Repair and maintenance


MAC valve actuator diagnostic device


The MAC diagnosis is an advanced motor-operated valve diagnosis service developed by our company with many years of experience and achievements in the maintenance of motor-operated valves. Comparing a conventional overhaul to an inspection with surgical precision, the MAC diagnosis is comparable to a complete medical checkup utilizing sensor technology. Because the motor-operated valves transmit motor power from the worm, worm wheel, stem nut, and to the stem (valve shaft), the behavior and status of each part will be seen as a change in the torque. The MAC diagnosis accurately measures this torque change during operation to quantify comprehensive soundness in a short period for the check and evaluation procedure.

This enables the disassembly and repair of specific parts only when needed without unnecessarily disassembly of motor-operated valves.

Characteristics of MAC diagnosis

  • – Checks the soundness of motor-operated valves quantitatively in a short period of time
  • – Abundant experience in diagnosis and high precision operation
  • – Measurement of torque during operation
  • – Enables readjustment of the torque and limit settings on-site
  • – Screening of valves subject to overhaul
  • – Prevention of human error
  • – Contribution to shortening of periodic inspections and cost reductions
  • – Compatible with all motor-operated valves used in domestic nuclear power plants

Major diagnostic items

  • – Insufficiency of preset torque value
  • – Change in behavior of running torque value
  • – Increase of valve pull-out torque
  • – Stem nut abrasion volume
  • – Motor current value
  • – Motor brake operating time
  • – Malfunction of electromagnetic switch in control panel
  • – Abnormal vibration (such as backlash of transmission system and defect in bearing)
  • – Limit switch operation position error
  • – Torque switch bypass operation position error
  • – Valve stop position error