Diagnostic tools identify faults in valves

Dow Corning has reduced the number of valves that are removed for service, following the introduction of valve diagnostic services to predict impending problems and initiate only necessary repairs

Emerson Process Management has been able to significantly reduce the number of valves that are removed for service at Dow Corning, following the introduction of valve diagnostic services to predict impending problems and initiate efficient repairs.

Emerson has a three year contract with Dow Corning, for control valve monitoring services at their Barry, South Wales plant.

The plant is the largest Dow Corning global manufacturing facility for silicon-based products.

Continuity of production is vital and, to ensure reliability, Dow Corning was regularly dismantling and repairing up to 60 percent of the control valves on the plant as part of its scheduled maintenance programme.

This was proving to be an expensive and time consuming exercise.

By applying advanced diagnostic tools within Emerson PlantWeb architecture, for example the AMS Suite: Intelligent Device Manager, and Flowscanning valve diagnostic services, on each control valve, Emerson service personnel are able to check valve performance.

By servicing only those valves that are identified as faulty, Dow Corning has been able to increase reliability and reduce maintenance costs.

For example, during a recent plant shutdown, a total of 191 valves on the plant were scanned.

While traditional practice is to fully service up to 60 percent of these valves, the flowscanning service verified that only 51 valves required further investigation and, of these, just 16 valves were pinpointed for a full service in the workshop.

Roy Phillips, Control Electrical Engineer at Dow Corning said, "Around a third of the valves that were scanned using Emerson diagnostics had a problem.

Some of these were minor while others were more significant.

If we had stroke checked these valves using a 4-20mA source in the traditional way, it is likely that only half of the IP problems and a quarter of the positioner faults would have been identified.

Significantly, we estimate that only two of the valve failures would have been picked up".

Because a reduced number of valves require full service, the demands on maintenance resources are significantly reduced.

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