_A pipe_ was originally a wind instrument of music, consisting of a
_tube or tubes_ of straw, reed, wood or metal; in the literature of
hydraulics this wind instrument becomes “_a long tube or hollow body
of wood, metal, earthenware, or the like_; especially, one used as a
conductor of water, steam, gas, etc.”
_A pipe fitter_ is one who fits pipes together, or applies pipes, as to
an engine or pump. A pipe fitter uses all the tools already described
and in addition several others, as stretched lines, the spirit level
and plumb-bob; he also uses special devices to aid in special cases;
these are sometimes invented by himself and sometimes belong to “the
trade-lore” transmitted in the long and varied operations of every
successful shop. _A pipe fitting_ is a piece, as a coupling, a valve,
etc., used for connecting lengths of pipe or as accessory to a pipe.
_Joint_ comes from the word join and means the place or part where two
things or parts are joined or united as a joint in a pipe. See note
below.
Narrow surfaces make better and safer joints than wide ones; they are
more quickly repaired with file or scraper, and they are less liable to
catch dirt at the moment of making a joint. The limit of narrowness is
that required to resist strains that might crush the metal and spoil
the face of the joint.
Unless the joint is made metal to metal, fitting without any orifice,
the jointing material is always softer than the pipes or other things
to be joined. In this way the jointing need not have dead-true
surfaces, but, yielding under pressure, it adapts itself to the space
it has to fill. It must be dense enough and hard enough to resist all
the working strains and influences that are likely to act upon it. The
jointing of a steam pipe must resist the temperature of the steam, the
water it carries with it, the changes of temperature when the pipe
cools during intervals of work, and the strains due to the weight of
the pipe, and also the internal pressure of the steam. If it expands
differently from the metal in the pipe, it must be sufficiently elastic
to compensate for this expansion, otherwise it will leak each time the
pipes cool down.
NOTE.—In proportion as steam pressure gets higher joints are made
thinner and flanges smoother. In the past rough turning succeeded
chipping, rough filing followed with an application of the surface
plate, and finally the scraper was used to produce a dead-true
surface, which is now only cleaned and wet with heavy mineral oil to
withstand any pressure whatsoever.
[Illustration: FIG. 643.]
[Illustration: FIG. 644.]
[Illustration: FIG. 645.]
The joint should be always inside the line of bolts, and if any joint
material extends beyond, it would only help to support the flange in
case it should spring. This, of course, indicates faulty design, for
flanges ought to bear the strains of jointing without perceptible
spring. Male and female flanges are best for high pressures.
A very popular joint is made with a planed or turned surface and a
sheet of paper of the quality used to wrap bales of paper. This is
the last survival of the millboard. Rubbed over the flange with a
dirty hand and cut out with a penknife on a board, this is one of the
cheapest jointings known. This paper has no lumps or grit in it, and
if smeared with mineral cylinder oil it may be separated several times
before it is spoiled. It is largely used on the faced joints of small
engines and steam pumps. The mineral oil increases the life of the
paper when exposed to high steam. Sheet asbestos is better.
_Hydraulic joints for high pressure_ require greater rigidity than
those of steam, but they do not have to bear high temperatures. The
jointing material may be more or less plastic, such as leather, rubber
or gutta percha. It is generally inclosed in a groove in the flange,
and compressed by a projection fitting the groove, so that expansion
of the jointing is arrested and the space is completely filled. There
is no better principle for joints than this where packing is used
between flanges. At a pressure of three tons to the inch, every square
sixteenth of an inch must resist a power equal to twenty-six pounds;
the joint must therefore be non-porous.
[Illustration: FIG. 646.]
[Illustration: FIG. 647.]
[Illustration: FIG. 648.]
[Illustration: FIG. 649.]
[Illustration: FIG. 650.]
[Illustration: FIG. 651.]
[Illustration: FIG. 652.]
_There are compounds used for making joints_ on which the plastic
matter, which is subject to much change of volume between the liquid
and solid state, is mixed with a neutral substance, like sand, which,
combining mechanically with it, replaces from 90 to 95 per cent. of the
total mass, and reduces its shrinkage to an inappreciable quantity.
[Illustration: FIG. 653.]
Another class of joints is that into which the jointing material is
poured in a liquid state. Most of those liquids, such as lead, pitch,
putty, sealing-wax, beeswax, or clay, shrink when they dry or cool.
Others, like _Portland cement_ and certain metallic alloys, do not
change in volume. Others, again, like sulphur and plaster of Paris,
increase in volume in setting. These substances all vary in their
elasticity, qualities of density, hardness, and powers of resisting
heat, cold and moisture. The duty of a joint must, therefore, be well
considered before the material is chosen, after which the recess in
which it is to lie must be carefully designed so as to firmly hold the
material and with the least possible waste.
[Illustration: FIG. 654.]
_Kerosene_, from its solvent powers, will destroy joints of rubber
or of cements compounded with oils. Kerosene tanks are, therefore,
rust-jointed and calked. As kerosene does not dissolve anything that
is soluble in water or alcohol, kerosene casks are coated with glue
to make them tight. India rubber may be used as a kerosene joint if
inclosed like the hydraulic joint, and prevented from swelling. It is
then unable to absorb the liquid. But leather is very much better.
_In making up a piece of piping_ in which several fittings are quite
close together, each fitting is tightened separately; do not follow
the common practice of making up loosely at first and then tightening
all together by applying a wrench to the fitting farthest from the
main connection, as this process does not insure tight joints and the
intermediate fittings, nipples, etc., are subjected to an unnecessary
torsional strain.
The proper arrangement of pipe connections have already been alluded to
in Part One, page 222; it is a subject whose importance can scarcely be
magnified for if any difficulty is experienced in making a pump work
properly when first started, it will generally be found to proceed from
imperfect connections, and this remains true quite to the end of the
usefulness of the pump. By a careful study of the illustration above
mentioned, a good degree of attention will be repaid.
Figs. 641 and 642 represent pipes which are specially intended for
_mine pump columns_ or discharge pipes. They are made in sizes from six
inches to thirty inches outside diameter; they are of wrought iron,
lap welded and tested to a pressure of five hundred pounds to the
square inch; they are fitted with cast iron or steel flanges, bolts and
gaskets which face square with the center line of the pipe.
These flanges are shrunk on the pipe as shown in the figures, expanded
and flared inside.
Fig. 643 represents a male and female flange joint metal to metal
combined with and forming a part of the pipe; it is used for special
work and conditions. Fig. 644 is the usual screwed sleeve threaded
connection with right hand coupling. Fig. 645 is a much used male and
female _flange union_ screwed for the reception of standard wrought
iron pipe. Fig. 646 illustrates the common threaded malleable iron
union and Fig. 647 the plain light _malleable iron tee_.
NOTE.—Attention of the reader is directed to that part of the
Glossary in the opening pages of Part One which relates to pipe and
fittings as being closely related to this division of the work and
which may be considered as an introduction to what is now added.
[Illustration: FIG. 655.]
[Illustration: FIG. 656.]
[Illustration: FIG. 657.]
_Steam Pipe Lines._ These are constructed of cast iron or wrought iron
and used for conveying a supply of steam from the boilers to engines,
pumps, turbines and other machines driven by steam. Usually these lines
are built up with straight pipe and “fittings.” The names of the latter
are as follows: elbows; forty-fives (45°); tees; plugs; caps; reducers
(or bushings); nipples; valves; unions (with ground, perishable, and
flange joints); couplings (reducing and right and left); crosses;
special fittings, such as elbows and tees of a nominal size reduced
at some point to a smaller size to avoid the use of reducers; angle,
check, and gate valves, and plug cocks; lock-nuts.
NOTE.—Cast iron was formerly entirely employed for steam pipe, but
now it is never used for high pressures.
While lead and iron pipe have taken the place of the old log pipes
of former days for carrying water and sundry purposes, there are
still uses for which wooden pipe is better adapted than any of the
metal pipes; a new kind of wire wound wooden pipe has been made. Each
length is built up of staves, wound with galvanized steel wire under
tension. The sizes are made 2 to 8 inches internal diameter. The
staves are kiln-dried, 7/8 inch to 1-1/2 inch thick. Joints are made
with a male and female socket on the small sizes, and a sleeve and
butt joint on the larger sizes, 8-inch pipe of this type, wound with
No. 4 copper wire, has been tried, where acid water rapidly destroys
ordinary pipes, with excellent results. This pipe has been tested to
500 pounds pressure, it is lighter to handle and is not so liable to
burst as cast iron.
_The proper anchoring and supporting of large steam mains is
important._ It is preferable to allow the system to expand in the
proper direction without stress and at the same time avoiding
vibration. The illustrations will give an idea of the method used in
supporting pipes and allowing for expansion. Fig. 657 shows a wall
bracket upon which the rollers supporting the pipe and allowing for the
expansion and contraction are attached. Fig. 655 shows a bracket with
an adjustable single roll, which may be adjusted to suit the pitch of
the pipe at the same time allow the pipe to expand.
_Fig. 655 shows a bracket_ with one adjustable roll designed for main
steam pipes. This is an elaborate device but would be appreciated in
buildings where everything is wanted to make up a strictly first class
line of details.
Fig. 657 represents an extension of the same idea in which one bracket
is made to carry two lines of pipe smaller than the one shown in the
preceding illustration. Fig. 656 is a support made of one inch round
iron and answers every purpose where all of these designs of pipe
hangers permit of free expansion and contraction of the pipes.
It is bad practice to support the main steam pipes over boilers by
hangers from the building as the building may settle in a different
degree from the boiler hence the steam pipes are not properly
supported, _i.e._, they are either strained unnecessarily by the strain
upon the hangers or they are permitted to support themselves; it is
better to support them by iron props underneath, made by screwing a
flange upon the end of a piece of pipe of proper length and having a
wrought iron crotch with thread and nut for adjustment inserted in the
upper end.
The flange on the prop rests upon the boiler walls while the crotch
fits the pipe and by means of the nut any desirable elevation of the
steam pipe may be secured. For when the boilers settle as they will the
pipes and connections all settle together.
[Illustration: FIGS. 658-666.]
Fig. 648 shows the common wrought iron _right-hand sleeve coupling_ and
Fig. 649 a plain lock nut.
Fig. 650 shows _the bell and spigot connection_ commonly used for
joining cast iron water or soil pipes, the joint being formed by
pouring melted lead into the cavity inside the bell. The melted lead is
prevented from escaping by damming up the opening with a turn of oakum
at the bottom and fire clay at the top of the joint. After the lead
cools it is calked with a calking tool. Fig. 651 is similar to Fig. 643
only the latter has plain flanges with a gasket, A, B, inserted.
Fig. 652 represents an improvement on the union shown in Fig. 646.
It is known as _the Dart-union_. The improvement consists in the
substitution of a ball and socket joint made of composition brass or
bronze ground joint and enclosed within the malleable iron case; unions
are particularly desirable for inaccessible locations where it would be
next to impossible to reach the union to renew the gasket.
Fig. 653 is an extra heavy _beaded malleable iron tee_, while Fig. 654
shows a common threaded _cast iron pipe plug_.
The figures on page 366 are one half end views, divided on the center
line, of brass and iron tubing; they are reduced in size, but show
their relative thickness, from one eighth inch up to four inches
inclusive.
The “_Standard_” sizes are shown in Figs. 663 and 664.
The “_extra strong_” are represented in Figs. 658, 661 and 662.
The _double extra strong_ is shown in Figs. 659, 660, 665 and 666.
All “tubing,” including boiler tubes, is measured by the _outside
diameters_, while gas and steam pipe, including cast iron water pipe is
designated by the inside diameter.
NOTE.—The best way of jointing hydraulic pipes has been the
subject of much practical experiment. A gutta percha ring has been
universally adopted as the best means of preserving the joint
watertight. Modified form of this joint is made by casting a
projection on the pipe beyond the flange, the bell and spigot being
formed on this projection. The effect is to increase the depth and
the strength of the flange, without an increase of its section at the
junction between the flange and the pipe.
Much might be said regarding duplicate pipe systems, both for and
against. The general practice is coming to be that of subdividing
into units, while in smaller plants the duplicate system is used. The
service and conditions govern the method of piping, which should be
such in every instance as to prevent a shut down due to accident in
some part of the system.
All the fittings in the pipe system of a plant should be of the best
quality, and the piping for high pressures should be extra heavy to
withstand the test of time and usage. Water pipes, when of commercial
wrought iron, should be galvanized.
In laying out a line of piping or in replacing a portion of an existing
line _the measurements should be taken from center to center_ of the
various fittings; the allowance for the threaded part of the pipe can
be made after the center-to-center and over-all measurements have been
made and before the pipe is cut. Experience teaches what to allow
for the threaded part on different sizes of pipe. The accompanying
engraving gives an illustration of how the measurements on a pipe
system are made.
[Illustration: Pipe System Measurements.]
As, for example, A represents the distance, center-to-center, from
elbow to tee; B, from the starting place to center of elbow; C, the
distance, center-to-center, of the two elbows; D, from the starting
place to the center of the globe valve; E, the center of the globe
valve to the center of the tee, and F, from the center of the tee to
the center of the elbow.
G shows the center of the elbow to the center of the union; H, from
the center of the union to the center of the tee, and I, from the
center of the tee to the center of the elbow; J, from the center of
the elbow to the center of the coupling, and K, from the center of
the coupling to the final tee; all as indicated by the arrow heads
and crosses.