Maxims and Instructions for the Boiler Room

Chapter X: Section 24: “Lever safety valves to be attached to marine boilers shall (3)

Text size

+---------+----------+----------+----------+-----------+----------+
| | Length | Weight | No. of | Contents |Weight of |
| Inside | of Pipe | per ft. | Threads | in |Water per |
|Diameter.|containing| of |per inch |Gallons[A] | foot of |
| |one Cubic | Length. |of Screw. |per foot. | Length. |
| | Foot. | | | | |
+---------+----------+----------+----------+-----------+----------+
| Inches. | Feet. | Lbs. | | | Lbs. |
| 1/8 | 2500. | .24 | 27 | .0006 | .005 |
| 1/4 | 1385. | .42 | 18 | .0026 | .021 |
| 3/8 | 751.5 | .56 | 18 | .0057 | .047 |
| 1/2 | 472.4 | .84 | 14 | .0102 | .085 |
| 3/4 | 270. | 1.12 | 14 | .0230 | .190 |
| 1 | 166.9 | 1.67 | 11-1/2 | .0408 | .349 |
| 1-1/4 | 96.25 | 2.25 | 11-1/2 | .0638 | .527 |
| 1-1/2 | 70.65 | 2.69 | 11-1/2 | .0918 | .760 |
| 2 | 42.36 | 3.66 | 11-1/2 | .1632 | 1.356 |
| 2-1/2 | 30.11 | 5.77 | 8 | .2550 | 2.116 |
| 3 | 19.49 | 7.54 | 8 | .3673 | 3.049 |
| 3-1/2 | 14.56 | 9.05 | 8 | .4998 | 4.155 |
| 4 | 11.31 | 10.72 | 8 | .6528 | 5.405 |
| 4-1/2 | 9.03 | 12.49 | 8 | .8263 | 6.851 |
| 5 | 7.20 | 14.56 | 8 | 1.020 | 8.500 |
| 6 | 4.98 | 18.76 | 8 | 1.469 | 12.312 |
| 7 | 3.72 | 23.41 | 8 | 1.999 | 16.662 |
| 8 | 2.88 | 28.34 | 8 | 2.611 | 21.750 |
| 9 | 2.26 | 34.67 | 8 | 3.300 | 27.500 |
| 10 | 1.80 | 40.64 | 8 | 4.081 | 34.000 |
+---------+----------+----------+----------+-----------+----------+

[Footnote A: The Standard U. S. gallon of 231 cubic inches.]

The division of process in the manufacture of pipe, takes place at 1-1/4 inch, 1-1/4 inch and smaller sizes being called butt-welded pipe, and 1-1/2 inch and larger sizes being known as lap-welded pipe; this rule holds good for standard, X-strong and XX-strong.

JOINTS OF PIPES AND FITTINGS.

The accompanying illustrations represent certain joints, couplings and connections used in steam and hot water heating systems.

For many years in the matter of pipe joints there has been little change. The cast-iron hub and spigot joint, Fig. 115, caulked with iron borings, is probably the oldest kind of joint. This is still generally adopted in hot water heating of a certain class, and was formerly used with low-pressure steam. A fairly regular smooth internal service is obtained, and once made tight is very durable. Cast-iron flanged pipes have also been a long time in use. These joints are made with a wrought-iron ring gasket, wrapped closely with yarn, Fig. 116, which is sometimes dipped in a mixture of red and white lead. It is placed between the flanges, it being of such a diameter as to fit within the bolts by which the joint was screwed up and a nest or iron joint, B B, caulked outside the annular gasket between the faces of the flanges.

The next step in cast-iron flange pipe joints was the facing or turning up of the flanges and the use of a gasket of rubber, copper, paper or cement, with bolts for drawing the faces together. These joints for cast-iron pipes have not been changed excepting for some classes of work where a lip and recess, Fig. 117, formed on opposite flanges, which makes the internal surfaces smooth and aid in preventing the gaskets from being blown out.

The introduction of wrought iron welded pipes has diminished the use of cast-iron pipes for many purposes, especially in heating apparatus and other pipe systems. Its advantages are lightness, the ease with which various lengths can be obtained and its strength. In wrought-iron pipe work the general practice in making joints between pipes is a wrought-iron coupling, Fig. 118, with tapered threads at both ends. The pipes do not meet at their ends, and a recess of about 3/4 inch or more long by the depth of the thickness of the pipes is left at every pipe end. A similar tapered thread is used in connecting the cast-iron fittings, elbows, tees, etc., Fig. 119, to the pipe, and a large recess is necessary in each fitting to allow for the tapping of the threads. Thus the inside diameter of the fitting is larger by 1/8 inch than the outside diameter of the pipe, and the internal projection of the thickness of the pipe and that of the thread of the fitting increases materially the friction due to the interior surfaces of pipe and fitting. This class of joint requires care in the tapping of the fittings and in the cutting of tapered threads on the pipes; much trouble is caused by an inaccurately cut thread, as it may throw a line of pipes several inches out of place and put fittings and joints under undue and irregular strains.

The right and left threaded nipple, Fig. 119, is used as a finishing connection joint and between fittings. Space equal to the length of the two threads is required between the two fittings to be connected in order to enter the nipple, and one or both fittings should be free to move in a straight line when the nipple is being screwed up. To make up this joint time and care are necessary. The right threaded end on nipple should be first firmly screwed with the tongs or wrench into the right threaded end of fitting, then slacked out and screwed up again by hand until tight, when it is screwed back by hand, at the same time counting the number of threads it has entered by hand. The same is done with the left threaded end of nipple and fitting. If the right and left threads of nipple have counted the same number of threads, each thread, when making the joint up, should enter the fittings at the same time if possible, and particular care must be taken that the fittings are exactly opposite, to facilitate catching on, prevent crossing threads, and that no irregular strain comes on the nipple while being screwed up.

In screwing up these nipples the coupling has to be turned with flats on the external surface to fit an internal wrench: in such cases the thread on nipple has one continuous taper. These special couplings are marked with ribs on the outside to distinguish them. Fig. 120 represents another joint in wrought-iron piping known as the “union” composed of three pieces of the washer. Unions are also made with ground joints, and the washer dispensed with. Radiator valves are now generally connected by them, but if the hole in the radiator is not tapped accurately, the union when drawn up will not be tight, or if tight, the valve will not be straight.

Fig. 121 shows right and left threaded nipple connecting elbow and tee with wrought-iron pipes.

The flange union, Fig. 122, is another joint generally used on wrought-iron pipes above 4 or 5 inches in diameter in making connections to valves, etc., and on smaller pipes in positions where it is a convenient joint. This joint consists of two circular cast-iron flanges with the requisite number of holes for bolts, and central hole tapped tapered to receive thread of pipe. The abutting faces of the flanges are generally turned and the holding bolts fitted into the holes.

STEAM AND HOT WATER HEATING.

The heating by means of pipes through which are conveyed hot water and steam is a science by itself and yet one claiming some degree of familiarity by all engineers, steam users, and architects.

In practice it requires a knowledge of steam, air and temperatures, of pressure and supply; a familiarity with heat and heating surfaces and with all contrivances, appliances and devices that enter into the warming and ventilation of buildings. So long as factories, public and private buildings are erected, so long will warming and ventilation keep progress with steam engineering and remain a part of the general mechanical science required of the supervisory and practical engineer.

In what is called _the system of open circulation_, a supply main conveys the steam to the radiating surfaces, whence _a return main conducts the condensed water either into an open tank for feeding the boiler, or into a drain to run to waste_, the boiler being fed from some other source; the system of what is called _closed circulation_ is carried out either with separate supply and return mains, both of which extend to the furthest distance to which the heat has to be distributed, or else with a single main, which answers at once for both the supply and the return, either with or without a longitudinal partition inside it for separating the outward current of steam supply from the return current of condensed water.

In either case suitable traps have to be provided on the return main, _for preserving the steam pressure within the supply main and radiators_. These two systems, in any of their modifications, may also be combined, as is most generally done in any extensive warming apparatus.

The system of closed circulation requires the boiler to be placed so low as will allow all the return pipes to drain freely back to it above its water-level. This condition has been modified mechanically by the automatic “trap,” a device frequently employed for lifting from a lower level, part or all of the condensed water, and delivering it into the boiler; it is, in fact, a displacement pump.

The same result has been attained by draining into a closed tank, placed low enough to accommodate all the return pipes, and made strong enough to stand the full boiler pressure with safety, and then employing a steam pump, either reciprocating or centrifugal, to raise the water from this tank to the proper level for enabling it to flow back into the boiler, the whole of the circulation being closed from communication with the atmosphere.

There are two systems of steam heating, known as the _direct_ and the _indirect_ system.

Direct radiating surfaces embrace all heaters placed within a room or building to warm the air, and are not directly connected with a system of ventilation.

Indirect radiation embraces all heating surfaces placed outside the rooms to be heated, and can only be used in connection with some system of ventilation.

For warming by direct radiation, the radiators usually consist of coils, composed of 3/4-inch and 1-inch steam pipes, which are arranged in parallel lines and are coupled to branch tees or heads. In a few exceptional cases, radiators of peculiar shapes are specially constructed. In all cases the coils must have either vertical or horizontal elbows of moderate length, for allowing each pipe to expand separately and freely. Sometimes short lengths of pipe are coupled by return-bends, doubling backwards and forwards in several replications one above another, and forming what are called “return-bend coils,” and when several of these sections are connected by branch, tees into a compact mass of tubing, the whole is known as a “box-coil.”

Steam and Hot Water heating have long been acknowledged as altogether most practical and economical in every way—and their universal adoption in all the better class of buildings throughout the country is positive proof of their superiority.

The heat from steam is almost exactly identical with that from hot water, and few can distinguish between the two systems when properly erected.

They are both healthful, economical and satisfactory methods of warming. They give no gas, dust nor smoke; are automatically regulated, and therefore allow of an even and constant temperature throughout the house, whatever be the condition of the weather outside.

The circulation of the steam through the warming pipes is effected in an almost unlimited variety of ways, and the cause producing the circulation throughout the pipes of the warming apparatus is solely the difference of pressure which results from the more or less rapid condensation of the steam in contact with the radiating surfaces.

A partial vacuum is formed by this difference of pressure _within the radiating portions of the apparatus_, and the column of steam or of water equivalent to this diminution of pressure, constitutes the effective head producing the flow of steam from the boiler, at the same time the return current of condensed water is determined by the downward inclination of the pipes for the return course.

POINTS RELATING TO STEAM HEATING.

No two pipes should discharge into a T from opposite directions, thus retarding the motion of both or one of the returning currents. This is called “butting” and is one of the most vexatious things to encounter in pipe fitting.

All steam piped rooms should be frequently dusted, cleaned and kept free from accumulation of inflammable material.

The use of the air valve is as follows: In generating steam from cold water all the free air is liberated and driven off into the pipe, with the air left in them, all of which is forced up to the highest point of the coils or radiators, and compressed equal to the steam pressure following it. Now, by placing a valve or vent at the return end of the pieces to be heated, the air will be driven out by the compression. Why the vent is placed at the return is, that the momentum of the steam, it being the lightest body, will pass in the direction of it, falling down into the return as it condenses, thus liberating the air. Otherwise, should the vent not work, and the air is left in the radiator, it will act as an air spring, and the contents of the pipes left stationary will be the result; no circulation, no heat; and the greater steam pressure put on, the greater the chances are of not getting any heat; and thus a little device, with an opening no larger than a fine needle, will start what a ton of pressure would not do in its absence.

If the drip and supply pipes are large there is very little danger of freezing, provided suitable precautions are taken to leave the pipes clear. They should be blown through, when left, and the steam valve should be closed. There should also be a free chance for air to escape in all systems of piping.

No rule can be given relating to capacity for heating pipes and radiators which do not require to be largely modified by surroundings.

The field of steam heating would seem to be limitless—in one public building it required recently 480,000 dollars to meet the expenditures in this single line. As an example of warming on an extensive scale may be taken a large office in New York, of which the following are the particulars:

Total number of rooms, including halls and vaults. 286
Total area of floor surface. sq. ft. 137,370
Total volume of rooms. cub. ft. 1,923,590

A second example is furnished by the State Lunatic Asylum at Indianapolis:

Length of frontage of building, more than. 2,000 lin. ft.
Total volume of rooms. 2,574,084 cub. ft.
Warming {indirect radiating surface 23,296
Apparatus {Direct 10,804
{Total 34,100 sq. ft.
Boilers {Grate area 180 sq. ft.
{Heating surface 5,863 sq. ft.

The “overhead” system of heating with steam pipes has several advantages. 1. The pipes are entirely out of the way 2. They do not become covered with odds and ends of unused materials. 3. If they leak the drip fixes the exact location of place needed to be repaired. 4. The room occupied overhead cannot be well otherwise utilized, hence in shops the system has proved efficient.

But for offices or store rooms the overhead system is not approved of owing to the heat beating down upon the occupants and causing headache.

When overhead heating pipes are used, they should not be hung too near the ceiling. If the room be a high one, it is better to hang them below, rather than above, the level of the belts running across the room, and they should not be less than three or four feet from the wall.

It is important to protect all wood work or other inflammable material around steam pipes from immediate contact with them, especially where pipes pass through floors and partitions. A metal thimble should be placed around the steam pipe, and firmly fastened on both sides of the floor, in such a way as to leave an air space around the steam pipe.

For indirect radiating surfaces, the box coils are the forms most used. The chambers or casings for containing them are made either of brickwork, or often of galvanized sheet-iron of No. 26 gauge, with folded joints. The coils are suspended freely within the chambers, which are themselves attached to the walls containing the air inlet flues. Besides coils of wrought iron tubes, cast-iron tablets or hollow slabs, having vertical surfaces with projecting studs or ribs, have been extensively used for the radiating surfaces.

As the amount of heat given off from the radiator cannot be satisfactorily controlled by throttling the steam supply, it is usual to divide all radiators into sections, each of which can be shut off from the supply and return mains, separately from the rest of the sections. This method of regulation applies to radiators for indirect heating as well as for direct.

Vertical pipe coils, constitute a distinctive form of radiator now largely used. In these a number of short upright 1-inch tubes, from two feet 8 inches to 2 feet 10 inches long, are screwed into a hollow cast iron base or box; and are either connected together in pairs by return-bends at their upper ends, or else each tube stands singly with its upper end closed, and having a hoop iron partition extending up inside it from the bottom to nearly the top. The supply of steam is admitted into the bottom casting; and the steam on entering, being lighter than the air, ascends through one leg of each siphon pipe and descends through the other, while the condensed water trickles down either leg, and with it the displaced air sinks also into the bottom box. For getting rid of the air, a trap is provided, having an outlet controlled by metallic rods; as soon as all the air has escaped and the rods become heated by the presence of unmixed steam, their expansion closes the outlet.

A thorough drainage of steam pipes will effectually prevent cracking and pounding noises.

The windward side of buildings require more radiating surface than does the sheltered side.

When floor radiators are used, their location should be determined by circumstances; the best situations are usually near the walls of the room, in front of the windows. The cold air, which always creates an indraft around the window frames, is thus, to some extent, warmed as it passes over the the radiators, and also assists in the general circulation.

Water of condensation will freeze quicker than water that has not been evaporated, for the reason that it has parted with all its air and is therefore solid.

Whatever the size of the circulating pipes, the supply and drip pipes should be large, to insure good circulation; the drip pipes especially so. This is also the more necessary when the pipes are exposed, or when there is danger of freezing after the steam is shut off.

It is important to see that no blisters or ragged pipes go into the returns, and also to make sure that the ends are not “burred in” with a dull pipe cutter wheel so as to form a place of lodgment for loose matter in the pipe to stop against.

Experiments recently made on the strength of bent pipes have developed some things not commonly known, or at least not recognized, that is, the strain on the inside of the angles, _due to the effort of the pipes to straighten themselves under pressure_. The problem is one of considerable intricacy, resolvable, however, by computation, and is a good one for practice. In the experiment referred to, a copper pipe of 6-3/4 in. bore, 3/16 in. thick, was used. The angle was 90 degrees, and the legs about 16 in. long from the center. At a pressure of 912 pounds to an inch, the deflection of the pipe was nearly 3/8 in., showing an enormous strain on the inner side, in addition to the pressure.

Steam valves should be connected in such a manner that the valve closes against the constant steam pressure.

Interesting experiments show that the loss by condensation in carrying steam one mile is 5 per cent. of the capacity of the main, and a steam pressure of seventy-five pounds carried in five miles of mains, ending at a point one-half mile from the boiler house only shows a loss of pressure of two pounds.

In steam warming it is necessary to bring the water to a boiling point to get any heat whatever; in hot water warming, a low temperature will radiate a corresponding amount of heat.

Never use a valve in putting in a low pressure apparatus if it is possible to get along without it. All the valves or cocks that are actually required in a well-proportioned low pressure apparatus are, a cock to blow off the water and clean out the return pipes, another to turn on the feed water. Of course the safety valves, gauge cocks, and those to shut fire regulators and such as are a part of the boiler, are not included in this “point.”

The most important thing in connecting the relief to return pipes is, that it should always be carried down below the line, the same as all vertical return pipes. In connecting the reliefs, so that the lower opening can at any time be exposed to the steam, there will be the difficulty of having the steam going in one direction, and the water in another.

The relief pipe should “tap” the steam at its lowest or most depressed points. It should always be put in at the base of all steam “risers” taking steam to upper floors.

In leaving the boiler with main steam pipe, raise to a height that will allow of one inch fall from the boiler to every ten feet of running steam pipe; this is sufficient, and a greater fall or pitch will cause the condensed water in the pipe to make at times a disagreeable noise or “gurgling.”

The flow pipe should never start from the boiler in a horizontal direction, as this will cause delay and trouble in the circulation. This pipe should always start in a vertical direction, even if it has to proceed horizontally within a short distance from the boiler. Reflection will show that the perfect apparatus is one that carries the flow pipe in a direct vertical line to the cylinder or tank; this is never, or but rarely possible, but skill and ingenuity should be exercised to carry the pipes as nearly as possible in this direction.

The flow of steam ought not to be fast enough to prevent the water of condensation from returning freely. All the circulating pipes should be lowest at the discharge end, and the inclination given them should not be less than one foot in fifty.

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.

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 from _one 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 page 246), 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 dies _with 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 about 3/4 of 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 the _end_ of 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.

---------+----------+---------+------------------+--------------------
| | |BURSTING PRESSURE.|COLLAPSING PRESSURE.
External | |Internal +------------------+--------------------
Diameter.|Thickness.|Diameter.|Per Square Inch of|Per Square Inch of
| | +--------+---------+---------+----------
| | |Internal| Section |External | Section
| | |Surface.|of Metal.|Surface. | of Metal.
---------+----------+---------+--------+---------+---------+----------
Inches. | Inch. | Inches. | Lbs. | Tons. | Lbs. | Tons.
1-1/4 | .083 | 1.084 | 7700 | 22.4 | 6500 | 21.7
1-3/8 | .083 | 1.209 | 6900 | 22.4 | 5800 | 21.3
1-1/2 | .083 | 1.334 | 6200 | 22.4 | 5200 | 21.0
1-3/4 | .083 | 1.584 | 5300 | 22.4 | 4300 | 20.3
2 | .083 | 1.834 | 4500 | 22.4 | 3700 | 19.7
2-1/4 | .095 | 2.060 | 4600 | 22.4 | 3600 | 19.0
2-1/2 | .109 | 2.282 | 4800 | 22.4 | 3600 | 18.3
2-3/4 | .109 | 2.532 | 4400 | 22.4 | 3100 | 17.7
3 | .120 | 2.760 | 4300 | 22.4 | 3000 | 17.0
3-1/2 | .134 | 3.232 | 4200 | 22.4 | 2700 | 15.7
3-3/4 | .134 | 3.482 | 3900 | 22.4 | 2400 | 15.0
4 | .134 | 3.732 | 3600 | 22.4 | 2100 | 14.3
4-1/2 | .134 | 4.232 | 3200 | 22.4 | 1700 | 13.0
4-3/4 | .134 | 4.482 | 3000 | 22.4 | 1600 | 12.3
5 | .134 | 4.732 | 2800 | 22.4 | 1400 | 11.7
5-1/2 | .148 | 5.204 | 2800 | 22.4 | 1200 | 10.3
6 | | 5.704 | 2600 | 22.4 | 1000 | 9.0
---------+----------+---------+--------+---------+---------+----------

VENTILATION.

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 Burnt | Speed of | Total Air |Air Exhausted |Temperature at |
| per Hour. |Current per| Exhausted |per Cubic foot| outlet. Normal|
| | Minute. | per Hour. | of Gas Burnt.| 62° Fahr. |
+-----------+-----------+-----------+--------------+---------------+
|Cubic Feet.| Feet. |Cubic Feet.| Cubic Feet. | |
| 1 | 205 | 2,460 | 2,460 | 82° |
| 2 | 245 | 2,940 | 1,470 | 92° |
| 4 | 325 | 3,900 | 975 | 110° |
| 8 | 415 | 4,980 | 622 | 137° |
+-----------+-----------+-----------+--------------+---------------+

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.

HEATING BY EXHAUST STEAM.

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. 144 is 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 pipes from the radiators; “8” is the pressure regulating valve from the boilers. Fig. 144 may 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.

CARE OF STEAM FITTINGS.

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.

+------+-------+--------+-------+---------+-------+-------+----------+
| | | | | | | | 1/4 and |
| | | | | | | | 3/8 in. |
+------+-------+--------+-------+---------+-------+-------+----------+
| | | | | | | | 1/2 in. |
+------+-------+--------+-------+---------+-------+-------+----------+
| | | | | | | | 1 in. |
+------+-------+--------+-------+---------+-------+-------+----------+
| | | | | | | |1-1/4 in. |
+------+-------+--------+-------+---------+-------+-------+----------+
| | | | | | | |1-1/2 in. |
+------+-------+--------+-------+---------+-------+-------+----------+
| | | | | | R’s | | 2 in. |
|Elbows| Tees. |Nipples.| Plugs.|Reducers.| and |Unions |couplings.|
| | | | | | L’s. | | |
+------+-------+--------+-------+---------+-------+-------+----------+
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 that row 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.

TOOLS USED IN STEAM FITTING.

Fig. 146 represents 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 pipe 1/8th 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. 149 represents a steam fitter’s vise which will “take” say, 2-1/2-inch pipe down to 1/8th. Fig. 150 shows 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. 151 shows a pair of gas-pliers which are used by steam fitters in gas-pipe jobs. Fig. 152 exhibits 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.

COCKS.

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.

VALVES.

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 in Fig. 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 Valve_ is 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 placed _so 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 Valve_ is 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 Valves_ constitute 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-bracket_ is a bracket fitted with a valve.

_The Valve-chamber_ is 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-coupling_ is a pipe coupling containing a valve.

_Valve-seat_ is the surface upon which a valve rests.

_Back pressure valves_ are 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-valve_ is one which forms part of an angle, see Fig. 137.

_The double-seat valve_ or double-beat valve presents two outlets for the water. In the Cornish steam engine this is called the _equilibrium-valve_, because the pressure on the two is very nearly equalized.

_Three-way cock_ is one having three positions directing the fluid in either of three directions. This is illustrated in Fig. 138. The _three-way valve_ is also illustrated on page 259, Fig. 136.

_Four-way cock_ is one having two separate passages in the plug and communicating with four pipes.

_Gate-valve_—a valve closed by a gate. This is illustrated in Fig. 140.

_Swing or straight-way valve_—this is shown in Fig. 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 valves_ are 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 valves_ are 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 1-1/4 inch in diameter, are wholly of gun-metal; the larger are commonly made with cast-iron bodies and gun-metal fittings. The smallest valves, from 1/4 up to 1/2 inch inclusive, have the disk solid with the spindle, and have an ordinary stuffing-box with external gland. Valves of 3/4 inch 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.

STEAM FITTINGS.

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 an _elbow_ with outlet. This is sometimes spelled with the capital L, and again as an ell.

Fig. 124 shows a long _nipple_.

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

Fig. 126 is a _cross tee_. This is frequently spelled with a capital T.

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

Fig. 128, page 254, illustrates a _lock nut_.

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

Fig. 130 is a _coupling_.

Fig. 131, page 255, represents a _reducing coupling_.

Fig. 132 is an illustration of a pipe _union_.

Fig. 133 is a plain _elbow_ (see also Fig. 123.)

STEAM PIPE AND BOILER COVERINGS.

This subject relates to the _radiation of heat_, which allows a reference to the laws of heat and tables of radiating power of various substances, as set forth on pages 212, 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 the_ CONDUCTING POWER _of various substances_.

By the above table may be judged the comparative value of different coverings; blotting paper with _its confined air_, standing at one end of the list, stone at the other. It should be noted that _the 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 to secure adhesion for the first coat, which is about l/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., shows _the value_ of various substances, taking wool felt as a _unit_.

TABLE OF RELATIVE VALUE OF NON-CONDUCTORS.

LINEAR EXPANSION OF STEAM PIPES.

Wrought iron is said to expand 1/150,000 of 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; divide this 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.

Figs. 153 and 154 show a properly designed arrangement of steam connections for a battery of boilers. To the nozzles, risers are attached by means of flanges, and from the upper ends of these risers pipes are led horizontally backwards into the main steam pipe. In this horizontal pipe, the stop valves, one to each boiler, are placed. These valves should have flanged ends as shown, so that they may be easily removed, if repairs become necessary, without disturbing any other portion of the piping. Unlike the engraving, the valve C should be arranged in another position: the stem should, of course, be horizontal or nearly so, in order that the valve may not trap water.

By this arrangement it will be seen that the movements of the boilers and the piping itself are compensated for by the spring of the pipes. The height of the risers should never be less than three feet, and when there are eight or ten boilers in one battery, they should be, if room permits, six to eight feet high, and the horizontal pipes leading to main steam pipe should be ten or twelve feet or more.

THE STEAM LOOP.

This is an attachment to a steam boiler, designed to return water of condensation. It invariably consists of three parts, viz.: the “riser,” the “horizontal” and the “drop leg,” and usually of pipes varying in size from three-fourth inch to two inches. Each part has its special and well-defined duties to perform, and their proportions and immediate relations decide and make up the capacity and strength of the system. It is, in fact, nothing but a simple return pipe leading from the source of condensation to the boiler, and, beyond this mere statement, it is hardly possible to explain it; it has, like the injector and the pulsometer pump, been called a paradox.

Previous Next

Comments

Maxims and Instructions for the Boiler RoomChapter X: Section 24: “Lever safety valves to be attached to marine boilers shall (3)

0%36 min left in chapter