Shutdown and Blowdown Valves - Partial Closing Techniques
For some years now there have been systems available to check and report on the operation of shutdown and blowdown valves by partially closing and validating the results.
There are various schools of thought on the technique, and whilst it does not fully validate the integrity of the valve, the partial closing does give the valve some exercise and monitor such things as break out torque and parameters over the 10-20% operation. This must improve the chances of operation during a true demand on the system and hence enhance integrity.
Also, of course, there usually are trips during operation, when this occurs a window of opportunity arises to capture all the valve status information across both the opening and closing stokes of the valve. This is usually achieved by a comparison against the "new footprint" or signature of the valve. Thus faults will be sensed by Torque changes, slower speed of operation etc. Data such as this is captured either by propriety software or Asset Management Systems. Hence the software can predict that the valve is going to fail and schedule in appropriate maintenance at an appropriate moment (rather than have a unplanned and rather expensive shutdown).