Total stroke variation of the high-temperature mixing valve in the sulfur unit
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There is a high-temperature mixing valve for a sulfur processing unit; after using it for some time, it was found that the stroke deviation was too large. The valve stem turned to the right, which caused a deviation in the feedback rod and consequently changed the stroke length. A Siemens positioner is being used. What could be the reason for the valve stem moving back and forth? It would be helpful to have internal diagrams along with a detailed explanation. Thank you
The connection between the valve stem and the actuator (usually at the location where the travel pointer is mounted) is not secured.
I checked it – it’s very tight; the rotation of the valve stem below causes the valve stem above to move as well
There are several possible reasons for the valve stem to rotate: 1. The valve connection piece is loose； (External inspection) 2. The internal fixing nut of the membrane head is loose ； (Continuously rotating) 3. The valve stem is subjected to a radial unbalanced force, causing it to rotate by a small angle. (It stops rotating when turned to a certain angle.) Mark the valve stem and the valve to observe the rotation.