It is difficult to overestimate the importance, in connection with a steam plant, of the appliance which supplies water for the boiler, not only, but a hundred other uses. Upon the steady operation of the pump depends the safety and comfort of the engineer, owner and employee, and indirectly of the success of the business with which the “plant” is connected. Hence the necessity of acquiring complete knowledge of the operation of a device so important.

Pumps now raise, convey and deliver water, beer, molasses, acids, oils, melted lead. Pumps also handle, among the gases, air, ammonia, lighting gas, and oxygen. Pumps are also used to increase or decrease the pressure of a fluid.

Pumps are made in many ways, and defined as rope, chain, diaphragm, jet, centrifugal, rotary, oscillating, cylinder.

Cylinder pumps are of two classes, single acting and double acting. In single acting—in effect is single ended—in double acting, the motion of the cylinder in one direction causes an inflow of water and a discharge at the same time, in the other; and on the return stroke the action is renewed as the discharge end becomes the suction end. The pump is thus double acting.

A direct pressure steam pump is one in which the liquid is pressed out by the action of steam upon its surface, without the intervention of a piston. A direct acting steam pump is an engine and pump combined.

A cylinder or reciprocating pump is one in which the piston or plunger, in one direction, causes a partial vacuum, to fill which the water rushes in pressed by the air on its head.

Note.—A suction valve prevents the return of this water on the return stroke of the piston, and a discharge valve permits the outward passage of the fluid from the pump but not its return thereto or to the reservoir through the suction pipe.

The force against which the pump works is gravity or the attraction of the earth which prevents the water from being lifted. This is shown by the fact that water can be led, or trailed, an immense distance, limited only by the friction, by a pump.

Note.—It may be noted that the difference between a fluid and liquid is shown in the fact that the latter can be poured from one vessel to another, thus: air and water are both fluids, but of the two water alone is liquid: air, ammonia, etc., are gases, while they are also fluids, i.e., they flow.

The idea entertained by many that water is raised by suction, is erroneous. Water or other liquids are raised through a tube or hose by the pressure of the atmosphere on their surface. When the atmosphere is removed from the tube there will be no resistance to prevent the water from rising, as the water outside the pipe, still having the pressure of the atmosphere upon its surface, forces water up into the pipe, supplying the place of the excluded air, while the water inside the pipe will rise above the level of that outside of it proportionally to the extent to which it is relieved of the pressure of the air.

If the first stroke of a pump reduces the pressure of the air in the pipe from 15 pounds on the square inch to 14 pounds, the water will be forced up the pipe to the distance of 2¹/₄ feet, since a column of water an inch square and 2¹/₄ feet high is equal in weight to about 1 pound. Now if the second stroke of the pump reduces the pressure of the atmosphere in the pipe to 13 pounds per inch, the water will rise another 2¹/₄ feet; this rule is uniform, and shows that the rise of the column of water within the pipe is equal in weight to the pressure of the air upon the surface of the water without.

There are pumps (Centrifugal) especially designed for pumping water mingled with mud, sand, gravel, shells, stones, coal, etc., but with these the engineer has but little to do, as they are used mostly for wrecking and drainage.

The variety of pattern in which pumps are manufactured and the still greater variation in capacity forbids an attempt to fully illustrate and describe further than their general principles, and to name the following general

Classification of Pumps.

1st. Pumps are divided into Vertical and Horizontal.

Vertical pumps are again divided into:

1. Ordinary Suction or Bucket Pumps.
2. Suction and Lift Pumps.
3. Plunger or Force Pumps.
4. Bucket and Plunger Pumps.
5. Piston and Plunger Pumps.

Horizontal Pumps are divided into:

1. Double-acting Piston Pumps.
2. Single-acting Plunger Pumps.
3. Double-acting Plunger Pumps.
4. Bucket and Plunger Pumps.
5. Piston and Plunger Pumps.

In Figs. 102 and 103 are exhibited the outlines of the double acting steam pump, which is undoubtedly the pattern most thoroughly adapted for feeding steam boilers, as it is equipped for the slowest motion with less risk of stopping on a centre.

From the drawing with reference letters may be learned the terms applied generally to the parts of all steam pumps: example: “k” shows the water valve stems, “K” the water cylinder heads.

It may be remarked that nearly all pump makers furnish valuable printed matter, giving directions as to repairs, and best method of using their particular pumps—especially valuable are their repair sheets in which are given cuts of “parts” of the pumps. It were well for the steam user and engineer to request such matter from the manufacturers for the special pump they use.

POINTS RELATING TO PUMPS.

Blow out the steam pipe thoroughly with steam before connecting it to the engine; otherwise any dirt or rubbish there might be in the pipe will be carried into the steam cylinder, and cut the valves and piston.

Never change the valve movement of the engine end of the pump. If any of the working parts become loose, bent or broken, replace them or insert new ones, in precisely the same position as before.

Keep the stuffing boxes nearly full of good packing well oiled, and set just tight enough to prevent leakage without excessive friction.

Use good oil only, and oil the steam end just before stopping the pump.

It is absolutely necessary to have a full supply of water to the pump.

If possible avoid the use of valves and elbows in the suction pipe, and see that it is as straight as possible; for bends, valves and elbows materially increase the friction of the water flowing into the pump.

See that the suction pipe is not imbedded in sand or mud, but is free and unobstructed.

All the pipes leading from the source of supply to the pump must be air-tight, for a very small air-leak will destroy the vacuum, the pump will not fill properly; its motion will be jerky and unsteady, and the engine will be liable to breakage.

A suction air chamber (made of a short nipple, a tee, a piece of pipe of a diameter not less than the suction pipe and from two to three feet long, and a cap, screwed upright into the suction pipe close to the pump) is always useful; and where the suction pipe is long, in high lifts, or when the pump is running at high speed, it is a positive necessity.

Never take a pump apart before using it. If at any time subsequently the pump should act badly, always examine the pump end first. And if there is any obstruction in the valve, remove it. See that the pump is well packed, and that there are no cracks in pipes or pump, nor any air-leaks.

In selecting a pump for boiler feeding it is well to have it plenty large enough, and also these other desirable features: few parts, have no dead points or center, be quiet in operation, economical of steam and repairs, and positive under any pressure.

Granted motion to the piston or plunger, a pump fails because it leaks. There can be no other reason, and the leak should be found and repaired. Leaky valves are common and should be ground. Leaky pistons are not so common, but sometimes occur. Repairing is the remedy. Leaky plungers are common. They need re-turning. The rod must be straight as far as in contact with the packing. The packing around the plungers is sometimes neglected too long, gets filled with dirt and sediment, and hardens and scores an otherwise perfect rod, and so leaks.

The lifting capacity of a pump depends upon proper proportion of clearance in the cylinder and valve chamber, to displacement of the piston and plunger.

An injector is a sample of a jet pump—this may either lift or force or both.

The most necessary condition to the satisfactory working of the steam pump is a full and steady supply of water. The pipe connections should in no case be smaller than the openings in the pump. The suction lift and delivery pipes should be as straight and smooth on the inside as possible.

When the lift is high, or the suction long, a foot valve should be placed on the end of the suction pipe, and the area of the foot valve should exceed the area of the pipe.

The area of the steam and exhaust pipes should in all cases be fully as large as the nipples in the pump to which they are attached.

The distance that a pump will lift or draw water, as it is termed, is about 33 feet, because water of one inch area 33 feet weighs 14.7 pounds; but pumps must be in good order to lift 33 feet, and all pipes must be air-tight. Pumps will give better satisfaction lifting from 22 to 25 feet.

In cold weather open all the cocks and drain plugs to prevent freezing when the pump is not in use.

When purchasing a steam pump to supply a steam boiler, one should be selected capable of delivering one cubic foot of water per horse-power per hour.

No pump, however good, will lift hot water, because as soon as the air is expelled from the barrel of the pump the vapor occupies the space, destroys the vacuum, and interferes with the supply of water. As a result of all this the pump knocks. When it becomes necessary to pump hot water, the pump should be placed below the supply, so that the water may flow into the valve chamber.

The air vessel on the delivery pipe of the steam pump should never be less than five times the area of the water cylinder.

There are many things to be considered in locating steam pumps, such as the source from which water is obtained, the point of delivery, and the quantity required in a given time; whether the water is to be lifted or flows to the pump; whether it is to be forced directly into the boiler, or raised into a tank 25, 50 or 100 feet above the pump.

The suction chamber is used to prevent pounding when the pump reverses and to enable the pump barrel to fill when the speed is high.

Suction is the unbalanced pressure of the air which is at sea level 14⁷/₁₀ per inch, or 2096.8 per square foot.

When a valve is spoken of in connection with a pump it may be understood that there may be several valves dividing and performing the functions of one.

A simple method of obtaining tight pump-valves consists simply in grooving the valve-sheets and inserting a rubber cord in the grooves. As the valves seat themselves the cord is compressed and forms a tight joint. An additional advantage is that it prevents the shock ordinarily produced by rapid closing and prolongs the life of the valve seat. The rubber cord when worn can be easily and quickly replaced.

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.