The value of active fire protection systems such as sprinklers is well-known in most industrialized countries. Recognition of fire-limiting construction – passive fire protection – for the building envelope is also growing. Despite these advancements, building owners are still missing out on a key property protection opportunity. In this article, we look at how the choice of performance-tested and certified cooling towers can prevent or significantly reduce losses to commercial, public and industrial buildings, and provide lower capital and operating costs.
While cooling towers are critical infrastructure for commercial, public and industrial facilities around the world, only a small fraction of these systems has been certified to loss prevention standards. Cooling tower systems are widely considered to be inherently safe from fire hazards because water flows through them. But in fact, cooling towers are vulnerable to fire, as they contain dry areas, electrical equipment and one or more combustible materials such as PVC, fiberglass-reinforced plastic and ABS. The risk of fire is further increased during regular maintenance as water flow may be turned off, allowing hot work, human element issues (e.g., smoking) or electrical arcing to potentially trigger fires. While fire is a serious concern, according to FM Global, a major worldwide commercial and industrial property insurer, wind and hail pose an even more costly peril to cooling towers (figure 1).
The use of rigorously tested and certified products and adherence to loss prevention guidance derived from scientific research and field study are important steps in not only limiting such losses, but preventing them from ever occurring. The choice of a cooling tower that has been tested and certified by a reputable agency can provide many benefits, including limited fire spread, minimal fire-induced property damage and mitigation of business interruption.
At commercial and industrial property insurer FM Global and business unit FM Approvals, the deep belief – backed by research and nearly two centuries of property loss experience and testing is that the majority of losses from natural and man-made causes can be prevented. Companies that embrace this philosophy can benefit from the use of planning tools, performance-tested FM Approved products, and proven installation and maintenance guidelines from FM Global to create well-protected facilities with significantly reduced potential for property loss due to fire and other hazards.
FM Approvals, which provides third-party certification of property loss prevention products, assesses the performance of cooling towers in accordance with Approval Standard 4930, Cooling Towers (FM 4930). This standard subjects cooling tower systems to multiple hazards, including full, intermediate and bench-scale fire and flammability tests; wind; and windborne debris resistance, as well as required engineering evaluations of wind and seismic loading. FM 4930 also includes an evaluation of a manufacturer’s quality control program, initial and ongoing manufacturing facility audits, installation inspections, and the requirement that manufacturers of FM Approved cooling towers notify FM Approvals of any product changes before they are implemented.
Designs, configurations and types
Cooling towers are available worldwide and can be single-cell or multi-cell, counterflow or crossflow and ground or rooftop mounted (figures 2 & 3). The design is dependent upon several factors, including:
- cooling requirements of the facility;
- need for district (i.e., centralized) versus individual systems;
- need to maintain cooling in the event of fire or other damage;
- presence of fire partitions or walls to limit fire spread; and
- need to save footprint space and take advantage of an elevated location by mounting on roofs.
These systems can also be factory assembled for speed of installation or field erected if large in size or if transportation of a complete cooling tower would be problematic.
Certification for loss prevention
Cooling towers come in a wide range of designs, configurations, types and sizes; and use a wide range of components and materials which are of different formulations. All of these factors can affect the performance of the completed cooling tower. In addition, changing one or more components or materials can have a significant effect on performance, if the change is not properly evaluated. As a consequence, cooling towers should be tested and certified as a complete assembly by a competent and reputable agency. In this way, property loss and business interruption can be prevented or reduced.
The testing and certification of cooling towers is a complex matter. To test cooling towers involves considering the various risks and natural hazards that they are exposed to. These include fire, static and cyclic air pressure (i.e., wind pressure) and windborne debris impact (if located in tropical cyclone zone areas that are subject to damage from large windborne debris). Resistance to seismic loads should also be determined when towers are used in areas at risk of an earthquake.
One important consideration when evaluating performance is to determine the combustibility of components in the cooling tower assembly. The most common combustible components include structural support members, fill, drift eliminators, louvers, fan, fan deck, piping, enclosure walls and partition walls. The combustibility of the most critical components can be evaluated through flammability characterization in accordance with ISO 12136. The material formulation of components should be tightly controlled and regularly audited in order to maintain consistent performance of individual elements and performance of the complete cooling tower. Even small formulation changes can lead to significant differences in combustibility. Cooling towers that have been evaluated in this way by a third-party testing agency may be certified as either non-combustible or of limited combustibility.
To fully evaluate cooling tower performance requires a series of tests and engineering evaluations to be carried out. These include:
- Combustibility (full-scale fire tests on complete cooling tower assemblies):
- Single-cell cooling towers should be able to withstand damage from a fire exposure and not impose a fire hazard to adjacent structures or surroundings.
- Multi-cell cooling towers should be able to confine damage from a fire to a single cell and not allow it to spread to adjacent cells or other structures.
- Rooftop-mounted single- or multi-cell cooling towers should demonstrate the ability to prevent burning debris from falling onto the roof surface or surroundings.
- Flammability characterization (e.g., bench-scale testing such as described in ISO 12136) should be conducted on cooling tower fill to determine a material’s chemical heat release rate and thermal response parameter.
- Intermediate-scale fire tests should be used to evaluate the performance of alternative types of fill, drift eliminators and other cooling tower components to establish a baseline against which future changes or revisions can be compared.
- Seismic loading – Cooling towers to be erected or installed within known earthquake zones should be evaluated and certified by a professional engineer.
- Wind loading – Cooling towers should be evaluated and certified by a professional engineer to verify the system can withstand anticipated wind loads.
- Debris impact tests on walls and fan stacks should be conducted – penetrations through an exterior component or the opening of a seam can reduce the efficiency of cooling towers or render them inoperable.
- Static and cyclic air pressure tests should be used to simulate the impact of wind pressure from various types of weather events.
Benefits for building owners and clients
Only a fraction of cooling towers worldwide are certified to loss prevention principles. Specifiers, such as insurers, builders, designers, consulting engineers and others, often have limited options when selecting cooling towers to minimize or reduce property loss and business interruption. To increase the number of certified cooling towers, there needs to be increased demand for loss prevention certification and therefore a better understanding of the benefits associated with cooling tower certification.
Potential benefits of third-party certified cooling towers include:
- An assurance of proven cooling tower design, manufacturing and product quality when certified and tested by a competent and reputable agency.
- Lower capital and lifetime costs, due to:
- Potential elimination of need for sprinkler system to be installed, maintained and tested per risk engineering best practices.
- Reduced risk of property damage due to fires and natural hazards.
- Longer cooling tower lifespans due to their enhanced performance and quality construction.
- Reduced build time, as installation of a sprinkler system may not be required.
- Reduced risk of business interruption in single- and multi-cell cooling towers.
- Improved sustainability, due to a longer lifespan which reduces use of resources in maintenance, repair and replacement; and non-combustible or limited combustibility construction which reduces smoke pollution in a fire.
The majority of all property loss is preventable when risk engineering best practices are followed. Cooling towers that have been evaluated for loss prevention performance by a competent and reputable testing agency can help provide long-term loss prevention, potentially reduce risk of downtime and provide longer service life. Likewise, by avoiding or minimizing cooling tower losses due to fires and other natural hazards, building owners can significantly improve business resilience and drive down the overall cost of risk.
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