Zwicker's Revised Practical Instructor IN QUESTIONS AND ANSWERS for Machinists, Firemen, Electricians and Steam Engineers

PUMPS

Content Tools

Q. What kinds of pumps are there?
A. There are many kinds, but we consider only single action and double action for feeding boilers and general use.

Q. How many valves has a single action plunger pump?
A. Two valves, a receiving valve and a discharge valve.

Q. How many valves has a double action?
A. Four, two receiving and two discharging. The double action receives and discharges both strokes. This kind of pump has a steam cylinder on one end. Large pumps have eight, sixteen and thirty-two small valves on water cylinder, according to the size of the pump.

Q. Why do large pumps have many small water valves and not a few larger ones in proportion?
A. The reason the pumps have small valves is that the valves do not have to open as much as larger ones, consequently the pump does not loose the quantity of water each stroke as it would with larger valves.

Q. How are pumps set up and leveled?
A. Set the pump so the receiving is from the boiler and the discharge toward the boiler, put in the same size receiving and discharge pipe as tapped in the pump, so the pump can have a good supply and discharge. The pump is leveled with a spirit-level or a square and plumb line. To level a double-action pump, some level across the frame and along the piston; the other way is to take the valve chamber cap off the water cylinder and level the valve seats, so the valves will rise and drop plumb. To level a single action pump, take off the valve chamber caps and level both ways.

Q. How are the steam valves of duplex pumps set and adjusted?
A. Take off the valve chest cover, shove the piston against one of the cylinder heads and mark the piston rod with a pencil at the packing-box gland, then shove the piston against the other cylinder-head and make another mark, find the center between the two marks and move the piston until the center mark reaches the packing-box gland where the first mark was made. Or in other words plumb the lever that connects the valve rocker shaft and the piston. After this is done, see how the steam valve is for lead; if equal at both ends the valve is set, if not, adjust by uncoupling the valve stem at the coupling outside of the packing box, and turn to suit the adjustments in equalizing the 'lead.'

Q. How is the water piston packed, and with what in the water cylinder?
A. It is generally packed with square canvas and rubber mixed packing; it generally takes two pieces; one piece is jointed on top, and the other at the bottom, to make what engineers call a broken joint. The packing runs from ? to 7/8 inch square. These are the general sizes used for common sized pumps.

Q. What other valve has a pump near the boiler?
A. A check valve.

Q. What is a check valve for?
A. To check the water in the boiler from coming back, in case there is any work to be done on the pump.

Q. Could you pump water into the boiler if you had four or five check valves on the discharge pipe?
A. Yes, I could force through all, but it would be more labor on the pump, because the plunger would have to force harder to raise the number of check valves.

Q. Where is a pet cock put on the pump barrel for cold water, and why?
A. It is put at the side and near the bottom of the pump barrel, and is there to show how the pump is working, and to drain the pump in winter to prevent freezing.

Q. How do you know when your pump is in good working order?
A. By opening the pet cock and seeing the stream that comes out.

Q. How does it show when the pump is in good working order?
A. Nothing in the suction stroke and full force in the discharge stroke.

Q. Where would you locate the trouble if it came full force both strokes?
A. I would locate it at check and discharge valves, both being caught up.

Q. Where would you locate the trouble if it came full force both strokes, moderate, tank or hydrant pressure?
A. At the receiving valve.

Q. Can you run a pump without a check valve?
A. If the discharge valve is in good order, it can; but if there is neither check nor discharge, it cannot.

Q. Can you feed a boiler without a pump?
A. If the pressure of the boiler is below the pressure of the feed water or city pressure, it can, by simply opening a water valve and letting in the amount of water required.

Q. What other way is a boiler fed?
A. By an injector or an inspirator.

Q. What is an injector or an inspirator?
A. They are devices to answer for a pump in feeding a boiler; they draw force and heat the water at the same time.

Q. State the principal upon which a jet of steam taken from the boiler at boiler pressure can force a stream of water back into the boiler through the injector?
A. It acts upon the principal of a light body moving at a high velocity giving a slower motion to a heavier body effecting an entrance by means of the momentum thus given to it. For instance, steam at the pressure of 80 lbs. to the square inch will escape into the air with a velocity of 1,821 feet per second or 1,241 miles per hour. This rapidly moving jet of steam causes, at first a vacuum in the casing of the injector, which fills with water. The steam then mingles with the water, condenses and imparts its velocity to it. The stream of water is then forced along the pipe and strikes the check valve with a force sufficient to open it and then enters the boiler.

Q. Will the injector work if the water that is supplied is too hot to condense the steam?
A. No.

Q. Why?
A. Because steam is highly elastic and bulky, and, of itself, would have no effect in driving the hot water in any particular direction. But when steam is moving at a high velocity and is condensed these particles of water have the power of driving the main body before it into the boiler.

The principal is easily explained, for instance: If a block of wood is laid upon the water it will float, but if it is thrown violently downward it will at first go below the surface. Then if there were something there to catch it and hold it, we would have a state of affairs similar to the injector, where the water enters the boiler by its own momentum and is held there by the check valve.

Q. Must a pump have a valve?
A. Yes, if a pump had no valve it would not do any work. A pump is not a pump unless it has a valve. There are common well hand pumps with one valve, called a receiving or suction valve, but a force pump has two valves, a receiving and discharge; the discharge is to retain the water after it is delivered, so the plunger can get a fresh supply. After the plunger has ascended and begins to descend, that water sets on top of the receiving and under the discharge; consequently, when the plunger descends it forces the receiving shut and the discharge open.

Q. Should there not be another valve near the boiler?
A. Yes, a globe valve between the check valve and the boiler.

Q. What is that for?
A. To close and keep the pressure in the boiler in case the check valve is caught up and needs repairing.

Q. Can you raise, lift or suck hot water with a pump?
A. Not very well.

Q. Why?
A. Because the pump would get steam bound. Hot water should be level or higher than the pump in order to work well.

Q. Where should a pet cock be put on the pump barrel for hot water?
A. At the top of barrel, immediately under the packing ring.

Q. Why is it put there?
A. To let out steam when steam bound, and air when air bound. There should be a pet cock tapped in the cap of the valve chamber to let off the steam or air when steam or air bound.

Q. If you had no pet cock on the valve chamber cap, what would you do?
A. Simply take a wrench and loosen one of the nuts a little until the air or steam was out, then tighten it again.

Q. Why is an air chamber put on a double action pump, and what is it?
A. It is simply a copper vessel air tight. When the pump is working, the water is forced up into the chamber, compresses the air, and the air acts as a cushion on the valves and piston head in the water cylinder.

Q. What is a cushion?
A. A cushion is anything that is compressed, and by its compression is formed into a higher and stronger pressure, consequently acting as a spring, deadening any knock that might have occurred otherwise, as water will cause a knock, it being nearly as solid as iron, so if a double action pump had no air chamber, there would be a continual thumping noise.

Q. What is a vacuum?
A. A vacuum is a space void of matter.

Q. Can a perfect vacuum be formed?
A. No, about 9 to 11 percent of the atmosphere, which is 14.7 pounds per square inch.

Q. What will a vacuum do?
A. It will lift water 33 feet, providing all pipes and connections are air tight.

Q. How is a vacuum created or made?
When the plunger of a pump is well packed and it lifts, it excludes the air out of the pump barrel and suction pipe, consequently the water, being at the other end of the pipe, it follows the plunger; or, in other words, the atmospheric pressure, being 14.7 pounds per square inch, forces the water up the pipe to fill the vacancy made by the plunger forming the vacuum.

Q. What should be placed at the bottom of the suction pipe?
A. A strainer made out of gauze wire, a foot valve and a pet cock to drain it.

Q. If your pump should not be working, your water running low, and you were asked to run a little while longer, would you run and let your water become dangerously low?
A. No, take no chances whatever, but shut down and go about repairing the trouble.

Q. Where would you look for trouble?
A. Open the pet cock of the pump, and that will very nearly tell where to look for it; if no water comes out, the water is shut off, or there is none, etc.

Q. What generally prevents a pump from working?
A. Not enough water, too small a suction pipe and obstruction of the valves to seat, by straws, sticks or anything that may be drawn through the suction pipe, or the pump valves becoming hot and sticking.

Q. If an accident happened, such as a broken pipe connected with the boiler and pump, or you could not get sufficient water to supply the boiler, what would you do?
A. Simply shut down the engine and all valves connected with the boiler, draw fire, raise flue caps, and close the damper, so as to keep what water there is in the boiler until the difficulty is repaired.

Q. If your suction pipe should spring a leak, what would you do?
A. Take a piece of sheet rubber, some copper wire, wrap around tight, and stop the leak temporarily.

Q. If your hydrant, that supplies pump with water, should happen to get broken, what would you do?
A. First see how much water was in the boiler, by trying gauge-cocks, then shut off the water in the street, or wherever the lazy cock lay, and try to wrap it, if possible, or repair it. If an injector or inspirator was attached, and was supplied from a tank or well, use either.

Q. For instance, if you had neither of these, what would you do?
A. Shut down the engine, close the damper, raise the flue caps and draw the fire, whichever suited the circumstances.

Q. If your pump was turned around, could you feed the boiler?
A. No.

Q. What would be the consequence?
A. If the packing in the pump held out, the plunger would exclude the air and collapse the discharge pipe.

Q. Would it not have a tendency to drain the water out of the boiler?
A. No, the check valve near the boiler would keep it back.

Q. If you had no check valve, what would it do?
A. The water would run out, that is, providing the pump was turned around.

Q. If the pump plunger is one-half the stroke of the engine, what should the diameter of the plunger be?
A. One-third the diameter of engine cylinder.

Q. How high should a valve lift to clear itself?
A. About one-fourth of its diameter or one-third of its area.

Q. What proportions should the valves be to any sized pump?
A. They should be one fourth the area of the pump.

Q. Suppose in the evening when you shut down, that the pump was in good working order, and when you started up the next morning and opened the pump pet cock a strong stream of water came out both strokes; where would you locate the trouble?
A. The trouble would be at both the check and discharge valves being caught up.

Q. Suppose you started the pump and it was in good order, and no water came; where would you locate the trouble?
A. The suction pipe is leaking, or it is out of water, or there is no water.

Q. State the usual area proportion of the cylinders of a steam pump?
A. The steam cylinder averages four times the area of the water cylinder.

THE ENGINE

Q. What is a steam engine?
A. A steam engine is a machine by which power is obtained from steam.

Q. What is steam?
A. Steam is a gaseous vapor from water, generated by heat, composed of hydrogen and oxygen.

Q. How do you know water is composed of hydrogen and oxygen?
A. Science shows that one pound of hydrogen with eight pounds of oxygen is equal to nine pounds of water.

Q. What is an engine composed of?
A. A bed plate, cylinder, connecting rod, crank, crank-shaft, main pillow block, out pillow block, cross-head, wrist-pin in cross-head, crank-pin, two cylinder heads, piston-rod, piston-head, follower head, bull-ring, packing-rings, follower plate and bolts, connecting rod and brasses, pillow-block brasses, a valve, and guides where the cross-head slides in, so the piston is kept central with the cylinder. The main pillow-block brasses are generally made into four pieces, called top, bottom and two quarter brasses four sides of shaft; they are made into four parts, so as to take up lost motion.

Q. What keeps the rod from running off the crank pin?
A. The shoulder on the crank-pin.

Q. Why are the stub ends of straps made heavier where the gib and key pass through?
A. To make up for the amount of iron taken out for the gib and key-way.

Q. If water should accumulate in the cylinder, what would be the consequence?
A. It is liable to crack the cylinder and disable the engine.

Q. If you had charge of an engine in the country, and the cylinder head should happen to crack, how would you remedy it?
A. If not broken too bad, try to patch it with pieces of iron or boards, and brace it from the wall with a piece of heavy scantling, then try and run the engine until a new cylinder head could be made.

Q. What size should a steam pipe and an exhaust pipe be to any size cylinder?
A. A steam pipe should be one-fourth and the exhaust pipe one-third the diameter of the engine cylinder itself.

Q. If your crank pin or other journals became hot, what would you do?
A. Try, while running, to get water on them, then oil them; if that would not do, stop and slack up the key a little, then start up again. All engine cylinders should be well drained and heated before starting, then the engine should be started slowly, as the water that accumulates in the cylinder may injure the piston, cylinder, or cylinder heads. Always leave the cylinder cocks open when not running, and they should remain so until the cylinder is heated by the steam,-after the engine has been running at full speed two or three minutes at least.

Q. If the cylinder had shoulders inside, and was out of a true circle, what would you do to remedy it?
A. Bore it, or have it bored out.

Q. In case the throttle valve should become loose from the stem and prevent the steam from entering the valve chest, what would you do to repair it?
A. Close the valve next to the boiler, if there was one; let the boiler cool down, then take the valve out and repair it.

Q. If your side-valve was not steam-tight, what would you do?
A. Have the valve planed, then chip, file and scrape the seat to a full bearing.

Q. If the crank and wrist-pins are worn out of true, what would you do?
A. Caliper and file them until they were round and true.

Q. What causes the wrist-pin in the cross-head and crank-pin to wear the way they do?
A. It is simply the motion they have; the crank goes all the way round, forming a circle, and the wrist only vibrates.

Q. If the cross-head or crank-pin brasses were brass-bound, what should be done?
A. They should be chipped and filed.

Q. How do you know when you have taken enough off?
A. By outside and inside calipers.

Q. How does steam enter the cylinder?
A. In common slide-valve engines it enters through one of the end ports and exhausts back through the same port, when the cavity of the valve has covered it and the exhaust port at the same time.

Q. What is a cushion?
A. Cushion is the resistance on the opposite side of the piston-head, formed by the steam being shut up in the cylinder, as the piston is nearing either dead center.

Q. What is meant by clearance?
A. Clearance is the space between the piston head, cylinder head and the valve face at each end of the stroke.

Q. How would you know the amount of clearance there was in that space?
A. By finding the number of cubic inches in a bucket of water, then fill up the space level with the steam port, and see how much water is left in the bucket; the difference is the contents in cubic inches.

Q. Why are gibs, keys and set screws used on both ends of the connecting rod?
A. They are there to take up lost motion.

Q. How would you do that?
A. By loosening up the set screw, and driving down the key; then tighten the set screw to keep the key from raising.

Q. Are there more square inches in one end of the cylinder than in the other?
A. In one sense of the word there are, and in the other there are not, as the piston rod takes up some of the space in one end of the cylinder, therefore there is not the same area in one end as in the other.

Q. What is a governor on an engine for?
A. It is to regulate the steam that passes from the boiler to the steam chest, when the throttle is wide open.

Q. How does it work?
A. It is regulated to allow the engine to run at a certain speed. The governor has a belt from the main shaft to a pulley on the governor. After the engine is running up to the speed it is intended to, it allows only enough steam to enter through the governor valve to keep the same speed; if the engine needs more power it begins to slack up, the governor balls drop, the valve opens and allows more steam to enter; consequently the engine must retain its speed; and if the load is taken off it will start to run away, the governor balls will rise, force the valve shut, and cut off the steam; consequently, the engine must come back to its regular speed.

Q. How does a governor valve look?
A. It is a round valve with grooves; there are different kinds, some have three or four openings, and some only two; the more openings the more sensitive the governor.

Q. Are there other makes of governors?
A. Yes, The Automatic governor on high speed engines, such as are used for running electric light dynamos, they are around the shaft, they work direct on the valve itself.

Q. What is a lubricator?
A. A lubricator is an appliance for holding oil, to be distributed into the valve chest and cylinder, to prevent cutting.

Q. How is it operated?
A. It is operated by steam forcing the oil out of the lubricator into the steam pipe.

Q. Where is the lubricator generally attached?
A. In the steam pipe immediately over the throttle or globe valve, used to start and stop the engine.

LINING AN ENGINE

Q. How would you line up an engine?
A. By stripping the engine, take off both cylinder heads, if convenient; then take out the follower-head, piston-rings, bull-ring; disconnect the piston from cross-head: also disconnect the connecting-rod from the cross-head and the crank-pin; then take a slotted stick and place it on one of the studs on the end of cylinder furthest from the crank; then draw a fine sea-grass line over the point of stick and through the center of cylinder, and attach it to a stick at the other end of the bed-plate, nailed to the floor or clamped to the bed-plate; then take a thin stick, the length of it being a half inch less than half the diameter of cylinder, stick a pin in each end of the stick, so they can be forced in or drawn out to suit the adjustment; then center the line at each end of the cylinder at the counter-bore from four sides.

Never center the line in the stuffing box where the piston passes through, but use the inside counter-bore under all circumstances, whether you can remove the back cylinder head or not. Some engine cylinder heads and frames are one; consequently, the head cannot and must not be moved.

Q. If one counter-bore would be out, or larger than the other, what would you do? Would it not throw the bore of the cylinder or the line out?
A. No; center it accordingly; it would not make any difference, only two centering sticks with pins are needed to bring the line central with the bore.

Q. Why do you use the counter-bore?
A. Because the counter-bore is the only true bore the cylinder has that is not worn; consequently, all the engineers and machinists must be governed by it.

Q. What is a counter-bore?
A. A counter-bore is each end of the cylinder bored from 1/16 to ? of an inch larger, from 1 to 4 inches long, according to the size and length of the cylinder.

Q. What is a counter-bore for?
A. To keep the piston from wearing a shoulder in the cylinder at each end.

Q. Why is it that the piston does not wear a shoulder in the cylinder?
A. Because the piston rings just pass over the edge of the regular bore, and by so doing no shoulder can be formed in the cylinder.

Q. How are the cylinders bored?
A. They are generally bored on a regular cylinder boring lathe, which has a table that can be raised or lowered to suit. The regular bore is first bored, then the counter-bore, then the two faces for the heads.

Q. How do you square a shaft when you have got the line centrally through the cylinder?
A. Move the crank-pin down to the line and see where the line touches the crank-pin between the two shoulders, then move the pin over to the other dead center, and see how it comes; if equal, the shaft is square.

Q. If you found it out of square ? inch, what would you do?
A. Move the out end pillow-block.

Q. Why not move the head-block?
A. Because it would alter the length of the connecting-rod, and be liable to knock out a cylinder-head.

Q. How would you level a shaft?
A. A shaft is leveled by a spirit level, or a plumb-line dropped past close to the line that comes through the cylinder directly in front of the center of the shaft; let it drop in a bucket of water to keep the plumb-bob from swaying around; then try the crank-pin at both half-strokes (the same principle as in squaring) top and bottom, and see how the crank-pin feels the line; if equal, the shaft is level.

Q. Is there no other way to level a shaft?
A. Yes, by the pulley wheel.

Q. How is it done?
A. Drop a plumb-line down from the ceiling, past the rim's edge of the wheel, directly over the center of the shaft; let the space between the plumb line and rim be one inch; mark the wheel with chalk for a starting and stopping point, and caliper the distance with inside calipers; then turn the wheel and shaft around, and continue calipering until the wheel has made a full revolution; if it calipers the same all the way around, the shaft is level. This principle answers for truing a wheel as well as leveling a shaft. The former way, by dropping a plumb-line in front of the crank face and feeling the line with the crank-pin at both half-strokes, is the proper way to level a shaft.

Q. If you found the shaft out of level, what would you do?
A. I would have to thin or thicken the brasses, or babbitt the main pillow and out block bearings, whichever the case may be.

Q. How would you know if the center of the shaft is in line with the line through the cylinder or not?
A. It can be found out by placing a two-foot steel square against the crank face, under the line through the cylinder, so that the heel of the square is at the center of the shaft, and see how the square touches the line; if it touches exactly, the shaft is in line; if too hard, the shaft is high; if not at all, the shaft is low.

Q. How would you raise your shaft?
A. There are various ways; by liners, babbitt, heavier or lighter brasses.

Q. If your crank face was oval, and you put a square against it, would that be right?
A. A spirit level could be placed on a square and bring it level, or drop a plumb-line, and put the end of the square against a crank-shaft center, and let it come against the plumb-line. This is a very true way.

Q. Now, after your shaft is in line, square and level, and you still find it out over line ? inch, what would you do?
A. I would take it off the crank-pin brasses and fill in the other side with a brass ring, or babbitt the side edge of brasses; in some cases the side of the connecting rod has to be chipped to allow it to pass free of the crank-face.

Q. Why would you not take it off the wrist-pin brasses in the cross-head?
A. Because the rod would then be out of the center of cross-head, and have a tendency to bind the piston in the cylinder and the cross-head in the guides, consequently cutting both.

Q. Would it not make a difference at the other end of the rod?
A. No, the closer the crank-face the better it would be.

Q. Now what would you do?
A. Level and line the guides by putting them in their place, and line them with a pair of calipers, by calipering them at both ends get them in line with the line through the cylinder, after having found the distance between the side of the cross-head and the center of the cross-head where the piston enters the cross-head. Level by spirit level, first taking spirit level and trying it in the cylinder, if a new one, or on top of the cylinder where it has been planed off when first bored, for they are the only things to go by.

Q. Would you use the valve seat to level by?
A. No, but alongside of it, where the steam chest rests on.

Q. If you had no spirit level, how would you do it?
A. With a plumb-line, by placing a square lengthwise on the guides, and try them by bringing the square against the line.

Q. If you had no two-foot square, and could not get any, how would you lay one off?
A. Take a pair of dividers, draw a circle, then find four points on the circle, scribe lines from point to point, which gives a square. This should be done very accurately, or 6, 8 and 10.

Q. Can a plumb line hang out of true?
A. It can not, provided it hangs clear of everything. If none of these were handy, a straight edge must be placed across the guides at one end, and see if the guides touch the straight edge equally at both edges, then caliper the distance between the line and the straight edge, also at the other end of the guides; if the same, the guides are level lengthwise with the cylinder and the line; then level the guides cross-wise with a plumb-line and square.

Q. How would you measure the connecting rod of an engine?
A. By finding the striking points.

Q. How would you do that?
A. By shoving the piston and cross-head up against the cylinder-head, and making a mark on the guides at one end of the cross-head with a scriber and center punch; then move the piston and cross-head back to the other cylinder-head and make another mark on the guide at the same end of the cross-head; then measure from the center of crank-pin to center of shaft; that gives the half-stroke; double this, gives full stroke. If half-stroke is 12 inches, the full stroke is 24 inches; then if the distance between the two striking points is 25 inches, and the stroke is 24 inches, the clearance between the cylinder-head and piston-head will be ? inch when the piston is at either end of the cylinder. Then move the cross-head ? inch back from the striking point, and bring the crank-pin toward the same dead center; then take a tram and measure from the outside center of crank-pin to the outside center of wrist pin in cross-head, which will give proper length of connecting rod, also the right division of clearance.

Q. What is meant by clearance in the cylinder?
A. It is the unoccupied space between the piston-head, cylinder-head and valve-face, when the crank-pin is at either dead center.

Q. Does the amount of clearance affect this engine's economy?
A. Yes, it does.

Q. How much clearance should there be between the piston and cylinder-head?
A. It depends upon the size; some have from ? to 7/8 of an inch.

Q. What is formed in that space or clearance when running?
A. A cushion.

Q. What is a cushion?
A. A cushion means the steam that enters the cylinder through the lead the valve has, and the resistance it makes on the piston head, cylinder-head and valve-face, as the engine is reaching the dead-center.

Q. What is a cushion for?
A. It is to catch the piston and weight of the machinery as it reaches the dead-center, and the lead is to give the engine power at the beginning of the stroke.

Q. How does it act?
A. The same as a spring on the end of a hammer.

Q. If you wished to shorten or lengthen the connecting-rod, how could it be done?
A. By placing tin or sheet iron liners between the brasses and stub-ends of the connecting-rod.

Q. Now, if the key had to be raised, how could this be done?
A. By putting liners between the straps and brasses.

Q. Would that not alter the length of the rod?
A. No.

Q. With what instrument would you measure a connecting-rod?
A. It is called a 'tram.'

Q. With what is an engine packed in the stuffing box?
A. Some engineers use hemp, others use black lead packing, and others use lead rings or metallic packing; there are several kinds. Every engineer to his own taste.