, Centrisys offers a number of spare rotating assemblies at various levels. Let’s review the advantages and what's important to know with each type of spare rotating assembly.
1. Bearing to Bearing
The Bearing to Bearing Rotating Assembly (RA) has installed inner main bearing retaining plates and main bearings. Centrisys recommends including a pulley, adaptor flange and a Viscotherm ROTODIFF® Hydraulic Drive.
- Reduces downtime for the centrifuge repair
- Reuse of the main pillow blocks allows for ultimate versatility with multiple centrifuges in the plant
- Does not require a separate alignment for additional pillow block sets
- Requires an on-site transfer of the existing pillow blocks during every centrifuge installation
- Requires a transfer or mounting of the pulley, motor, and adapter for each centrifuge installation at the plant
- It can be difficult to monitor the condition of pillow blocks; there’s a risk of reusing one in poor condition
- The installation requires a thorough inspection to check for areas of friction
2. Full Spare Rotor
The Full Spare Rotor is an RA that includes new pillow blocks, a new pulley, and the ROTODIFF adapter. The Full Spare Rotor does not include the ROTODIFF Hydraulic Motor.
Allows for a very quick swap with reduced downtime
- Allows time to properly and completely repair the replaced RA
- Fits for the pulley, adaptor, and pillow blocks can be monitored and altered to prevent unnecessary vibration
- Requires a one-time, on-site, comprehensive, pillow block dial-in alignment procedure
- If there are multiple centrifuges on-site, the dial-in procedure needs to be performed for placement into each new frame
- Requires a thorough inspection after the installation to check for areas of interference
- Unless the pillow blocks are swapped, this version does not allow the RA to be placed into other centrifuge frames; this requires a dial-in alignment procedure for all locations
- Requires separate monitoring of the ROTODIFF and RA conditions
3. Complete Spare Rotor
The Complete Spare Rotor represents an RA as if it was lifted from the centrifuge frame. This version includes the feed pipe and the ROTODIFF Hydraulic Motor.
- Allows for the quickest swap with the least downtime
- Allows for the necessary time to properly and completely repair the replaced RA
- Pulley, adaptor, and the pillow block fits are monitored and altered to prevent unnecessary vibration
- ROTODIFF is inspected and kept in optimal condition
- Requires a one-time on-site comprehensive pillow block dial-in alignment procedure
- If there are multiple centrifuges on-site, the dial-in procedure needs to be performed for placement into each new centrifuge frame
- Requires a thorough inspection after the installation to check for areas of friction
- Unless the pillow blocks are swapped, it does not allow the RA to be placed into other frames; this requires a dial-in alignment procedure for every centrifuge RA
Additional Points to Consider
- Plant operators may not have the available skill set to dial-in an RA. This requires the coordination and scheduling of a Centrisys field technician.
- Customers with multiple centrifuges often misinterpret the flexibility of Full and Complete Rotor installations. Check with Centrisys for further clarification of benefits vs. the difficulties for each RA level.
- Anytime a dial-in is required, NEW roll pin locations are necessary. It's important to not rely on the original taper pins or metaligners.
- Pillow blocks have only one added location for roll pins, limiting the number of combinations of RA to frame pairings for multiple centrifuge locations.
- Multiple centrifuge locations best benefit from Bearing to Bearing RA versions for flexibility.
As with any decanter centrifuge, it’s essential to perform routine service and rebuilding of the rotating assembly as part of a maintenance plan. You can minimize repair costs in the long term by allowing Centrisys to recommend a proper maintenance plan and spare parts inventory. Operation by trained personnel is highly recommended along with regular centrifuge inspections to monitor noise and vibration levels - including an annual inspection for a more thorough check for wear and damage.Eager to learn more about spare rotating assemblies and how Centrisys can be your go-to-resource for decanter centrifuge service and repair? Contact one of our knowledgeable centrifuge technicians today.