In the last installment of the Apparatus Architect series (January 2002), we discussed concepts regarding the design development of engine company apparatus and how two fire departments addressed their needs with their new units. With this article we will begin to detail some of the critical aspects...
To access the remainder of this piece of premium content, you must be registered with Firehouse. Already have an account? Login
Register in seconds by connecting with your preferred Social Network.
Complete the registration form.
Front bumper extensions should be the minimum length to achieve the proper fit-up for all the options that the fire department may require. Excessively long extensions increase the swing clearance of the apparatus and can reduce the angle of approach. Many accidents occur when backing the apparatus out of a driveway or narrow road. As the apparatus is backed out the operator is looking in the mirrors and neglecting the front of the apparatus. During this maneuver, the front bumper extension will find a utility pole, mailbox or street sign and could incur significant damage. However, unless you have an extreme overall length problem with your pumper, providing some type of bumper extension with the appropriate reinforcement will increase the safety margin for the front end of the apparatus.
Photo by Tom Shand
Kentland, MD, Engine 333, a 2000 Pierce Dash, carries both 100-foot and 150-foot bumper lines. Note the hose load and the bumper-mounted warning lights.
Piping that is run for front suction lines should employ a minimum number of bends and should use sweep style elbows rather than 45- or 90-degree fittings. This is critical where the piping goes along the chassis frame and over the front axle. With many chassis requiring 12.25- or 13-inch-wide front tires, the suction piping may be restricted in this area, or the steering geometry may be affected by the piping arrangement. Consider developing a performance specification for the front suction piping and note whether the department intends to use the front suction for drafting purposes. Additional taps from the pump primer or other designs may have to be considered to improve the performance from the front suction.
Operationally commercial apparatus make poor candidates for front suction intakes, unless the vehicle is going to be equipped with a front mount pump. Generally, the chassis are delivered to a manufacturer and then the manufacturer must figure out how to plumb the front intake back to the pump. This process generally includes hiring a pipe urchin to install a series of 45- and 90-degree fittings through the pre-existing axle, steering box, engine and other chassis components. This addition of a front intake in this manner is expensive and as it relates to water flow into the pump is not very effective. Having a front intake installed on a custom chassis, particularly by a manufacturer that builds the apparatus from the ground up, costs less and tends to create greater flows into the pump due to the lack of multiple 45- and 90-degree bends.
This theory was proven to be fact at a recent water supply course. In comparing the front intake flows of a commercial pumper vs. a custom pumper, the custom pumper produced an additional 200 gallons per minute (gpm) of water flow. Then a comparison was made between the custom pumpers front intake to the side intake. Due to the unobstructed flow right into the pump from the side, the side intake produced 300 gpm more water flow than the front intake from the same custom pumper. So given a choice from a tactical point of view, it is beneficial to use the side intake vs. the front intake. These facts are not meant to sway your purchasing decision one way or the other but rather to enhance your department's knowledge so that you maybe able to make a more educated informed decision.
Photo by Tom Shand
Note the position of the front suction swivel and the headlights on Warminster, PA, Engine 91. Be careful not to block forward-facing lights with bumper-mounted appliances and fittings.
Also, it is important to relate to you an experience from an emergency vehicle operators course. This particular department had recently taken delivery of a custom pumper that had added a front intake after the chassis was delivered to the body manufacturer. As this pumper was making it way though the serpentine on the driving course it was noticed that the vehicle could make left turns fairly easily, but it had trouble making a right turn. It was further learned that the cramp angle (steering angle) was much better on a left turn than it was on a right turn. Upon an apparatus inspection, on the driving course it was found that when the front intake was installed that the right steering arm actually hit the front intake piping, causing the vehicle to have an inferior right turning radius.
When specifying discharge piping to the front bumper, consider what type of flows will be required. If the front discharge will be used to supply a hoseline that will be used for small outside fires, vehicle and dumpster fires, then a two-inch discharge that can provide flows of up to 200 gpm should be sufficient. If the discharge will be used to pump lines to hydrant valves or supplying other apparatus, then a 2 1/2-inch or three-inch discharge line should be specified. If the discharge line is going to terminate with a chicksan-style swivel, then this fitting should be specified to be the same size as the piping.