VENTILATION.

Fig. 138.

Fig. 139.

Fig. 140.

Fig. 141.

The general rule is to lay the main pipes from the boiler so that the pipe will drain from the boiler. Where this is done it is necessary to have a drip just before the steam enters the circulation. This drip is connected to a trap, or, if the condensed water is returned to the boiler, the drip is arranged accordingly.

But it is the best practice to lay the main pipe with the lowest part at the boiler, so that the drip will take care of itself, and not require an extra trap, nor interfere with the return circulation.

When steam is turned into cold pipes the water of condensation gets cold after running a short distance, and if it has to go through a small drip pipe full of frost it will probably be frozen. Then, unless it is followed up with a pail of hot water, the whole arrangement will be frozen and a great many bursted pipes will result. Whenever turning steam on in a system of very cold pipes, only one room should be taken at a time, and a pail of hot water should be handy so that if the pipe becomes obstructed it can be thawed immediately without damage.

When pipes become extensively frozen there is nothing to do but take them out and put in new ones.

Fig. 142.

Fig. 143.

The manner in which a temperature too low to start rapid combustion in wood in steam pipes, operates in originating a fire is by first reducing the oxide of iron (rust) to a metallic condition. This is possible only under certain external conditions, among them a dry atmosphere.Just as soon as the air is recharged with moisture, the reduced iron is liable to regain, at a bound, its lost oxygen, and in doing so become red hot.This is the heat that sets the already tindered wood or paper ablaze.

Where there is no rust there is no danger from fire with a less than scorching temperature in the pipe or flue. Hence the necessity of keeping steam or hot water fittings in good order.

The indirect system of heating is the most expensive to put in; as to the cost of providing nearly double the heating surface in the coils must be added the cost of suitable air boxes, pipes and registers. For a large installation, this is a serious matter, although for office warming the advantages gained on the score of healthfulness and greater efficiency of employees much more than counterbalance the extra expense.

One horse power of boiler will approximately heat 6,000 to 10,000 cubic feet in shops, mills and factories—dwellings require only one horse power for from 10,000 to 20,000 cubic feet.

From seven to ten square feet of radiating surface can be heated fromone square foot of boiler surface, i.e., the heating surface of the boiler and each horse power of boiler will heat 240 to 360 feet of 1-inch pipe.

The profession most nearly related to that of steam engineers is the working steam fitters’ occupation. Strictly speaking, the engineer should produce the steam, and it is the steam fitters’ place to fix up all the steam pipes and make all the necessary connections: but where the steam plants are small, the engineer may be steam fitter also: hence the introduction in this work of these “Points” which are necessary to be known for the proper care and management of any system of steam or hot water heating.

The care and patience, the mental strain and not infrequently the physical torture incident to fitting up a complicated pipe system cannot adequately be set forth in words.

It is stated to be a fact, that in high pressure hot water heating the water frequently becomes red hot, pressures of 1000 to 1200 pounds per square inch being reached, and when the circulation of the system is defective the pipe becomes visibly red in the dark.

Pipes under work benches should be avoided, unless there is an opening at the back to permit the escape of the heated air, which would otherwise come out at the front.

When both exhaust and live steam are used for heating, many engineers prefer to use independent lines of pipe for each, rather than run the risk of interference and waste caused by admitting exhaust and live steam into the same system at the same time. Nevertheless, the advantages gained by being able to increase the heating power of a system in extremely cold weather by utilizing the entire radiating surface for high pressure steam, are so great that it is probably better so to arrange the system of pipes and connections that this can be done.

Double extra heavy pipe (XX) is used for ice and refrigerating machines (see page246), as a general rule, makers of this class of machinery obtain but little satisfaction in the use of the ordinary thread joining and use special dieswith uniform taper—both for couplings, flanges and threading the pipe itself. They do this to protect their reputation and guarantees.

Welding boiler and other tubes.—The following is a good way in cases of emergency and can be done on a common forge:

Enlarge one end of the shortest piece, and one end of the long piece make smaller, then telescope the two about3⁄4of an inch. Next get an iron shaft as large as will go into the tube and lay across the forge with the tube slipped over it.Block the shaft up so that the tube will hang down from the top of the shaft.By such an arrangement the inside of the tube will be smooth for a scraper. When the tube gets to a welding heat strike on theendof the short piece first, with a heavy hammer, then with a light and broad-faced hammer make the weld. Borax can be used to good advantage, but it is not necessary. The next thing is to test the tube, which can be done in the following manner: Drive a plug in one end of the tube, stand it up on that end, and fill it with water, if it does not leak the job is well done, if a leak exists the welding must be again done.

Solid-drawn Iron Tubes: Calculated Bursting and Collapsing Pressures.

ExternalDiameter.Thickness.InternalDiameter.Bursting Pressure.Collapsing Pressure.Per SquareInch ofInternalSurface.Per SquareInch ofSectionof Metal.Per SquareInch ofExternalSurface.Per SquareInch ofSectionof Metal.Inches.Inch.Inches.Lbs.Tons.Lbs.Tons.11⁄4.0831.084770022.4650021.713⁄8.0831.209690022.4580021.311⁄2.0831.334620022.4520021.013⁄4.0831.584530022.4430020.32.0831.834450022.4370019.721⁄4.0952.060460022.4360019.021⁄2.1092.282480022.4360018.323⁄4.1092.532440022.4310017.73.1202.760430022.4300017.031⁄2.1343.232420022.4270015.733⁄4.1343.482390022.4240015.04.1343.732360022.4210014.341⁄2.1344.232320022.4170013.043⁄4.1344.482300022.4160012.35.1344.732280022.4140011.751⁄2.1485.204280022.4120010.365.704260022.410009.0

The quantity of air for each minute for one person is from four to fifteen feet—and from one-half to one foot should be allowed for each gas jet or lamp.

Heated air cannot be made to enter a room unless means are provided for permitting an equal quantity to escape, and the best places for such exit openings is near the floor.

For healthful ventilation the indirect system of steam heating is by far the best yet devised, for it not only warms the room, but insures perfect ventilation as well. In this system, the air for warming the room is introduced through registers, having first been heated by passing over coils of pipe or radiators suitably located in the air ducts. There is a large volume of pure air constantly entering the room, which must displace and drive out an equal quantity of impure air. This escapes principally around the doors and windows, so that not only is the ventilation effected automatically without the use of special devices, but all disagreeable indraft of cold air is prevented.

One of the cheapest and best methods of ventilation is to have an opening near the floor, opening directly into the flue, or some other outlet especially constructed for it,with hot water or steam pipes in this opening. A moderate degree of heat in these pipes will create a draft, and draw out the bad air. Only a few of these pipes are necessary, and the amount of hot water or steam required to heat them is too small to be worthy of consideration.

The use of a small gas-jet, burning continuously, in a pipe or shaft has been found to be a most admirable method of ventilating inside rooms, closets and similar places where foul air might collect if not replaced by fresh. The following table exhibits the result of careful experiments made by Mr. Thomas Fletcher, of England, with a vertical flue 6 inches in diameter and 12 feet high:

Table.

Gas Burntper Hour.Speed ofCurrent perMinute.Total AirExhaustedper Hour.Air Exhaustedper Cubic footof Gas Burnt.Temperature atoutlet. Normal62° Fahr.Cubic Feet.Feet.Cubic Feet.Cubic Feet.12052,4602,46082°22452,9401,47092°43253,900975110°84154,980622137°

EXHAUST STEAM HEATING.Fig. 144.

Taking the experiments as a whole, it will be seen that in a flue 6 inches in diameter, the maximum speed of current which can be obtained with economy is about 200 feet per minute; and this was realized with a gas consumption of 1 cubic foot per hour—1 cubic foot of gas removing 2,460 cubic feet of air.

It should, however, not be required of any system of heating to more than aid in ventilation. It is the architect’s or builder’s performance to so arrange lower and upper openings to drive out the bad air.

There are two methods of warming by steam heat—one with live steam direct from the boiler, and the other with exhaust steam. These two are frequently carried out in combination, and in fact generally so where exhaust steam is used at all for warming.

In nearly all manufacturing establishments, office buildings, etc., the exhaust steam produced will very nearly, if not quite supply sufficient exhaust steam to furnish all the heat required for heating the building during average weather, although in extremely cold weather, a certain amount of live steam might be necessary to use in connection with the exhaust to supply the required amount of heat.

A simple and convenient device operating upon the suction principle has been found to be most efficient. By this the exhaust steam is drawn almost instantly through the most extensive piping; preventing condensation, freezing and hammering, after which it is condensed and purified, and fed back into the boiler by the means of a reciprocating pump.

It is claimed that a given quantity of exhaust steam can be circulated by this vacuum system and uniformly distributed through double the amount of heating pipes than could be accomplished by the same quantity of exhaust steam when forced into the heating system by pressure.

Fig. 144is a well-tried system of heating by exhaust steam in which “7” represents the steam exhaust pipe, with “6” showing back pressure valve with weight to adjust amount of back pressure; “4” “4” are steam supply pipes to radiators; “5” “5” are risers; “9” “9” are condensation return pipesfrom the radiators; “8” is the pressure regulating valve from the boilers.Fig. 144may also be said to represent the general method of piping used in steam and hot water heating, which is difficult of illustration owing to the fact that each locality where it is used requires a different adaptation.

Many steam fittings are lost through carelessness, particularly in taking down old work, but the great bulk are simply “lost” for lack of method in caring for them. This task properly falls upon the engineer, as he usually is intrusted with the selection and ordering of the necessary work. A great saving in the bill of “findings” can be effected by proper attention.

The same systematic care exercised over the other fittings, tools, appliances, oil, fuel, etc., used or consumed in the engine and boiler room may be urged with equal emphasis.

1⁄4and3⁄8in.1⁄2in.1 in.11⁄4in.11⁄2in.ElbowsTees.Nipples.Plugs.Reducers.R’s and L’s.Unions2 in.couplings.Fig. 145.

Fig. 145 shows a case for keeping fittings, which will enable one to find any particular piece without a moment’s delay. In this admirable arrangement it will be seen that the heavy fittings are all at the bottom, the light ones at the top. In the top row of all, the one-quarter and three-eighth inch fittings are placed, being so small that a partition may be put into thatrow of boxes, and then have plenty of room, and giving twice the capacity to that row of pigeon holes.

Above this case, which is built of one inch boards, may be put a set of four cupboards, double doors being fitted to each, and thus making a door over each compartment in the fitting rack. The shelves run through these cupboards from end to end, and are not divided by vertical partitions. The necessary brass fittings are kept on these shelves, and the doors are secured by good locks. The lightest fittings are placed on the lower shelves in this cupboard, being in greatest demand.

Fig. 146.

Fig. 146represents one form of a pipe cutter which is made to use by hand; cutters are also made for use by power, which are capable of cutting off pipes of immense size. In an engineer’s outfit of steam fitting tools 2 sets are advisable—one to cut pipe1⁄8th inch to 1 inch, and the other to cut 1 to 2-inch pipe. Figs.147,148, represent different forms of pipe tongs—the former called “chain” tongs which will readily hold three-inch pipe.Fig. 149represents a steam fitter’s vise which will “take” say, 21⁄2-inch pipe down to1⁄8th.Fig. 150shows a set of taps and dies for small bolts and nuts which is ordinarily to be found in a steam fitter’s outfit although used very generally by machinists and others.Fig. 151shows a pair of gas-pliers which are used by steam fitters in gas-pipe jobs.Fig. 152exhibits the old-fashioned alligator wrench.

In ice and refrigerating jobs of pipe fitting special tubes are used to assure a niceness of joints and fitting which is not called for in steam and water service.

Fig. 147.

Fig. 148.

Fig. 149.

The first means in the earliest times of steam engineering, for opening and shutting the passages in the pipes of steam engines were cocks and these were all worked by hand and required close attention. A boy named Humphry Potter being in charge of one of the cocks of Newcomen’s pumping-engines, and desiring time for play, it is said, managed to fasten the lever-handles of the spigots by means of rods and string to the walking beam of the engine, so that each recurrent motion of the beam effected the change required. This was the first automatic valve-motion.

Fig. 150.

Fig. 151.

Fig. 152.

The valve is any device or appliance used to control the flow of a liquid, vapor or gas, through a pipe, outlet, or inlet in any form of vessel. In this sense the definition includes air, gas, steam, and water cocks of any kind.

The bellows was probably the first instrument of which they formed a part. No other machine equally ancient can be pointed out in which they were required.

By far the most important improvement on the primitive bellows or bag was the admission of air by a separate opening—a contrivance that led to the invention of the valve, one of the most essential elements of steam, of water, as well as pneumatic machinery.

Valves and Cocks.—Generally described, a valve is a lid or cover to an opening, so formed as to open a communication in one direction and close it in another by lifting, turning, or sliding—among the varieties may be classed as, the cock, the slide-valve, the poppet valve and the clack-valve. A common form of this valve is shown inFig. 139, page 261.

An every day example of a valve, and almost the simplest known, is that of an ordinary pump where the valve opens upward to admit the water and closes downward to prevent its return.

A valve has a seat, whether it be a gate or circular valve, and is generally turned by a circular handle fitted to the spindle.

Difference between a cock and valve.—The cock is a valve, but a valve is not a cock; the cock is a conical plug slotted and fitted with a handle for turning the cone-shaped valve, with its opening in line, or otherwise, with the opening of the pipe.

Globe Valveis a valve enclosed in a globular chamber,Fig. 135. This, like many other valves, takes its name from its shape.

Globe valves, whenever possible, should be placedso that the pressure comes under the valve, or at the side, for if the valve should become loose from the stem (which they often do) if the pressure is on top, there would be a total stoppage of the steam.

Relief Valveis a valve so arranged that it opens outward when a dangerous pressure or shock occurs; a valve belonging to the feeding apparatus of a marine engine, through which the water escapes into the hot well when it is shut off from the boiler.

Hinged Valvesconstitute a large class, as for example the butterfly-valve, clack-valves, and other forms in which the leaf or plate of the valve is fastened on one side of the valve seat or opening.

Valve-bracketis a bracket fitted with a valve.

The Valve-chamberis where a pump valve or steam valve operates.

Valve-cock.—A form of cock or faucet which is closed by dropping of a valve on its seat.

Valve-couplingis a pipe coupling containing a valve.

Valve-seatis the surface upon which a valve rests.

Back pressure valvesare ball or clack valves in a pipe which instantly assume the seat when a back pressure occurs. They are illustrated in “6,”Fig. 144. Their name signifies their use—to maintain a constant back pressure in heating systems.

Ball-valve—a faucet which is opened or closed by means of a ball floating in the water. It constitutes an automatic arrangement for keeping the water at a certain level.

Bib-cock—a faucet having a bent-down nozzle.

Check-valve—a valve placed between the feed pipe and the boiler to prevent the return of the water, etc.

Brine-valve—a valve which is opened to allow water saturated with salt to escape. In marine service it is “a blow-off valve.”

Ball-valve—a valve occupying a hollow seat. These valves are raised by the passage of a fluid and descending are closed by gravity.

Angle-valveis one which forms part of an angle, seeFig. 137.

The double-seat valveor double-beat valve presents two outlets for the water. In the Cornish steam engine this is called theequilibrium-valve, because the pressure on the two is very nearly equalized.

Three-way cockis one having three positions directing the fluid in either of three directions. This is illustrated inFig. 138. Thethree-way valveis also illustrated on page 259,Fig. 136.

Four-way cockis one having two separate passages in the plug and communicating with four pipes.

Gate-valve—a valve closed by a gate. This is illustrated inFig. 140.

Swing or straight-way valve—this is shown inFig. 141, page 261.

Throttle-valve.—This is the valve used to admit steam to the engine and so termed to distinguish it from the main stop-valve located near the boiler—to throttle means to choke—hence the throttling of the steam.

Rotary valvesare those in which the disc, or plug, or other device used to close the passage, is made to revolve for opening or closing, the common stop cock being an illustration.

Lifting valvesare those in which the full cone or stopper is lifted from the valve seat by pressure from below, the poppet, and safety valves being examples.

Pressure regulator valve—this is sometimes called a reducing valve and is illustrated in Figs.142,143, on page 262. It is designed to reduce the pressure from a high point in the boiler to a lower one in a system of piping, etc.

Usually the smaller valves, not exceeding 11⁄4inch in diameter, are wholly of gun-metal; the larger are commonly made with cast-iron bodies and gun-metal fittings. The smallest valves, from1⁄4up to1⁄2inch inclusive, have the disk solid with the spindle, and have an ordinary stuffing-box with external gland. Valves of3⁄4inch and upwards have the disk loose from the spindle; up to 3 inch valves the spindles are screwed to work inside the casing; above that size the screwed portion is outside the casing. Above the 3-inch size the nozzles of the cast-iron bodies are generally flanged instead of tapped.

A few of the principal sorts have been illustrated in this work and still others will be described in the“Index”at the close of the work.

Fig. 123, page 251, illustrates anelbowwith outlet. This is sometimes spelled with the capital L, and again as an ell.

Fig. 124shows a longnipple.

Fig. 125, page 253, exhibits abushing, used to reduce one size pipe in a line to another.

Fig. 126is across tee. This is frequently spelled with a capital T.

Fig. 127is aplug—used to stop apertures in plates or pipes.

Fig. 128, page 254, illustrates alock nut.

Fig. 129shows a T, as illustrating the difference between a T and a cross T,Fig. 126.

Fig. 130is acoupling.

Fig. 131, page 255, represents areducing coupling.

Fig. 132is an illustration of a pipeunion.

Fig. 133is a plainelbow(see alsoFig. 123.)

This subject relates to theradiation of heat, which allows a reference to the laws of heat and tables of radiating power of various substances, as set forth on pages212, 215.

The importance of a protection of exposed surfaces from radiation of heat is now undisputed, and many experiments have determined very closely the relative value of the various non-conducting substances.

Table of theConducting Powerof various substances.

Substance.ConductingPower.Blotting Paper.274Eiderdown.314Cotton or Wool, any density.323Hemp, Canvas.418Mahogany Dust.523Wood Ashes.531Straw.563Charcoal Powder.636Wood, across fibre.83Cork1.15Coke, pulverized1.29India Rubber1.37Wood, with fibre1.40Plaster of Paris3.86Baked Clay4.83Glass6.6Stone13.68

By the above table may be judged the comparative value of different coverings; blotting paper withits confined air, standing at one end of the list, stone at the other. It should be noted thatthe less the conducting power the better protection against radiation.

A non-conducting coating for steam pipes, etc., used for many years with perfect satisfaction, can be prepared by any steam user. It consists of a mixture of wood sawdust with common starch, used in a state of thick paste. If the surfaces to be covered are well cleaned from all trace of grease, the adherence of the paste is perfect for either cast or wrought iron; and a thickness of 1 inch will produce the same effect as that of the most costly non-conductors. For copper pipes there should be used a priming coat or two of potter’s clay, mixed thin with water and laid on with a brush. The sawdust is sifted to remove too large pieces, and mixed with very thin starch. A mixture of two-thirds of wheat starch with one-third of rye starch is the best for this purpose. It is the common practice to wind string spirally around the pipes to be treated tosecure adhesion for the first coat, which is aboutl⁄5th of an inch thick. When this sets, a second and a third coat are successfully applied, and so on until the required thickness is attained. When it is all dry, two or three coats of coal tar, applied with a brush, protect it from the weather.

A very efficient covering may be made as follows: 1, wrap the pipe in asbestos paper—though this may be dispensed with; 2, lay slips of wood lengthways, from 6 to 12 according to size of pipe—binding them in position with wire or cord; 3, around the framework thus constructed wrap roofing paper, fastening it by paste or twine. For flanged pipe, space may be left for access to the bolts, which space should be filled with felt. Use tarred paper—or paint the exterior.

While a very efficient non-conductor, hair or wool felt has the disadvantage of becoming soon charred from the heat of steam at high pressure, and sometimes taking fire. The following table, prepared by Chas. E. Emory, Ph. D., showsthe valueof various substances, taking wool felt as aunit.

Table of Relative Value of Non-Conductors.

Non-Conductor.Value.Wood Felt1.000Mineral Wool No. 2.832Do. with tar.715Sawdust.680Mineral Wool No. 1.676Charcoal.632Pine Wood, across fibre.553Loam, dry and open.550Slaked Lime.480Gas House Carbon.470Asbestos.363Coal Ashes.345Coke in lumps.277Air space, undivided.136

Wrought iron is said to expand1⁄150,000of an inch for each degree of heat communicated to it; to make the calculation take the length of the pipe in inches, multiply it by the number of degrees between the normal temperature it is required to attain when heated, and divide this by 150,000. Suppose the pipe is 100 feet long, and its temperature zero, and it is desired to use it to carry steam at 100 pounds pressure—equal to a temperature of 338 degrees—multiply 100 feet by 12 to reduce it to inches, and by 338, the difference in temperature; dividethis by 150,000, and the result will be 2.7 inches, which would be the amount of play that would be required, in this instance, in the expansion joint.

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