Diagnosed Cases

Diagnosed Cases Image

Polymer adhesion was caught in time to prevent valve malfunction

By tracking parameters that indicated valve sticking, the buildup of polymer inside the control valve was detected, preventing the malfunctions and sticking that could otherwise have occurred.

Checking of the stick-slip monitoring screen

The stick-slip monitoring screen: When strokes are smooth and normal, the values appear close to the baseline. When strokes are not smooth, with a lot of stick-slip,* values fall above the threshold.

Checking the maximum operating speed monitoring screen

The maximum operating speed monitoring screen: Sudden increases in max. operating speed, Stroke abnormality

Switch to the bypass and do an overhaul inspection

After switching to the bypass and doing an overhaul inspection, polymer was found sticking to the gland packing.

* Stick-slip is when the valve shaft repeatedly sticks and then slips during a stroke.
This causes increases in the shaft’s operating speed.
At this chemical plant, stick-slip occurs when polymerization progresses inside control valves.

Abnormalities in the instrument were detected
before the process was affected

A valve shaft was diagnosed as behaving abnormally, leading to an inspection where the feedback pin was found to be loose.
Since there were no problems with controllability and no process alarms were generated, the loose feedback pin could have been overlooked.

Checking the assessment results in the valve diagnosis report

The assessment results in the valve diagnostic report: Valve shaft was diagnosed as having abnormal friction

On-site check

Site: When operation was checked, a multitude of zero-point abnormalities had occurred, Safe operation after maintenance, When the valve was checked at the site, the feedback pin was found to be loose.Valve operation stabilized, even though it had been regarded as normal since it had begun operating. The increase in total stroke distance improved significantly.

Optimizing the selection of valves for maintenance

During advance diagnosis, a valve that was not scheduled for repair under the regular time-based maintenance plan was diagnosed as “Maintenance required” and “Check thoroughly.” A step response test revealed something abnormal, and the diagnosis was verified in an overhaul inspection. Were it not for the diagnosis, a “sudden” problem would have occurred later at startup or during operation.

Figure: Optimizing the selection of valves for maintenance
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Contact information for inquiries about the Valve Diagnostics Service

Inquiry contact

For Valve Diagnostics Service consultations or questions ...

Azbil Corporation
Advanced Automation Company