INTRODUCTION

There are situations where it may be desirable to operate defensive streams utilizing hydrant pressure. Certain hazardous materials incidents call for application by unmanned monitors and it may not be the best choice to leave an engine in close proximity to the event pump to the monitor. Environmental or exposure conditions may not be suitable for safely positioning an engine to supply defensive streams at some structure fires.

High volumes using hydrant pressure

Straight tip hose evolutions do not require high discharge pressures and can be effective utilizing hydrant pressure in locations that have mains of adequate diameter and good working pressures. In such circumstances straight tip streams deployed for defense and exposure protection will be easy to deploy, require less manpower and apparatus, and will provide reliable service.

FIELD TRIALS

We set up a "real time" exercise at Joaquin Moraga Intermediate School. We used a hydrant at the rear of the school which would likely not be accessible by an engine in the winter when the ground was soft. The feed main on the street is 16" so an engine pumping at the front of the school would have little impact on the performance of the hydrant at the rear of the school. Our test evolution assumed engine companies would be attacking a fire in one area of the school building using the hydrant on the street and our mission was to deploy a ground monitor and 2½" safety loop using a single crew to protect the uninvolved portion of the complex. (Since the hydrant behind the school had been upgraded to 2½" x 2½" x 4½", it could supply two simultaneous hand lines, a monitor and a hand line with 1¼" tip, or a monitor and two hand lines with 1" tips.) Performance Objectives Based on the flow test characteristics of the hydrant, we expected to deploy: A ground monitor flowing 600 GPM supplied by 4½" hose A 2½" safety loop flowing 325 GPM supplied by 150' of 2½" hose Required pressures were 80 p.s.i. for the monitor and 50 p.s.i. for the safety loop. We had no difficulty maintaining 600 GPM through the monitor. To supply the safety loop, we had to restrict the hydrant discharge as to fully open the 2½" line ran the nozzle pressure up to 70 p.s.i. with the monitor simultaneously flowing.

Flowing from direct hydrant layout Pressure Gauge Readings: Hydrant Static: 116 psi Hydrant Residual: 94 psi 1½" Monitor Tip: 79 psi 1¼" Hand Line Tip: 70 psi Flows Obtained 1½" Monitor Tip: 600 GPM 1¼" Hand Line Tip (50 psi): 315 GPM 1¼" Hand Line Tip (70 psi): 360 GPM

CONCLUSIONS

Hydrant pressure evolutions are practical in situations where hydrants can support them. The friction loss through the monitor appliance flowing 600 GPM was nearly equal to the friction loss of 150' of 2½" hose flowing 325 GPM. The monitor could be placed virtually anywhere in the rear area of the school as the friction loss in the 4½" hose was negligible. The hand line would operate effectively up to 300' away from the hydrant. The hand line using a 1¼" tip was easily manageable by one fire fighter at 80 psi using a safety loop, and had nearly the same reach as the monitor. When access by fire apparatus behind the school is questionable, a very practical alternative is to carry hose lines to the rear and work off of hydrant pressure using straight tips.