The drive unit can monitor several operational functions, including damper position, frequency of motor reversals, and actuator internal temperature. Values are stored in the electronics unit for performance analysis. ABB Smart Vision Interface Software, an available option, can be loaded on a PC to help in such analyses.
A smart move
The key to “smart” operation of the Contrac actuator is the configurable, microprocessor-based Power Electronics Unit (PEU). It is a separate unit that can be field-mounted near the actuator (Figure 3) and provides digital control and acts as the interface between the actuator and the DCS. When the DCS control signal calls for continuous positioning, the PEU varies the actuator motor frequency, without stepping, until the actuator moves the damper to a new position at the right torque that satisfies the setpoint value.
To configure the PEU for a specific actuator application, such as the damper drive, the electronics unit has a local control panel (LCP), located on the front of the unit under a protective cover (Figure 4).
Figure 4. Local panel and power unit
Rutkoski presses a button on the LCP, which is under the cover on the front of the PEU. The auto-manual switch is located on the post at the far left, and is connected to the PEU by a cable. An operator can use the handwheel (visible on top left side of drive) to manually position the damper.
By means of pushbuttons and LEDs that guide the procedure, an operator can program the basic settings for actuator operation without the use of a PC. Basic settings include defining end positions for lever arm travel, adapting the actuator to the operating range, and effective direction. For special applications, a PC with Smart Vision software can be used to configure the actuator and the PEU.
Also shown in Figure 4 is an automatic-manual switch cable-connected to the PEU. In manual mode, an operator can use the handwheel on the actuator to position the damper. Alternatively, if electric power is on, he can use the LCP’;s raise/lower pushbuttons.
ABB’;s Contrac drive has given Equistar Chemical control over its dampers, saving them big bucks.
Joshua I. Anderson is production engineer of utilities for Equistar and Adolfo B. Aparicio is reliability instrument engineer. E-mail them at firstname.lastname@example.org and Adolfo.Aparicio@equistarchem.com, respectively. Anderson and Aparicio work at the Corpus Christi, Texas, plant of Equistar Chemical LP. Scott T. Rutkoski is resident instrument specialist at CCO. He is employed by the maintenance contractor, consulting firm Zachry Inc. in San Antonio. E-mail him at email@example.com.