Compressed air foam systems are becoming more widely used throughout the fire service as more fire departments discover that it is an effective and very versatile tool.
CAFS is more efficient than plain water, and therefore is able to extinguish fire quicker and with less water. Its efficiency and high energy also mean firefighters can attack from a longer distance and be exposed to the hazard for a shorter time. This increase in firefighter safety is compressed air foam’s biggest benefit.
The versatility of the system is not limited to fighting fire. It also includes effective exposure protection and the availability of a high volume air compressor on the apparatus for a variety of operations.
The numbers of new apparatus being equipped with CAFS are growing every year. At the same time, there are a large number of in-service apparatus that were built without CAFS. Most of these have many years of service life left and may be candidates for a CAFS retrofit.
There are two main reasons for a fire department to retrofit with CAFS. First, the department may want to take advantage of the benefits of the technology while not yet ready to purchase a new apparatus. Second, the department may have purchased a new apparatus with CAFS and wants to bring the rest of its fleet up to the same capability to standardize operations throughout the department.
If a department has an apparatus to upgrade to CAFS, certain criteria need to be examined to determine if it is a viable retrofit candidate. These include the condition of the apparatus, the expected remaining service life, the apparatus power train, space available for CAFS components and existing foam systems.
A Significant Investment
CAFS retrofits represent a significant investment for a fire department. The apparatus to be upgraded should be well maintained and in good mechanical condition. A poorly maintained rig will require more time and cost more money to retrofit due to additional work that may have to be performed.
The apparatus should also have a significant service life left before replacement to make the investment in CAFS a viable option. The department may want to divide the cost of the retrofit by the number of years that the apparatus will remain in service to determine if upgrading the technology is cost effective. A truck with only a three-to-five-year life expectancy may not be a good candidate, while a truck with 10 to 12 years left would be.
Compressed air foam systems are available in various configurations. The differences are the size of the system and how the compressor is powered. Compressor size ranges from 60 cfm to 200 cfm. Configurations include auxiliary engine powered slide-in and cross-mount systems, auxiliary powered compressors, pto-powered systems, under hood compressors, hydraulically-driven systems and systems powered off a mid-ship pump.
The method for powering the air compressor must be determined. This requires looking at the apparatus power train. An available pto port is a good choice for powering the compressor. If there is an open pto port with room to run a driveshaft and mount the compressor, the system can be run directly off of the pto. If the pto port is available, but space in the area is limited, an option may be to use the pto to drive a hydraulic pump, which in turn will drive the compressor mounted in a remote location.
If no pto port is available the compressor may have to be driven by an auxiliary engine. This option, while providing a way to do the retrofit, does require more space for the engine along with additional weight, cost, and maintenance requirements. The fire department may have to be willing to sacrifice some space in the dunage area or possibly a compartment to house the compressor and drive engine.
Some compressors can also be mounted under the hood and driven by a belt off the apparatus engine. These are typically small volume compressors. Before installing this type of system, check with your vehicle’s manufacturer with regard to any possible warranty concerns due to the installation.
Compressed air foam systems have several components that must be mounted on the apparatus, some of them large. They include the compressor, sump, separator, hydraulic filter, cooler, foam proportioner, foam and air manifolds, check valves and various lines and hoses. Some of them must be mounted in certain locations to work properly. The apparatus candidate must be assessed to determine the location of each one. Some components will also require access for service and fluid level checks.
Consideration should be given to whether the apparatus has an existing foam proportioning system. If no system is on the apparatus, the price of adding the proportioner must be figured into the retrofit. If a foam system is installed, it must be examined to determine if it is usable for CAFS. The unit must be an automatic proportioning system, meaning that it automatically adjusts to changes in water pressure and flow while maintaining the correct foam solution percentage.
The proportioner for CAFS is typically an electronic direct injection system. Around-the-pump foam systems and built-in eductors are not capable of providing the foam solution needed for compressed air foam.
Once the apparatus has been determined to be a candidate, its mission must be assessed to guide in choosing the appropriate system configuration.
Wildland apparatus will typically flow smaller hose lines and volumes of foam, so a smaller system would be appropriate. Typical compressor size would 60 cfm to 120 cfm. These apparatus are often required to pump and roll. While pump-and-roll is possible with a pto-driven compressor, the compressor speed is tied directly to road speed. This may limit the effective range for pump-and-roll operations.
A better choice may be an auxiliary-powered system, which is completely independent and can be operated effectively at any speed. Many wildland rigs have skid-type pump units. When upgrading these apparatus to CAFS, it is much easier and more cost effective to simply replace a water-only skid with a new CAFS skid as opposed to trying to add CAFS to the existing unit.
Structure fire engines will require higher flows than wildland, so the compressor and proportioner must be sized appropriately. Typical compressor sizes would range from 80 cfm to 200 cfm. The size needed is determined by the number and size of discharges that the department desires to be CAFS capable. Pto-driven systems are good choice for this application as they are versatile and cost effective, and pump-and-roll capabilities are typically not required.
When planning the retrofit, consideration must be given as to which of the discharges will be CAFS capable. Flexibility in this decision will help keep the installation cost reasonable, and plumbing is a prime consideration. Since each CAFS discharge will need to be plumbed to the foam manifold, some discharges will be easier and therefore cheaper to plumb than others. By choosing the proper discharges, it may be possible to have more CAFS capable lines for close to the same cost.
Retrofits are done by numerous fire apparatus dealers and service centers. Some OEMs are also set up to handle retrofits. A well-equipped fire department shop with experienced technicians may be able to handle the job as well. Be prepared to have the apparatus out of service for a while, with the length of time determined in a large part by the complexity of the retrofit.
The cost of the retrofit will vary with the existing configuration of the apparatus, the complexity of the system, how the compressor is powered and the existence of an appropriate proportioner. The amount of labor required will be a significant factor. The shop doing the retrofit will need to thoroughly examine the apparatus to determine an accurate cost estimate.
Diligent homework done by both the fire department and the retrofit installer prior to the project is critical. Installing a retrofit CAFS will require some compromises and realistic expectations by the fire department. Research and planning can help produce a cost effective installation that will operate correctly.
When planning a retrofit, do not forget the all-important training component. Make certain the price of the retrofit includes instruction by an experienced, qualified CAFS instructor at your facility. Proper operational instruction is critical to effectively implementing the use of CAFS in your fire department.