MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

until the air pressure within it exceeds the force of the inflowing water.The check valve is then forced shut, causing the water above it to flowup the delivery pipe, while the falling water again flows through thewaste valve. This cycle occurs rather rapidly--25 to 100 times per minute.The valves can normally be adjusted to vary the strokes per minute (spm)which in turn regulated the discharge. More water is needed to operateat slower spm's, but a higher percentageof water is also driven up thedelivery pipe. This variation in performance is a function of the size andtype ram used, as well as the ratio between driving head and delivery head.Table 3.8, part A, lists some ram sizes by pipe diameters, and typicalminimum driving (or falling) discharges (Q,) necessary for them tooperate. The efficiency of rams is usually about 60 percent. Some typicalcombinations of Q rand H r are given in Table 3.8, part B. Rams usuallyneed a minimum H fof 18 inches to operate. With sufficient Hf , somerams are capable of Hdls up to 500 feet. Discharges (Q,) vary fromless than 1 gpm to about 1600 gpm.Rams vary in cost,depending on size and make, from about $200 to$3000. This usually includes a drive pipe strainer, but does not includepipe or other plumbing accessories. Double-acting rams are $80 to $300more. Because the ram is a rather simple device (i.e., has few movingparts, no high-speed drive connection, no close tqlerances, etc.),several designs have been made available which only need materials that canbe obtained in most plumbing or hardware stores; e.g., metal rod, concrete,pipe, bolts, rubber washers, etc. (Kaufman, 1948). A similar, easy-toconstructdesign has been set forth by VITA for use in developing countries(Kindel, 1975).