A suction valve with double strainer is represented by Fig. [599], in which the outer screen is raised for cleaning. In lowering, it is guided to its place by the cage around the foot valve chest, as will be seen in Fig. [600], which is a sectional view of this same valve. The suction pipe extension enables the pump to draw water when its surface has fallen below the top of strainer and also below the foot valves. This is often a great advantage where water is scarce and every gallon is needed.
This foot valve is a “double clack” hinged in the center. There are no openings or perforations in the bottom plate. Fig. [601] is a very convenient form of strainer for large pipes and where it is an advantage to have the strainer in the engine-room or near the pump. This strainer, like Fig. [597], can be lifted out for cleaning by removing the claw and bonnet. The chamber may be washed out by removing the plug at the bottom.
Fig. 599.
Fig. 600.
A most convenient vacuum chamber and strainer is represented in Fig. [602]; it is located near the pump. By removing the suction chamber the basket or strainer may be lifted out by the handle under the arrow. The outlet is generally attached directly to the pump. The pump may be charged by removing the “priming plug” and inserting a hose, with water turned on.
Steam boiler feed water impurities consist mainly of chemical substances which are unaffected—as may be readily supposed—by mechanical devices just described; these impurities are largely invisible being dissolved in the water and hence, also, considering their variety, are most difficult to contend with. How to avoid the actual evils arising from the presence of foreign matter in feed water is of the first importance in steam economy; enormous losses of money, danger to life and property are involved in it. It has been said that there are more millions of treasure to be made by properly “treating” the water which enters the steam generators of the world than can be extracted from its gold mines.
