How to effectively protect a SCADA control panel in a water/wastewater environment using Stahlin Non-Metallic Enclosures

The Situation

Fishbeck, Thompson, Carr & Huber, Inc. (FTC&H) is a professional civil engineering, environmental consulting, architectural/engineering, and construction management firm. They specialize in the design of water and wastewater treatment plants for municipalities and industry.

One of their clients, a water filtration plant, was concerned about the early corrosion of metallic enclosures that housed critical SCADA PLC Control Panels. The corrosion level is unusually high in this environment due to the control units placed above an open top tank containing chlorinated water.

The Challenge

chlorine creates an overall breakdown of the passive film that coats stainless steel thought to protect the metal from chemical attack. This results in the entire surface of the metal developing a uniform “spongelike” appearance. The rate of attack can be affected by the fluid concentration, temperature, fluid velocity and stress on the metal components exposed to the chlorine.

As a general rule, the rate of attack will double with a temperature increase of 18° Fahrenheit (10° C.) in either the product or the metal substrate.

In the case of this water filtration plant, FTC&H was fighting a tough battle against corrosion and needed to switch to a different material which would not be affected by the high exposure to chlorine in the facility. Consequently, they began to explore non-metallic alternatives.

FTC&H needed to find an enclosure that could house a PLC with local I/O rack/chassis, UPS, and relays inside the enclosure. They also needed space on the front panel to secure analog indicators, pushbuttons, pilot lights and selector switches. In addition, the client required a “double seal” to protect the contents of the enclosure from the affects of the corrosive environment.

The Solution

Thoughts from FTC&H on the success of using Stahlin enclosures: “Our solution was clear. We were impressed by Stahlin’s N-Series Wall-Mounted, Non-Metallic Composite Enclosure because its polyurethane seamless gasket provided us with a water and dust-tight environmental seal. And of added benefit, non-metallic enclosures are easier to modify than metallics!”

"We knew we had made the correct choice when our customers at the Water Filtration Plant made it a point to comment about the quality of their Stahlin product, despite their repeated use of metallic enclosures in their facility."

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