Determination of Fire Hose Friction Loss Characteristics

Abstract

Friction loss characteristics of fire hose have changed as a result of evolving hose manufacturing technology. Published friction loss characteristics may be overly conservative. While conservatism in fire protection is generally good, in this case it may lead to excessively high pump discharge pressures as the operator applies general rules-of-thumb. The overall objective of this research project was to develop friction loss characteristics for hose currently used by the fire service. A total of 86 tests were performed by three fire service organizations on 82 fire hose samples spanning 1–5 inches in diameter. Recorded hose dimensions, pressure, flow and friction loss data were used to calculate the friction factors. Three friction factors were calculated: C, the factor now used in published data; and, CD and f. The traditional C factor combines hose diameter and roughness into a single constant. The CD and f factors use the measured diameter to calculate a friction factor closely associated with hose interior roughness. The data indicate that most C factors calculated for the tested hose fall below the currently published values. The CD and f factors provide more insight into friction loss characteristics, since the effects of actual inside diameter are considered. Overall, the friction loss characteristics observed for individual tested hose sections are a factor of the inside diameter and roughness. Inside diameter alone was not a predictor of the magnitude of the friction loss across all samples. A fairly large degree of variability was observed in the data.