U.S. patent number 3,665,154 [Application Number 05/016,788] was granted by the patent office on 1972-05-23 for method for constructing transportation pipes and heat generating pipes utilizing skin-effect current.
This patent grant is currently assigned to Chisso Corporation. Invention is credited to Masao Ando.
United States Patent |
3,665,154 |
Ando |
May 23, 1972 |
METHOD FOR CONSTRUCTING TRANSPORTATION PIPES AND HEAT GENERATING
PIPES UTILIZING SKIN-EFFECT CURRENT
Abstract
Units of transportation pipes heated by the skin-effect current
flowing concentratedly only through the inner wall skin portion of
a ferromagnetic pipe in which an insulated conductor line forming a
primary circuit is placed to pass AC therethrough are constructed
by electrically connecting the skin-effect current heat-generating
pipes at all connecting parts of the transportation pipe so as to
form a secondary circuit in all units of the transportation pipe by
an electric connection between the said unit of the transportation
pipe and the corresponding part of the skin-effect current
heat-generating pipe.
Inventors: |
Ando; Masao (Yokohama,
JA) |
Assignee: |
Chisso Corporation (Osaka,
JA)
|
Family
ID: |
12097519 |
Appl.
No.: |
05/016,788 |
Filed: |
March 5, 1970 |
Foreign Application Priority Data
|
|
|
|
|
Mar 26, 1969 [JA] |
|
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44/22974 |
|
Current U.S.
Class: |
392/469;
392/480 |
Current CPC
Class: |
F16L
53/34 (20180101); H05B 6/108 (20130101) |
Current International
Class: |
H05B
6/10 (20060101); H05b 003/40 () |
Field of
Search: |
;219/300,301 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Staubly; R. F.
Claims
What is claimed is:
1. Apparatus for heating a transportation pipe including a
plurality of discontinuous heat-generating pipe sections, a source
of electrical energy, an insulated conductor connected to said
source forming a primary current path, said discontinuous
heat-generating pipe sections forming series-connected portions of
a secondary current path, other series-connected portions of said
secondary current path being formed of portions of said
transportation pipe.
2. The apparatus of claim 1 wherein said transportation pipe is
made of a metallic material.
3. The apparatus of claim 2 wherein said discontinuous
heat-generating pipe sections are welded to said transportation
pipe.
4. The apparatus of claim 1 wherein said transportation pipe is
made of non-metallic material, said plurality of discontinuous
heat-generating pipe sections are attached to said transportation
pipe and said discontinuous heat-generating pipe sections are
mutually connected electrically.
5. A method for constructing units of transportation pipe heated by
skin-effect current flowing through the inner wall skin portion of
a ferromagnetic pipe including the steps of,
providing said ferromagnetic pipe of a length shorter than said
units of transportation pipe,
providing a source of electrical current,
providing a primary circuit path for said current comprising an
insulated conductor passing through said ferromagnetic pipe and
connected to said source,
providing a portion of a secondary path for said current through a
wall of said ferromagnetic pipe,
and providing a further secondary path for said current comprising
a portion of said units of transportation pipe to form the
respective secondary circuits in said units of transportation pipe.
Description
BACKGROUND OF THE INVENTION
This invention relates to a method for constructing liquid
transport pipes heated by the skin-effect current appearing in
attached heat-generating pipes made of highly ferromagnetic
metal.
The principle of the heat-generating pipe which utilizes the
skin-effect current applied in the method of the present invention
will be explained by referring to FIGS. 1 to 3.
In FIG. 1, 1 is a heat-generating pipe having a strong magnetic
property such as a steel pipe, 2 is an insulated conductor line
passed through the steel pipe, one end of which is connected to one
terminal of an electric source and the other end of which is
farther from the electric source and connected to the end of the
steel pipe which is farther from the electric source. A conductor
line 4 connects the remaining other end of the electric source to
the other end of the steel pipe which is nearer to the electric
source to form an electric circuit.
In such a circuit, let a resistivity of the steel pipe be
.phi.(.OMEGA.cm), a permeability be .mu., frequency be f (Hz),
S(cm) which is called a depth of skin is expressed by a formula
If there are relations expressed by formulas
t> 2S, d>>S, 1>>d (2)
Between S(cm), thickness t(cm), length 1(cm), and inside diameter
d(cm) of the steel pipe, alternating current flows concentratedly
only through the neighborhood of the inside surface of the steel
pipe and no potential appears on the outside surface thereof. In
other words, even when two points of the outside surface of the
steel pipe are shorted with a low impedance conductor, no electric
current flows therethrough.
There is an invention which utilizes the above-mentioned
phenomenon; for example, U.S. Pat. No. 3,293,407 entitled
"Apparatus for Maintaining Liquid being Transported in a Pipeline
at an Elevated Temperature."
FIG. 2 shows a case where an electric source is of single phase and
two heat-generating pipes are used.
FIG. 3 is a case where an electric source is of three phases and
three heat-generating pipes are used. The circuits of FIGS. 2 and 3
are the fundamental circuits utilized in the present invention.
According to the transportation pipe to which a heat-generating
pipe is attached, two or more single phase circuits such as that of
FIG. 2, i.e., even numbers such as 4, 6 and 8 of heat-generating
pipes; two or more three phase circuits such as that of FIG. 3,
i.e., a multiple of 3, such as 3, 6 and 9, of heat-generating pipes
are used.
In FIG. 2, 1 and 1' are heat-generating pipes having strong
magnetic property e.g., steel pipe, and 2 and 2' are insulated
conductor lines passed through the steel pipes. One circuit is
formed by an electric source 3, a conductor line 2, a short-circuit
line 7 which connects the steel pipes 1 and 1', a connecting line
5, the heat-generating pipe 1, another short-circuit line 6 and a
connecting line 4. Another circuit is likewise formed by an
electric source 3', a conductor line 2', a short-circuit line 7, a
connecting line 5, the heat-generating pipe 1', another
short-circuit line 6 and a connecting line 4. If two circuits are
equivalent, it is possible to omit connecting lines 4 and 5 or 4
and make the electric sources 3 and 3' into one source. Of course
in this instance the short-circuit lines 6 and 7 remain connected
and form a secondary circuit relative to the electric source.
In FIG. 3, 1, 1' and 1" are heat-generating pipes having strong
magnetic property, e.g., steel pipes, and 2, 2' and 2" are
conductor lines passed through these steel pipes. A circuit is
formed by an electric source 3, a conductor line 2, short-circuit
line 7 which connects the steel pipes 1 and 1' wherein the
conductor lines 2 and 2' are passed, a connecting line 5, another
short-circuit line 6 which connects the steel pipes 1 and 1'
wherein the conductor lines 2 and 2' are passed and a connecting
line 4. Similarly, respective circuits are formed with regard to
electric sources 3' and 3". If each phase is electrically balanced
with the phases as in FIG. 2, either or both of connecting lines 4
and 5 can be omitted. Of course in this case of FIG. 3,
short-circuit lines 6, 7, 6', 7', etc., remain as in FIG. 2 and
form a three-phase secondary circuit relative to the electric
source. According to the study of the present inventor, if the
respective circuits of heat-generating pipes are electrically
balanced with each other in FIGS. 2 and 3, either or both of the
connecting lines 4, 5 can be omitted; therefore, the method of the
present invention utilizes this fact to provide the readiness of
fabrication in constructing an apparatus of long transportation
pipe heated by skin-effect current. Namely when a transportation
pipe is long, unit transportation pipes of a unit length having a
plurarity of suitable heat-generating pipes of skin-effect current
which are made convenient for its transportation and construction,
are constructed on the spot. In such a case, it is often desirable
to avoid use of a heat-generating steel pipe which is electrically
connected so perfectly as shown in FIGS. 1 to 3, because the
fitting of heat-generating pipes on the spot by way of, e.g.,
welding or the like is difficult or even when the fitting is
possible, fabrication cost, safety and the like often prevent its
use.
As above-mentioned, in the method of the present invention, such an
arrangement is made that a part of the secondary circuit is formed
in every unit heat-generating pipe relative to the primary current
flowing through the conductor line passing through the inside of
the heat-generating pipe.
The above-mentioned arrangement will be illustrated referring to
FIGS. 4 to 7. FIGS. 4 and 5 show single-phase circuits which
correspond to FIG. 2 of the fundamental drawing and FIG. 6 is a
cross-sectional view.
In FIGS. 4 to 6, 1 and 1' are heat-generating pipes having strong
magnetic property, e.g., steel pipes and are electrically connected
to a unit transportation pipe 8, e.g., by way of welding. 2 and 2'
are conductor lines passed through the inside of these steel pipes.
In the drawing, an electric source is omitted but these conductor
lines form a go- and-return circuit relative to the electric
source.
In FIG. 4, a unit transportations pipe 8 has flanges 9 by which the
unit transportation pipe 8 is connected to the next one on the spot
to complete the arrangement. In this instance, since a
heat-generating pipe 1 is attached, e.g., by welding to the
transportation pipe 8 as a unit heat-generating pipe, it is fairly
difficult to connect neighboring heat-generating pipes
mutually.
In FIG. 4, however, when a unit transportation pipe 8 is an
electric conductor such as a steel pipe, each heat-generating pipe
is not necessarily to be connected with each other. Of course, the
conductor lines 2 and 2' must be connected as above-mentioned. As
shown in FIG. 4, when the heat-generating pipes 1 and 1' are
divided by a flange part 9, a secondary current which flows from
the heat-generating pipes 1 and 1' into the transportation pipe,
further flows into a part 6 - 7 of the transportation pipe thereby
to form a secondary circuit as in case of FIG. 2 wherein the
heat-generating pipes constitute the secondary circuit relative to
the primary circuit constituted by the conductor lines 2 and 2'.
Since the part 6 - 7 of the transportation pipe has extremely low
impedance, this current never flows to the outside of the
transportation pipe. Particularly since the transportation pipe of
this kind is enclosed by a heat-insulating layer 11, there is no
danger of contact of the metal part with an outside material. Even
provided that the contact of the metal part should happen, the
leakage current between two neighboring heat-generating pipes is
only a trifle extent as much as several tens milivolt and
practically negligible because the distance between the two
neighboring heat-generating pipes is usually less than 1 meter.
FIG. 5 shows a case where neighboring unit transportation pipes 8
are laid by welding and heat-generating pipes are connected by a
connecting box 10. The method which uses this connecting box can
also be used in case of the flange connection as shown in FIG. 4
where unit transportation pipes 8 are connected with a flange
9.
Even when such a connecting box 10 is used, it is often difficult
to electrically connect the connecting box by e.g., welding
perfectly.
According to the method of the present invention, even when
heat-generating pipes are not electrically connected mutually by a
special way, the heat-generating pipe constitutes a secondary
circuit and generates heat as in case of FIG. 4.
Namely in FIG. 5, insulated conductor lines 2 and 2' form a go-
and-return primary circuit relative to an electric source after
passed through the insides of heat-generating pipes 1 and 1' though
the electric source and parts of terminal connection are omitted in
the drawing. 9 is a connecting part of unit transportation pipes.
In this case, the welding of transportation pipe provides a
connection which is almost electrically perfect; hence a part of
the secondary circuit formed in the transportation pipe 8 appears
also at such a part as 6 and 7 of FIG. 5.
On account of the existence of a connecting box 10 in one part 12
of the heat-generating pipe in which the neighboring parts of the
heat-generating pipes 1 and 1' and the connecting box 10 are not
welded as shown in FIG. 5, the secondary current which flows
through the inside surface skin of the heat-generating pipes 1 and
1' passes the outside skin of the heat-generating pipe and appears
in one part of the transportation pipe, i.e., 6 and 7. Accordingly,
it should be noted that in the part 12 of the heat-generating pipe,
current flows through both the inside and the outside surface skins
and the amount of heat generation is increased there compared with
that in other parts of the heat-generating pipe.
In FIG. 4, a case is shown when neighboring flanges 9 are mutually
electrically insulated, and in FIG. 5, a case is shown where a
connecting box 10 is made of an insulating material. However, in
actual case, flanges and connecting boxes are, mostly, made of a
material such as steel which allows electric current to flow, hence
one part of the secondary current flows through this part as a
separate stream.
In actual transportation pipe facility, distribution of currents in
FIGS. 4 and 5 are slightly different but they have nothing to do
with the true nature of the method of the present invention.
FIGS. 6 and 7 are cross-sectional views of the part which are close
to the connecting part of a transportation pipe 8 in which the
method of the present invention is applied.
FIG. 6 shows a case of single phase where two heat-generating pipes
1 and 1' are used and FIG. 7 shows a case of three phases where
three heat-generating pipes are used. In both the cases, 2 is a
conductor line passed through the inside of a heat-generating pipe
and 6 or 7 is a path of current.
The foregoing explanation is directed to cases where transportation
pipes are constructed with a material having electric conductivity
such as steel, but when unit transportation pipes are constructed
with a material having electric insulating property such as
plastic, it is possible to connect heat-generating pipes mutually
in such a way that the impedance of the connecting part is as low
as possible by use of a material having a good electric
conductivity instead of the paths of the current on the surface of
the above-mentioned transportation pipe 6, 7, 6', 7', etc.
* * * * *