15 October 2009
The Iggesund mill is one of the most advanced, fully integrated pulp and paperboard mills in the world. It has an annual capacity of 330,000 tonnes of Invercote, a multilayered solid bleached board. In order to maximise availability, the plant has moved away from scheduled maintenance of control valves to the predictive maintenance approach.
At the mill, diagnostic information from Fisher FIELDVUE digital valve controllers is delivered to Emerson’s AMS Suite predictive maintenance software for access by plant personnel. The AMS ValveLink software application delivers the valve health data, enabling plant personnel to eliminate unplanned shutdowns, reduce inventory of new valves and spare parts, and decrease maintenance time.
“Almost ten years ago we realised that our methods of maintaining control valves and field instrumentation could be improved.” said Peder Hägglund, the technical manager at the Iggesund mill. “Over time we have installed over 200 of Emerson’s FIELDVUE controllers and used the diagnostic capabilities extensively.”
“We have worked with many end user organisations across all industries, helping them to develop operating procedures around control valve diagnostics,” said Wendy Nancarrow, the European director for Emerson’s Fisher valve instrumentation business. “Of all the companies we have worked with, we believe that Iggesund are one of the world leaders in the use of online control valve diagnostics technology to drive plant performance improvements.”
The FIELDVUE diagnostics are accessible online. The real-time predictive diagnostics give a fast and accurate insight into the health of the valves. The ValveLink software can be used to quiz the FIELDVUE devices for additional information or to run advanced diagnostic tests. Travel Deviation alerts are a primary indicator of control valve problems.
“The Travel Deviation alert is triggered when the control valve has not moved to its required position within a certain period of time,” said Tommy Nielsen, the sites control valve specialist. “This alert can indicate many potential faults, such as an increase in friction, air leaks, mechanical faults or a physical blockage. Other alerts that we find most useful, are the Cycle Counter and the Travel Counter.”
The Cycle and Travel Counter alerts can be used to determine control loop stability since both are indicators that the loop may be oscillating. Oscillations can cause poor control and can, in extreme circumstances, lead to the loop being put into manual control. Poorly tuned loops can lead to quality issues, excessive raw material usage, an increase in energy consumption and premature valve wear. The maintenance department at Iggesund is increasingly employing these two alerts as they look to improve the overall performance of the mill.
“The success of control valve diagnostics at our mill can be attributed to many factors.” continued Hägglund. “We have a genuine interest in innovative technologies, an enthusiastic team who have perfected the use of online control valve diagnostics; and the success they experienced has motivated people throughout the organisation to drive the necessary improvements.”
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