FRICTION LOSSES AND PIPES.

Southland Times, Issue 20205, 16 June 1927, Page 5

FRICTION LOSSES AND PIPES.

To the Editor. Sir, —May I offer a few further remarks and opinions on the question of Invercargill’s water supply, and the question, of pumping versus gravitation? There has been considerable discussion and diversion of opinion as to the probable loss of head by friction in the proposed Dunsdale pipe line, 25.2 miles long, 18in. in diameter, when delivering at the rate of 2,000,000 gallons per day. In the reference department of the Public Library there is a very admirable technical book—“A Text Book on Practical Hydraulics,” by Professor James Park, of the Otago University, one of the highest (if not the highest) authorities on hydraulic engineering in this country. On pages 32-35 are given tables showing the loss of head by friction in each 100 feet of pipe line of various diameters and varying velocities of flow. In an 18in. diameter pipe with a velocity of flow of 2.2 feet per second the loss of head by friction is given as .16 feet for each 100 feet, therefore, in 25 miles of 18 inch diameter pipe line with a velocity of flow of 2.2 feet per second which is equal to a delivery at the rate of 2,097,000 gallons per day the loss of head by friction will be 211.2 feet. On page 26 of the same book Cox’s formula for calculating the loss of head by friction in pipes is given. By this formula the loss of head for the same pipe line under the same conditons would be 207.5 feet. If these figures are correct and they have been verified by an eminent hydraulic engineer, it will be necessary to boost the pressure by pumping during hours of maximum draw off, observing that the maximum draw last summer exceeded the rate of 2,000,000 gallons daily. As previously stated the above work—“A Text Book on Practical Hydraulics,” by Professor James Park is on the shelves of the reference department of the Public Library. It should be noted that the above figures are for clean straight pipes, no allowance is made for bends, joints, etc., or for used piping. Naturally the friction increases with use.—l am, etc., “PERSISTENT.”