Repair and maintenance


SAM automatic stem nut abrasion measurement system


When the threads of the stem nuts mounted in motor-operated valve actuator abrade and cause falling of the stem, the valves become inoperable, requiring a lot of time and effort to restore the system. It is important for managing the safety of motor-operated valves to accurately determine the status of abrasion of the stem nuts and replace them at the right time. SAM can measure the abrasion volume of the stem nuts quantitatively, using dedicate sensor and software that can set the actuators in a simplified manner without disassembling them. Furthermore, accumulated measurement data manages the tendencies for determining the time to replace the stem nut.


  • – Improved reliability compared to conventional measuring method
  • – Quantitative check of abrasion volume in a short period of time
  • – Storage and accumulation of electronic data of measurement and diagnostic results
  • – Inspection without disassembly

Mechanism of abrasion measurement

Switch the motor-operated valve actuator to manual mode, and rotate the stem nut by turning the handle. There is a gap between the stem nut and stem, and the stem nut spins until the threads of the nut contact the threads of the stem. Upon completion of the spin, the rotation of the stem nut is transmitted to the stem and the stem starts to operate. The abrasion volume can be measured by entering the specifications of the stem of each valve to be measured and measuring the spinning angle from when the stem nut starts to rotate until when the stem starts to travel.