Upgrading a Wired Public Address System with a Wireless Option

The management at a 1,094-MW coal-fired power plant in the Midwest sought to augment their hardwired public-address (PA) system. With hundreds of employees working in varied conditions, a means of communicating messages to everyone on site was needed, whether their normal daily activities were limited to a few blocks or if they traversed the entire 200 acres and multiple buildings. What the plant found was a wireless PA system so effective that it actually supplanted the original model.

A Mixed Bag

Communications in this facility, as in many plants where components are added over the years, was a mixed bag. There was a hardwired PA system in place, but the staff wanted to supplement it with a system that could interface with it. The new system had to be loud enough to be heard by employees wearing hearing protection, but soft enough for those working in confined areas like trailers or offices.

Messaging had to be broadcast throughout the 200-acre facility, even reaching employees who might be traversing decommissioned areas of the plant. Additionally, many (though not all) employees carry portable radios, which needed to be integrated into the new system. As an added wrinkle, the plant was planning to upgrade to a digital radio system and wanted the ability to integrate the new radios into the supplementary PA system. Given the many nuances of the “messaging footprint,” coupled with installation concerns and pricing questions, the project was neither routine nor easy.

Site officials contacted Cardinal Wireless, which supplied a demonstrator model of a Ritron LoudMouth wireless PA system to test at the facility. Plant and Cardinal Wireless representatives toured the site, stopping in areas where communications were a concern—like those with high ambient noise, elevated temperatures, and the decommissioned areas. After the demonstration, the company decided to proceed with the system.

Installation Benefits of a Wireless System

Installation of the wireless PA system was far simpler than for a traditional hardwired PA and was accomplished at a fraction of the price. Still, one challenging aspect was finding suitable mounting surfaces.

Though the facility has abundant I-beams and catwalks, it was not replete with flat mounting surfaces. So installation crews from the local electrical contractor used beam clamps and other innovative methods to secure the wireless speakers (Figure 1). Each installation, in the absence of a difficult mounting surface, took about 30 minutes.

1. Public address speakers mounted on an I-beam. Courtesy: Ritron Inc.

Significant time was saved due to the wireless nature of the product, which avoided trenching and re-wiring the entire facility. Installation costs were reduced by eliminating the need for thousands of feet of copper wiring and the labor required to install it.

Can You Hear Me Now?

The wireless system did not sacrifice sound volume or clarity. Recall that many of the employees are equipped with two-way radios, so it could be argued that reaching these personnel would be more effective with a radio broadcast than with a traditional PA announcement.

Areas with high ambient noise posed additional problems because employees in these areas wear foam ear inserts to protect their hearing. Again, the wireless nature of the system makes it easy to add additional speakers to ensure that messages are clearly audible even when employees are wearing hearing protection (Figure 2).

2. Public address speakers mounted in a high-noise area. Courtesy: Ritron Inc.

Wireless PA Speeds Response Time

Another advantage is that the LoudMouth allows faster response times because of its ability to make announcements through the two-way radios from a nonspecific location. Previously, personnel would have had to travel to one of the PA stations to make an announcement. With the wireless system, any radio-equipped employee can make an announcement, eliminating travel time and allowing emergency messaging to occur in real time.

Flexibility Yields Additional Benefits

Because portions of this plant built in the 1920s, many areas posed a challenge for locating PA speakers. There were portions of the plant that had been decommissioned but through which personnel routinely travel, so these were included in the messaging footprint.

Certain areas of the cavernous facility were where the flexibility of the speaker installation really came into play. Some of the zones had large open areas where speakers needed to be located. In some instances, installers were able to locate speakers on alternate floors and still achieve adequate coverage. In other cases, there were rooms within rooms, so they had to deal with each area individually.

The ability of each receiver to support two PA speaker horns was helpful in customizing areas with appropriate sound levels. With two speaker horns installed, and though effective sound pressure level is reduced by half, the PA speakers can each be positioned independently—for example, 180 degrees from each other—providing added flexibility to cover more areas with a single installation point (Figure 3).

3. Public address speakers positioned 180-degrees. Courtesy: Ritron Inc.

Each receiver can be fine-tuned for volume as well, depending upon ambient noise and environmental conditions. Speaker volume was set at 90% for the first 225 speakers installed, though those in office areas or control rooms were much lower. Following some complaints, volume was turned down in four or five areas—mainly job trailers and control rooms—while speakers in areas like the gas turbine facility continue to blast their messages at a high level.

While many of the receiver installations are protected from the elements, those that are not can be put into all-weather boxes. It is also possible to place them within National Electrical Manufacturers Association enclosures, when necessary.

Nuts and Bolts of the Installation

The contract was signed in November 2012 and the project—including 300 speakers—was delivered in January 2013.

The facility uses approximately 100 portable radios with two or three repeaters, providing four or six talk paths. This LoudMouth system uses one analog repeater, which provides communication capability throughout the facility based on its strategic location.

The new wireless PA system has been so successful in delivering messages that it has supplanted the hardwired system that it was originally intended to augment. It was installed in much less time and at a fraction of the cost of a traditional hardwired PA system. In addition to delivering audible messaging throughout the 200-acre, multi-building facility, each receiver is fine-tuned to the ambient noise and working environment in which it is located. This allows delivery of routine and emergency messages—in real time—to all of the facility’s hundreds of employees, regardless of where they work. And although the time and cost savings are important, the ability to safeguard employees is the most important aspect of the new system. ■

Steve Rice is president of Ritron Inc.

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