Butterfly valves help reduce process variability by 5%

24 January 2011

INEOS Chlor, a producer of chlor-alkali and chlorine derivatives, has succeeded in reducing process variability by 5% at its Runcorn plant in the UK.

The company has achieved this reduction by replacing traditional butterfly valves with Fisher Control-Disk valves from Emerson Process Management. The reduced variability enabled the plant to increase throughput, avoid several unplanned shutdowns that could have cost as much as €450,000, and achieve a 96% Overall Equipment Effectiveness (OEE) rating for the unit where the valves were installed.

“For a plant of this size, even a modest reduction in variability can have a significant payback," said Barry Makepeace, INEOS Chlor control & instrumentation engineer. "The Control-Disk valve applications not only saved us money, but also enabled us to optimise process control without sacrificing flow capacity or needing to re-pipe.”

Previously, the plant had used traditional butterfly valves to control the temperature and flow of cooling water to the primary condensers. Tight control is essential because if the condensers’ temperature is too low, there will be residual chlorine in the system, which has to be removed. If the temperature is too high, there is an increased risk of a safety trip or plant shutdown. Each trip and subsequent unplanned shutdown can cost INEOS Chlor up to €75,000.

Unfortunately, the traditional valves had a small control range and a large deadband, which reduced their ability to respond to temperature changes. In the previous 12 months, the plant had experienced 23 trips leading to a significant loss of production.

INEOS Chlor therefore made the decision to replace four traditional butterfly valves with the new Fisher Control-Disk design. Its effective control range (between 15% and 70% of travel) approaches that of a segmented ball valve. Tighter, more reliable valve control enabled plant operators to optimise temperature set points and avoid at least six unplanned shutdowns.

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