Do You Know What Your Clarifier is Doing?

By Nils R. Young, PE, Managing Director

The DBS 4-20 mA remote torque monitoring and loss motion detection allow for minimal maintenance. DBS type H and type F drives keep your clarifier flowing. With positive torque overload protection and accurate analog output, you can efficiently monitor process conditions and equipment operation.

Positive torque overload protection means that the scraper drive is designed to produce a controlled preset maximum torque, or stall torque. The drive will run continuously at this torque, but when necessary, it will safely produce a higher, controlled, short-term running torque to keep your solids moving.

When an overload occurs in a clarifier with a DBS drive, first the DBS torque alarm switch triggers an alarm. If the overload increases, then the DBS torque cut off switch shuts off the drive motor, topping the mechanism.

On other manufacturers' typical drives, if the torque overload switches are overridden, or if the overload is instantaneous, the unit would probably break a shear pin or wear out a slip clutch and the rake and solids would stop moving. The solids build up until someone notices.

Once someone notices the situation, operators routinely jog the drive or override the failsafe. Unfortunately, in the process of attempting to correct the situation, they may tear up a scraper/collector assembly and corkscrew the column or rake cage.

Most clarifier drive electric motors can produce up to three times their full load torque. In addition, most design standards require the motor to be sized at or below full load when at drive cut-out torque. As a result, most clarifiers can structurally fail if the torque overload system isn't accurate and reliable.

DBS' F-type and H-type drives eliminate these problems. We design our F-type and H-type drives to consistently push and not tear up your rakes. If a F-type or H-type drive experiences load demands above the cut-off setting, the drive will simply slip, without overheating or overstressing. This feature enables you to overcome a process upset without the risk of damaging equipment.

DBS' accurate 4-20 mA analog torque output allows your operators to continuously monitor scraper load in clarifiers, gravity thickeners, softeners, or whatever hydro-separator process you use. The continuous remote analog signal lets operators observe process change and respond promptly for optimal results.

DBS loss motion detection provides a simple, immediate, positive indication that the mechanism has stopped moving, for whatever reason. Because most clarifiers turn at low speeds and are observed infrequently in real-world conditions, DBS' monitoring features provide a very effective means of helping you keep your operations running smoothly.