STRAINERS FOR SUCTION PIPES,
It is very desirable to place an efficient strainer on the suction pipe of a pump where there is the least suspicion that the water contains any sediment or floating matter.
Several of these useful pump attachments have been already shown, connected with pumps, in previous sections of this work, but a few more are here added.
Fig.597exhibits a cross section of a strainer of large capacity of long and satisfactory use. It has a semi-cylindrical vessel located in one side of the side pipe. Holes are drilled through the flat side extending across the diameter of the side pipe; any floating matter which will not pass through the holes collects in this strainer vessel and may be easily removed.
Figs. 597 and 598.
Figs. 597 and 598.
Fig.598represents a longitudinal section of this strainer. The top of the chamber is covered by a bonnet secured by a claw having one bolt, so that by unscrewing this bolt the claw and bonnet may be unfastened and the settling chamber with perforated plate withdrawn.
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 ofthis 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.601is 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. 599.
Fig. 600.
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 impuritiesconsist 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.
Fig. 601.
Fig. 601.
Fig. 602.
Fig. 602.
Note.—Strangely, investigation has proved that water of this purity rapidly corrodes iron, and attacks even pure iron and steel more readily than “hard” water does, and sometimes gives a great deal of trouble where the metal is not homogeneous. Marine boilers would be rapidly ruined by pure distilled water if not previously “scaled” about1⁄32of an inch.
Note.—Strangely, investigation has proved that water of this purity rapidly corrodes iron, and attacks even pure iron and steel more readily than “hard” water does, and sometimes gives a great deal of trouble where the metal is not homogeneous. Marine boilers would be rapidly ruined by pure distilled water if not previously “scaled” about1⁄32of an inch.
To deal properly with this subject the science of chemistry must be largely drawn upon; chemically pure water is that which has no impurities, and may be described as colorless, tasteless, without smell, transparent, and in a very slight degree compressible, and, were a quantity evaporated from a perfectly clean vessel, there would be no solid matter remaining. Now, in dealing with the impurities inside a boiler, it is to be observedthat in no sense do they change the essential nature of water itself. The impurities are simply foreign bodies, which have no legitimate place in the boiler, and are to be expelled as thoroughly as possible.
The chemical substances to be eliminated are indicated in the note below. Water, on becoming steam, separates from the impurities which it may have contained, and these form sediment and incrustation. This is an important fact.
Corrosionis simply rusting or wasting away of the surfaces of the metals. Incrustation means simply a coating over.
Several approved recipes and “notes” of instruction for removing sediment and incrustation from steam boilers will be found near the close of this volume.
Note.—Analysis of average boiler scale. Parts per 100 parts of deposit.Silica.042partsOxides of iron and aluminium.044„Carbonate of lime30.780„Carbonate of magnesia51.733„Sulphate of sodaTraceChloride of sodiumTraceCarbonate of soda9.341„Organic matter8.060„Total solids100.parts
The percentage only of each ingredient the scale is composed of is given, as it cannot be told how much water was evaporated to leave this amount of solid matter.
The percentage only of each ingredient the scale is composed of is given, as it cannot be told how much water was evaporated to leave this amount of solid matter.