N. Hawkins

“There are many fingers pointing to the value of a training in science, as the one thing needful to make the man, who shall rise above his fellows.”—Frank Allen.

ancient device using steam to lift a ball

“The motto marked upon our foreheads, written upon our door-posts, channeled in the earth, and wafted upon the waves is and must be ‘Labor is honorable and Idleness is dishonorable.’”—Carlyle.

“A heavy wager has been laid
That there are tricks in every trade.”

USEFUL NOTES
Relating to Pumps and their Management

It happens at times that a pump, with the full pressure against which it is expected to work, resting upon the discharge valves, refuses to lift water for the reason that air within the pump chamber is not dislodged, but only compressed by the motion of the plunger. It is well, therefore, to arrange for running without pressure until the air is expelled and water follows. This is done by placing a check valve in the delivery pipe, and providing a waste cock in the discharge chamber to be closed after the pump has caught water. A stop valve is also required for shutting off the back pressure when the pump can be opened for examination of the valves.

* * *

If any difficulty is experienced in making a pump work properly when first started, it will generally be found in leaks through imperfect connections, or from the temporary stiffness to be expected in a new machine, or perhaps leaky valves.

* * *

If, when standing at the suction end of a centrifugal pump, looking over pump shell toward pulley, the top of shaft revolves from right to left, or against the sun, the pump is right hand, and if from left to right, or with the sun, it is left hand.

* * *

A pump should be located in a convenient as well as a clean place. It should be well set upon a suitable foundation, so that it may be free from vibration or jar; this “note” applies to direct-acting, self-contained pumps, as well as to others.

* * *

The economical operation of a pump depends, to a great extent, upon the kind and condition of the packing in the stuffing-boxes and pistons, its quality, adaptability to particular requirements, and the method of placing it in the stuffing-boxes and plungers.

* * *

Almost all the stuffing-boxes on pumps are too shallow and the glands too short. To keep a rod tight under these conditions the packing must be of the proper size and quality, and it must be put in with a view to securing the greatest possible degree of elasticity, so that the rod may be kept tight with the least pressure on the packing.

* * *

To do this, it is best to select packing which will permit a number of narrow rings to be used instead of a few wide rings. The rings next to the bottom will become dry and hard before those next to the glands of the box are half worn out. If a number of narrow rings are used, the dry ones may be removed and duplicated by new ones and replacing the rest of the packing in the stuffing-box. This method economizes packing and secures a tight yet freely working rod.

* * *

When patent square packings are used, it makes less difference whether the rings are narrow or wide, because the surface in contact with the rod will be nearly continuous in either case.

* * *

When cutting packing rings, the length should be such that the ends do not come together within ¹/₈ inch when put into the stuffing-box, and the rings are put in to break joints, which prevents leakage through them.

When inserting this packing, the rings are put in one at a time, using a piece of hard wood to push them to the bottom of the stuffing-box and firmly against one another. The stuffing-box should be filled as full as it can be, and start the nuts on the studs by hand. Screw up the nuts with the hand and then start the pump slowly. If leakage occurs do not attempt to tighten the nut while the rod is in motion, and in all cases tighten it only enough to stop the leakage. A slight leakage at the water end is not harmful. A little cylinder oil and graphite occasionally applied to the rod will tend to keep it smooth and bright, which condition is favorable to the durability of the rod and of the packing.

* * *

When cutting rings of packing for the water piston or plunger, the rings should be ¹/₈ inch short, as previously described, page 372.

* * *

Packing should fit the grooves in solid pistons moderately tight, so that the packing can be pushed into the grooves with the fingers. The depth of the packing should be such that the piston will fit the bore of the water cylinder snugly when first put in. If packing of the proper depth cannot be obtained, it is better to have the grooves turned to receive standard sizes of packing and not require special sizes. Cutting hydraulic packing is a tedious job, consuming a great deal of unnecessary time.

* * *

It takes less power to feed into the bottom of a tank than it does into the top, on account of the weight of water in the tank. The bottom of the tank holds up all the water except the column directly over the opening of the delivery pipe, so that the additional pressure on the pump is due only to the depth of water in the tank, not to the size of the body, and it is impossible to feed into the top without increasing the height of the column fully as much. It makes no difference whether the height is due to the depth of the water inside the tank or an additional length of pipe outside.

* * *

The duty of the air pump is solely to get rid of the water and air in the condenser. It adds to the efficiency of the condensing apparatus, and renders its operation continuous; its valve being thrown by the action of its own piston, it must complete its stroke in length whether the piston is moving in air, water or vapor.

Pumps should be kept clean internally and externally. In order to keep a pump clean internally it must be inspected and oiled internally at regular intervals the same as it is externally.

* * *

When pumps fail to work properly the difficulty is generally located in one of three places, viz.: the water end, the steam end or the suction pipe.

* * *

The several parts of the valve gear of a single cylinder pump should be marked when the pump works properly, then any trouble due to the slipping of the collars or tappets can readily be remedied; if the nuts and set screws are kept tight, derangements occur only at long intervals.

* * *

The principal difficulties encountered with steam pumps are not generally due to improper steam distribution, but to wear, as may be seen; hence by inspecting pumps at regular intervals many unpleasant occurrences and accidents can be avoided.

* * *

The steam pipe leading to a pump should be so arranged that the water of condensation, while the pump is idle, may not pass through the steam chest and cylinders, and wash off the lubricating oil. Drip cocks should be attached to steam pipes and all large pipes should have separators and steam traps.

* * *

Pumps that are generally operated at moderately high speeds and with high lifts may be made to work more smoothly by placing a vacuum chamber on the suction pipe.

* * *

Valves in the suction pipe should have the stems carefully packed and kept tight; air leaks in valve stem stuffing-boxes are too often overlooked.

* * *

Stoppage of the suction pipes or chamber is generally indicated by a jerky action and pounding of the plungers or water pistons, while a dull thud at the ends of the stroke is more often due to a lack of air in the air chamber, or when the speed is high, to a lack of capacity in the air chamber.

* * *

The steam ends of pumps require the same lubrication as the cylinders and valves of engines. Intermittent lubrication is never to be recommended even for slow running pumps. Sight feed oil cups are always preferred.

* * *

A sight feed lubricator connected to the steam pipe below the throttle or to the steam chest is automatic in its operation. All that is necessary is to fill it. When the speed increases the feed increases and when the pump stops the feed stops. An oil hand pump is also desirable to introduce a mixture of oil and graphite, about 10 per cent. of graphite.

* * *

The water end stuffing-boxes of a pump may be lubricated by putting a heavy grease on the piston rods, or good cylinder oil may be used when grease is not at hand. Some of the grease works into the stuffing-boxes and furnishes better lubrication than can be obtained by the water alone. Care must be used not to use too much oil as it must not go beyond the stuffing-boxes and contaminate the water.

* * *

When a pump works properly under high pressures and fails to work under low pressures, the difficulty is generally found in the lift of the valves.

* * *

When the water end of a pump is known to be in good condition failure to run properly will in all probability be discovered in the steam end, and in single cylinder pumps the fault is generally caused by clogging of the auxiliary valves and ports. Sometimes pieces of packing break off and get into these small ports, thus shutting off the admission or release of steam.

* * *

When one side of a duplex pump makes a quick stroke it indicates either that the stuffing-box gland of the opposite side is too tight or that the packing in the cylinder of the side making the quick stroke is wearing out or has, perhaps, given way. A broken discharge or suction valve will also cause a “jerky“ motion of the pistons.

* * *

Pumps should be examined frequently in order to know what parts are beginning to wear and how fast the wear is taking place. When this is done the worn parts can, in the majority of cases, be taken out and replaced by new ones before they give out entirely, thus avoiding delay, but what is better, duplicated parts kept on hand ready at a moment’s notice.

* * *

The regular inspection of the screen in the separating chamber in the suction pipe renders frequent inspections of the interior of the pump unnecessary, the inspection previously alluded to is generally easier and more quickly done.

* * *

Considerable wear can and frequently does take place in a pump in the course of six months, and for this reason it is advisable to inspect the interiors at shorter intervals, say four months for general service pumps and once in three months for boiler feed pumps. More frequent inspections should be made when handling dirty water.

* * *

When a pump has to run faster one week than the week previous in order to supply approximately an equal volume of water, the plungers and valves should be examined, because such behavior indicates leakage.

* * *

The sight feed lubricator should be filled in the morning so as to be empty by night, thus permitting the water to be drained out without wasting oil. Draining the delivery valve chest will also drain the delivery pipe up to the check valve if those pipes are above the chest and without water seals in them. If this pipe is arranged below the pump, then separate drain cocks should be provided and should be placed at the lowest positions in the piping.

* * *

When a pump fails to start after standing for some time it should be primed by filling the barrel with water and starting the pump slowly. If after priming it fails to raise water, the suction pipe should be examined and also the plungers and the valves. If the plunger packing has become dry and hard, merely filling the water end with water will not at once remedy the trouble because the packing must be thoroughly soaked before it will work properly.

* * *

Pumps should be packed with the same care and consideration as is used with the best steam engines. The rods should be packed just tight enough to prevent leakage, and the packing renewed often enough to keep it soft and pliable, in which state it readily absorbs oil. Old packing will upon examination be frequently found full of sand and small particles of grit.

* * *

Metallic packings are now extensively used on steam piston rods and upon the rods of air pumps.

* * *

When priming and draining a pump the air cock in the air chamber should also be opened. The drain and cylinder cocks at the steam end should be opened before closing the throttle; the steam should be shut off at the boiler when stopping at night so as to drain the entire pipe.

* * *

Pumps that are exposed to low temperatures in winter should be provided with removable drain plugs or drain cocks for emptying the cylinders and valve chambers of water and also allowing the water to flow out of the suction pipe.

* * *

The friction in pipes, whether of cast iron, steel or copper, depends upon the internal smoothness of the pipe and the velocity of the water, as well as the number and kind of ells, tees and valves in the pipe. Wrought iron lap welded pipe, for steam, is preferable to either cast iron or copper. It is smoother internally than cast iron, and is lighter and costs less than copper, and is much stronger and safer than either.

* * *

It may be said when an engine is run without a condenser the steam with which the cylinder is filled at the end of the stroke has to be forced out against the pressure of the atmosphere, about 15 pounds to the square inch. It is possible from the nature of steam to remove the atmospheric pressure with a decided gain in almost all cases.

* * *

One pound of steam at atmospheric pressure occupies 1,642 times as much room as it does in the state of water. If, therefore, when the stroke has been completed, and we are ready for the piston to come back, we inject a little cold water into the spent steam, it will condense to about one 1600th of its volume, and leave a vacuum into which the piston can return without having to force back the atmosphere. This is the way the earlier vertical engines were run, the condensation taking place in the cylinder itself, and, moreover, the vacuum was all that made the engine operative, for the steam carried was but little above atmospheric pressure.

* * *

The velocity of water entering a suction pipe depends upon two things, the vacuum in the pipe and the vertical lift of the water. The longer the suction pipe, vertically, the greater the frictional resistance to the flow of water; the flow of water through small discharge pipes should not exceed four hundred feet per minute, and for large pipes five hundred feet per minute.

* * *

A locomotive-boiler compound. The lines of a certain great R. R. traverse a country where the water is very hard and they are compelled to resort to some method of precipitating the lime that is held in solution. After many tests and experiments they have made a compound and use it as follows: in a barrel of water of a capacity of fifty gallons they put 21 lbs. of carbonate of soda, or best white soda ash of commerce, and 35 lbs. of white caustic soda; the cost, per gallon, is about 2¹/₂ cents. The compound is carried in this concentrated form, in calomine cans on the tender of each locomotive. A certain amount, according to the necessities of the case, is poured into the tender at the water tank at each filling. This amount is determined by analysis, and varies all the way from two to fifteen pints for two thousand gallons of water. The precipitating power of this compound may be taken roughly at ²/₃ of a pound of the carbonate of lime, or equivalent amount of other material, per pint of the compound. On their western lines where they are dealing with alkali waters and those containing sulphates, the company use merely 60 pounds of soda ash to a barrel of water. When the water is pumped into the boiler the heat completes the precipitation and aggregation of the particles, and this does away with all trouble of the boiler or injector tubes clogging up.

* * *

It has been recently determined by some German experimenters that sugar effects a strong action in steam boilers; it has an acid reaction upon the iron which dissolves it with a disengagement of hydrogen. The amount of damage done increases with the amount of sugar in the water. These results are worthy of note in sugar refineries and places where sugar sometimes finds its way into the boilers by means of the water supplied. The experiments in question also show that zinc is strongly attacked by sugar; copper, tin, lead and aluminium are not attacked.

* * *

White oak bark, used by tanners, has an excellent effect on boiler incrustations. It may be used as follows: Throw into the tank or reservoir from which the boilers are fed a quantity of bark in the piece, in sufficient quantity to turn the water to a light brown color. Repeat this operation every month at least, using only half the quantity after the first month. Add a very small quantity of the muriate of ammonia, about one pound for every 2,000 gallons of water used. This will have the effect of softening as well as disintegrating the carbonate of lime and other impurities deposited by the action of evaporation.

Among the best samples of boiler compounds ever sent to the laboratory for analysis were those found to be composed of:

This solution was formerly sold at a good round figure, but since its nature became more generally known, it is not found in the market, but it is largely used, consumers putting it up in lots sufficient to last a year or so at a time.

The above is strongly recommended by those who have used it, one pound of the mixture being added to each barrel of water used, but after the scale is once thoroughly removed from the boiler, the use of sal-soda is all that is necessary.

* * *

There are other evils sometimes inherent in hard waters above the mere production of a crust. Some waters contain a great deal of soluble magnesia salts, together with common salt. When this is the case there is a great probability of corrosion, for the former is attacked by steam at high pressure in such a way that muriatic acid fumes are produced, which seriously corrode the boiler, and what is far worse, passes with the steam into the engine, and sets up corrosion in the cylinders and other delicate fittings with which the steam comes in contact. All this can, however, be obviated by the removal of the magnesia from the water.

* * *

When water attains a high temperature, as it does under increasing pressure, ranging from 175° to about 420° Fahr., all carbonates, sulphates and chlorides are deposited in the following order:

First. Carbonate of lime at 176° and 248° Fahr.

Second. Sulphate of lime at 248° and 420°.

Third. Magnesia, or chlorides of magnesium, at 324° and 364°.

It is to take advantage of this fact that mechanically arranged jets, sprinklers and long perforated pipes are introduced into the interior of a steam boiler; these tend to scatter the depositing impurities and also to bring the feed water more quickly to the highest possible temperature.

Where fuel is expensive and pumps are used for continuous service under high and unusually high pressures it is oftentimes advisable to operate the pumps condensing. This may be done, when the pump lifts water by suction, without a separate condenser by connecting the exhaust pipe with the suction pipe, as shown in Fig. 667. Assume that the pump has been working properly for from 3 to 5 minutes with the valve A nearly closed and the valve B a little open, the valve A is now quickly closed and B opened. In operating these valves both hands should be used, so that they may be opened and closed simultaneously.

So penetrating is water at high pressure that only special qualities of cast iron will be tight against it. In the early days of the hydraulic jack it was no uncommon thing to see water issuing like a fine needle through the metal, and the water needle is said to penetrate the flesh as readily as one of steel.

The engraving, Fig. 668, represents a novel device for preventing the bursting of water pipes by freezing. This is simply an air chamber placed in the horizontal part of the pipe, with the chamber on top side so that the ice may expand into this chamber, and so its force is expended upon the air instead of bursting the pipe.

This device also acts as an air chamber and prevents “water hammer.” It is made by the Anti-bursting pipe Co., Pittsburg, Pa.

When it becomes necessary to make a quick connection into a main steam pipe without breaking joints, a saddle such as either of those shown in Fig. 669 and Fig. 670 may be applied by simply cutting or drilling a hole through the main steam pipe.

To make the joint, the rough lumps should be filed off the outside of the pipe and red lead rubbed on to mark the surface, to show when the fit is properly made. Then lay on with a brush a thin mixture of red lead and varnish and quickly screw the saddle in place. Such joints seldom or never leak when allowed to thoroughly dry before use.

When it becomes necessary to cut square packing to reduce its depth, place the packing in a vise, allowing the stock to be removed to project above the jaws, as shown in Fig. 671. With the aid of a draw-knife the work can be quickly and easily done. It is difficult to cut the packing evenly. If the rings have an uneven bearing on the bottom of the grooves leakage is likely to occur when the pump is first started.

The follower type of water piston can readily be packed without removing it from the cylinder, providing rings of the proper depth and length are at hand. The old packing rings can be removed with a packing hook. Take the new ring and start one end with a soft stick, and push the remainder of the ring firmly against the collar or flange at the inner end of the piston, as shown in the engraving, Fig. 672. Arrange the several rings so as to break joints.

Method of packing a follower piston. Coat the sides of the rings with a thick paste of cylinder oil and Dixon’s Flake graphite, which will prevent the rings from sticking together.

Pump packing cannot be readily examined and is liable to fail at any time, therefore several rings, cut to the proper length, should be kept on hand. This may be easily done by making a pattern ring, which is nothing more or less than a ring of packing which has been fitted into the piston and is known to be of the proper length. The extra rings can then be cut at odd times, and when occasion demands it the water piston can be packed very quickly and the pump started.

Care should be taken when about to pack a boiler feed pump or other pump subjected to high pressure to see that the cylinders are relieved before loosening the cylinder head bolts. This may be accomplished by closing the valve in the delivery pipe, and also in the suction pipe; if the pump receives water under pressure, open the air cock on the air chamber and cylinder cocks.

Pump slip or slippage represents the difference between the calculated and the actual discharge of a pump, which is generally expressed as a percentage of the calculated discharge. Thus, when the slippage is given as fifteen per cent. it indicates that the loss due to slip amounts to fifteen per cent. of the calculated discharge. Slippage is due to two causes, the time required for the suction and discharge valve to seat, due to excessive speed. When the piston speed is so high that the water cannot enter the pump fast enough to completely fill the cylinder only a partial cylinder full of water is delivered at each stroke. High speeds also increase slippage, due to the seating of the valves.

Graphite as a lubricant is almost without a rival. It is one of the forms under which carbon appears in nature; it is also known under the name of plumbago and black lead; it is soft and oily to the touch; it is a conductor of electricity; it is a lubricant that allows pipe joints to be screwed up to the tightest possible fit. Graphite remains upon the threads preventing rust, and it so preserves its peculiar properties that pipe can be unscrewed without effort eight or ten years after the joints have been made.

It is difficult to lift hot water by suction, but not everyone can explain the cause; the reason is as follows:

In Fig. 674, let A be a vessel in which a vacuum exists, and let it communicate by a tube, as shown, to the lower vessel containing water. The pressure of the atmosphere upon the surface will force the water up into the pipe until the column is high enough to exert a pressure per square inch equal to that of the atmosphere. A cubic inch of water weighs about ¹/₂₈ of a pound, so that it will take 28 cubic inches to weigh a pound, or a column 28 inches high to exert a pressure of one pound per square inch. The atmospheric pressure is 14.7 pounds, or to avoid fractions, say, 15 pounds. This pressure would then support a column (15 × 28)/12 = 35 feet high; that is, the column a-c in Fig. 674 would be 35 feet in height. Attach a gauge at or above the top, a, of a column, and it will indicate a perfect vacuum; if the gauge were attached 28 inches below a, it would indicate a pressure of one pound above absolute zero, or a vacuum of 15-1 = 14 pounds; and if the gauge were moved further downward, it would indicate an increasing pressure, that is, a diminishing vacuum, at the rate of one pound for every 28 inches of the water column above it, until at the level of the water in the tank the pressure would be 15 pounds absolute, and the vacuum would be zero.

Now, suppose the pipe to be lowered until the distance from the bottom of the vessel, A, to the water level, c, is 21 feet. In that case we will have the pressure of the atmosphere (15 pounds) forcing the water up into the vessel, and the column 21 feet high, or (21 × 12)/28 = 9 pounds, opposing it. The difference, 15-9 = 6 pounds, is available to force the water into the chamber. This arrangement is shown in Fig. 673, where A is a pump cylinder; then the difference in pressure, 6 pounds, lifts the valve, and the water enters the pump chamber with a velocity due to that pressure. In order to insure smooth and quiet running of the pump, it is necessary to keep the speed of the piston inside of the velocity with which the cylinder would fill under this pressure, reduced by the friction of the water, the pressure required to lift the valves, etc.

But this supposes that there is a perfect vacuum in A, and we cannot realize this in contact with hot water. Water at any temperature will boil unless it is under a pressure equal to or greater than that corresponding with the temperature. Water at 60 degrees F. will boil if the pressure upon its surface is reduced to a quarter of a pound per square inch, and in the case shown in Fig. 674, it would boil and fill the space A with steam at that absolute pressure.