Solid-State Sensors And Space Exploration
Technical papers were also part of the four-day conference, with authors outlining their presentations and answering questions.
In one such session, Irma Ylikangas, product line manager for Vaisala of Vantaa, Finland, reviewed various methods of ammonia leak detection in refrigeration systems.
She noted, "The purpose of ammonia detection for refrigeration applications is to sense and communicate the presence of ammonia to protect people and property. Such applications can be very demanding. The temperature range over which they must operate is great. Also fluctuating humidity levels and various odors may lead a sensor to alarm even when ammonia is not present. These demanding operating conditions make it very difficult to choose a reliable ammonia leak detection system."
She reviewed some of those products, "all of which have benefits and weaknesses."
Electrochemical sensing involves the diffusion of gases across a permeable membrane into an electrolyte solution within the sensor unit. She noted the electrolyte is ammonia-specific "and therefore has few cross sensitivity problems with other gases." She did note the warm-up time for the sensor (two to eight hours) could be a detriment.
Polymer thin-film capacitive sensors detect changes in the capacitance caused by absorbed ammonia. The technology is also selective to ammonia to reduce cross sensitivity to other background gases. She did say that the time required for water desorption process could slow the response time of the sensor.
Charge carrier injection sensors "selectively bind ammonia with a gas-sensitive material." Such units, she said, have low maintenance and are less prone to false alarms than typical solid-state sensors. But she added that the "probability of nuisance alarms increases in the 15- to 35-ppm range because of the detection limits of this technology."
Solid-state sensors are "typically made with a sensing material composed of a metal oxide and a catalyst." Because the solid-state sensor "is not consumed in the ammonia detection process, these sensors last at least five years"; however, "background gases may interfere with these sensors. Installing filters on the sensing element can minimize this."
Integrating ControlsAnother paper focused on integrating advanced controls into plant processes and management programs. The speaker, Paul Stiller of Rockwell Automation in Cleveland, contended that energy management controls are sometimes not given the attention they deserve.
"Most manufacturing facilities have modern automation tools in process areas," he said. "Plant engineers maintain and upgrade process automation equipment and software so the facility can remain competitive.
"However, energy-related controls and automation are often assigned a lower priority. A typical manufacturing plant makes unnecessary energy expenditures because energy-related automation has not been given appropriate attention. There is an opportunity to reduce energy-related manufacturing costs by extending modern process automation technology to energy systems."
He outlined a variety of technologies with a focus on water pump, motor, and drive efficiency, and called on those involved in decisions within a facility to have what he called "maintenance action planning (MAP)." He said an effective MAP solution needs to include:
Is This Really Normal?Former astronaut Mike Mullane used his experience on three space missions with the National Aeronautics and Space Administration (NASA) and recent shuttle tragedies to urge his audience of business people to guard against what he called "normalization of deviance."
He described this as "a phenomenon in which individuals or teams repeatedly accept a lower standard of performance until that lower standard becomes the norm."
Mullane said the space shuttle Challenger tragedy resulted from an extended period of time in which "the NASA team accepted a lower standard of performance for the solid rocket booster O-rings until that lower standard became the norm.
"By the dawn of Challenger, the NASA team had become so comfortable with seeing occasional O-ring damage and getting away with it that the original standard, in which any O-ring damage was defined an intolerable deviance, was no longer considered."
He encouraged businesses "to maintain their high standard of performance" by setting the highest standards, and connecting the dots to ensure multiple problems will not lead to "the normalization of deviance."
Publication date: 06/07/2004