Improve clarifier/thickener runnability

Do you currently operate Dorr and Hedemora drives, perhaps installed as early as the 1960s-1970s? If so, you are running a significant risk of unscheduled downtime. Read on to see why it's time to replace them with drives incorporating modern technology.

The oldest Dorr and Hedemora drives were installed in the 1960s-1970s. It's time to replace them with drives incorporating modern technology. The problem - old drives
The rake in clarifiers/thickeners is subjected to considerable forces. With your old drives, there is no way to measure the drive’s torque, as there is no continuous monitoring. This means that there is a risk of damaging the rake and the drive during operation, with costly operational stoppages as a consequence.

The solution - a Metso CRD kit
To help you avoid this runnability problem, Metso now offers CRD kits to replace Dorr and Hedemora drives. These conversion kits for replacing drives in clarifiers and thickeners provide improved reliability, control and supervision.

The new drives from Metso incorporate a series of improvements in the causticizing process:

Improved supervision and control. The CRD, which is controlled and monitored from the control room, contributes to improved supervision and control of the underflow.
Improved reliability and availability. The continuous monitoring of the rake’s torque results in a significant improvement in reliability and availability compared to older clarifier and thickener drives.
Fewer operational stoppages. Increased reliability and availability minimizes the risk of expensive operational stoppages. The technical design contributes to increased reliability. It includes a mechanical torque limiter that is tripped prior to overload, as well as a continuous indication of the rake’s height above the bottom of the clarifier.

Benefits
There are several additional reasons to upgrade your old Door and Hedemora drives with a Metso CRD kit, including:

Continuous monitoring of the rake’s torque is provided, with alarm levels that are configured in the mill’s DCS system.
A echanical torque limiter will trip prior to overload and before the rake sustains damage.
The operator receives continuous indication of the rake’s height above the bottom of the clarifier.
The mill’s DCS system can operate the pump for the underflow, and hence the height of the sludge bed. The change to a modern drive thereby contributes to improving production performance.
The gears are made of standard units from well-known manufacturers - a major advantage when it comes to supplying spare parts.
The new drive can be dismantled without emptying the tank to support the rake.

What's included?
The conversion kit contains a combination gear with safety system. A beam bracket for installation onto the tank’s roof beams is also provided.

The kit includes a shaft journal with flanged connection to the existing rake’s centre shaft (incl. seal to the tank roof). Standard electrical and instrument installations are additional.

Quality assurance
As with any Metso product coming out of R&D and receiving our seal of approval, startup quality is assured by the availability of a worldwide staff of experts. The replacement of the drive is always preceded by an analysis and evaluation of the mill’s processing conditions and operating method. Implementation takes place in consultation with a Metso representative. The entire installation is handled by our service personnel and can be performed during your mill’s regular stoppages.

For further information, please contact Pierre.Massicotte@metso.com +1 514 333 2341.