Diakont Electromechanical Actuators Successfully Perform Main Steam Valve Control At Nuclear Power Plants For Over Five Years

  • July 07, 2015
  • Diakont
  • News

San Diego, CA – Diakont, a leading high-tech engineering and manufacturing company, has successfully replaced more than 20 legacy hydraulic actuators with Electromechanical Actuators (EMA) for the main steam valve controls at nuclear power plants. The integration of the first EMA units was completed in 2009 and the systems continue to operate successfully. Retrofitting the main steam valve control systems with Diakont EMAs has improved plant performance and yielded greater responsiveness, more precise control, and reduced maintenance challenges.

The original main steam mechanical-hydraulic control systems (HCS) at the power plants presented multiple challenges. As the systems aged, maintenance became increasingly cumbersome as new replacement parts became less readily available. In addition, hydraulic systems lacked system control, were prone to trips, and presented a significant fire hazard from the vast amounts of oil. Replacing aging hydraulic actuators with Diakont’s EMAs eliminated these risks while improving overall system performance.

Diakont EMA units provided a significant increase in valve control that reduced backpressure fluctuations in the nuclear steam supply system (NSSS). Diakont’s steam valve control system reduced the variance of full-load backpressure from ±4.25 PSI to ±0.5 PSI, increasing power output by 2.0 MWe per reactor with no corresponding change in thermal power output. Diakont actuators are able to complete a full linear stroke in less than 50 ms, significantly increasing turbine safety. The EMA dual-redundant design also increased reliability and reduced trips with dual control channels, dual motors, and redundant sensors.

Diakont has incorporated elements of the technologies that were used in nuclear power plant projects and applied them to the standardized DA Series actuator. These elements include a precisely-machined roller screw and a high-force Permanent Magnet Synchronous Motor (PMSM) integrated into a single unit, thus providing exceptional performance in a compact footprint. Roller screw actuators are ideal for critical applications including positioning systems, CNC machine tools, robotic weld guns, servo presses, bending machines, injection molding machines, factory automation, and discrete manufacturing applications. Roller screws also offer better lifetime ratings and higher speeds compared to ball screws while offering lower operating costs than hydraulic and pneumatic actuators. Designed to facilitate easy integration into existing motion control systems, Diakont EMAs are compatible with many servo drives and amplifiers.

“Diakont EMA’s are made with advanced roller screw technology that provides multiple points of contact within the gear. This greatly increases the lifetime, load capacity and axial stiffness of the EMA, making it an ideal solution for applications that require high positioning accuracy over millions of cycles without maintenance and repair,” stated Steve Schustek, Technical Sales Executive with Diakont.

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