New Options for Monitoring

Employers can get high-tech help to ease the burden of monitoring remote emergency equipment.

• By Casey Hayes
• Jun 01, 2003

INDUSTRIAL accidents tend to occur where work is performed. Therefore, emergency equipment needs to be strategically placed where it can be most efficiently and rapidly used. However, decentralized, and often remote, placement of drench showers and eyewashes generates difficult challenges for safety and emergency personnel.

The safety staff's responsibility for administering immediate and follow-on aid requires immediate notification of any accident event, regardless of its location. In significant-sized facilities, this communication imperative is most often addressed through the use of centralized monitoring stations, where electro-mechanical telltale devices advise safety and emergency staffs that drench showers or eyewashes have been activated. Until now, virtually all of these monitoring systems have been hard-wired installations.

In practicality, hard-wired monitoring systems are very expensive to install, with conduit installation alone costing as much as $50 per foot. And because typical hard-wired installations have exposed componentry and wiring conduit, they can also be prone to the normal frailties and failures that can occur in an industrial environment.

Wireless Monitoring for Emergency Equipment
Using today's state-of-the-art wireless communications technologies is proving to be a very sound alternative to traditional safety monitoring approaches. Wireless safety monitoring systems bring intelligent, reliable, and cost-effective communication technologies to emergency safety showers and eyewashes, without the traditional expense of hard wiring between the safety sensor and the remote monitor.

Multiple shower and eyewash installations are integrated into a single system, using modules that wirelessly connect to virtually any brand of standard emergency equipment and report activation to a centralized control location. Typically, the range of packaged systems such as this is about 1,500 feet, with up to 32 showers and/or eyewashes monitored from a single location. When properly installed, multiple independent systems can be operated in close proximity without interference.

At each emergency shower or eyewash location, an ultra high frequency radio transmitter is connected to a safety sensor attached to the equipment. When the shower or eyewash is activated, the sensor changes state, typically from "closed circuit" to "open circuit," and the transmitter broadcasts an accident signal. A receiving station identifies the unique signal from the transmitter and issues an immediate alert identifying the location of the accident.

Annunciation of the accident can be through a monitor integral to the centralized receiving station, relay outputs in the receiving station, or existing user control systems. This allows for tremendous flexibility in integrating wireless technology into existing communications systems.

Operating Overview
In system use, the ultra high frequency radio transmitter is referred to as a data transmission module (DTM). As mentioned, DTMs are located at each emergency shower or eyewash and communicate wirelessly with a centrally located receiver.

Packaged systems typically provide for full-system calibration to determine optimal local performance capabilities and wireless unit positioning. Obviously, proper placement of the wireless components is important, as is the need to locate them outside of ready access to avoid curiosity and tampering concerns.

In operation, the receiver generates an alarm when a DTM detects emergency equipment in operation; the DTM is connected to and is typically activated by a flow switch or a proximity switch. Using ultra high frequency radio communication (radio frequency, or RF), the DTM modules report emergency equipment operation immediately. The DTM broadcasts the "change of state" of the sensor and its unique identity number for monitoring by a Data Receiver Module (DRM) or Data Monitoring Module (DMM).

Using the data monitoring module to pick up DTM transmissions, an LCD text display indicates alarms, dual relays provide for external annunciation, and an RS232/485 link allows for transfer of information to other existing computerized systems, when required.

Typical Monitoring Installation
Henry Newman, the sales manager of Freeport, Texas-based AWC Inc., applauds the use of advanced technology to better monitor safety.

"AWC is a process control instrumentation company, and our clients have been seeking a better way to monitor their safety operations," Newman said. "The technological advancements of wireless monitoring are a very welcome change! Not only is the monitoring system much less expensive to install, because of the elimination of laying conduit, but it also provides significant solid-state advantages over traditional hard-wired products." Newman said he appreciates that these products use advanced RF technologies to also continuously monitor system integrity, status, and operation.

That's an important point. Unlike most hard-wired installations, packaged solid-state systems feature constant "handshaking" between components. To ensure that each DTM remains "visible" to the DRM or DMM module to which it has been programmed, every two minutes a "heartbeat" signal is sent from the DTM. The DRM/DMM is anticipating this periodic signal and will raise a "loss of communication" alarm if contact is lost or not established.

Packaged systems typically also include two-way RF communication between DTM and DRM/DMM. This facilitates the handshake between DTM and DRM/DMM modules. In the case of a missed DTM "heartbeat," the errant DTM has no acknowledgement from the DRM/DMM and "retries," to avoid generation of a nuisance alarm.

Along with each DTM "heartbeat" comes battery life information. This is used to generate a low power warning several months before battery depletion under normal "heartbeat" conditions. However, this feature is typically not active when the DTM is externally powered.

"Wireless monitoring helps first response aid to be rapidly directed to the correct location, with maximum cost and operational effectiveness," Newman concluded. "And, for those systems that use a 902-928mhz spread spectrum operational frequency, there are no licensing requirements. Welcome to the future . . . wireless central monitoring systems for safety equipment are a great example of using technology to advance the cause of industrial safety."

This article originally appeared in the June 2003 issue of Occupational Health & Safety.