Improvements in Means for Superheating Steam
Year: 1893

page_text: Date of Application, 28th Oct., 1893
Complete Specification Left, 28th July, 1894-Accepted, 15 h Sept., 1894
PROVISIONAL SPECIFICATION.
Improvements in Means for Superheating Steam.
JAMES MUSGRAVE Engineer and Cotton Spinner Atlas Mills and GEORGE
DIXON Engineer Globe Iron Works both of Bolton in the County of Lancashire
do hereby declare the nature of this invention to be as follows:-
Our invention enables us to produce dry or superheated steam, for use in steam
engines, or for general purposes, with minimum variations in temperature, & we so
construct the superheating apparatus, as to be readily accessible for inspection, or
repair.
We superheat a portion only of the steam produced in the boiler, & inject this
portion into the main body of the steam, on or after it leaves the boiler. Suitable
valves are provided for controlling, & regulating, the proportion of superheated,
to saturated steam, so as to produce as uniform a temperature as possible. These
valves may either be operated by hand, or automatically, through the medium of
the expansion or contraction of metal rods, or tubes, under changes of temperature,
& placed either in the main, or superheated steam pipe, or both.
The expansion & contraction of mercury, may also be employed to effect the same
purpose.
The superheated steam, may be more thoroughly mixed with the saturated steam,
by being conveyed through perforated pipes, projected into the main steam pipe,
leading from the boiler, or injector nozzles may be employed, both for this purpose,
& also to induce the flow of the superheated steam, through the superheating
apparatus.
We construct our superheater, of tubes of small diameter bent in the form of
a U, with large radius, for ease in bending. The ends are brought as near together
as possible, & are secured by any suitable means, into a single tube plate, or box,
provided with a division, to separate the ends of the tubes. The steam enters on
one side of the division, & after traversing the tubes, is discharged upon the other
side.
When used in connection with Cornish, or Lancashire, or similar boilers, we
prefer to place the superheater directly behind the boiler, so that the hot gases
issuing from the flues, may impinge upon the tubes of the superheater. The tube
plate, or box, would be so situated above the flue, as to be readily accessible.
When applied to the ordinary type of marine boiler, we prefer to place the
superheater in the uptake, the tubes being so placed, as to allow the gases issuing
from the boiler tubes, to impinge upon them.
In locomotive, or boilers of similar type, we place the superheater in the smoke
box.
In order not to obstruct the cleaning of the boiler tubes, in locomotive, marine,
or similar boilers, we construct the tube plate, or box, with a hinge, so that the
superheater can be turned aside, leaving the front of the boiler tubes clear.

page_text: Where necessary, we protect the tubes of the superheater from direct impinge-
ment of the hot gases, by screens of brick. Dampers may be employed, operated
by hand, or automatically, so as to direct the whole, or only a portion of the hot
gases, around the superheater.
Dated this 27th day of October 1893.
Improvements in Means for Superheating Steam.
We, JAMES MUSGRAVE, Engineer and Cotton Spinner, of The Atlas Mills,
and GEORGE DIXON, Engineer, of The Globe Iron Works, both at Bolton, in the
County of Lancashire, 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:-
Our invention is designed to enable dry or superheated steam for use in steam
engines or for general purposes to be produced with minimum variations in
temperature, and to so construct the superheating apparatus, as to render it readily
accessible for inspection or repair.
We superheat a portion only of the steam produced in the boiler, and inject this
portion into the main body of the steam, as or after it leaves the boiler. For this
purpose suitable valves are provided for controlling and regulating the proportion
of superheated to saturated steam, so as to produce as uniform a temperature as
possible. These valves may either be operated by hand, or automatically through
the medium of the expansion or contraction of metal rods, or tubes, under changes
of temperature, and placed either in the main or in the superheated steam pipe, or
both. The expansion and contraction of mercury may also be employed to effect
the same purpose.
The superheated steam may be more thoroughly mixed with the saturated steam,
by being conveyed through perforated pipes projecting into the main steam pipe
leading from the boiler; or injector nozzles may be employed, both for this purpose,
and also to induce the flow of the superheated steam through the superheating
apparatus.
We construct our superbeater of tubes of small diameter bent in the form of
a U, with large radius, for ease in bending. The ends are brought as near
together as possible, and are secured by any suitable means, into a single tube plate
or box provided with a division, to separate the ends of the tubes. The steam
enters on one side of the division, and after traversing the tubes, is discharged at
the other side.
When used in connection with Cornish or Lancashire or similar boilers, we prefer
to place the superheater directly behind the boiler, so that the hot gases issuing
from the flues may impinge upon the tubes of the superheater. The tube plate,
or box, would be so situated above the flue, as to be readily accessible. When
applied to the ordinary type of marine boiler, we prefer to place the superheater
in the uptake, the tubes being so placed, as to allow the gases issuing from the
boiler tubes to impinge upon them.
In locomotive, or boilers of similar type, we place the superheater in the smoke
box.
In order not to obstruct the cleaning of the boiler tubes, in locomotive, marine,
or similar boilers, we construct the tube plate, or box, with a hinge, so that the
superheater can be turned aside, leaving the front of the boiler tubes clear.
Where necessary, we protect the tubes of the superheater from direct impact of
the hot gases, by screens of brick. Dampers may be employed, operated by hand,

page_text: or automatically, so as to direct the whole, or only a portion, of the hot gases
around the superheater.
In the accompanying drawings,
Fig. 1 shows partly in longitudinal section and partly in side elevation, a portion
of a Lancashire boiler and its setting with superheating apparatus according to this
invention applied thereto.
Fig. 2 is a sectional end elevation, showing two boilers with combined super-
heating apparatus, the section being taken through the flues at the rear ends of the
boilers.
Figs. 3, 4, and 5 are respectively a side elevation partly in section, a plan
and an end elevation, showing, to a larger scale than Figs. 1 and 2, a steam super-
heater constructed according to this invention.
Figs. 6 and 7 are cross sections on the lines y y and x x respectively of Fig. 3.
From each boiler 1 extends a vertical steam pipe 2 provided with a regulating
valve 3 and connected by a pipe 4 to a main steam pipe 5 that may be common,
as shown, to several boilers. From the steam pipe 2 on the boiler side of the
valve 3, extends a second pipe 6 provided with a valve 7 and connected with the
inlet 8 of a superheater 9-10 the outlet 11 of which is connected to a pipo 12 that
is provided with a valve 13 and is connected to a perforated pipe 14 projecting into
the main steam pipe 5. The two pipes 12 may, when used with a single main steam
pipe 5, be united as shown. The pipe 14 may be formed with numerous small
perforations throughout its length or nearly so, or with a less number of long slots
at its front end as shown to a larger scale at 14 in Fig. 8. Or its front end portion
may, as shown in Fig. 9, be fitted with a flaring extension 14* formed with curved
openings 14 through which the saturated steam will pass and mix with the super-
heated steam flowing through the pipe 14. Or the forward end of the pipe 14
may, as shown in Fig. 10, be provided with conical nozzles 14° through and between
which saturated steam will pass so as to induce a flow of steam through the
superheating apparatus and become thoroughly mixed with the issuing super-
heated steam. The steam may, if desired, be supplied from the boiler to the
superheater through a pipe 6 and valve 7 independent of the pipe 2, as shown in
dotted lines in Fig. 1.
The superheaters proper are each suspended with their tubes 9 within the
flue 13 at a point directly behind the rear ends of the furnace flues 1ª so that
such tubes will be more or less in the path of the issuing flame and hot gases,
the action of which on the said tubes can be controlled to some extent by a suitably
arranged damper 13ª (Fig. 1). Each superheater comprises, as shown in Figs. 3
to 7 inclusive, a number of tubes 9 bent approximately to a U-shape but with
a bend of large radius and ends brought near together and secured, it may be by
nuts as shown, to the detachable bottom plato 10% of a box 10. This box is
provided internally with a vertical division 15 that serves to divide its interior
into two compartments one of which, viz. 15", is in communication with the inlet 8
and one end of each of the tubes 9, whilst the other compartment, viz. 15b is in
communication with the other end of each tube and with the outlet 11. 15° is a
horizontal division arranged in the compartment 15ª below the steam inlet 8 for
the purpose of distributing the steam supply as uniformly as possible to all the
tubes 10. When in use the box 10 is supported by a plate or frame 16 arranged
at the top of the rear end of the flue 13 and through a hole in which the super-
heating tubes 9 project downward as shown. The edge of this plate or frame
is preferably formed as a channel as seen in cross section in Figs. 3 and 5, so as
to enable it to receive and hold jointing material such as fire clay whereby cold
air is readily prevented from entering the flue 13 at this part.
With the construction and arrangement described it will be seen that by suitably
regulating the valves 3 and 7 by hand, any desired proportion of the steam entering
the pipe
can be sent through the superheater wherein it will be superheated,
and afterwards be mixed in the main steam pipe 5 with the saturated steam
entering this pipe by the pipe 4. In this way superheated steam can be produced

page_text: at a more uniform temperature and with apparatus of much less size and cost
than would be the case if the apparatus were constructed with ordinary U-tubes
and the whole of the steam were superheated. Furthermore it will be seen that
the superheater is simple in construction and is so arranged that it is easily
accessible for inspection and repair, since it is capable of being readily and quickly
hoisted up from the flue 13, examined and cleaned, and returned to its place.
Figs. 11 and 12 are respectively a vertical section and a side elevation showing
a modified construction of vertical steam pipe 2 wherein a single butterfly valve 3*
is used instead of the two valves 3 and 7 in the herein previously described
arrangement for regulating the proportion of superheated steam to saturated
steam. The valve is mounted upon a spindle 17 and can be adjusted by a hand
wheel 18 through a worm 19 and toothed segment 20. The steam pipe 2 is
constructed with branches 2 and 2 for connection respectively with pipes
corresponding to 6 and 12 (Figs. 1 and 2) leading to and from the super-
heater 9-10. In this arrangement the superheated steam arriving by the 1
branch 2b mixes in the upper part of the pipe 2 with the saturated steam that
has passed the valve 3*, the mixture passing off by the branch 2º.
Figs. 13 and 14 show a similar construction of steam pipe with controlling
valve 3* to that shown in Figs. 11 and 12, but with the outlet and inlet
branches 2 and 2b arranged side by side instead of one over the other.
Figs. 15 and 16 are longitudinal and transverse sections respectively, showing
the application of superheating apparatus according to this invention to an
ordinary type of marine boiler. The superheater tubes 9 in this case are beut
near their junction with the box 11 so as to hang vertically in the uptake 21 of
the boiler in the path of the hot gases passing therethrough, and the superheater
box 10 is hinged at 22 to the inlet and outlet valve casings 6* 12*, so that the
superheater can, after the front door of the uptake 21 has been opened, be turned
upward about such hinge sufficiently to enable the boiler tubes 23 to be readily
cleaned. At this time the valves in the casings 6* and 12* may be closed. The
steam pipe 2 with steam regulating valve is, in this example, of the construction
shown in Figs. 13 and 14.
Fig. 17 shows in plan, a modified arrangement of hinge in which the inlet and
outlet branches 8 and 11 of the superheater are mounted to turn in stuffing
boxes 6 12 that are fitted with glands of the usual form and are connected
with the steam inlet and outlet pipes 6 and 12 respectively. The hinge may, if
desired, be dispensed with and the superheater lifted vertically until clear of the
tubes for cleaning purposes.
Figs. 18 and 19 are diagrammatic views showing the application of superheaters
according to this invention to water tube boilers of the Yarrow type. In Fig. 18
the superheater comprises a box 10 divided by a horizontal division into two
chambers with which are connected two sets of depending superheater tubes 9, 9ª
arranged at opposite sides of and within the longitudinal flue 24 which extends
along the upper part of the boiler. The boiler casing 25, which forms the outer
wall of this flue, is formed with openings, normally closed by doors, for gaining
ready access to the superheater tubes.
In Fig. 19 a separate superheater 10, such as shown in Figs. 5 to 7 inclusive, is
provided at each side of the flue 24, the superheater tubes extending through the
top of the boiler casing 25 upon which the boxes 10 rest so as to permit of ready
removal of the superheaters.
Fig. 20 is a vertical section showing a steam pipe 2 with regulating valve 3*
like that shown in Figs. 11 and 12 and main steam pipe 5 in conjunction with a
thermostat or means for automatically regulating the proportion of superheated
steam to saturated steam, so that the mixture thereof shall be of a nearly uniform
temperature. The thermostat consists of a spiral tube 26, shaped like that of a
Bourdon pressure gauge and filled with a liquid, for example mercury. This tube
is arranged in the main steam pipe 5 so as to be heated by the steam passing
therethrough and has its inner end connected to a stationary bar 27 its outer free

page_text: end being connected to the regulating valve 3* by a link 28, lever arm 29,
spindle 30 that passes steam tight through the side of the main pipe 5, lever
arm 31, link 32, and lever arm 33 which is fixed upon the valve spindle 17. By
this arrangement upon the temperature of the steam passing through the main 5
rising or falling, the mercury in the tube 26 will expand or contract thereby
opening or closing the coil 26 and thus more or less opening or closing the
valve 3*, so that a less or a greater proportion of steam respectively will be sent
through the super heater with the result that the variation in temperature of the
mixture of superheated and saturated steam passing through the main pipe 5 will
be very small. The thermostat shown is very sensitive to changes of temperature,
provides sufficient force to operate an equilibrium valve such as the one shown, and
provides a greater range of movement than could be conveniently obtained by a
thermostat consisting of straight metal rods or tubes alone. Where however a
sufficient length of steam pipe is available in a straight line, metal rods or tubes
placed inside the pipe may be used, these being fixed at one end and connected at
the other with the valve to be regulated. The rods or tubes could be perforated to
secure greater surface for the steam to act upon, or they may be provided with
vanes for a like object.
The proportion of superheated steam to saturated steam used will depend upon
circumstances. Thus if a boiler is lightly loaded, the furnace gases will be cooler
than when the boiler is fully loaded and the steam passing through the superheater
will consequently not be superheated to so high a degree, so that it will then be
necessary to superheat a greater portion of the steam. We have obtained
satisfactory results-saving about 20% in fuel consumption-when using about
equal quantities of superheated and saturated steam.
As will be obvious a superheater such as shown in Figs. 3 to 7 inclusive, can
with advantage be used in cases where the whole of the steam used is to be
superheated.
We know it has been proposed to construct a superheater with U-shaped tubes,
and to pass part of the steam from a boiler through such superheater and
afterwards mix it with moist steam and we do not claim these features, but only
the peculiar construction of our apparatus as herein above described with
reference to and illustrated by the drawings, and hereinafter claimed in our
claiming clauses; furthermore we are aware it has been proposed to regulate the
superheating of steam by the automatic opening of a valve or actuating a feeding
mechanism for the purpose of introducing a liquid into the steam to be regulated,
such valve or feeding mechanism being opened or actuated by the expansion of a
body under the influence of the steam when the latter exceeds a determined
temperature or pressure, but this method is distinct from our invention and is not
claimed by us.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:
1. A steam superheater of the U tube type comprising a number of small
U tubes so bent that the limbs of the U are nearer together at the tube ends than
at the widest part of the bend, and having their ends brought near together and
secured into a tube plate or box provided with a division that separates the
adjacent ends of each tube, so that steam entering at one side of the division will
traverse the tubes and escape at the opposite side of the division substantially as
herein described and shown in the drawings.
2. For superheating steam the combination and arrangement as shown in and
described with reference to Figs. 1 and 2 of the drawings of a steam generator and
main steam pipe, a superheater such as referred to in the preceding claim, pipe
connections between the superheater and the boiler and main steam pipe, and
valves (or a valve) whereby a regulated proportion of the saturated steam leaving
the boiler can be sent through the superheater, and after becoming superheated

page_text: therein, can be mixed with saturated steam in the main steam pipe, substantially
as herein described for the purpose specified.
3. Steam superheating apparatus wherein a portion of the steam supply is
directed through a superheater by a valve controlled by a thermostat placed in the
main or superheated steam pipe, the arrangement being such that the proportion
of superheated steam to saturated steam will be regulated or controlled in an
automatic manner so as to produce as uniform a temperature as possible of the
mixture of superheated and saturated steam as set forth.
4. A steam superheater constructed as hereinbefore described with reference to
and shown in Figs. 3 to 7 inclusive of the accompanying drawings.
5. Steam superheating apparatus constructed and arranged substantially as
hereinbefore described with reference respectively to and shown in Figs. 1 to 7
inclusive; in Figs. 15 and 16 or modified according to Fig. 17; in Fig. 18; and
in Fig. 19 of the drawings annexed, whether or not the valve (or valves) for
regulating the proportion of superheated steam to saturated steam be controlled
by hand as shown in Figs. 1 and 2, or in Figs. 11 and 12; or in Figs. 13 and 14, or
automatically by a thermostat as in Fig. 20, and whether or not the pipe 14 be
modified as shown in Figs. 8, 9 and 10, of the said drawings.
Dated Ha
W. Lloyd Wise,
JAMES MUSGRAVE.
GEORGE DIXON.
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.