CALCULATIONS RELATING TO PUMPS.
To find the pressure in pounds per square inch of a column of water, multiply the height of the column in feet by .434, Approximately, we say that every foot elevation is equal to 1⁄2 lb. pressure per square inch; this allows for ordinary friction.
To find the diameter of a pump cylinder to move a given quantity of water per minute (100 feet of piston being the standard of speed), divide the number of gallons by 4, then extract the square root, and the product will be the diameter in inches of the pump cylinder.
To find quantity of water elevated in one minute running at 100 feet of piston speed per minute. Square the diameter of the water cylinder in inches and multiply by 4. Example: capacity of a 5 inch cylinder is desired. The square of the diameter (5 inches) is 25, which, multiplied by 4, gives 100, the number of gallons per minute (approximately).
To find the horse power necessary to elevate water to a given height, multiply the weight of the water elevated per minute in lbs. by the height in feet, and divide the product by 33,000 (an allowance should be added for water friction, and a further allowance for loss in steam cylinder, say from 20 to 30 per cent.).
The area of the steam piston, multiplied by the steam pressure, gives the total amount of pressure that can be exerted. The area of the water piston, multiplied by the pressure of water per square inch, gives the resistance. A margin must be made between the power and the resistance to move the piston at the required speed—say from 20 to 40 per cent., according to speed and other conditions.
To find the capacity of a cylinder in gallons. Multiplying the area in inches by the length of stroke in inches will give the total number of cubic inches; divide this amount by 231 (which is the cubical contents of a U. S. gallon in inches), and product is the capacity in gallons.
The temperature 62° F. is the temperature of water used in calculating the specific gravity of bodies, with respect to the gravity or density of water as a basis, or as unity.
Fig. 104.
Important stress has been laid upon keeping all floating objects, gravel, etc., away from the acting parts of the pump. In [Fig. 104] is presented a cut of an approved strainer which can be removed, freed from obstruction, and replaced by simply slacking one bolt, the entire operation occupying one minute. The advantages of this strainer will be readily apparent.