US3398262A - Pipe heating arrangement - Google Patents

Description

Aug. 20, 1968 w. c. KAHN PIPE HEATING ARRANGEMENT- Filed Sept. 14, 1967 QM QM INVENTO ATTORNEY United States Patent 3,398,262 PIPE HEATING ARRANGEMENT Walter C. Kahn, Westport, Conn., assignor to Electro-Trace Corporation, Danbury, Conn.

Continuation-impart of application Ser. No. 297,875,

July 26, 1963. This application Sept. 14, 1967, Ser.

Claims. (Cl. 219-301) ABSTRACT OF THE DISCLOSURE A pipe heating arrangement comprising, in combination, metallic pipe means adapted to contain a fluid and including at least two pipe portions having respective end portions adjacent to but spaced from each other; bridging means overlying the surface of the respective end portions over part of the circumference thereof and bridging the space between said pipe portions; a thin fiat elongated heating strip including a thin resistance element, a pair of elongated electrodes electrically connected with said resistance element so that current flows transversely through said resistance element across the length of the same, electrical insulating means surrounding and substantially coextensive with said resistance element and electrodes, and connector means at one end of said strip and having terminals connected with said electrodes, respectively, said strip being disposed on the surface of said metallic pipe means and bridging means extending along the length of both and said electrical insulating means insulating said heating strip from said metallic pipe means and from said bridging means; and thermal insulating means surrounding said pipe means and said heating strip so as to minimize heat radiation to the ambient atmosphere.

This application is a continuation-in-part of my copending application, entitled Pipe Heating Arrangement, Ser. No. 297,875, now abandoned, filed on July 26, 1963.

Background of the invention The present invention relates to a pipe heating arrangement in general, and more particularly to arrangement for heating pipes through which a fluid or liquid flows so that the fluid or liquid is maintained at a desired temperature, or freezing of a liquid in a pipe is prevented.

It is known to provide electric heating elements on pipes, and more particularly on pipes enveloped in a thermal insulating material. However, the arrangements of the prior art have the disadvantage that narrow heating elements disposed between the pipe and the insulating material create longitudinal air gaps between the pipe and the insulating material. Furthermore, it is necessary to connect the heating element, which has terminals at the ends thereof, at both ends of the pipe to a source of voltage, so that access to both pipe ends, and to both ends of the heating element is necessary. These disadvantages have been overcome with the arrangement disclosed in my above-mentioned copending application.

However, other problems still exist in connection with such pipe heating arrangements, particularly in installations in which the elongated strip-shaped heating element disclosed in my copending application is to be used on pipes which are interrupted by valves or pipe connectors, or on pipes from which branch pipes extend with both the main pipe and the branch pipe requiring the application of heat.

In arrangements of this type it is obviously not possible to simply fasten the heating strip to the pipe along the entire length thereof, because the valves, pipe connectors or similar elements project outwardly beyond the outer surface of the pipe and force the heating strip to remain out of contact with this surface in their respective area.

Summary of the invention The present invention remedies the above-enumerated shortcomings of the prior art.

More particularly, the present invention provides a pipe heating arrangement in which a thin, flat, stripshaped heating element can be mounted on a pipe means regardless of substantial surface irregularities caused on this pipe means by valves, pipe connectors and the like.

Briefly stated, one feature of my invention resides in the provision of a pipe heating arrangement comprising, in combination, metallic pipe means adapted to contain a fluid and including at least two pipe portions having respective end portions adjacent to but spaced from each other; bridging means overlying the surface of the respective end portions over part of the circumference thereof and bridging the space between said pipe portions; a thin flat elongated heating strip including a thin resistance element, a pair of elongated electrodes electrically connected with said resistance element so that current flows transversely through said resistance element across the length of the same, electrical insulating means surrounding and substantially coextensive with said resistance element and electrodes, and connector means at one end of said strip and having terminals connected with said electrodes, respectively, said strip being disposed on the surface of said metallic pipe means and bridging means extending along the length of both, and said electrical insulating means insulating said heating strip from said metallic pipe means and from said bridging means; and thermal insulating means surrounding said pipe means and the heating strip so as to minimize heat radiation to the ambient atmosphere.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The investigation itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

Brief description of the drawing FIG. 1 is a cross sectional view illustrating the principle of heating an insulated pipe by means of a heating strip;

FIG. 2 is a perspective view illustrating an embodiment of the invention;

FIG. 3 is a section taken on the line III-III of FIG. 2; and

FIG. 4 is a fragmentary perspective view of a bridging member in accordance with the present invention, as used in the illustrations of FIGS. 2 and 3.

Description of the preferred embodiment Referring now to the drawing, and firstly to FIG. 1, a pipe 1 is enveloped by a thermal insulating material 2 provided with a cutout 2a which may be located at the end of the insulated pipe.

A thin flat elongated heating strip 3 is disposed on the outer surface of pipe 1 inwardly of the insulating material 2.

Heating strip 3 has two outer layers of an insulating material, for example of the trademarked materials Teflon or Aclar, heat bonded to each other and to a glassasbestos layer which is sandwiched between the outer layers and protected by the same from heat and moisture. A conductive resistance layer 311 is embedded in the glassasbestos fiber layer. Parallel to the lateral longitudinal edges of the strip, two band-shaped copper electrodes 3b are disposed in conductive contact with the lateral portions of the resistance element 3a and covered by the glass-asbestos layer. A voltage applied to the electrodes 3b causes current to flow transversely to the elongation of the strip across the resistance element 3a. Consequently, the same heat per unit of arearegardless of the length of the strip-is produced when current diows through the resistance element 3a. Heating strips of this type, but without the Teflon or Aclar cover are known, and US Patents 2,952,761, 2,803,566 and 3,002,862 disclose related subject matter.

A connector means 4 is provided at the end of strip 3 and includes a flexible bag-shaped insulating end piece 4a to which a threaded connector piece 4b is attached into which wires, 7, 7' are inserted. A pair of wires 7a is connected to the ends of wires 7, and a pair of wires 7a is connected to the wires 7'. Wires 7a, 7a are connected to the respective electrode 3b. When a voltage source is connected to wire 7, current flows through the electrodes 3b and across the heating element 3a.

Annular straps 5 embrace pipe 1 and heating strip 3 to hold the same in place. The width of heating strip 3 is, for example, 3 which is less than the circumference of the pipe 1, so that the insulating material 2 is in direct contact with the greater part of the outer surface of pipe 1, particularly since the heating strip is very thin, for example less than & thick. The usual oversize insulation is therefore not required, and there are no inefficient air spaces between the insulating material and the pipe 1. Tracer pipes or heating cables, and the cost of labor and material for bonding the tracers to the pipe are eliminated.

Since the heat output is spread evenly over a three inch wide surf-ace, the heat density is low, for example 1 watt per square inch, eliminating coking or spoilage due to overheating or particularly hot spots. After a shutdown, the heat is gradually increased so that the temperature of a fluid in the pipe is restored without harm to even the most sensitive fluids.

Due to the fact that the source of voltage need be connected only to one end of the strip, any length of pipe can be heated by a correspondingly long strip attached thereto, while only that portion of the pipe must be accessible for service and repair on which the connector 4 is located.

However, problems develop when the heating strip is to be placed onto a pipe from which branch pipes extend, or in which valves or pipe connectors are inserted of the type which project outwardly beyond the outer pipe surface, i.e. which have a greater outer diameter than the pipe itself.

Such an arrangement is shown in simplified manner in FIG. 2, where the insulating material 2 has been omitted for the sake of greater clarity.

As shown in FIG. 2, two pipe sections 11a and 11b are separated by a vlave 10. Pipe sections 110 and 11b have a heating strip 13a secured thereto, for instance by non-illustrated straps, and a connector means 14a provided at one end of strip 13a is connected by a wire means 14b to a switching means 20, which in turn is connected by a wire 20a to a non-illustrated source of voltage, and by another wire to a thermostat 21. Wire means 14b corresponds to the wire 7 in FIG. 1 and comprises two wires connected to the electrodes of the heating strip.

It is evident that the strip 13a cannot lie flat over the valve 10 whose outer diameter is greater than that of pipe sections 11a and 11b. Therefore, a gap develops between the strips 13a and the outer surfaces of pipe sections 11 and 11b in the region where the strip 13a is unsupported by these surfaces at either axial end of the valve 10. The strip 13a, however, cannot be subjected to mechanical stresses which it would not be able to withstand. It is therefore necessary to support the heating strip 13a with a suitable bridging member.

How this is accomplished is shown most clearly in FIG. 3 which represents a secton taken on the line III Cit III of FIG. 2 As illustrated, a flexible bridging strip 30 of steel or other suitable material is placed over the valve 10 in such a manner that its two ends rest on the outer surface of the sections 11a and 11b, respectively, while intermediate these ends the bridging strip rises from these surfaces and overlies the valve 10 in engagement therewith. It is to be understood, of course, that the strip 30 must be flexible enough to permit such a configuration, and that it must be of a length requisite for accomplishing the required bridging.

Steel, which has been mentioned above, is by no means the only suitable material for the strip 30. Other materials oan also be used, as long as they have good heatconductive qualities so that heat-transmission to and from the respective pipes is not noticeably impaired by the strip 30.

To facilitate application of the strip to the area to be bridged, the strip may have at least one side treated with a suitable adhesive so as to be self-adhering. A cover paper 31 or the like will be normally provided to cover the treated side (see FIG. 4) to prevent undesired adhesion during transport or storage, and the installer need simply peel this cover off, place the strip on the pipe, and press the strip 30 in place. Thereupon, installation of the heating strip 13a and the insulation proceed as usual, with the heating strip 13a overlying the bridging strip 30 wherever the latter is provided.

It is of course conceivable to substitute a heat-conductive cement for the strip 30, and to apply such cement in the area to be bridged. However, this is much more cumbersome and time-consuming than use of the strip, and requires prolonged waiting periods while the cement dries and before the heating strip 13a can be applied. Therefore, the use of such conductive cement by itself does not provide the above advantages. However, if desired, such cement can be used to fill the spaces which remain between the underside of the bridging strip 30 and the pipe surface, it being understood that with the strip 30 in place the installation of heating strip 13a and insulation can proceed without any need for awaiting drying of such cement. Another modification which is possible, is to make both sides of the strip 30 self-adhesive, in which case the heating strip 13a can be quickly and simply bonded to the bridging strip by pressing it into engagement with the latter.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of pipe heating arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in pipe heating arrangement incorporating electric heating elements, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A pipe heating arrangement comprising, in combination, metallic pipe means adapted to contain a fluid and including at least two pipe portions having respective end portions adjacent to but spaced from each other; bridging means overlying the surface of the respective end portions over part of the circumference thereof and bridging the space between said pipe portions; a thin flat elongated heating strip including a thin resistance element, a pair of elongated electrodes electrically connected with said resistance element so that current flows transversely through said resistance element across the length of the same, electrical insulating means surrounding and substantially coextensive with said resistance element and electrodes, and connector means at one end of said strip and having terminals connected with said electrodes, respectively, said strip being disposed on the surface of said metallic pipe means and bridging means extending along the length of both and said electrical insulating means insulating said heating strip from said metallic pipe means and from said bridging means; and thermal insulating means surrounding said pipe means and said heating strip so as to minimize heat radiation to the ambient atmosphere.

2. A pipe heating arrangement as defined in claim 1, wherein said bridging means is metallic and heat conductive.

3. A pipe heating arrangement as defined in claim 1, wherein said bridging means is an elongated bridging strip of flexible metallic material.

4. A pipe heating arrangement as defined in claim 3, wherein said metallic material is steel.

5. A pipe heating arrangement as defined in claim 3, wherein said bridging strip has two sides, at least one of said sides being self-adhesive, whereby said bridging strip is adapted to be mounted on said pipe portions by being placed into contact therewith.

6. A pipe heating arrangement as defined in claim 2, wherein said pipe portions have a predetermined outer diameter; and further comprising an intermediate element interposed between and communicatingly connecting said pipe portions, said intermediate element having an outer diameter greater than said predetermined outer diameter, and wherein said bridging strip overlies said intermediate element and bridges the differential in said outer diameter.

7. A pipe heating arrangement as defined in claim 6, wherein one of said pipe portions extends at an angle to the other.

8. A pipe heating arrangement as defined in claim 6, wherein said intermediate element is a pipe connector.

-9. A pipe heating arrangement as defined in claim 6, wherein said intermediate element is a valve housing.

10. A pipe heating arrangement as defined in claim 6, wherein parts of said bridging strip are spaced from said surfaces of said end portions adjacent the connection of said pipe portions with said intermediate element due to the differential in said outer diameters; and further comprising heat-conductive cement disposed in and filling the thus existing spaces.

References Cited UNITED STATES PATENTS 2,274,839 3/1942 Marick 219301 X FOREIGN PATENTS 527,759 10/1940 Great Britain.

RICHARD M. WOOD, Primary Examiner.

C. L. ALBRITTON, Assistant Examiner.

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