A Network's Protective Coat

Just as a coat protects you from the environment, enclosures covering your vital equipment keep your network healthy. Because network equipment requires a stable environment to function at optimum levels, enclosures are just as important as the equipment they protect. Hazards such as wind, water, extreme temperatures and dust can destroy sensitive base-station equipment. Without a protective barrier, thousands of dollars of equipment are worth nothing, said Bryan Haas, GFRC Shelters marketing manager. Selecting that protective barrier isn't easy. To find the best solution, you must consider all characteristics on a site-by-site basis.

MATERIALSNo two materials are the same. Broad categories include concrete and metal, but within these categories, there are as many unique compositions as there are companies producing cabinets and shelters. Traditional shelters, or 1-room buildings, were built with concrete, and this still is one of the most durable long-term product materials.

Although solid hard rock structures are the heaviest and most traditional, several vendors have developed lighter reinforced structures as an alternative to the traditional material. For example, using glass fiber reinforced concrete (GFRC) adds strength and reduces the shelter's weight. GFRC and other steel-reinforced buildings use a steel rebar in the walls to add additional strength. Usually these reinforced concrete enclosures are lighter weight than solid concrete buildings, which means they are easier to transport and install, and are flexible for a variety of site locations.

Concrete shelters are available in several exterior finishes. Kevin McCann, Fibrebond director of sales and marketing, said earthtone exposed aggregate is the most common finish, however other finishes are available. Some carriers request different finishes to meet specific zoning restrictions, or they need to match existing designs in either a residential or commercial setting. For these cases, Fibrebond uses a patterned form liner to pour the concrete to give a different look. Common forms include fluted fin, which provides a thin, vertical striping of the concrete; ship lap, which offers a wider horizontal striping that looks like vinyl or wood siding; and a brick template. In addition to forms, vendors can color concrete to make the pattern better match existing structures in the area.

Metal is another common shelter material, especially for cabinets. Metal variations include aluminum, painted steel, steel frame and stainless steel. Often these units are insulated and have built-in air conditioning. But you will have to consider rust and corrosion issues when dealing with metal shelters. Viktor Jegers, Pentair Enclosures engineering manager, said you must be careful during installation because a simple scratch on a painted steel surface can cause rust problems later.

Stainless steel is an enclosure option that may provide the best protection depending on environmental factors. Jegers said that although stainless steel is the most corrosive-resistant metal option, it costs about twice as much as aluminum.

"Right now, the material of choice is aluminum because it has better-than-average corrosion resistance and is ideal for rooftop applications," he said.

Rittall's controlled-environment cabinets are made of aluminum and have environmental gasketing. Stan Craver, market manager for the company's telecom division, said the cabinets are designed to meet numerous environmental field conditions for 20 years.

Plastic is another material gaining attention in the enclosure market. According to Brian Mahoney, GE Plastics spokesman, high-performance plastics are dent, chemical, corrosion and heat resistant; flame retardant; withstand harsh weather conditions and prevent water seepage. In addition, the company said plastic outdoor enclosures can be less expensive because plastic helps consolidate parts, and eliminates secondary welding and grinding operations. Mahoney added that plastic is a great material for aesthetics because it prevents denting, rusting and weathering.

OTHER CONSIDERATIONSMost vendors design enclosures with installation in mind. For example, Enviro Buildings' structures are lightweight and modular for on-site installation. Mike Phillips, Enviro Buildings vice president of engineering, said the units have a 4-inch, insulated foam core panel with galvanized steel sides. You can have unit parts shipped to any site and put them "together like tinker toys."

Fiberglass is another lightweight material and often is available in modular sections that you can use for rooftop applications, for sites that are hard to access or where you need lightweight protection.

Co-location presents its own set of shelter considerations. For existing sites, adding more antennas may mean adding another shelter. For new sites where co-location is expected, you can prepare ahead of time with your shelter selection because vendors are designing new shelters just for co-location situations.

Rohn offers larger structures with multiple access points and inside space that is partitioned by fencing so that each carrier has its own entrance and exclusive equipment access. Each door has its own alarm.

Fibrebond has built structures as large as 72 feet long with three or four rooms for co-location sites or for a build-to-suit company that anticipates leasing out space to different carriers.

Safety is another critical issue to consider when selecting enclosures. Airadigm's Tom McGahan, director of engineering, said in cold climates, especially at sites on high structures, you must protect the area from icy conditions. At ground-level sites, you need ice protection so that technicians and equipment aren't harmed from ice falling off the tower.

Often, equipment cabinets are not enough protection for these wet and cold climates, McGahan said. Opening the cabinet in such conditions exposes all of the equipment to the elements. With a shelter or building, a technician can access equipment in a moisture-free room.

SITE ACCESSWill you lift your shelter by crane to a rooftop, set it on a slab in an open area or trek it up a mountain? Phillips said site access is the first thing you need to consider when selecting a shelter.

For difficult site access, lightweight and modular units are an obvious solution, but not the only one. Fibrebond's McCann said remote locations don't always mean concrete is out of the question. One option is a skid-mounted unit, which you can pull in by bulldozers where roads aren't available for mountaintop locations.

Typically, concrete structures are too heavy for rooftop installations. Once a rooftop site is secured, Omnipoint obtains a permit so it can use a crane to lift base-station units and metal cabinets to the specific site, said Joseph Walsh, Omnipoint technical director for the New York region. For sites where there is little ground space, cabinets are an option because you can mount them on the pole, Rittal's Craver said.

Enclosure selection also depends on zoning considerations. Antennas are not the only site equipment that you have to disguise. Some municipalities want units to have a low profile, or one that blends in with the surroundings.

Pentair's Jegers said one Dallas suburb had a specific zoning request for a carrier's shelters. The carrier asked if it could use car wax on the shelter, because the upscale community wanted the box to stay shiny. The idea was to wax it once a month. Yes, Jegers said, you can use car wax.

GETTING THE JOB DONERegardless of what material or shelter you select, maintenance is critical. Although shelters and enclosures are designed to protect equipment from environmental conditions, each carrier faces unique risks depending on its market locations.

According to Walsh, one of the carrier's biggest problems in New York is soot, which can have a detrimental effect on equipment. If filters get clogged, the unit gets too hot and triggers an alarm at the network operations center, which shuts down the unit. As a result, Omnipoint makes cabinet maintenance a high priority. It routinely checks and replaces cabinet filters.

Often equipment enclosures don't get the attention other high-tech areas receive. In a high-tech world, an enclosure just isn't glamorous. In addition, equipment enclosures are one of the least expensive network elements.

"The enclosure is a small fraction of a site's cost, but it performs one of the most important functions," Jegers said.

Although an enclosure's sole responsibility is protecting equipment, be sure you consider all of these site characteristics before you select the barrier that will protect critical equipment.

Each cabinet and shelter material has its own advantages and disadvantages, depending on each site's circumstances. Here's a quick glimpse at some material attributes.

Concrete: Traditional, durable, long-term product, but heavy

Reinforced Concrete: Lighter than solid concrete, but less durable

Stainless Steel: Most corrosive-resistant metal option and most expensive

Painted Steel: Rust and corrosion sensitive

Aluminum: Somewhat corrosion sensitive and less expensive than steel

Plastic: Weather and corrosive resistant, reduces manufacturing costs