Pumps and Hydraulics, Part 1 (of 2)

by N. Hawkins

Fig. 279.

Fig. 280.

The exhaust steam may be allowed to flow into the atmosphere or into the suction chamber as desired. A valve is located in the base of the pump, which changes the course of the steam from the atmospheric discharge to the suction chamber. The valve is operated by a lever shown by dotted lines. When the lever is turned down toward the steam end, the steam is directed into the atmospheric exhaust, and when turned in the opposite direction the steam will enter the pump suction and be condensed.

There is no valve setting to be done on this pump. Should the pump fail to work properly, due to the failure of the steam end, all that is necessary is to take out the valve and piston and clean them thoroughly and after replacing them and starting the pump to see that these parts are properly lubricated. The remainder of the pump requires the same care and attention that is, or should be, given all pumps.

THE SNOW.

The auxiliary valve of this pump is a plain flat slide operated by a valve stem, the latter being moved back and forth by means of a rocker shaft, as shown in the engraving, the upper end of which alternately comes in contact with the collars on the stem.

The outer end of the valve stem passes through a sleeve attached to a pin in the upper end of the rocker arm, as shown. A knuckle joint near the stuffing-box permits the rod to vibrate without causing any derangement in the alignment of valve stem through the stuffing-boxes.

On the valve stem at either end of the auxiliary valve is a spring, which tends to keep the valve in a central position, so that when the rocker arm engages one of the collars, the valve is drawn against the spring toward that end of the stroke. The result is that the stem and valve follow the rocker arm on the return stroke to its mid-position, and are started on the latter half of the stroke by the stem, but without shock or lost motion. This arrangement is particularly valuable in the case of condensers, and in pumps where the first part of the stroke is made quickly, and the piston is then suddenly stopped by coming in contact with a solid body of water, the latter part of the stroke being made much more slowly. The springs on either side of the auxiliary valve take up lost motion and keep the parts in absolute contact, thus preventing shocks and unnecessary wear.