SUCTION HOSE FRICTION LOSSES DETERMINED BY TESTS AT U. OF W.
Friction Data on Three Sizes Made Available by Henry S. Morton, LCDR, U. S. N., following Comprehensive Tests
DURING the past year, Lieutenant Commander Henry S. Morton carried out a project at the hydraulic laboratories of the University of Washington, on friction loss determinations in hard suction hose of 4 1/2-inch, 5-inch and 6inch diameters for varying flows.
These data will very effectively supplement those secured in a series of experiments by John R. Freeman, which were conducted in 1889 on the flow of water through fire hose, of which the values of friction factors, at velocities ranging between ten and thirty feet per second, were obtained. The hose included in the Freeman tests was all soft, flexible hose, non-reinforced. To date, very little information has been published on friction factors for hard, wirereinforced rubber hose.
The principal object of the U. of W investigation was to determine friction losses for various rates of flow in reinforced rubber hose.
The selection of the hose was limited to the material available in the Seattle area, where the laboratory investigations were carried out.
The 4 1/2″ hose obtained was new suction hose which was in the custody of the Public Works Department of the Naval Receiving Station, Seattle, Washington. In order to obtain an accurate inside diameter of the hose, the hose was filled with water and the volume of water was weighed. It was necessary to bend the hose in a U shape position in order to get a volume measurement. However, the results of the volume testing indicated that the average inside diameter of the hose was 4.46 inches. By using inside micrometers the inside diameter was measured at 4.50 inches throughout the entire length.
The length of hose used for the test was a 15-foot section wire reinforced fire department suction hose. The actual length of the exposed rubber hose surface was 14 feet, 6 1/2 inches. The inside diameter of the spanner rings and hose couplings was 4-17/32 inches. The hose, in general, meets the military specifications MIL-H-15100A (Ships), of 15 August 1951. The maximum allowable inside diameter tolerance is plus or minus 1/32 of an inch. The distance between the piezometer pressure takeoff connections was 15.56 feet. There was approximately 0.47 foot of length between the piezometer pressure takeoff and the commencement of the rubber hose surface. This length was polished brass with slightly varied diameters due to coupling construction and spanner ring rolling methods. All burrs were removed and the joints were, carefully aligned to provide a smooth entrance and exit surface. The joints were again examined after the tests for burrs and any obstruction or signs of roughness. The hose was suspended in the horizontal plane and supported by a rigid angle iron bar to prevent sagging. The installation contained no curves or bends.
All static pressures were measured in feet of fluid by means of water columns and a mercury U-tube. Both water columns and the U-tube were connected to the piezometer rings by high pressure hoses with facilities and pet-cocks arranged so that the air could be easily bled from the system. The system was purged prior to each test.
The temperatures of the water flowing through the system were measured in degrees Fahrenheit upon entering the receiving tank prior to weighing.
The rate of flow of water through the hose was determined by recording the time required to discharge a given weight of water in the receiving tank. The quantity of water flowing across the piezometer ring was determined by dividing the weight of the water in the receiving tank by the time and density of the water. The average velocity of the water flowing across the piezometer connection was measured by dividing the quantity flowing by tile cross sectional area.
The test conditions and limits of the experiment were entirely dependent upon the facilities available in the hydraulics laboratory. In addition, the type, style, and quality of the hose was restricted to the material available locally. A mercury U-tube monometer was used for measuring the pressure differential as a check against the readings obtained on two independent water columns. The maximum quantities ot water which could flow through the test section were dependent upon the ability of the drains within the laboratory to handle the large quantity of water.
Prior to the commencement of any set of tests, the system was operated at maximum capacity, all air drained out of the lines, and all values checked for leakage. In addition, it was desired, where possible, to obtain a constant temperature. Usually all tests were conducted using the maximum rate of flow and slowly “gating” the system for each individual test.
Water column readings were read prior to the commencement of the test, and again at the termination of the test. Since the duration of some tests was as low as thirty-five seconds, it was impracticable to obtain temperature and pressure readings during the actual test. Water temperature readings were obtained at the commencement and completion of each test, and recorded to 1/2 degree F. In some tests, where large quantities of water are involved and extreme accuracy was required, water was routed into the receiving tank and weighed by routing the water from the receiving tank in partial quantities to the weighing tank. The weighing tank had insufficient capacity to handle the entire quantity of water in the receiving tank. However, the weighing tank was calibrated so that on several tests it was not necessary to weigh each quantity of water. Where low flow rates were used, the water was routed direct to the weighing tank for measuring. Timing of water rates was accomplished by use of a tenth-second interval stopwatch.
Tests were conducted on 4 1/2-inch, 5inch and 6-inch hard suction hose. The tables herewith give the friction losses for all three sizes at varying flows.