. Canadian engineer. ncy issecured when the submergence is times the lift, andthat the cfTiciency falls off more rapidly for a reductionin the submergence than for an increase. It is a goodplan, therefore, to have the submergence more than thatcalculated for the best efficiency rather than less. Thisallows for the usual occurrence, vie, that the pumping liftincreases as more wells are sunk or during a dry season. Pro\ious to this test the length of the air pipe in thiswell had been varied with a view to finding out the bestflow at which to operate the well. The important dataare given belo
. Canadian engineer. ncy issecured when the submergence is times the lift, andthat the cfTiciency falls off more rapidly for a reductionin the submergence than for an increase. It is a goodplan, therefore, to have the submergence more than thatcalculated for the best efficiency rather than less. Thisallows for the usual occurrence, vie, that the pumping liftincreases as more wells are sunk or during a dry season. Pro\ious to this test the length of the air pipe in thiswell had been varied with a view to finding out the bestflow at which to operate the well. The important dataare given below and plotted in Fig. 3 :— Length of Pumping Air Pipe. Flow. Head. Efficiency. Duty. Feet. Gal. per min. Feet. Per cent. (iai. per hr. 224 > .493 47-5 1,630 208 .459 45-8 31-5 1,640 184 44-3 3- 1,670 162 39-4 1,790 142 1,299 37-7 1,920 124 1,2ig 37-5 2,070 •05 1,106 37 I 2,340 86 1,008 32-5 33-4 2,450 79 904 29-3 31-3 2,530 67 802 30-5 2,750 43 bgo Fig. 3. The air supply was apparently adjusted so as to getthe best efficiency for each submergence. This test shows an anomalous variation of the rela-tion of pumping head to rate of flow, which is probablydue to the coming into action of a second water-bearingstratum, there being two cut by the well, when the levelof the water had dropped 33 feet on account of the opera-tion of the lift. The writer believes that pump duty, water pumpedper unit of energy supply, should be made the criterionof operation rather than mechanical efficiency. He has,therefore, calculated the last column. This shows that the duty of the lift increases as therate of pumping is decreased, which is due primarily tothe decrease in the pumping head. The variation will besmall for a free-flowing well, or one in which the drop April 1916. THE CANADIAN ENGINEER 439 due to pumping is small in comparison with the pumpinghead. This dictates that llie well should be pumped atthe minimum rate at whi
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