Date: November 20, 2013
Retrofitting Existing Apparatus with Compressed Air
In today’s economy, many departments are postponing new apparatus purchases and are instead keeping their existing apparatus in service. A large number of these apparatus were built without foam capability, but many may be candidates for foam or compressed-air foam system (CAFS) retrofits. A retrofit to add Class A foam capability would involve adding a foam proportioner to the unit; for CAFS, an air compressor system would also be needed.
There are two main reasons to retrofit an apparatus with CAFS: First, the department wants to upgrade and take advantage of the benefits of foam/CAFS technology. Second, the department may have purchased a new apparatus equipped with CAFS and wants to bring the rest of their fleet up to speed with the same capability. This helps standardize operations throughout the department.
Upgrade Criteria & Considerations
If a department has an apparatus that it would like to upgrade with the addition of CAFS, certain items need to be examined to determine whether the rig is a viable retrofit candidate:the condition of the apparatus, the expected remaining service life, the apparatus power train, existing discharges and existing foam systems.
Other considerations: The apparatus to be upgraded should be well maintained and in good mechanical condition. A poorly maintained rig will require more time and be more costly 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. To determine whether upgrading the technology is a cost effective choice, divide the cost of the retrofit by the number of years that the apparatus will remain in service. 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.
CAFS Configurations & PTOs
CAFS are available in various configurations. Variables include the size of the system and how the compressor is powered. Compressor size ranges from 60–200 cfm. Configurations include auxiliary engine-powered slide-in and cross-mount systems, auxiliary powered compressors and power-take-off (PTO)-powered systems.
The method by which the air compressor will be powered must also be determined, which requires a look at the apparatus power train. One good choice for a power source: an available (PTO) port. If there’s 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 no PTO port is available, the compressor may have to be driven by an auxiliary engine. Note: This option, while providing a method to do the retrofit, does require more space for the engine, along with additional weight, cost and maintenance requirements. It may also require the fire department to be willing to sacrifice some space in the dunnage area or possibly a compartment to house the compressor and drive engine.
What Is Your Mission?
Once the apparatus has been determined to be a candidate, its mission must be assessed to determine the appropriate system configuration.
Wildland apparatus will typically flow smaller hoselines and volumes of foam, so a smaller system would be appropriate. Typical compressor size runs between 60 and 120 cfm. These apparatus are also often required to perform pump and roll operations. Although pump and roll is possible with a PTO-driven compressor, the compressor speed is tied directly to road speed, which may limit the effective range for pump-and-roll ops. A better choice may be an auxiliary-powered system, which is completely independent and can be operated effectively at any speed.
In addition, many wildland rigs are equipped with skid-type pump units. Tip: When upgrading these apparatus to CAFS, it’s 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.
Structural Firefighting Engines
Structure engines will require higher flows, so the compressor and proportioner must be sized appropriately. Typical compressor sizes would range from 80 to 200 cfm. The size needed will be determined by the number and sizes of discharges that the department wants to be CAFS-capable. PTO systems are a good choice for this application, as they’re versatile, cost effective and structural engines don’t typically perform pump and roll ops.
When planning the retrofit, consideration must be given to which of the discharges will be made CAFS-capable. Flexibility in this decision will help keep the installation cost reasonable, but the possibilities may be driven by the existing plumbing on the rig. Each CAFS discharge will need to be plumbed to the foam manifold, so some discharges will be easier and therefore cheaper to plumb than others. By choosing the proper discharges, it may also be possible to have more CAFS-capable lines for almost the same cost.
Consideration should also be given to whether the apparatus has an existing foam proportioning system. If no system is currently 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 whether it can be used with CAFS. Important: 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 most common proportioner for CAFS is an electronic direct-injection system.
Where to Go & What to Expect
Retrofits are done by numerous fire apparatus dealers and service centers. Some original equipment manufacturers 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 period of time. The length of time will be determined in a large part by the complexity of the retrofit. The cost of the retrofit will also 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.
Do Your Homework & Train!
Diligent homework 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 will help ensure a cost-effective installation that will operate correctly.
Lastly, don’t forget the all-important CAFS 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.
Article by: Keith Klassen, Waterous CAFS Instruction Coordinator