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 of engine company apparatus and how these factors can help you and your apparatus committee in the specification development process.
One of the most important missions of the engine company is to stretch and operate hoselines at structural fires. The purpose of this first line is to protect the primary means of egress for occupants of the building and to insure that fire department personnel can safely operate within the structure.
In order to perform this mission, the engine company must be able to secure a water supply to insure that the hoselines will have a continuous and reliable water supply for the duration of the incident. For those of us who operate with fire hydrants, this water supply may be readily available. In rural areas, this water supply may be from tankers, fixed water sources or a combination of both. We must constantly reinforce that in the design of the pumper, we cannot lose sight of this most basic, yet important mission of the engine company.
Starting At The Front
We will begin our discussion of engine company apparatus at the front bumper. This is one area where many pump intake and discharge connections can be provided, along with other tools and pieces of equipment. Back in the 1970s and '80s, it was fairly common to have the front end accommodate a front intake, mechanical and electronic siren, and maybe a warning light. Today's pumpers routinely are equipped with a gated front intake, front discharge or trash line each with hose wells, air horns, sirens and multiple warning devices. It is not uncommon to have $8,000 to $10,000 worth of components located in the front bumper area. There is not a problem with providing all of this; however, you have to ask yourself, "What is protecting the front of my apparatus?"
Most apparatus are built with a 10- or 12-inch-high stainless steel bumper that can be extended 18 to 26 inches ahead of the cab. Quite often, there is very little protecting all of this real estate other than the bumper itself and some aluminum treadplate. One only has to look at the front end of a unit damaged in an intersection accident to see that this area can sustain heavy damage that can place the apparatus out of service with expensive repairs. Intersection accidents may not represent the largest percentage of apparatus accidents in a given year, but they represent the most dollars lost every year.
Insurance companies pay out hundreds of thousands of dollars annually in apparatus repairs and certainly the construction of the front of the apparatus has a major impact on these payouts. Consideration should be given to specifying full steel channel reinforcement for the front bumper. This will aid in the prevention of intersection accident damage. This reinforcement is placed behind the bumper across the front and ties the sides back into the chassis.
The Boston Fire Department used this style of bumper reinforcement on the front end of the pumpers and also used a tubular steel design to protect the bumper area. Units operated by the Washington, D.C. Fire Department and the FDNY employ a painted steel bumper, fabricated of 80,000 psi material that is three-eighths of an inch thick. The number of holes cut into the bumper is minimized to maintain the integrity of the entire assembly.
Bumper Extensions
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.
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.
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.
Other Considerations
Hose trays or wells may be constructed of either smooth aluminum or stainless steel and should be bolted to the top of the bumper deck rather than welded in place. Bolted assemblies are easier to replace and less costly to repair. If your department has designed an engine company with a front trash line, you should consider what length of hoseline that you are going to run in this location and exactly how the hose in going to be loaded in the tray. Loading the hose flat or in an accordion fashion will put numerous folds in the line that can kink when the line is charged.
There are several ways to load the hose that will enable one firefighter to stretch the line and minimize the number of folds in the line. Several departments in the Maryland area have developed effective hose loads for the trash line. In particular, the Kentland Fire Department, Engine Company 33, in Prince George's County has developed a very effective hose load combining a modified horseshoe load with a double donut roll for both 100- and 150-foot bumper-mounted attack lines. The emphasis should be to design the trash line and soft suction hose wells so that the hoselines may be easily and safely deployed by one person. Other tools and fittings can be positioned on the front bumper deck, but these need to be secured and make sure that they do not block headlamps or warning lights.
Intersection warning lights are required by the National Fire Protection Association (NFPA) 1901 standard and these lights will be typically placed at the forward surface of the bumper or on top of the bumper deck. Consideration should be given to placing forward-facing warning lights at the bumper level, which may be more readily seen by passenger cars that are immediately in front of the apparatus. It may also prove beneficial to provide cornering lights or bumper guide markers that will clearly identify and illuminate the forward most portions of the apparatus. Since so many apparatus accidents occur while traveling through intersections, the front bumper area deserves special attention to enhance safety for the apparatus and crew.
When designing engine company apparatus, the committee should evaluate the ability of the pumper to deliver its rated capacity through a sufficient number of discharges, with a minimum of five pre-connected attack lines. As pump capacities increase, it is important that the pumper carry supply line of an adequate size to support the rated capabilities of the fire pump.
In the next installment of the Apparatus Architect we will cover the area of the pump panel and piping that is required to meet these objectives.
Tom Shand, a Firehouse
