It was a discovery of importance, that by coupling two or more pumps in series, so that each pump worked against only a part of the total delivery head, water could easily be raised to even two thousand feet or any reasonably high head with satisfactory efficiency. Pumps connected in this way will throw more water at a given speed than when operated separately, and are therefore attended by less wear and tear.
Fig. 501.
Pumps worked in series are built compound, triple or quadruple as required by service either belt driven or directly connected to engines. Owing to the fact that they have no valves or absolutely close-parts, they are able to pump muddy or gritty water with sand in suspension, and are, therefore, especially in the vertical type, the only ones that can be successfully used for draining deep mines.
Fig. [501] is designed to illustrate a four stage centrifugal pump, or a quadruple compound pump capable of lifting water 250 feet.
Fig. 502.
Explanation of diagram page 225. In determining the requirements best suited as regards rotation of shaft and connection with the suction and discharge pipes, in installing a pump, the figure [502], will be found a convenience. It is important to run the most direct pipes with the least number of elbows or bends.