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Making sense of sensors.

Sometimes it pays to replace your sensors with new ones that can do more than the original.

Few plant operators are willing to risk expensive unscheduled downtime when a small but crucial sensor is nearing the end of its life expectancy. Whether it's a $50 limit switch or a $2,000 pH probe, the cost of the sensor pales in comparison to the potential costs of lost production and labor.

Although sensor replacement can be done using exactly the same sensor provided by the original equipment manufacturer (OEM), oftentimes a different type of sensor from the aftermarket can offer better wear resistance, accuracy or reliability in harsh environments.

As the food industry becomes more competitive, scrap losses and downtime eat into already skinny profit margins and provide an entre for new or different sensor technologies.

"One of the main drivers (of the sensor aftermarket) is the maturation of industry," says Jack Nehlig, vice president of electromechanical and industrial products for Honeywell Micro switch in Freeport, Ill. "Our customers are trying to drive to higher efficiency rates. As you get into those high levels of efficiency, low levels of scrap and high throughputs, you go back and probably add things in the aftermarket."

Edward N. Deck, senior product specialist for Yokogawa Industrial Automation in Newnan, Ga., says mean times between failures, accuracy, drift, frequency of calibration, the ability to handle process parameters, chemical poisoning of electrodes, abrasiveness of processes which may etch the electrodes, and unique design characteristics of the electrodes which might make the sensors resistant to pressure surges or temperature spikes are all reasons a company may opt to go outside the OEM market for new sensors.

"If customers experience enough grievances with their current selection, they'll start looking (to the aftermarket)," says Deck.

An example of the aftermarket's ability to improve productivity, says Nehlig, came about several years ago after complaints from dairy operators that electrical sensing equipment could not withstand the frequent high-pressure and high-temperature washdowns and acid and alkaline scrubbings required of that industry. Nehlig says Honeywell Micro switch developed a new sensor industry test protocol that took this type of harsh duty into account, and now replacement sensor manufacturers routinely make sensors that can withstand 1,200 psi of high-temperature washdown.

Opting for a new type of sensor may also be fueled by changes in product offerings themselves. Jim Jerschefske of Allen-Bradley in Milwaukee notes the switch by beverage makers to clear bottles and products. Photo-electric sensors that handled the old product line without difficulty suddenly were unable to "see" the new clear product. New sensor technology was developed using sensor heads with logic programs that detect minute changes in light patterns.

Retrofitting production lines to improve safety or quality control may also provide sensor aftermarket opportunities. Nehlig points out his company's new light curtain that shuts down dangerous equipment when a worker breaks its broad light beam. Another example is cable pull limit switches that can be installed to halt product lines due to a safety or quality control problem.

How much technology a sensor manufacturer builds into its products and which segment of the market it serves determines how big a player that manufacturer is in the sensor aftermarket. Honeywell Micro switch, says Nehlig, serves the traditional industrial market for limit switches, photoelectric sensors and proximity sensors. Eighty percent of Honeywell Micro switch's sales go to the company's well-entrenched OEM customer base. Conversely, Allen Bradley, noted for its high-end industrial automation systems, sells 80 percent of its sensor line to the replacement market. Jerschefske says Allen Bradley's products tend to have the full complement of technology built into them, which may price the products out of some OEM markets but fits in nicely with specialized applications in the aftermarket.

Deck sees the sensor market as markedly stratified and skewed to the low end of the bell curve. He says vendors who manufacture only sensors usually offer a broader spectrum of high- and low-end sensor models from which to choose.

Yokogawa Industrial Automation manufactures pH, conductivity, inductive conductivity and dissolved oxygen probes aimed at high-end users. Many of the company's sales in the food industry go to the brewery and beverage trade, where unionized labor costs provide incentive to find probes that last two or three times longer than less expensive counterparts. In cases where downtime or maintenance costs, environmental fines or quality control specifications demand the greatest level of accuracy and reliability, says Deck, spending an extra 10 percent or even 500 percent on a better-quality sensor actually may prove to be a great savings to the manufacturer.

Deck says the global market for sensing equipment is increasing, especially in the developing regions of Eastern Europe and the Pacific Rim, where new consumer markets are emerging. The North American market for sensors is stable, he adds, because the industrial base here is already mature. Regulatory pressures and costs of labor, energy and raw product are the primary economic driving factors that affect sensor manufacturers' penetration into a given marketplace, says Deck.
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Title Annotation:bottling sensors
Author:Hoch, G. Jeffrey
Publication:Food Processing
Date:Oct 1, 1997
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