Valve Maintenance

Ball Valve
  • Operation of handwheel is jerky
    • Line debris is increasing the required closing torque.
      Flush or clean valve to remove the debris.

      Actuator/shaft adaptor misaligned.
      The actuator mounting must be realigned. This is done by loosening the bolting and then repositioning the actuator on the mounting plate.

      Packing is over-tightened.
      Loosen packing bolts to hand tight and then reapply torque. Torque values are found in the standard maintenance manuals which can be downloaded from the Velan website.

      For pneumatic actuator, air supply pressure is inadequate.
      Verify either on the submitted drawings or with Velan what is the required level of air pressure. If the supply pressure is low, make sure that there are no leak paths in the air supply line.

      The shaft key has sheared, disconnecting the stem from actuation.
      To identify this problem, remove the actuator and inspect the drive nut for signs of damage. This problem can usually be solved by installing new components.

      The actuator duty cycle was exceeded causing the actuator motor to burn out.
      Replace the actuator motor.

      There is problem with the actuator other than those listed above.
      At this point, the actuator should be inspected by an expert to determine the cause of problem and the best possible solution.
  • Valve stem won't rotate
    • Line debris is increasing the required closing torque.
      Flush or clean valve to remove the debris.

      Actuator/shaft adaptor misaligned.
      The actuator mounting must be realigned. This is done by loosening the bolting and then repositioning the actuator on the mounting plate.

      Packing is over-tightened.
      Loosen packing bolts to hand tight and then reapply torque. Torque values are found in the standard maintenance manuals which can be downloaded from the Velan website.

      For pneumatic actuator, air supply pressure is inadequate.
      Verify either on the submitted drawings or with Velan what is the required level of air pressure. If the supply pressure is low, make sure that there are no leak paths in the air supply line.

      The shaft key has sheared, disconnecting the stem from actuation.
      To identify this problem, remove the actuator and inspect the drive nut for signs of damage. This problem can usually be solved by installing new components.

      The actuator duty cycle was exceeded causing the actuator motor to burn out.
      Replace the actuator motor.

      There is problem with the actuator other than those listed above.
      At this point, the actuator should be inspected by an expert to determine the cause of problem and the best possible solution.
  • Opening/Closing torque is excessive
    • Line debris is increasing the required closing torque.
      Flush or clean valve to remove the debris.

      Actuator/shaft adaptor misaligned.
      The actuator mounting must be realigned. This is done by loosening the bolting and then repositioning the actuator on the mounting plate.

      Packing is over-tightened.
      Loosen packing bolts to hand tight and then reapply torque. Torque values are found in the standard maintenance manuals which can be downloaded from the Velan website.

      For pneumatic actuator, air supply pressure is inadequate.
      Verify either on the submitted drawings or with G M Engineering what is the required level of air pressure. If the supply pressure is low, make sure that there are no leak paths in the air supply line.

      The shaft key has sheared, disconnecting the stem from actuation.
      To identify this problem, remove the actuator and inspect the drive nut for signs of damage. This problem can usually be solved by installing new components.

      The actuator duty cycle was exceeded causing the actuator motor to burn out.
      Replace the actuator motor.

      There is problem with the actuator other than those listed above.
      At this point, the actuator should be inspected by an expert to determine the cause of problem and the best possible solution.
  • What bolt torque values are recommended for valves?
    • Ball valve torque values are specified in the maintenance manuals for the each valve type. Maintenance manuals can be requested from the Field Engineering Services.