So why isn’t wireless technology used more in industrial settings for fixed gas detection systems?
The reasons to go wireless are simple: increased functionality, substantial system flexibility and significant cost savings.
Wireless fixed-monitoring systems by Industrial Scientific employ spread-spectrum technology. Originally developed by the military for encryption of secret data, spread-spectrum technology is virtually impenetrable to interference.
Here’s how it works: Gas detection controllers are placed in a central location, just as hard-wired systems would be. The sensors are placed in the field. The controllers call out to the sensors every few seconds via broadband radio signals operating between 902-928 Mhz. The sensors respond instantaneously with pertinent data.
The spread-spectrum technology ensures constant reliability because it operates in such a broad range. There actually are 65,536 different patterns of signals that the sensors and controllers use to keep in constant contact. This means that there is zero interference with wireless fixed system communications between controllers and sensors.
Despite this level of sophistication, wireless gas monitoring systems do not require any license to operate by the Federal Communications Commission. And since the communications are digitally based, it has all of the advantages of digital technology — including being accessible via the Internet.
While system reliability is an obvious reason for the wireless approach, another is cost savings. Typical hard-wired systems, by their very nature, are expensive to install. Point-to-point sensor connections that feed back to a controller are hard wired, requiring knowledgeable engineers and skilled electricians to meet stringent codes. It’s a very labor-intensive process.
Early adapterMillennium Inorganic Chemical Inc.’s Hawkins Point Plant in Baltimore, Maryland, is one of the early adapters of wireless monitoring. Millennium is the world’s second-largest producer of titanium dioxide (TiO2), a critical ingredient used in coatings, paints, plastics, paper, rubber, and other applications.
One of the methods used to produce the pigment is the chloride method, during which chlorine is introduced into a large, refractory-lined vessel called a chlorinator via 90-ton rail cars, explains Chris Davi, the facility’s safety, health and environmental superintendent. Millennium’s chloride process area has a hard-wired, fixed monitoring system in place to warn of any chlorine leakage. These monitoring systems are located in close proximity to the chlorine rail car unloading station.
But it is the surrounding area that Millennium sought to protect by introducing Industrial Scientific’s wireless gas monitoring system.
“From a Responsible Care® standpoint, our license to operate depends upon two things — that we operate safely and that we protect the community around us,” Davi says.
The Hawkins Point Plant measures some 160 acres, and is nestled along a major highway adjacent to the Francis Scott Key Bridge that carries vehicular traffic over the Patapsco River.
“When it comes to perimeter monitoring, that’s our most sensitive off-site receptor,” says Davi. “Based upon EPA’s Risk Management Program (RMP), our calculated ‘alternate case scenario’ would be a release of two tons of chlorine. We determined the placement of sensors based upon the chlorine area as the source-point vertex and what shape the plume may take in the event of that type of release under normal wind conditions and normal atmospheric conditions.”
Millennium installed 16 chlorine detectors with a wireless interface and two controllers. The wireless network will monitor chlorine leaks migrating from the fenced perimeter, approximately 400 feet from the processing facility.
A big selling point, according to Davi, is that solar panels are used to power the perimeter monitoring sensors. “This saved us money that we would have spent on installing the conduit into the ground for electricity,” he says.
Solar collection panels offer an economically viable method for powering fixed-system gas detection monitors in remote locations, such as compressor stations, well sites, and other perimeter operations where local AC or DC power is unavailable or economically unfeasible.
Millennium’s system is expected to be completely installed and operational by early January 2001.