It’s no secret that fire apparatus are becoming more multifunctional as budgets and personnel allocations decline—combining rescue trucks with pumpers (rescue-pumpers) or pumpers with aerials (quints). However, one area that is often overlooked is the increasing amount of equipment that is carried on the apparatus and the effect this has on vehicle weight.
Additional Weight Ramifications
It is easy to add a rescue tool to the front bumper tray or put some air bags and cribbing in a compartment—just a few hundred pounds extra here and there. Later come some self-contained breathing apparatus (SCBA) bottle racks and maybe tool boards. Before you know it, a few hundred pounds becomes several thousand pounds.
NFPA 1901, Standard for Automotive Fire Apparatus, has made provisions for estimating sample equipment and hose in-service weight allowances on a fire apparatus. It also spells out the purchaser’s responsibility for determining specifically what the correct equipment and hose weight allowance should be on its particular apparatus. Specifically, NFPA 1901 states:
12.1.1: The manufacturer shall establish the estimated in-service weight during the design of the fire apparatus.
12.1.2: The estimated in-service weight shall include the following:
- The chassis, body, and tank(s).
- Full fuel, lubricant, and other chassis or component fluid tanks or reservoirs.
- Full water and other agent tanks.
- * 250 pounds (114 kg) in each seating position.
- Fixed equipment such as pumps, aerial devices, generators, reels, and air systems as installed.
- Ground ladders, suction hose, and designed hose loads in their hosebeds and on their reels.
- An allowance for miscellaneous equipment that is the greatest of the values shown in Table 12.1.2, a purchaser-provided list of equipment to be carried with weights, or a purchaser-specified miscellaneous equipment allowance.
12.1.3: The manufacturer shall engineer and design the fire apparatus such that the completed apparatus, when loaded to its estimated in-service weight with all movable weights distributed as close as is practical to their intended in-service configuration, does not exceed the (gross vehicle weight rating (GVWR).
12.1.4: A final manufacturer’s certification of the GVWR or gross combined weight rating (GCWR), along with a certification of each gross axle weight rating (GAWR), shall be supplied on a label affixed to the vehicle.
* The 250-pounds (114 kg) in each seating position does not include the weight of SCBA and tools carried by a firefighter.
Miscellaneous Equipment Allowance
Table 12.1.2 spells out miscellaneous equipment allowance for all types of apparatus, from initial attack to tankers to quints. For simplicity let’s look at pumpers. There are two categories.
Table 12.1.2 Miscellaneous Equipment Allowance (Pumpers)
|Apparatus Type||Apparatus Size||lb.||kg|
|Pumper fire apparatus||Less than 250 ft3 (7 m3) compartment space*||2,000||910|
|Pumper fire apparatus||250 ft3 (7 m3) or more of compartment space||2,500||1,135|
*Compartment space for pumpers is calculated based on the inside dimensions of the enclosed compartment.
The apparatus manufacturer can tell you the total capacity of the compartment arrangement you have selected in cubic feet. If you do not inform the apparatus manufacturer otherwise, the equipment capacity listed on the above chart will typically be used to calculate the in-service weight of the apparatus. This may or may not accurately reflect what you actually carry on your pumper. Item 7 above states that “a purchaser-provided list of equipment to be carried with weights or a purchaser-specified miscellaneous equipment allowance must be provided” if the equipment you intend to carry exceeds the NFPA allowance. So, how do you know if your equipment will exceed the NFPA minimum? On the Fire Apparatus Manufacturers’ Association (FAMA), Web site you can find a weight and cube calculator for most of the items you may carry.
Once you have determined the total weight and cubic feet requirements for your equipment, you need to consider where the equipment will be placed on the apparatus. If you do not specify a location, the manufacturer will generally allocate equipment loading evenly distributed for each compartment.
The manufacturer is responsible for determining the weight of fixed equipment on the apparatus including generators, reels, air systems, ladders, hard suction hose, etc. as installed. However if the dealer or customer is going to install some of these items after the truck is completed, the manufacturer must be informed of that fact to appropriately account for the corresponding weight and space requirements.
The manufacturer is responsible for calculating the GAWR and GVWR of the apparatus, including the equipment it will be carrying. The location of equipment relative to the front and rear axle can affect the size (GAWR) requirements for each axle. In addition, NFPA 1901 requires that the apparatus, fully loaded, shall have a side-to-side tire load variation of no more than seven percent of the total tire load for that axle. The manufacturer may not be able to accurately calculate the side-to-side loading without knowing where on the apparatus the equipment is intended to be carried. On a 23,000-pound rear axle, the variance is no more than 1,610 pounds. Not maintaining a balanced side-to-side loading can result in a chassis lean to the heavy side and possible handling issues with the apparatus. Therefore, it is important to share where you intend to load or carry equipment with the apparatus manufacturer.
Another significant equipment weight factor is the hose load you intend to carry. NFPA 1901 defines a minimum hose storage capacity of 30 cubic feet of 2½-inch or larger hose and two areas of 3.5 cubic feet each for 1½-inch or larger preconnected hose for pumpers. To put this in terms of weight, 30 cubic feet of 2½-inch hose is approximately 1,200 feet of hose or 684 pounds. It is possible that departments carry a lot more than this. However, if you do not tell the manufacturer what you intend to carry, it would be perfectly compliant with NFPA for the apparatus manufacturer to provide just the minimum hose requirements (relative to cubic feet, size, and weight), although that estimate may actually be grossly inadequate.
Compare the above minimum requirements to 2,000 feet of five-inch large-diameter hose (LDH), which requires a minimum of 80 cubic feet and has an associated weight of approximately 2,300 pounds. Hose loading can also affect side-to-side weight balance. If you carry all of your LDH on one side of the hosebed, have rooftop compartments, or have overhead ladder racks that intrude into the hosebed, you can easily be out of balance side-to-side.
Think of the Future
Once you have accounted for all the equipment, hose, generators, etc. you plan to carry, consider what the future may bring. Five years ago, who would have thought that drones or bulletproof vests would become part of the fire service? Your apparatus may stay in service for 20 years or more, so it would be prudent to allow for some reserve weight capacity as more tools and equipment evolve.
To avoid being “overweight,” communication is critical. It is extremely expensive to change an axle, suspension, and tires to increase carrying capacity. It reflects badly on both the manufacturer and customer when an apparatus is overweight after being put into service. Customers should inform dealers and manufacturers in advance of the bid process if their requirements exceed NFPA minimums. Waiting until a pre-construction conference can result in unforeseen expensive changes to axles or compartment arrangements.
FAMA is committed to the manufacture and sale of safe, efficient emergency response vehicles and equipment. FAMA urges fire departments to evaluate the full range of safety features offered by its member companies.