Improvements in the Manufacture of Metal Pipes.
Year: 1889

page_text: [Communicated from abroad by JAMES COPPER BAYLES, of East Orange, New Jersey,
United States of America, Mechanical Engineer.]
Improvements in the Manufacture of Metal Pipes.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co., Patent Agents,
Southampton Buildings, in the county of Middlesex do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention relates to composite metallic pipes which consist of an external shell
of cast iron and an adhering internal shell of comparatively thin sheet steel or wrought
iron. The adherence of the cast iron to the sheet steel or wrought iron is effected by
first forming the sheet steel or wrought iron into a tube, then introducing such tube
into a pipe mould and filling it with sand and employing it as a core around which the
external shell is cast.
The internal shell may be made like ordinary stove pipe in short sections having
their longitudinal joints either rivetted or seamed and having sufficient longitudinal
taper to permit the insertion for a short distance of the smaller end of one section
into the larger end of the next adjoining section, but it is preferred to make the
interior shell from a ribbon of steel or wrought iron wound spirally with overlapping
edges.
The cast iron shell may be re-inforced by a steel collar in the mould, or by being
made thicker at any place where it is desired to have a screw thread cut upon its
exterior surface, and it may be enlarged in diameter and flared at the end to form
the usual hub for the pipe.
By thus encasing a tube or pipe of steel or wrought iron of light gauge in a shell of
cast iron the inside retains the strength and impermeability of steel or wrought iron,
while the outside is given the ability of resisting destructive oxidation which is
possessed in a peculiarly high degree by cast iron.
In the accompanying drawing,
Figure 1 is an elevation of a sheet steel or wrought iron tube made like an ordinary
stove pipe in short sections with slip joints.
Figure 2 is an elevation showing the manner of constructing the internal tube from
a ribbon of steel wound spirally with overlapping edges.
Figure 3 is a central longitudinal section of an ordinary pipe mould showing the
steel tube filled with sand and used as a core barrel around which the cast iron shell.is
cast.
Figure 4 is a central longitudinal section of a portion of a pipe mould and the
adjoining portion of the steel covered core barrel showing a recess formed in the wall
of the mould to provide for a greater thickness of the casting at that point, or to provide
room for the reception of the re-enforcing collar of malleable metal which in the sub-
sequent operation of casting thus becomes attached to the part of the pipe requiring
to be provided with an exterior screw thread.
The essential characteristics of the improved composite pipes illustrated in the
drawing are the interior tube, A, made of comparatively thin sheet steel or wrought
iron, and the exterior cast iron shell, B, adhering to the outside of the interior tube, A.
The exterior shell may if desired be provided at either end with a laterally enlarged
and flanged extension or hub, b, or may be otherwise so formed as to adapt
it for employment in connection with either of the common methods of coupling pipe
sections to each other.
If desired the place where an external screw thread is to be cut on the cast iron
shell, B, may be reinforced by the steel or wrought iron collar, C, which can be
effectively fastened to the cast iron shell by depositing it in a suitable recess, C,
formed in the pipe mould, D, preparatory to the casting of the shell after the

page_text: introduction into the mould of the core barrel composed of the sheet steel or wrought
irou tube, A, filled-interiorly with sand.
If the composite pipe is to be provided with a hub the mould is provided with the
usual annular recess, D³, at the top and the hub-core, 61, prepared in the ordinary way
from straw rope and loau, is placed upon the upper end of the core barrel, as shown
in Figure 3.
The operation of casting is performed in the usual manner by pouring the molten
iron into the mould and thereby filling the space in the mould outside the core barrel.
In the construction of the inner tube for the purposes of this invention thin sheet
steel and wrought iron may be regarded as equivalent but steel is preferred and,
preferably, the interior tube is made of a ribbon, a, of steel wound spirally with over-
lapping edges, a¹, as illustrated in Figure 2.
This winding may be done cold; there is no need of uniting the overlapping edges
by welding, riveting brazing or other means, the contact of the edges being
sufficient for the purposes of the invention whether the overlapping edges are or are
not fastened together.
The steel tube filled with sand becomes the core around which the cast iron is
poured. The objects of filling it with sand, rammed to the degree of hardness which
may be necessary in the judgment of the founder, are to sustain the steel shell and
prevent its collapsing when the hot iron is poured around it, and also to enable it to
be brought nearly to the temperature of the melted metal. The tube of steel filled
with sand thus becomes the core barrel around which the pipe is cast and obviates the
necessity for any other core barrel, except when the pipe is to be provided with a
hub, b, as has been explained.
When the molten iron is poured into the mould it fills any seam which it can
penetrate in the shell and closely adheres to the surface of the steel core.
When the metal has cooled sufficiently the sand is removed and the resulting
composite pipe is prepared for market in the usual way.
It will of course be understood that the outside of the steel shell may be coated
with a flux if desired, but it will usually be found that the cast iron shell adheres to
the steel sufficiently without the use of the flux.
The composite pipe thus made is very much stronger than the same sized pipe made
of cast iron alone, and may be made very much lighter. The construction insures
absolute tightness which in a light cast iron pipe is frequently prevented by the
presence of blow holes, sand holes or other defects in the casting.
The density and imperviousness of the steel is not in any way impaired, nor is its
high tensile strength reduced by its contact with melted iron in the mould."
With a core of steel 035", "049" or '065" thick (Nos. 20, 18 or 16 B.W.G.) and
external shells as light as can be run-from " to " thick-it is possible to secure
strengths greater than are usual in heavy cast iron pipes. The saving in weight of
material is from 50 to 75% more or less according to diameter cast and the strength
desired. Slight defects in the casting, which would render a cast iron pipe incapable
of withstanding pressure are of no consequence in the composite pipe described, for
the reason that such defects are usually the result of bubbles in the iron formed by
steam or gases, suddenly generated and finding no means of escape, and these never
occur in practice opposite a seam in the inner steel shell, because any steam or gases
generated at that point escape through the seam and into the sand filling of the core,
and are immediately followed by the iron which seals the seam tightly in cooling.
The protecting value of the cast iron casing is not impaired by any ordinary
imperfections in the casting because such imperfections can be filled with asphaltum
or other plastic substances which resist decomposition in the ground.
The composite pipe described has great value for uses involving considerable
pressures. Cast iron as is well known is a brittle material, and the grades of pig
iron which are especially suitable for pipe making because of their fluidity when
mélted are, as a rule especially brittle. Cast iron pipes are also unsuitable for use as
conduits for fluids or gases under high pressure, for the reason that cast iron even if
free from defects, is to a greater or less degree porous.

page_text: Hence cast iron pipes are not usually considered suitable conduits for natural gas,
and are not employed for the conveyance of compressed air or steam or of water
under a greater pressure than 150 lbs. per square inch, to carry which pressure with
safety they need be made excessively heavy.
In the present invention no dependence for strength is placed upon the cast iron.
The value of the pipe as a conduit lies chiefly in the steel shell. For illustration:
A shell of soft steel 20" in diameter, made of metal 049" thick (No. 18 B.W.G.)
has an ultimate strength of 319 lbs. per square inch.
Re-enforced with the lightest shell of iron which can cast around it, say " thick,
such a pipe will be safe and tight under a working pressure of 250 lbs. per square
inch. It will weigh 61.78 lbs. per lineal foot. A 20" cast iron pipe, as now made to
safely carry a pressure of 150 lbs., would need to be not less than 1" thick, and would
weigh, if of that thickness, about 206 lbs. per lineal foot.
The spirally wound shell of steel is preferred to any other form for the reason that
it gives the greatest strength with the least weight. The effect of internal pressure is
not to open the spiral seam, but to close it. The spiral cannot expand unless the edges
can slip, which is impossible when they are held in place by a casing of cast iron, and
as no form of internal pressure, circumferentially exerted, has any tendency to separate
the edges, as in the case of a longitudinal seam, a spirally wound core will be found to
possess a strength equal to the ultimate strength of the metal. This form of pipe is
safe under pressure, even when tested to rupture. It will not fly apart like bursted
cast iron, but will tear slowly and only so far as is needed to relieve the strain upon
it. Owing to superior lightness as well as strength, it can be manufactured, trans-
ported, handled and laid very much more cheaply than correspondingly strong cast iron
pipes.
The external collar, C, of soft steel affords a body of malleable metal into which to
cut threads for a screw joint, and hence may be applied when it is desired to adapt the
composite pipes for the use of the screw couplings employed in connecting wrought
iron pipes. If the thread is deeper than the thickness of the steel collar, it will still
make a good screw joint. The cast iron will furnish the broad base of the pyramidal
thread, and the steel the more slender apex for which cast iron would be too brittle.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent I declare that what I claim
First. The composite metal pipe herein described which consists of a tube composed
of comparatively thin sheet steel or wrought iron exteriorly encased by an adherent
shell of iron cast thereon.
Second. In a composite metal pipe the combination as herein set forth of a tube
composed of a ribbon of steel or wrought iron wound spirally with overlapping edges,
and an iron shell cast upon the exterior of the said tube.
Third. A composite metal pipe consisting of a tube composed of comparatively thin
sheet steel or wrought iron contained within and adhering to the interior of the barrel
of a cast iron pipe cast upon it and provided at one end with a laterally enlarged
extension to serve as a hub.
Fourth. A composite metal pipe consisting of a cast iron cylindrical shell re-enforced
by an adherent exterior collar of malleable metal provided with a screw thread, and
an interior lining composed of comparatively thin sheet steel or wrought iron.
Firth. The improvement in the art of manufacturing composite metal pipes herein
described which consist in casting in a suitable mould, a cast iron pipe around the
exterior of a sheet steel or wrought iron tube filled with sand and supported within
said mould.
ated this 31st day of December 1889.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.