The slurry valves at Owensboro Power Plant (Kentucky, USA) were malfunctioning in the scrubber area. Many maintenance hours were being invested replacing faulty limit switches. Operations at the power plant had resorted to by-passing switches that did not work in order to minimise downtime and struggled to find a reliable solution. TopWorx reviewed their current application, to understand what was causing the problem.
As is typical for power plant applications, the environment was very harsh and required high-pressure wash down. The existing mechanical limit switches were unable to adequately withstand the high-pressure wash down. As a result, they were being penetrated by water, dirt and limestone. The ingression of water and caustic material was causing the switches to fail. Owensboro Power Plant had tolerated faulty switches for years. They wanted to replace their existing switches with a switch that was reliable and durable enough to withstand limestone, dirt and wash down. They wanted a totally sealed switch that would not be susceptible to moisture ingression. Ideally, it would have no target contact or wearing situation, so there would be no maintenance. In short they wanted a 'fit and forget' solution.
A leverless solution!
The TopWorx 70-Series GO Switch was found to be the solution. It uses a unique, hybrid technology to detect the position of a ferrous target via an electro-magnetic field and has been proved reliable and durable in processing and manufacturing plants for over 30 years. Since it is a leverless limit switch, it does not require a lever arm to make it move. Therefore, there is no metal-to-metal contact, and virtually nothing to wear out.
These switches are built to last for high cycle, dirty and physically abusive applications.
With an IP65 rating, their design prevents ingression of caustics, moisture and particulate. They are completely potted and sealed, so no moisture can affect their operation. Other options include Nema 7, 9, 12, and IP 68 (submersible). Some models are even rated for use at 6000 metres underwater!
These features were a great attraction to the power plant. Budgets were tight, but the cost of a switch not working was even greater. They were impressed with the reliability of the GO Switch and optimistic about moving forward.
In the scrubber area alone, they installed one hundred of these switches. "We have been very pleased with the GO Switch installation. We like the way they work, because they are reliable. We do not have to worry when we wash down. They suit our needs real well," stated Bill Keach, maintenance planner for Owensboro Power Plant.
For more information contact Francois van der Westhuyzen, Switches International, +27 (0)11 462 4253, [email protected], www.switches.co.za
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