A COLOR-CODED GRADE INDICATOR FOR AERIAL APPARATUS
APPARATUS/EQUIPMENT
Determining the number of men and amount of equipment (load) an aerial ladder can safely support is not always easy, especially when the fire apparatus is positioned on a grade. The percent of the grade must be considered when calculating the aerial’s angle and load; and it is often difficult to estimate the percent of grade accurately.
The Camp Hill, Pa., Fire Department resolved this problem by developing a grade indicator which reduces the guesswork of the aerial operator and provides a safety factor in accordance with the aerial manufacturer’s specifications.
According to the operator’s manual for the department’s aerial apparatus, which is 85 feet and mounted on a Duplex chassis, if a chassis can be leveled to a point that the angle of the aerial’s turntable does not exceed a 6 percent grade (if the street does not slope upward more than 6 feet in a 100-foot distance), loads up to 700 pounds can be maintained through a 360-degree operation. It the angle of the turntable is between 6 and 14 percent, the basket weight should be no more than 350 pounds.
The grade indicator consists of a pendulum-type angle indicator and a colorcoded stainless steel plate. If the tip of the pendulum points to the green area on the color-coded plate, the turntable is within a 6 percent grade. If the plate s yellow area is indicated, a 6 to 14 percent grade is designated; the red area indicates a grade greater than 14 percent. Inside the turntable pedestal’s control cover, the department posted color-coded labels showing maximum recommended basket weights for the various turntable grades (when no water is flowing).
The department verified its interpretation of the percent of grade information given in the operator’s manual with the aerial apparatus manufacturer, and checked the accuracy of the color-coded steel plate with an engineer.
Before two grade indicators were attached to the control pedestal, two spirit levels, positioned at 90-degree angles to each other, were used to check that the turntable was level. The grade indicators can be seen not only from the pedestal operator’s position, but also by the aerial operator ascending the rear of the apparatus to the turntable and by fire fighters preparing to ascend the ladder. The colors can be quickly noted on both grade indicators for a quick determination of the maximum safe basket loading under normal conditions.
Aerial apparatus loading varies from one manufacturer to another, so be sure to study your operating manuals and contact the manufacturer for clarification before adding grade indicators to your specific apparatus. If your aerial apparatus already has a grade indicator of one type or another located on it, become familiar with its operation and use it properly for safe operation of the piece.
Having worked successfully for over a year, the two grade indicators were recently deemed sufficient by the National Testing Agency as a means of determining turntable level.
