LIKE MANY COAL-FIRED power plants, Salt River Project’s Coronado plant in northeastern Arizona has experienced problems with the cylinder actuators on its fly-ash distribution system. Because of excessive maintenance and loss of availability of the fly-ash distribution system, plant management decided to test alternative cylinder actuators from different manufacturers.
Coronado uses 85 cylinder actuators to operate the fly-ash distribution system’s process control valves. When ash exits the furnace, the valves are used to direct the ash in and out of hoppers. From the hoppers, the fly-ash is dumped into a collection unit, where it is mixed with water before being transported to a final storage area.
On average, the old cylinders were replaced every two to three years, an unacceptable replacement frequency for the plant’s managers. A reliability-centered maintenance (RCM) system is used at the plant to balance equipment criticality with preventive maintenance activity. An RCM analysis of the cylinder actuator failures revealed that the plant was losing half of the mean time between failures on the cylinders.
In 1996, Sun Pneumatics supplied Coronado with three small-bore (3.5 inch bore x 6 inch stroke) cylinders-manufactured by Numatics Actuator-for testing on the fly-ash distribution system. During the test period, the cylinder actuators were subjected to excessive heat in the summer, extreme cold in the winter and the abrasive action of the fly-ash, but they operated without any problems.
According to Sun Pneumatics, the test was so successful that plant management decided to convert all of the cylinders at the plant as they wear out. Over the long term, the plant is expected to save thousands of dollars in maintenance and repair costs, said Mike Brown, maintenance supervisor for Salt River Project.
Installation of Numatics Actuator system on fly-ash system at Salt River Project’s Coronado Power Plant