What A Mesh!

During open-circuit events, this wireless system contacts key personnel, telling them what PPE to bring for repairs.

IT'S an imperfect world. All tends toward entropy, dissolution, and decay; things break, fall out, shrivel. In industrial environments, belts snap, parts erode, fuses blow. The latter happens more often than you might think.

Cooper Bussmann Inc., an Ellisville, Mo.-based manufacturer of power fuses and circuit protection products, conducted a comprehensive study of facilities in the automotive, petrochemical, and metals manufacturing industries and found opencircuit events caused by short circuits and overloads happened an average of 382 times annually per facility. Each event resulted in an average 41 minutes of unscheduled downtime costing hundreds of thousands of dollars per incident— sometimes millions of dollars. In the auto industry, for example, where cars come off the assembly line at a rate of roughly one per minute, even 15 minutes of downtime caused by one blown fuse or tripped circuit breaker can cost in the neighborhood of $330,000, the study showed.

“When a circuit opens, for whatever reason, what happens is maintenance has to go out and troubleshoot it,” says Joe Fox, Cooper Bussmann director of systems and services. “They have to figure out why the equipment is not operating and where the problem is. Once they determine they have a fuse open, they have to figure out why it’s open and what kind of fuse it is, and then they have to go get the replacement part and put it in there. It can be very time consuming.”

What if the circuits themselves could automatically alert those maintenance workers? What if the circuits were able to call, e-mail, or fax the workers, telling them the exact location of the event, the exact replacement part to bring, and the appropriate level of PPE to have with them for the work? These were the seemingly far-fetched musings that led to the introduction earlier this year of the Cooper InVision™ Downtime Reduction System, a monitoring and communication system that uses wireless technology to provide precisely these kinds of notification.

Intelligent Circuitry
At the heart of the InVision system is a “self-healing” wireless mesh network of routers, or data transmitters, that engineers install at a customer’s facility after doing an initial site assessment that includes tests of the facility’s physical and radio environments to determine how many routers are needed and where they should be placed for optimal transmission. The “brains” of the system, meanwhile, are the battery-powered intelligent fuse and intelligent circuit monitors (IFMs and ICMs) that oversee circuits and initiate the transmissions, sending alerts to the routers when they detect problems.

Unlike traditional point-to-point wired and wireless systems, which can lose data when anything interrupts the primary path between a transmitter and receiver, the InVision routers “talk” to each other in different directions. So if a connection is lost or blocked between any two routers— when, say, a moving metal platform or forklift gets in the way—another router picks up the message. Such route redundancy is designed into the system so an alternate path will guarantee communication between the IFMs/ICMs and a device called the “gateway,” a component installed at the customer’s facility that encrypts data received from the routers before sending it on to dedicated servers at Cooper Bussmann’s access-restricted data center via a secure Internet connection.

The servers that receive the transmission, collectively called the “command center,” display the status of monitored circuits and allow for easy configuration of alert escalation and trending reports. The command center also sends the automatic voice, e-mail, or fax alerts using information provided by a customer’s facility manager. The necessary level of PPE and replacement part information programmed into the system is determined by a fuse’s or circuit’s location within a site’s electrical system and the potential hazards surrounding that particular room or panel. The facility manager also designates who receives the alerts, ensuring that only qualified personnel get the messages.

Sensor Sensibility
Cooper Bussmann software engineer Michael Pearce describes the InVision system as “self contained” but adds that it works with a customer’s existing network and Internet connection. “All the devices in the system have their own microprocessors in them, and they provide all the functionality to communicate up to our servers,” he says. “But this is not a standard- based wireless protocol. It’s not 802.11, it’s not ZigBee, and it’s not Bluetooth. It’s nothing you’ve ever heard of. It’s tailored specifically to our application, which allows us to have a large number of devices that can conserve battery power.”

The number of devices needed to compose the mesh at a facility contributes to the system’s price, which Fox says can vary significantly, depending on the site’s size and environment and how many critical loads are monitored. The system has a capacity of 200 routers per gateway, but multiple gateways can be installed. The batteries powering the IFMs and ICMs last up to 4.5 years. For more information and an online downtime cost calculator, visit www.cooperbussmann.com.

This article originally appeared in the July 2007 issue of Occupational Health & Safety.

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