Keeping control valve maintenance in line
December 1, 1999 By Pulp & Paper Canada
In the past, paper mills often shut down for an extended period for maintenance. The maintenance staff would work through the shutdown taking equipment off line and rebuilding it. Today’s paper mills …
In the past, paper mills often shut down for an extended period for maintenance. The maintenance staff would work through the shutdown taking equipment off line and rebuilding it. Today’s paper mills can no longer afford these lengthy shutdowns.
The Shotton Paper Company, Great Britain’s leading manufacturer of newsprint, operates 365 days a year, 24 hours a day, including Christmas and New Year’s. Its average shutdown is from eight to 24 hours.
In 1996, the company established a maintenance development department under the direction of project engineer Ray von der Fecht. The department’s purpose was to investigate equipment failures and determine the causes, how they might be prevented in the future, and to acquire a “condition monitoring” capability for predicting failures in control systems before they result in costly process disturbances or unplanned shutdowns. Control valves were one of the first pieces of equipment the department reviewed.
Shotton Paper asked Neles Controls (now part of Neles Automation, and its main supplier of control valves) to help the mill develop a condition monitoring system to predict valve failures. Company technicians using the Nelscope portable diagnostic system monitored critical control valves on PM 2. The control valves at Shotton Paper were equipped with electronic positioners. Fifty-one control valves were chosen for monitoring during two planned shutdowns about five weeks apart.
The team of technicians equipped with Nelscope systems checked the condition of a greater number of control valves in a shorter period of time than the conventional process the mill used.
Mill personnel noticed that repairs and adjustments made as a result of the Nelscope condition monitoring process resulted in significant improvements in the papermaking system’s performance, particularly in the areas of consistency control and stock proportioning.
Ed Macys, pulp and paper industry manager, Neles Automation North America.
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