CA1078906A - Method and means for segmentally reducing heat output in a heat-tracing pipe - Google Patents
Method and means for segmentally reducing heat output in a heat-tracing pipeInfo
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- CA1078906A CA1078906A CA324,224A CA324224A CA1078906A CA 1078906 A CA1078906 A CA 1078906A CA 324224 A CA324224 A CA 324224A CA 1078906 A CA1078906 A CA 1078906A
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Abstract
METHOD AND MEANS FOR SEGMENTALLY REDUCING
HEAT OUTPUT IN A HEAT-TRACING PIPE
ABSTRACT OF THE DISCLOSURE
This invention relates to an improvement in a heat-generating pipe made up of a ferromagnetic pipe having an insulated conductor extending through it to a given point so that both the pipe and conductor may be connected in series with a power source of alternating current. The invention is directed to both a method and means for reducing the heat output over a desired segment of the pipe by reducing the magnetic field created by the alternating current flowing in the insulated conductor and that segment of the pipe. The means may be: a second electrical conductor internal and parallel to the heat reduced segment; a segment of nonferro-magnetic electrically conductive pipe; an electrically noncon-ductive pipe extending throughout the desired segment shunted by a second conductor; or a portion of the insulated conductor that is exterior to the ferromagnetic pipe along the segment so that it is magnetically decoupled from the pipe in which a reduced heat output is desired. The method comprises the requisite steps of connecting an electromagnetic field-decreasing means in the series circuit to reduce the alternating magnetic field produced in the pipe by the alter-nating current flowing through the conductor inside the pipe.
HEAT OUTPUT IN A HEAT-TRACING PIPE
ABSTRACT OF THE DISCLOSURE
This invention relates to an improvement in a heat-generating pipe made up of a ferromagnetic pipe having an insulated conductor extending through it to a given point so that both the pipe and conductor may be connected in series with a power source of alternating current. The invention is directed to both a method and means for reducing the heat output over a desired segment of the pipe by reducing the magnetic field created by the alternating current flowing in the insulated conductor and that segment of the pipe. The means may be: a second electrical conductor internal and parallel to the heat reduced segment; a segment of nonferro-magnetic electrically conductive pipe; an electrically noncon-ductive pipe extending throughout the desired segment shunted by a second conductor; or a portion of the insulated conductor that is exterior to the ferromagnetic pipe along the segment so that it is magnetically decoupled from the pipe in which a reduced heat output is desired. The method comprises the requisite steps of connecting an electromagnetic field-decreasing means in the series circuit to reduce the alternating magnetic field produced in the pipe by the alter-nating current flowing through the conductor inside the pipe.
Description
002 Field of the Invention 003 This invention relates to a system for reducing heat 004 output in a specific segment of an internal wire impedance 005 system for heating a pipeline.
007 Pipelines often require the fluid flowing in them to 008 have lower viscosities than they would have at the ambient 009 temperature of the pipe. In order to reduce the viscosity of 010 the fluid, heat is generally transferred into the fluid. A way 011 to achieve this is through steam tracing, that is, a system 012 which uses steam flowing in a separate conduit adjacent to the 013 one transporting the fluid. Another system is one using 014 alternating electrical current and the effects of a magnetic 015 field produced by the current to increase the temperature of 016 the fluid in the flow pipe. This second method has in the past 017 been called "skin effect heating", or more correctly, "internal 018 wire impedance heating".
019 Industry has used the skin effect or internal wire 020 impedance heating which, under current practice, uses a ferro-021 magnetic pipe attached substantially parallel and either 022 interior of or exterior to a fluid-flow pipe. The 023 ferromagnetic pipe has longitudinally extending through it an 024 electrically insulated metallic wire that is electrically 025 connected to the ferromagnetic pipe at a point remote from the 026 point of entry of the insulated wire so that both the wire and 027 pipe may be connected in series with each other and an 028 alternating current (AC) source of power. Thus, the electric 029 current flows through the insulated wire and returns through 030 the wall of the ferromagnetic pipe. Due to the skin effect, 031 most of the current flows near the inside wall of the pipe, 032 with essentially no current flowing at the outside wall.
~035 -3-~078906 001 ~eat is generated in the wall of the ferromagnetic 002 pipe by: magnetic hysteresis resulting from a type of internal 003 friction as the magnetic domains within the pipe wall are 004 reversed; eddy currents in the pipe wall due to the presence of 005 the pipe wall in a changing magnetic field which induces 006 currents to circulate throughout the pipe wall yielding and I2R
007 heating effect; and the I2R effect of the current returning 008 through the pipe wall. Additional heat is also generated in 009 the insulated wire according to Joule's Law, i.e., the I2R
010 effect of the current flowing in it.
011 A point worth mentioning here is the reason for using 012 a pipe having the property called "ferromagnetismn. It simply 013 is that this property greatly increases the magnetic field in 014 the pipe wall due to the alternating current through the OlS conductor which results in significant heating by hysteresis 016 and eddy currents. Examples of ferromagnetic elements are 017 iron, nickel and cobalt. Additionally, some alloys may have 018 components which by themselves are not ferromagnetic, but when 019 combined together as an alloy show this property, e.g., MnBi.
020 In prior installations of internal wire impedance 021 heating systems of which I am aware, there is no known way to 022 decrease the heat output of a given segment of the pipe for any 023 length of time while the rest of the pipe is at higher heat 024 output. The present invention, however, includes several 025 embodiments which do reduce the heat output for a given segment 026 without affecting the heat output of the adjacent pipe. The 027 utilization of the present invention results in both an 028 economical and efficient use of electrical power, such as where 029 a heat reduction segment connects two or more noncontiguous 030 fluid-flow pipes that are heated by a single heat-generating 031 pipe. For example, a heated pipeline in a refinery may have a 032 termination point a short distance away from a second heated iO78906 pipeline which continues on to another place in the refinery.
When a common internal wire impedance system is used for heat-ing each of them, a heat-reduction section is desirable in the space between the two lines since there is no need to heat that space. It is also usable whenever less heat is required in a segment of a continuous fluid-flow pipe, such as a segment where the heat loss is less due to reduced size in a segment of the pipe, better thermal insulation, or a supplementary source of heat.
SUMMARY OF THE INVENTION
In accordance with one aspect of this invention there is provided a method for reducing the heat output of a segment of heat generating pipe, comprising the steps of: electrically connecting one end of a first electrical conductor means to a first terminal of an alternating current power source; extend-~- ing the opposite end of said first conductor means into a , .
ferromagnetic pipe up to an extreme point of said ferromagnetic pipe where heat is desired and electrically connecting said opposite end to said ferromagnetic pipe at said extreme point; ;~
electrically connecting a second terminal of said power source to said ferromagnetic pipe at a preselected point on said ferromagnetic pipe spaced apart from said extreme point; -connecting in place of a segment of ferromagnetic pipe located ~`
between said extreme point and said preselected point an electrically non-conductive non-ferromagnetic section of pipe to reduce the magnetic field and heat output produced within said segment of pipe; and providing a second electrical con-ductor means extending through said non-conductive non-ferro-magnetic section of pipe and connected at each end of said non-conductive non-ferromagnetic section of pipe to said ferromagnetic pipe in order to establish a current path across ~ - 5 -.
iO789~)6 said non-conductive non-ferromagnetic section of pipe.
In accordance with another aspect of this invention there is provided in a system for reducing the heat output of a segment of heat-generating pipe, said heat-generating pipe including a ferromagnetic pipe having a first electrical con-ductor means extending through said ferromagnetic pipe up to an extreme point of said ferromagnetic pipe where heat is desired, one end of said first conductor means connected to said ferromagnetic pipe at said extreme point, the opposite end of said first conductor means connected to a first - terminal of an alternating current power source, a second terminal of said power source connected to a preselected point on said ferromagnetic pipe spaced apart from said extreme point, the improvement comprising: an electrically non-conductive non-ferromagnetic section of pipe connected in place of a segment of ferromagnetic pipe located between said extreme point and said preselected point to reduce the magnetic field and heat output produced within said segment of pipe; and a second electrical conductor means extending through said non-conductive non-ferromagnetic section of pipe and connected at each end of said non-conductive non-ferro-magnetic section of pipe to said ferromagnetic pipe in order to establish a current path across said non-conductive non-ferromagnetic section of pipe.
By way of added explantion, in one aspect the present invention provides a novel system that reduces the heat output of a segment of an internal wire impedance system.
In an internal wire impedance system, a continuous insulated electrical conductor means extends longitudinally through a ferromagnetic pipe and is connected at one end to a source of alternating current and at the other end to a return path means.
- ~ - 5a -The return path may be the ferromagnetic pipe or an electrical conductor; in either case, they must be respectively connected to the source of alternating current.
An electromagnetic field-decreasing means is pro-vided in the series circuit to reduce the alternating magnetic field produced by the current flowing through the electrical conductor. The means may be located inside a segment of the pipe and parallel to the electrical conductor extending longitudinally throughout the pipe to diminish the alternating magnetic field induced in the wall of the ferromagnetic pipe.
This arrangement results in a corresponding reduced heat output, Similarly, another embodiment of the present in-vention requires replacing a segment of the ferromagnetic pipe with a non-ferromagnetic but electrically conductive segment.
- 5b -` " 1078906 001 When this replaced segment is in series with the ferromagnetic 002 pipe, it is the segment of reduced heat output because no heat 003 is generated in the nonferromagnetic pipe by hysteresis and the 004 heat generated by eddy currents is significantly reduced. The 005 foregoing may be accomplished with an electrically noncon-006 ductive means, provided an electrically conductive means is 007 introduced into the series circuit to complete a return path 008 for the current to the source of alternating current.
009 An alternate embodiment further described below uses 010 a ferromagnetic pipe with a first and a second means for ;=
011 passing the insulated conductor through the wall of the pipe at 012 each end of the segment where the reduced heat output is 013 desired. The insulated conductor means, which extends longi-014 tudinally in the pipe, is positioned through the first means 015 extended adjacent to the exterior of the pipe wall, and back 016 through the second means from where it continues inside the 017 pipe. A ferromagnetic field is not created within the pipe 018 segment between the two means when the insulated conductor is 019 located in the foregoing manner, since there is no current flow 020 in that segment.
021 This invention also includes a step-by-step procedure 022 for reducing the heat output of a segment of a heat-generating 023 pipe that is located internally or externally to a pipeline.
024 In brief, the steps include electrically connecting an insu-025 lated conductor means to a first terminal of an alternating 026 current power source; extending the insulated conductor means 027 through the ferromagnetic pipe and directly connecting it up to 028 an end point in the pipe where heat is desired. The second 029 terminal of the power source is then connected to the pipe to 030 make a complete electrical series circuit. Next~ an 031 electromagnetic field-decreasing means for reducing the 032 alternating magnetic field described above is electrically ~ ' ' 10789~6 ~01 connected into the series circuit. The steps may include 002 connecting the electromagnetic field-decreasing means in the 003 form of a second electrical conductor internal and parallel to 004 the segment of reduced heat output and in series with the pipe 005 to produce an alternating magnetic field which is equal and 006 opposite to a similar field produced in the insulated conductor 007 means. Alternatively, when the electromagnetic field-008 decreasing means is a nonferromagnetic pipe, the above step 009 becomes connecting this pipe in series with the ferromagnetic 010 pipe which may have an additional step of connecting an 011 electric-wire bypass to make a complete series circuit. As a 012 result, a changing magnetic field and the corresponding heating 013 effects do not occur in the newly connected section.
014 Moreover, the method may take the steps of passing 015 the insulated electrical conductor means through the wall of 016 the ferromagnetic pipe and extending it along the exterior of 017 the pipe to the end point of the segment where a reduced heat 018 output is desired, and then passing it through the wall of the 019 pipe. When the preceding steps are carried out, alternating 020 current does not flow in a conductor within the pipe in this 021 segment, and consequently the alternating magnetic field within 022 the pipe wall is reduced a predetermined amount.
024 The above-described embodiments and advantages will 025 be further illustrated and described in the drawings and the 026 following description of the preferred embodiment.
027 FIG. 1 illustrates schematically a first embodiment 028 of the present invention having an electrical conductor 029 parallel to the reduced heat output segment.
030 FIG. 2 is a schematic illustration of another embodi-031 ment of the present invention having a nonferromagnetic but 036 ~7~
10789C~6 001 electrically conductive section throughout the length of the 002 segment where a reduced heat output is desired.
003 FIG. 3 schematically depicts an alternate embodiment 004 of the present invention wherein a segment having both elec-005 trically nonconductive and nonferromagnetic properties is 006 connected to the ferromagnetic pipe to form the segment with a 007 reduced heat output.
008 FIG. 4 is a schematic diagram of an embodiment of the 009 present invention where the electrically conductive means which 010 extends longitudinally through the ferromagnetic pipe passes 011 outside the pipe along the segment wherein a reduced heat 012 output is sought.
014 Referring to FIG. 1, ferromagnetic pipe 100 has a 015 segment where a reduced heat output is sought, designated by 016 point A and point B. Throughout the following discussion, 017 point A is considered the beginning of the segment of reduced 018 heat output and point B is the end of this segment within pipe 019 100. A power source of alternatingcu~rent 101 is directly 020 connected to a point D that is adjacent to the entering point 021 of an insulated conductor means 102 which terminates at a 022 remote point C. At point C conductor 102 is directly connected 023 to pipe 100 so that the flow path for the current is through 024 the ferromagnetic pipe. Internal to pipe 100 is an 025 electromagnetic field-decreasing means for reducing the heat 026 output, such as means 103, characteri~ed by being electrically 027 conductive, which is electrically connected to pipe 100 028 respectively at points A and B. The means 103 is a path for 029 the alternating electrical current to flow past the reduced 030 heat segment on its return path to the source of alternating 031 current. Most of the current will flow through this means 032 since it is the path of least impedance. The current in the ~078906 001 electromagnetic field-decreasing means 103 sets up an opposite 002 and approximately equal magnetic field to that created in 003 conductor means 102. In effect, the two magnetic fields cancel 004 each other.
005 Particularly referring to FIG. 2, the electromagnetic 006 field-decreasing means in this embodiment is a nonferromagnetic 007 electrically conductive means 104 which is electrically 008 connected in series with pipe 100. This means 104 may be an 009 aluminum pipe that allows the alternating current generated 010 from power source 101 to return through it; but, because of the 011 aluminum's nonferromagnetic characteristics, the heat generated 012 in the pipe by the alternating magnetic field produced by 013 current flowing through the insulated conductor means 102 is 014 substantially reduced.
015 The embodiment illustrated in FIG. 2 may give rise to 016 galvanic corrosion when dissimilar metals are used for the 017 electromagnetic-field-reducing means 104 and the ferromagnetic 018 pipe 100. To avoid galvanic couples that lead to corrosion, a 019 pipe fitting such as a dielectric union between means 104 and 020 the pipe 100 is suggested. When a dielectric union of the type 021 which electrically insulates one pipe segment from another is 022 used with means 104, the wall of means 104 cannot be used as 023 the return path for the alternating current. In this case, an 024 electrical bypass of segment 104 is necessary.
025 Another embodiment of the electromagnetic field-026 decreasing means is shown in FIG. 3, where an electrically 027 nonconductive segment 105 is physically connected in series 028 with pipe 100. Also included is a second electrically 029 conductive means 106, electrically connected in series with 030 pipe 100, either external (not illustrated) or internal to pipe 031 100, thus bypassing the segment 105. This arrangement prevents 032 the creation of a magnetic field, yet allows the alternating 035 _9_ ` 1078906 001 current to bypass this nonconductive segment through conductor 002 105.
003 An alternative embodiment of the electromagnetic 004 field-decreasing means is diagrammatically illustrated in FIG.
005 4, which is advantageous in the case where the ferromagnetic 006 pipe 100 is desired to be continuous, e.g., where pipe 100 is 007 used as the fluid flow pipe. In this embodiment, insulated 008 conductor means 107 is electrically connected to power source 009 101. The conductor means 107 passes through pipe 100 at point 010 A and is continuous with a second insulated conductor means 011 108, which is the electromagnetic field-decreasing means. The 012 conductor means 108 passes through the wall of pipe 100 at 013 point B and is continuous with a third wire means 109.
014 In situations where the pipe 100 is also the conduit 015 for fluid flow, the passage of the conductor means through the 016 pipe wall may be made fluid-impermeable by using appropriate 017 fittings 110 so that the contents of the pipe 100 will not leak 018 at these places. Thus, the means for passing the conductor 019 through the pipe may be a grommetted penetration, a screwable 020 or weldable fitting or other leak-proof means. Additionally, 021 this particular embodiment may have instead of the three 022 separate insulated conductors one continuous wire means which 023 passes through the wall of pipe 100 to become the 024 electromagnetic field-decreasing means and returns through the 025 wall at the end of the segment of reduced heat output. The 026 conductor is then connected in series with the power source.
027 In general, instead of pipe 100 being the return path 028 for the current, it may be an electrical conductor, preferably 029 insulated, which is in series with the insulated conductor 030 means extending longitudinally through the ferromagnetic pipe 031 and the power source. Alternatively, a combination of the pipe --. . . - ..
107~9~)6 001 100 and an electrical conductor may form the return path for 002 the current.
003 Although only selected embodiments of the present 004 invention have been described in detail, the invention is not 005 to be limited to any specific embodiments, but rather only by 006 the scope of the appended claims.
007 Pipelines often require the fluid flowing in them to 008 have lower viscosities than they would have at the ambient 009 temperature of the pipe. In order to reduce the viscosity of 010 the fluid, heat is generally transferred into the fluid. A way 011 to achieve this is through steam tracing, that is, a system 012 which uses steam flowing in a separate conduit adjacent to the 013 one transporting the fluid. Another system is one using 014 alternating electrical current and the effects of a magnetic 015 field produced by the current to increase the temperature of 016 the fluid in the flow pipe. This second method has in the past 017 been called "skin effect heating", or more correctly, "internal 018 wire impedance heating".
019 Industry has used the skin effect or internal wire 020 impedance heating which, under current practice, uses a ferro-021 magnetic pipe attached substantially parallel and either 022 interior of or exterior to a fluid-flow pipe. The 023 ferromagnetic pipe has longitudinally extending through it an 024 electrically insulated metallic wire that is electrically 025 connected to the ferromagnetic pipe at a point remote from the 026 point of entry of the insulated wire so that both the wire and 027 pipe may be connected in series with each other and an 028 alternating current (AC) source of power. Thus, the electric 029 current flows through the insulated wire and returns through 030 the wall of the ferromagnetic pipe. Due to the skin effect, 031 most of the current flows near the inside wall of the pipe, 032 with essentially no current flowing at the outside wall.
~035 -3-~078906 001 ~eat is generated in the wall of the ferromagnetic 002 pipe by: magnetic hysteresis resulting from a type of internal 003 friction as the magnetic domains within the pipe wall are 004 reversed; eddy currents in the pipe wall due to the presence of 005 the pipe wall in a changing magnetic field which induces 006 currents to circulate throughout the pipe wall yielding and I2R
007 heating effect; and the I2R effect of the current returning 008 through the pipe wall. Additional heat is also generated in 009 the insulated wire according to Joule's Law, i.e., the I2R
010 effect of the current flowing in it.
011 A point worth mentioning here is the reason for using 012 a pipe having the property called "ferromagnetismn. It simply 013 is that this property greatly increases the magnetic field in 014 the pipe wall due to the alternating current through the OlS conductor which results in significant heating by hysteresis 016 and eddy currents. Examples of ferromagnetic elements are 017 iron, nickel and cobalt. Additionally, some alloys may have 018 components which by themselves are not ferromagnetic, but when 019 combined together as an alloy show this property, e.g., MnBi.
020 In prior installations of internal wire impedance 021 heating systems of which I am aware, there is no known way to 022 decrease the heat output of a given segment of the pipe for any 023 length of time while the rest of the pipe is at higher heat 024 output. The present invention, however, includes several 025 embodiments which do reduce the heat output for a given segment 026 without affecting the heat output of the adjacent pipe. The 027 utilization of the present invention results in both an 028 economical and efficient use of electrical power, such as where 029 a heat reduction segment connects two or more noncontiguous 030 fluid-flow pipes that are heated by a single heat-generating 031 pipe. For example, a heated pipeline in a refinery may have a 032 termination point a short distance away from a second heated iO78906 pipeline which continues on to another place in the refinery.
When a common internal wire impedance system is used for heat-ing each of them, a heat-reduction section is desirable in the space between the two lines since there is no need to heat that space. It is also usable whenever less heat is required in a segment of a continuous fluid-flow pipe, such as a segment where the heat loss is less due to reduced size in a segment of the pipe, better thermal insulation, or a supplementary source of heat.
SUMMARY OF THE INVENTION
In accordance with one aspect of this invention there is provided a method for reducing the heat output of a segment of heat generating pipe, comprising the steps of: electrically connecting one end of a first electrical conductor means to a first terminal of an alternating current power source; extend-~- ing the opposite end of said first conductor means into a , .
ferromagnetic pipe up to an extreme point of said ferromagnetic pipe where heat is desired and electrically connecting said opposite end to said ferromagnetic pipe at said extreme point; ;~
electrically connecting a second terminal of said power source to said ferromagnetic pipe at a preselected point on said ferromagnetic pipe spaced apart from said extreme point; -connecting in place of a segment of ferromagnetic pipe located ~`
between said extreme point and said preselected point an electrically non-conductive non-ferromagnetic section of pipe to reduce the magnetic field and heat output produced within said segment of pipe; and providing a second electrical con-ductor means extending through said non-conductive non-ferro-magnetic section of pipe and connected at each end of said non-conductive non-ferromagnetic section of pipe to said ferromagnetic pipe in order to establish a current path across ~ - 5 -.
iO789~)6 said non-conductive non-ferromagnetic section of pipe.
In accordance with another aspect of this invention there is provided in a system for reducing the heat output of a segment of heat-generating pipe, said heat-generating pipe including a ferromagnetic pipe having a first electrical con-ductor means extending through said ferromagnetic pipe up to an extreme point of said ferromagnetic pipe where heat is desired, one end of said first conductor means connected to said ferromagnetic pipe at said extreme point, the opposite end of said first conductor means connected to a first - terminal of an alternating current power source, a second terminal of said power source connected to a preselected point on said ferromagnetic pipe spaced apart from said extreme point, the improvement comprising: an electrically non-conductive non-ferromagnetic section of pipe connected in place of a segment of ferromagnetic pipe located between said extreme point and said preselected point to reduce the magnetic field and heat output produced within said segment of pipe; and a second electrical conductor means extending through said non-conductive non-ferromagnetic section of pipe and connected at each end of said non-conductive non-ferro-magnetic section of pipe to said ferromagnetic pipe in order to establish a current path across said non-conductive non-ferromagnetic section of pipe.
By way of added explantion, in one aspect the present invention provides a novel system that reduces the heat output of a segment of an internal wire impedance system.
In an internal wire impedance system, a continuous insulated electrical conductor means extends longitudinally through a ferromagnetic pipe and is connected at one end to a source of alternating current and at the other end to a return path means.
- ~ - 5a -The return path may be the ferromagnetic pipe or an electrical conductor; in either case, they must be respectively connected to the source of alternating current.
An electromagnetic field-decreasing means is pro-vided in the series circuit to reduce the alternating magnetic field produced by the current flowing through the electrical conductor. The means may be located inside a segment of the pipe and parallel to the electrical conductor extending longitudinally throughout the pipe to diminish the alternating magnetic field induced in the wall of the ferromagnetic pipe.
This arrangement results in a corresponding reduced heat output, Similarly, another embodiment of the present in-vention requires replacing a segment of the ferromagnetic pipe with a non-ferromagnetic but electrically conductive segment.
- 5b -` " 1078906 001 When this replaced segment is in series with the ferromagnetic 002 pipe, it is the segment of reduced heat output because no heat 003 is generated in the nonferromagnetic pipe by hysteresis and the 004 heat generated by eddy currents is significantly reduced. The 005 foregoing may be accomplished with an electrically noncon-006 ductive means, provided an electrically conductive means is 007 introduced into the series circuit to complete a return path 008 for the current to the source of alternating current.
009 An alternate embodiment further described below uses 010 a ferromagnetic pipe with a first and a second means for ;=
011 passing the insulated conductor through the wall of the pipe at 012 each end of the segment where the reduced heat output is 013 desired. The insulated conductor means, which extends longi-014 tudinally in the pipe, is positioned through the first means 015 extended adjacent to the exterior of the pipe wall, and back 016 through the second means from where it continues inside the 017 pipe. A ferromagnetic field is not created within the pipe 018 segment between the two means when the insulated conductor is 019 located in the foregoing manner, since there is no current flow 020 in that segment.
021 This invention also includes a step-by-step procedure 022 for reducing the heat output of a segment of a heat-generating 023 pipe that is located internally or externally to a pipeline.
024 In brief, the steps include electrically connecting an insu-025 lated conductor means to a first terminal of an alternating 026 current power source; extending the insulated conductor means 027 through the ferromagnetic pipe and directly connecting it up to 028 an end point in the pipe where heat is desired. The second 029 terminal of the power source is then connected to the pipe to 030 make a complete electrical series circuit. Next~ an 031 electromagnetic field-decreasing means for reducing the 032 alternating magnetic field described above is electrically ~ ' ' 10789~6 ~01 connected into the series circuit. The steps may include 002 connecting the electromagnetic field-decreasing means in the 003 form of a second electrical conductor internal and parallel to 004 the segment of reduced heat output and in series with the pipe 005 to produce an alternating magnetic field which is equal and 006 opposite to a similar field produced in the insulated conductor 007 means. Alternatively, when the electromagnetic field-008 decreasing means is a nonferromagnetic pipe, the above step 009 becomes connecting this pipe in series with the ferromagnetic 010 pipe which may have an additional step of connecting an 011 electric-wire bypass to make a complete series circuit. As a 012 result, a changing magnetic field and the corresponding heating 013 effects do not occur in the newly connected section.
014 Moreover, the method may take the steps of passing 015 the insulated electrical conductor means through the wall of 016 the ferromagnetic pipe and extending it along the exterior of 017 the pipe to the end point of the segment where a reduced heat 018 output is desired, and then passing it through the wall of the 019 pipe. When the preceding steps are carried out, alternating 020 current does not flow in a conductor within the pipe in this 021 segment, and consequently the alternating magnetic field within 022 the pipe wall is reduced a predetermined amount.
024 The above-described embodiments and advantages will 025 be further illustrated and described in the drawings and the 026 following description of the preferred embodiment.
027 FIG. 1 illustrates schematically a first embodiment 028 of the present invention having an electrical conductor 029 parallel to the reduced heat output segment.
030 FIG. 2 is a schematic illustration of another embodi-031 ment of the present invention having a nonferromagnetic but 036 ~7~
10789C~6 001 electrically conductive section throughout the length of the 002 segment where a reduced heat output is desired.
003 FIG. 3 schematically depicts an alternate embodiment 004 of the present invention wherein a segment having both elec-005 trically nonconductive and nonferromagnetic properties is 006 connected to the ferromagnetic pipe to form the segment with a 007 reduced heat output.
008 FIG. 4 is a schematic diagram of an embodiment of the 009 present invention where the electrically conductive means which 010 extends longitudinally through the ferromagnetic pipe passes 011 outside the pipe along the segment wherein a reduced heat 012 output is sought.
014 Referring to FIG. 1, ferromagnetic pipe 100 has a 015 segment where a reduced heat output is sought, designated by 016 point A and point B. Throughout the following discussion, 017 point A is considered the beginning of the segment of reduced 018 heat output and point B is the end of this segment within pipe 019 100. A power source of alternatingcu~rent 101 is directly 020 connected to a point D that is adjacent to the entering point 021 of an insulated conductor means 102 which terminates at a 022 remote point C. At point C conductor 102 is directly connected 023 to pipe 100 so that the flow path for the current is through 024 the ferromagnetic pipe. Internal to pipe 100 is an 025 electromagnetic field-decreasing means for reducing the heat 026 output, such as means 103, characteri~ed by being electrically 027 conductive, which is electrically connected to pipe 100 028 respectively at points A and B. The means 103 is a path for 029 the alternating electrical current to flow past the reduced 030 heat segment on its return path to the source of alternating 031 current. Most of the current will flow through this means 032 since it is the path of least impedance. The current in the ~078906 001 electromagnetic field-decreasing means 103 sets up an opposite 002 and approximately equal magnetic field to that created in 003 conductor means 102. In effect, the two magnetic fields cancel 004 each other.
005 Particularly referring to FIG. 2, the electromagnetic 006 field-decreasing means in this embodiment is a nonferromagnetic 007 electrically conductive means 104 which is electrically 008 connected in series with pipe 100. This means 104 may be an 009 aluminum pipe that allows the alternating current generated 010 from power source 101 to return through it; but, because of the 011 aluminum's nonferromagnetic characteristics, the heat generated 012 in the pipe by the alternating magnetic field produced by 013 current flowing through the insulated conductor means 102 is 014 substantially reduced.
015 The embodiment illustrated in FIG. 2 may give rise to 016 galvanic corrosion when dissimilar metals are used for the 017 electromagnetic-field-reducing means 104 and the ferromagnetic 018 pipe 100. To avoid galvanic couples that lead to corrosion, a 019 pipe fitting such as a dielectric union between means 104 and 020 the pipe 100 is suggested. When a dielectric union of the type 021 which electrically insulates one pipe segment from another is 022 used with means 104, the wall of means 104 cannot be used as 023 the return path for the alternating current. In this case, an 024 electrical bypass of segment 104 is necessary.
025 Another embodiment of the electromagnetic field-026 decreasing means is shown in FIG. 3, where an electrically 027 nonconductive segment 105 is physically connected in series 028 with pipe 100. Also included is a second electrically 029 conductive means 106, electrically connected in series with 030 pipe 100, either external (not illustrated) or internal to pipe 031 100, thus bypassing the segment 105. This arrangement prevents 032 the creation of a magnetic field, yet allows the alternating 035 _9_ ` 1078906 001 current to bypass this nonconductive segment through conductor 002 105.
003 An alternative embodiment of the electromagnetic 004 field-decreasing means is diagrammatically illustrated in FIG.
005 4, which is advantageous in the case where the ferromagnetic 006 pipe 100 is desired to be continuous, e.g., where pipe 100 is 007 used as the fluid flow pipe. In this embodiment, insulated 008 conductor means 107 is electrically connected to power source 009 101. The conductor means 107 passes through pipe 100 at point 010 A and is continuous with a second insulated conductor means 011 108, which is the electromagnetic field-decreasing means. The 012 conductor means 108 passes through the wall of pipe 100 at 013 point B and is continuous with a third wire means 109.
014 In situations where the pipe 100 is also the conduit 015 for fluid flow, the passage of the conductor means through the 016 pipe wall may be made fluid-impermeable by using appropriate 017 fittings 110 so that the contents of the pipe 100 will not leak 018 at these places. Thus, the means for passing the conductor 019 through the pipe may be a grommetted penetration, a screwable 020 or weldable fitting or other leak-proof means. Additionally, 021 this particular embodiment may have instead of the three 022 separate insulated conductors one continuous wire means which 023 passes through the wall of pipe 100 to become the 024 electromagnetic field-decreasing means and returns through the 025 wall at the end of the segment of reduced heat output. The 026 conductor is then connected in series with the power source.
027 In general, instead of pipe 100 being the return path 028 for the current, it may be an electrical conductor, preferably 029 insulated, which is in series with the insulated conductor 030 means extending longitudinally through the ferromagnetic pipe 031 and the power source. Alternatively, a combination of the pipe --. . . - ..
107~9~)6 001 100 and an electrical conductor may form the return path for 002 the current.
003 Although only selected embodiments of the present 004 invention have been described in detail, the invention is not 005 to be limited to any specific embodiments, but rather only by 006 the scope of the appended claims.
Claims (2)
1. A method for reducing the heat output of a segment of heat generating pipe, comprising the steps of: electrically connecting one end of a first electrical conductor means to a first terminal of an alternating current power source; extend-ing the opposite end of said first conductor means into a ferromagnetic pipe up to an extreme point of said ferromagnetic pipe where heat is desired and electrically connecting said opposite end to said ferromagnetic pipe at said extreme point;
electrically connecting a second terminal of said power source to said ferromagnetic pipe at a preselected point on said ferromagnetic pipe spaced apart from said extreme point;
connecting in place of a segment of ferromagnetic pipe located between said extreme point and said preselected point an electrically non-conductive non-ferromagnetic section of pipe to reduce the magnetic field and heat output produced within said segment of pipe; and providing a second electrical con-ductor means extending through said non-conductive non-ferro-magnetic section of pipe and connected at each end of said non-conductive non-ferromagnetic section of pipe to said ferromagnetic pipe in order to establish a current path across said non-conductive non-ferromagnetic section of pipe.
electrically connecting a second terminal of said power source to said ferromagnetic pipe at a preselected point on said ferromagnetic pipe spaced apart from said extreme point;
connecting in place of a segment of ferromagnetic pipe located between said extreme point and said preselected point an electrically non-conductive non-ferromagnetic section of pipe to reduce the magnetic field and heat output produced within said segment of pipe; and providing a second electrical con-ductor means extending through said non-conductive non-ferro-magnetic section of pipe and connected at each end of said non-conductive non-ferromagnetic section of pipe to said ferromagnetic pipe in order to establish a current path across said non-conductive non-ferromagnetic section of pipe.
2. In a system for reducing the heat output of a segment of heat-generating pipe, said heat-generating pipe including a ferromagnetic pipe having a first electrical con-ductor means extending through said ferromagnetic pipe up to an extreme point of said ferromagnetic pipe where heat is desired, one end of said first conductor means connected to said ferromagnetic pipe at said extreme point, the opposite end of said first conductor means connected to a first terminal of an alternating current power source, a second terminal of said power source connected to a preselected point on said ferromagnetic pipe spaced apart from said extreme point, the improvement comprising: an electrically non-conductive non-ferromagnetic section of pipe connected in place of a segment of ferromagnetic pipe located between said extreme point and said preselected point to reduce the magnetic field and heat output produced within said segment of pipe; and a second electrical conductor means extending through said non-conductive non-ferromagnetic section of pipe and connected at each end of said non-conductive non-ferromagnetic section of pipe to said ferromagnetic pipe in order to establish a current path across said non-conductive non-ferromagnetic section of pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA324,224A CA1078906A (en) | 1974-11-04 | 1979-03-27 | Method and means for segmentally reducing heat output in a heat-tracing pipe |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52081574A | 1974-11-04 | 1974-11-04 | |
| CA237,449A CA1064561A (en) | 1974-11-04 | 1975-10-10 | Method and means for segmentally reducing heat output in heat-tracing pipe |
| CA324,224A CA1078906A (en) | 1974-11-04 | 1979-03-27 | Method and means for segmentally reducing heat output in a heat-tracing pipe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078906A true CA1078906A (en) | 1980-06-03 |
Family
ID=27164154
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA324,224A Expired CA1078906A (en) | 1974-11-04 | 1979-03-27 | Method and means for segmentally reducing heat output in a heat-tracing pipe |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1078906A (en) |
-
1979
- 1979-03-27 CA CA324,224A patent/CA1078906A/en not_active Expired
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