The purpose of FM Approvals Standard for Cooling Towers, Class FM4930, is to state the requirements for cooling towers that do not need automatic sprinkler protection. When going through the Approval process one of the key steps is to build a full-sized representative tower cell that contains the specific configuration of various components, including, but not limited to, structural members, wall panels, decking material, fans, louvers, fill, and drift eliminators that are to be Approved which will then be evaluated to “demonstrate its ability to withstand damage from a fire exposure and retain operational integrity and not impose a fire hazard to adjacent structures or surroundings.” The test procedure involves lighting a specified amount of heptane and then witnessing the burning characteristics of the tower with its specific configuration of all the components. Approval is based upon the amount of damage, loss of operational capability, structural integrity of the tower cell and fan support, and containment of the fire.
It must be noted that FM Approvals does not approve individual components for use in cooling towers. Approval is only extended to the entire cooling tower system as it was tested and the components contained within it as a complete system. Thus, while the FM Approvals Guide lists various components that constitute FM Approved towers, those components are only considered to be FM Approved, “for use when installed in the prefabricated factory assembled units as described.” As an example, if ABC Cooling Tower Company builds tower model# CT100 which contains FILL123, and model# CT100 receives FM Approval, FILL123 cannot be installed into model# CT999 to make CT999 an FM Approved tower. It also does not mean that model# CT999 utilizes “FM Approved Fill” since that is a misapplication of the FM Approved Components listing.
The ramifications of this go even further. If an FM Approved galvanized steel cooling tower is being repaired or rebuilt and OEM components that are identical to the original parts are used in the refurbishment, but the cold water basin is sand blasted, sealed, and coated to prevent corrosion, the basin coating would invalidate the FM Approved status of that tower since the coating used on the basin was not part of the original tower that FM burned and Approved.
It is not uncommon to find job specifications for rebuilding a cooling tower that requires coating either or both the hot and cold water basins, and also specify that the tower use FM Approved fill materials with the intention of maintaining the FM Approval certification of the cooling tower. In these cases the job specifications are contradictory and do not conform to the actual FM Approvals certification.