The cellular network in the USA continues to expand at an exponential rate, as the battle for who can provide the fastest and most widespread coverage wages on. In 2010, the four biggest carriers (Verizon, T-Mobile, AT&T and Sprint) averaged a collective download speed of around 5Mbps, whereas now some networks can boast up to 200Mbps. This increase shows no sign of slowing and has also presented an opportunity for the deployment of polymeric solutions. This has been proven by one of Belzona’s US distributors (Belzona Technology Washington), which has had major success from cold-bonding mobile phone antennae mounts on to tanks and other structures.
Attaching this mobile phone equipment on the top or sides of water tanks makes perfect sense. Rather than developing new sites, tanks throughout the wastewater industry represent ideal multi-purpose locations for the antennae and simultaneously facilitate faster network growth. However, many asset owners require an alternative to welding these fixtures and fittings because of the side effects associated with hot work. For instance, when welding a bracket onto a tank, the application area can heat up to in excess of 1,600°C. This option will almost certainly damage the tank’s internal protective lining.
Therefore, to minimise the risks associated with hot work, cold-applied materials are preferable. Yet available methods - such as bolting - still necessitate perforating the metal structure and leaving the tanks susceptible to corrosion. Another option is magnets, but they are a very expensive and relatively untested option. Finally, there are solvent-free epoxy systems, which are both cold-applied and proven to support the weight of the antennae in the field.
Belzona offers a range of materials that make excellent high strength structural adhesives for metal bonding. The application of a Belzona adhesive produces heat equivalent to a ‘room temperature’ – up to 27°C. In comparison to welding, this eliminates the potential for heat affected zones (HAZ) and need for stress relieving. Moreover, such exotherm is perfectly safe for all tank linings.
Cold bonding prevails
Since 2013, Belzona Technology Washington has worked with local engineering companies and contractors to mount cell antennae onto water tanks, increasing network coverage across Washington State. Directly approaching the engineers who create the detailed schematics for these installations means that the best material and optimum procedure can be specified for the application.
Grady Knight, manager at Belzona Technology Washington, explains: “When we first approached engineering houses, they were familiar with methods of cold bonding but had seen or heard of many failures. We highlighted that this was due to two fundamental reasons. Firstly, some of the previously used shop-bought adhesives were prone to shrinkage. Belzona’s systems are 100% solids, so there will be no shrinkage due to solvent evaporation. Secondly – and perhaps most importantly – insufficient surface preparation could be blamed for these failures. This could be easily rectified via supervised application with a Belzona technical consultant on site.”
Case study
Over a five-year period, the distributor has completed more than 110 applications of varying size and scale. Of these, one of the largest occurred in October 2013 on a 220ft water tower. The system chosen to carry out the application was Belzona 1111 (Super Metal), a corrosion-resistant composite material capable of exceptional levels of adhesion. Once the number of plates per antenna was determined, the bonding areas of the tank and plates were sufficiently prepared in line with the specification. Particular care was taken on uneven areas, especially where the mounts needed to bond over weld seams; therefore, the existing paint was removed without compromising the integrity of the weld itself.
Belzona 1111 was then thoroughly mixed and brush-applied onto both surfaces, before being pressed firmly together to ensure optimum bond strength. Since installation, the material has performed well in service, much to the satisfaction of the tank asset owner and the network provider.
Not only tanks
It is not only water tanks that have been used to increase network coverage across the state. In addition, concrete structures and municipal buildings have become agreed locations on which cell antennae can be established. Concrete walls and parking structures have featured frequently, as well as one example on a Seattle high-rise building. Following the removal of roofing insulation, steel beams were embedded using one of Belzona’s concrete rebuild solutions. This then allowed the mounts to be cold bonded with a Belzona adhesive, avoiding complications with pre-stressed concrete and providing a significant advantage over drilling holes in the substrate.
Trend signals a promising future
Failure of the mounts can cost the mobile phone company tens of thousands of dollars in fallen equipment, plus the potential physical danger to anyone in the area below. Belzona’s multipurpose adhesives mitigate these risks, making them ideal solutions because of their cold-applied nature and excellent adhesive properties. As well as the bonding of mobile phone antennae mounts and brackets, often this application extends to cable mounts and trays on to the side of the structures due to success experienced with previous applications.
Indications suggest that over the next two years, the application of phone antennae (and therefore their mounts) will triple in size across the USA. With cold bonding and its accompanying application procedures now featuring prominently in the installation schematics, this marks promising growth for the partnership of polymeric adhesives and the mobile phone network
