Challenge

High-purity water is essential for producing steam that will not scale turbine blades with silica, minerals and other contaminants. In 1981, a mixed bed deionizer was purchased by a Michigan utility to produce the type of high-purity water required by the coal-fired electric generating station. The mixed bed deionizer was equipped with an electro-mechanical timer-relay controller.

• Considered state-of-the-art at the time, the 20+ year old controller had stopped functioning properly:
• Airborne coal dust and corrosion had attacked it
• No replacement parts were available
• An operator had to stay by the controller for 3 hours to time and manually initiate each of the steps for every regeneration cycle

The technician for the utility needed technical expertise and a quick, dependable solution.

Solution

Through the EnControl Controls Upgrade Program, a controls specialist:

• Teleconferenced with operating personnel to determine current maintenance procedures, operating conditions and expectations
• Reviewed operating data and sequences, drawings and operating and maintenance manuals
• Provided a proposal, including recommendations, detailed specifications and operational overview

Results

The existing controller was upgraded to an Allen-Bradley SLC controller with a crisp graphical operator interface display screen and keypad which:

• Enhanced overall operation of the water treatment system
• Dramatically reduced manpower requirements and allowed personnel to perform other duties
• Protected the electronics from contamination by airborne dust and water because of its NEMA 4/12 gasketed, painted, carbon steel enclosure
• Electrical schematics, pneumatic tubing diagrams, PLC logic print-outs and vendor literature were provided to utility personnel as part of the documentation package supplied with each controls upgrade.

With the comprehensive documentation package, plant personnel were able to quickly install the new panel and tube the valves to the appropriate solenoids.