Control Valve Positioner Maintenance

K

Thread Starter

Khalid

I just want to know if the Positioner of Control Valve requires any sort of maintenance?

Regards,
 
A
The frequency of the maintenance for a positioner is very less if it is installed properly in accordance with valve performance. However, some of the maintenance activities related to a positioner involves lubrication of the linkages and general checking of the bellows in case of rupture. Sometimes, its good to check the feedback link for a damages.

Generally it doesnot come under preventive maintenance rather it comes under react ive maintenance (i.e attending when it fails to deliver the reqd performance)
 
G
A periodic (typically yearly) actuator diaphragm leak-down test (if it is diaphragm type) and correctly performed positioner calibration will typically reveal most problems before they cause an in service failure.

Greg Ponto
Lead Combustion Turbine Specialist
Elwood Energy
Office ph. 815-423-2232
Cell ph. 815-671-2383
[email protected]
 
S

Sajid Ali Khan

> I just want to know if the Positioner of Control Valve requires any sort of maintenance?

==
Dear Khalid,
You have not mentioned whether you query is about a smart positioner or a conventional fully pneumatic positioner. Assuming you are referring to the latter, my suggestions are:

1. Yes, it does need periodic maintenance, typically frequency can be once a year. However, in case the valve controlling a critical loop, needs maintenance include the positioner as well, even if the elapsed time in less than a year.

2. You can start with a performance inspection of positioner, and check the response time, hysteresis, dead band, minimum and maximum opening and of course calibration.

3. Check the valve both without positioner in circuit and then with positioner in service to isolate the problems in valve or positioner.

4. I would stress check the valve by feeling the very minor movements on minute input changes, as that is normally what is demanded by controllers, whether single loop or on DCS.

5. In case of performance degradation through inspection of the positioner is required, e.g. flapper (pitting at the nozzle may be found), relay diaphragm brittleness or leakage, relay's correct amplification usually 1:4), play in linkages, leakages in fittings, bellows or valve diaphragm, increased valve stiction, valve stem straightness are few of the culprits.

Regards,
Sajid Ali Khan
[email protected]
 
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