Surviving Harsh Environments

Turning to capture growing markets with harsh environments, manufacturers are creating a new breed of sensor with the operating temperatures, materials and functionality that make them more rugged. "As automation has evolved from the automotive industry to others such as food and beverage, solar panel production, wind power generation and more, a new class of sensors designed to handle the harsh environments is required," says Howard Minnick, president of ASI.

Although increasing ruggedness is one characteristic — along with longer range and smaller packages — for which sensor customers continually look for improvement, there are certain applications that require more from the sensor.

The burgeoning food and beverage industry, for example, is attracting more attention from suppliers. "There is a trend to develop products that are more designed for the environmental requirements of that industry," says Craig Brockman, marketing manager, proximity sensors, for Rockwell Automation. "In the past it's been trying to take existing products and make them work in that industry." These days, sensor developers look more at what the unique requirements are for the food and beverage industry.

Where food comes in direct contact with machines, for example, the need to clean that equipment to make sure no bacteria is allowed to grow on it presents some unique requirements. "Sensor innovations have been driven by many industries, including food and beverage, that require wash downs to maintain a sterile environment," says Melissa Schumann, product manager at Turck.

Those wash downs are done at high pressure and with hot water, making it necessary for sensors to be rated to IP69K standards (the "9" classifying protection from close-range, high-pressure spray downs; and the "K" signifying high-temperature water). But there's more to it than that, including caustic chemicals and bacteria working their way into small spaces.

The hot water is often mixed with cleaning chemicals, making stainless steel 316 a popular material for sensors in the food industry. "A lot of sensors are made out of nickel-plated brass or other materials that maybe over time might rust, or if they're made out of plastic they may not hold up to the caustic cleaning chemicals," Brockman says.

Sensors in the food and beverage industry also require wider operating temperatures, not only to stand up to the high-temperature wash downs, Brockman says, but also because they may be used in a freezing tunnel or by an oven. Most standard sensors have an operating temperature range of -25 to 70 °C, but sensors in this industry require -40 to 80 °C or higher. ASI has a range of rugged sensors that can operate at temperatures as low as -60 °C and as high as 250 °C, Minnick notes.

Finally, manufacturers are also looking for new ways to avoid food and bacteria traps within the sensors. A standard inductive sensor, for example, might have threading on the barrel, which could retain food regardless of how well the machine is cleaned. So suppliers are coming up with new ways to mount the sensors to avoid the threading, Brockman notes. Rockwell has also come up with a new way to program its photoelectric sensors that does away with external pots or pushbuttons to further avoid food traps.

All the innovations lead to increased uptime, important not because the sensors are expensive to replace, but because lost manufacturing time is costly. "The user benefit is clear," Schumann says. "The sensor survives in the wash-down environment, leading to less downtime and fewer maintenance calls."

Changes made on behalf of the food and beverage, or pharmaceutical industries can be advantageous in other industries as well, Brockman points out. They could be of benefit in the mobile industry, including off-road equipment, agricultural equipment and construction equipment, which all use sensors. "If you're making a crane, you don't know if that crane's going to end up in the desert or Arctic Circle," he says. "Having housing that can withstand wash down or being exposed to outdoor elements and not corrode is a benefit as well."