Motor-operated valves (MOV) are used in pipelines with large diameters and valves requiring high torque. Flow through the pipelines in which MOVs are installed is generally high. Generally, butterfly or gate valves are used with MOV. Today, we will see one incident related to MOV in which the MOV’s valve body was damaged.
Motor Operated Valve Lesson
The Motor-operated valve (MOV) had a frequent issue of getting jammed. A maintenance job was performed by the Instrument team to solve this issue. After performing a maintenance job on this MOV, the MOV started operating smoothly.
After 20 days, abnormal sounds started coming from the MOV’s body when the MOV started opening and at closing time. The Motor-operated valve gets jerks while opening and at closing time. MOV was then dropped for the inspection of the body.
Maintenance
What did the Instrument team do in the maintenance job when the problem was first reported?
The instrument team checked the stroke of the Motor-operated valve and found that the MOV’s body got stuck when it was given the open command and sometimes did not open at all.
The handwheel was not operational due to mechanical issues, and it needed a spare, which was not available. So, to tackle this issue, the Instrument team increased the opening torque from 60 % to 70 %. The MOV started operating smoothly.
The Motor-operated valve worked well for 20 days and then an abnormal sound was heard when MOV started opening and also when closed fully. So, MOV was dropped for an inspection job and after dropping MOV, the disc as well as the seat were found in damaged condition.
What might have gone wrong?
The most probable reason for the damage to the disc and the seat is the increased torque. Normally, the torque setting in the Motor-operated valve is 40 % to 60 %. Increasing torque beyond this value will damage the body of the MOV.
Never increase the torque value directly. Check the physical condition if the MOV is taking torque more than 60 %.
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