WO2001067816A1

WO2001067816A1 - Skin effect heating system for a structural member

Info

Publication number: WO2001067816A1
Application number: PCT/US2000/005944
Authority: WO
Inventors: Douglas V. Heitzenrater; Walter P. Mastin; John E. Galanko; Thomas J. Burg
Original assignee: Daimlerchrysler Ag
Priority date: 2000-03-07
Filing date: 2000-03-07
Publication date: 2001-09-13
Also published as: AU2000237291A1

Abstract

A skin effect heating system (30) is adapted to be attached to a structural member (32) having a vehicle carrying portion with a first side (42) and a second side (44). A plurality of clamps (45) is secured at spaced intervals along the second side (44) of the vehicle carrying portion. The clamps (45) each include a stud (46), a plate member (48) cooperating with the stud (46), and a locking member (50) retaining the plate member (48) on the stud (46). A continuous skin effect heater (60) is held in removable contact with the second side (44) of the vehicle carrying portion.

Description

SKIN EFFECT HEATING SYSTEM FOR A STRUCTURAL MEMBER BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a skin effect heating system for attachment to a structural member and, additionally, a method of attaching a skin effect heater to a structural member.

2. Description of the Prior Art

Rail systems utilizing electrical energy conducted by the rails themselves are becoming increasingly popular for use in mass transit systems. Such systems are frequently employed in large metropolitan airports for moving people between terminals or from terminals to parking areas. In addition, these electrified rail systems are being used in rail and light rail mass transit systems around large population centers. Ice formation on the rails of such rail systems is a well-known problem in the art. Ice formation on the electrified rails disrupts power to the conveying vehicle . The most common approach for reducing the accumulation of ice and snow on the rails is to apply heat directly to the rails through the physical attachment of electric resistance heating wires or cables to the rails. This approach to solving the rail icing problem is well-known in the art as evidenced by U.S. Patent Nos . : 814,671 to Burns; 1,474,161 to Packer; 1,524,223 to Wells; 2,009,979 to Abbott; 4,429,845 to Stover et al . ; and 4,854,244 to Rhodes et al . The foregoing prior art references each disclose electrical resistance heating units that include a resistance heating element, such as a resistance wire or cable. The units are intended to be attached to the side of a rail at spaced intervals along the rail. Typically, the units are relatively short in length. Hence, the resistance wires or cables typically must be powered separately over relatively short distances. Consequently, resistance heating elements are inherently inefficient and require a substantial amount of electrical energy to operate.

One proposed solution to overcome the disadvantages of resistance heating elements is through the application of skin effect heating to the rails. Skin effect heating is a special form of impedance heating m which a single insulated conductor is run inside a ferromagnetic heating envelope. Skin effect heating systems have been used in the oil industry for the heating of oil pipelines, as discussed in an IEEE article entitled "IEEE Recommended Practice for Electrical Impedance, Induction, and Skin Effect Heating of Pipelines and Vessels", March 21, 1991, Reference No. Std. 844-1991 (Revision of Std. 844-1985) and is incorporated herein by reference. This is because long heating circuits are feasible with skin effect heating, thus making skin effect heating systems particularly well suited for the long distances associated with oil pipelines. In these prior art systems, the heating envelope is normally laid parallel to the pipeline and physically bonded to the pipeline through welding or heat transfer cement.

A typical prior art skin effect heating system 10 for use with a pipeline is illustrated m Figs. 1-3. In Figs. 1-3, a single insulated conductor 12 is run inside a ferromagnetic heating envelope 14. The conductor 12 is connected to the heating envelope 14 at a first end 16, and a source of AC power 18 is connected by cables 19 between the conductor 12 and the heating envelope 14 at a second end 20 (i.e., a supply end) . Current flows from the power source 18 through the insulated conductor 12 to the first end 16 and returns through the envelope 14.

In skin effect heating, heat is generated in the wall of the heating envelope 14 by the loss of the return current flow, and by hysteresis and eddy currents induced by the alternating magnetic field around the conductor 12. This heat is transferred by a heat transfer bridge 22 to a pipe 24 of the pipeline. The heat transfer bridge 22 connects the heating envelope 14 to the pipe 24 of the pipeline. The pipe 24 and the heating envelope 14 are enclosed by a thermal insulation layer 26. The inductive interaction between the current in the conductor 12 and the return current in the heating envelope 14 causes the current in the heating envelope 14 to concentrate at its inner surface. In the skin effect heating system 10, the voltage drop on the surface of the heating envelope 14 is extremely low. If the heating envelope 14 and, therefore, the power source 18 are grounded at the supply end or second end 20, the entire heating envelope 14 will remain at essentially ground potential.

The inventors are aware of one attempt to apply a skin effect heating system to a rail system. In this prior art arrangement, the skin effect heating tubes of the system were welded directly to a structural component . The heating tubes of the skin effect heating system were provided in approximately twenty foot lengths and joined together at the ends. As time passed, it was found that the resulting heated structural component suffered from extensive cracking and had to be replaced. The structural component was intended for use as a bridge component for carrying an electrically powered "people mover" vehicle.

Any structural component that is adapted to carry a vehicle is treated as a bridge component and, therefore, is identified as a "fracture critical member" . Fracture critical member design is governed by the AASHTO Standard Specification for Highway Bridges and the AWSD1.5 Bridge Welding Code. It is advantageous for any structural component which is to be used as a bridge component to have a Category C stress detail or less according to AASHTO Bridge Code. It was found that the previously discussed structural component, having the skin effect heating system welded thereto, had a Category E stress detail, making it undesirable for use as a bridge component. Designation as Category E stress detail requires all welds on the structural component be inspected - by ultrasonic testing (UT) examined and repaired, or replaced if found defective, which significantly lengthens fabrication time for the structural component . A welded attachment Category E stress detail results in an allowable fatigue stress level of 4.5 KSI according to the AASHTO Bridge Code. In contrast, a Category C stress detail, for example, results in an allowable fatigue stress level of 10 KSI according to the AASHTO Bridge Code .

In addition, it was found that the welded attachment of the skin effect heating tubes or pipes to the structural component had additional disadvantages. For example, the heating pipes had to be placed in a desired location with all tolerances in place and held fixed throughout the welding process. In addition, continuous or stitch welds had to be placed in confined spaces as, for example, between the webs of a girder section or inside a box beam.

In view of the foregoing, it is an object of the present invention to provide a skin effect heating system for attachment to a structural component that results in a more favorable fatigue stress category for the structural component. In addition, it is an object of the present invention to simplify and reduce the costs associated with fabrication and installation of a skin effect heating system for a structural component. Furthermore, it is an object of the present invention to provide a skin effect heating system which affords flexibility for future changes and improvement s to the system.

SUMMARY OF THE INVENTION The present invention is a skin effect heating system for attachment to a structural member. The structural member is generally adapted to carry a vehicle and includes a vehicle carrying portion with a first side and a second side. The first side of the vehicle carrying portion defines a vehicle carrying surface upon which the vehicle travels. A continuous skin effect heater is removably attached to the second side of the vehicle carrying portion and in contact therewith. The continuous skin effect heater is preferably held in removable contact with the second side of the vehicle carrying portion along substantially an entire length of the skin effect heater. The continuous skin effect heater may have having a length of about fifteen hundred feet. The system may further include a clamp attached to the second side of the vehicle carrying portion. The clamp may hold the skin effect heater m removable contact with the second side of the vehicle carrying portion. The clamp may include a threaded stud secured to the second side of the vehicle carrying portion. A plate member preferably cooperates with the stud. A removable locking member is preferably positioned on the stud to retain the plate member on the stud and, further, hold the plate member in engagement with the skin effect heater such that the skin effect heater is held in removable contact with the second side of the vehicle carrying portion. The system may include a plurality of threaded studs secured at spaced intervals along the second side of the vehicle carrying portion. A plurality of plate members preferably cooperate with the studs. A plurality of removable locking members may be positioned on the studs to retain the plate members on the studs and, further, hold the plate members m engagement with the skm effect heaters such that the skin effect heaters are held in removable contact with the second side of the vehicle carrying portion. The studs may be spaced at about six inch intervals along the second side of the vehicle carrying portion. The studs may also be welded to the second side of the vehicle carrying portion. The locking members may be provided as locknuts tightened on the studs to about forty-five foot-pounds of torque.

The clamps used in the system may be saddle clamps. Thermal insulation may be supported on an elongated portion of the studs and enclose the skin effect heater.

The present invention is also a combination of a box beam adapted to carrying a vehicle and a continuous skin effect heater. The box beam generally includes a first member, a second member spaced from the first member and two elongated members connecting the first and second members. The first member is a vehicle carrying portion of a box beam and includes a first side and a second side. The first side of the vehicle carrying portion defines a vehicle carrying surface upon which the vehicle travels. The continuous skin effect heater is removably attached to the second side of the vehicle carrying portion of the box beam and in contact therewith. The combination preferably includes a vehicle having a plurality of spaced-apart wheels in contact with the first side of the vehicle carrying portion. In addition, the combination may further include a plurality of skin effect heaters removably attached to the second side of the vehicle carrying portion and positioned along the second side of the vehicle carrying portion opposite from the spaced-apart drive wheels of the vehicle.

The present invention is also a method of attaching a skin effect heater to a structural member that is adapted to carry a vehicle. The structural member generally includes a vehicle carrying portion with a first side and a second side. The first side defines a vehicle carrying surface upon which the vehicle travels. The method may include the steps of: securing a plurality of studs at spaced intervals along the second side of the vehicle carrying portion; receiving a plurality of plate members on the studs, respectively; receiving a plurality of removable locking members on the studs, respectively, with the locking members retaining the plate members on the studs such that spacing exists between the respective plate members and the second side of the vehicle carrying portion; guiding a continuous skin effect heater into the spacing between the respective plate members and the second side of the vehicle carrying portion; and securing the locking members on the studs such that the respective plate members engage the skin effect heater and hold the skin effect heater in removable contact with the second side of the vehicle carrying portion.

The studs may be threaded studs and the locking members may be locknuts received on the studs. The method may further include the step of tightening the locknuts on the threaded studs. In addition, the method may include the step of providing a source of electrical power to the continuous skin effect heater. Furthermore, the method may include the step of initially providing the continuous skin effect heater as a coil prior to guiding the continuous skin effect heater into the spacing between the respective plate members and the second side of the vehicle carrying portion.

Further details and advantages of the present invention will become apparent in the following detailed description, in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic and perspective view of a prior art skin effect heating system; Fig. 2 is a front perspective view of detail II in Fig. 1;

Fig. 3 is a cross-sectional view along lines III- III in Fig. 1;

Fig. 4 is a cross-sectional elevational view of a skin effect heating system attached to a structural member and made in accordance with the present invention,- Fig. 5 is a top plan view of the system of Fig. 4 with a vehicle carrying portion of the structural member removed for clarity; Fig. 6 is a cross-sectional view of a skin effect heater made in accordance with the present invention;

Fig. 7 is a cross-sectional end elevational view of the system of Fig. 4 further including fiberglass insulation; Fig. 8 is an end elevational view of the system of Fig. 4; and Fig. 9 is a top perspective view of a plate member of a saddle clamp used to attach the skin effect heating system to the structural member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 4 shows a skin effect heating system 30 made in accordance with the present invention. The system 30 is attached to a structural member 32. The structural member 32 is preferably adapted to carry a vehicle (not shown) , such as a people mover or other electrically powered vehicle, such as the vehicle disclosed in U.S. Patent No. 4,090,452 to Segar which is incorporated herein by reference. A vehicle's drive wheels 31 are shown in phantom in Fig. 4. The structural member 32 shown in Fig. 4 is a box beam. The box beam generally includes a first member 34, a second member 36 and two elongated members 38, 39 connecting the first and second members 34, 36. The first member 34, the second member 36 and the two elongated members 38, 39 are preferably welded together using full penetrating welds. The structural member 32 may also be a rail (not shown) adapted to carry a rail vehicle, or any type of structural member that requires heating. The rail will include top and bottom flanges that are interconnected by a web portion, as is well-known in the art.

Referring now to Figs. 4 and 5, the first or top member 34 of the structural member 32 generally defines a vehicle carrying portion 40 of the structural member 32. The vehicle carrying portion 40 includes a first side 42 and a second side 44. A plurality of clamps 45 is attached to the second side 44 of the vehicle carrying portion 40. The clamps 45 each include a stud 46, a plate member 48 cooperating with the stud 46, and a locking member 50 positioned on the stud 46 to retain the plate member 48 on the stud 46. The studs 46 for the respective clamps 45 are secured at spaced intervals along the second side 44 of the vehicle carrying portion 40. The studs 46 are typically spaced at about six inch intervals along the second side 44 of the vehicle carrying portion 40. The studs 46 are preferably externally threaded and welded at one end to the second side 44 of the vehicle carrying portion 40. The studs 46 are preferably ). x 2^ inch steel studs that are zinc-plated. The plate members 48 for the respective clamps 45 cooperate with the studs 46. The plate members 48 define an aperture 49 shown in Fig. 8 sized to cooperate with the studs 46. The plate members 48 are preferably made of steel and are about % of an inch in thickness and 254 inches in length. The locking members 50 are positioned on the studs 46 and retain the plate members 48 on the studs 46. The locking members 50 may be nut and lockwasher combinations or, preferably, locknuts that are configured to engage the threads on the studs 46. The clamps 45 are preferably saddle clamps with saddle-shaped plate members 48, as shown in Fig. 8.

At least one, but preferably a plurality of continuous skin effect heaters 60, also known as heating tubes, is received between the plate members 48 and the second side 44 of the vehicle carrying portion 40. The locking members 50 positioned on the studs 46 retain the plate members 48 on the studs 46 and, further, hold the plate members 48 in engagement with the skin effect heaters 60 such that the skin effect heaters 60 are held in removable physical contact with the second side 44 of the vehicle carrying portion 40. The plate members 48 are preferably formed with a saddle shape, as shown in Fig. 8, so as to engage the outer surface of the skin effect heaters 60. The skin effect heaters 60 generally operate in a similar manner to the skin effect heating system 10 discussed previously in connection with Figs. 1-3, and are preferably manufactured by Thermon Manufacturing Company, San Marcos, Texas. However, the skin effect heaters 60 preferably are not enclosed by thermal insulation and no welded connection is required. Referring briefly to Fig. 6, the skin effect heaters 60, or heating tubes, generally include an insulated conductor 62 enclosed by a ferromagnetic envelope 64.

Referring now to Figs. 4-6, the continuous skin effect heaters 60, or heating tubes, are held in removable contact with the second side 44 of the vehicle carrying portion 40 by the respective studs 46, plate members 48 and locking members 50. The skin effect heaters 60, or heating tubes, are held in removable contact with the second side 44 of the vehicle carrying portion 40 preferably along their entire length. The skin effect heaters 60, or heating tubes, are preferably provided in lengths of about fifteen hundred feet and, for ease of installation, are provided in coil form. However, it will be appreciated by those skilled in the art that the length of the skin effect heaters 60, or heating tubes, are limited only by the voltage limitation of the insulated conductor 62 of the respective skin effect heaters 60. With 600V insulation, the skin effect heaters 60, or heating tubes, may have lengths of up to approximately five thousand feet . The skin effect heaters 60, or heating tubes, may have lengths of up to seventy-five hundred feet with supply voltages of 3,000V. Above 3,000V, shielded cable is appropriate.

Referring again to Figs. 4 and 5, the system 30 generally provides for the heating of the skin effect heaters 60, or heating tubes, up to approximately 250°F when 600V AC single phase current is supplied to the skin effect heaters 60. As stated previously, the skin effect heaters 60 are held in removable physical contact with the second side 44 of the vehicle carrying portion 40 by the studs 46, plate members 48 and locking members 50. Preferably, the locking members 50 are provided as removable locknuts, which are tightened to secure the skin effect heaters 60 in place against the second side 44 of the vehicle carrying portion 40. Preferably, the locking members 50 are received on the studs 46 and tightened to about forty-five foot-pounds of torque. This assures adequate contact between the skin effect heaters 60 and the second side 44 of the vehicle carrying portion 40. However, the skin effect heaters 60 still may be removed from contact with the second side 44 of the vehicle carrying portion 40 by loosening the locking members 50 and lowering the plate members 48. In this manner, should the skin effect heaters 60 ever need replaced, they may be removed without much difficulty. Hence, according to the present invention, the skin effect heaters 60 are held in removable physical contact with the structural member 32 without being bonded to the structural member 32 through the use of welds used in the prior art skin effect heating systems discussed previously. The arrangement of the present invention maintains the physical contact of the skin effect heaters 60 with the structural member 32 without requiring a welded connection between the skin effect heaters 60, or heating tubes, and the structural member 32.

Referring to Fig. 7, the studs 46 may be elongated so that thermal insulation 70, such as conventional fiberglass insulation, may be installed adjacent the skin effect heaters 60 and preferably enclose the skin effect heaters 60. In particular, first and second plate washers 72, 73 are received on each of the studs 46. The first washer 72 received on each of the studs 46 contacts the locking member 50 previously positioned on each of the studs 46. The insulation 70 is received on an elongated portion 74 of the studs 46 and held in place on each of the studs 46 by a sleeve 76, a third plate washer 78, and a second locking member 80. The sleeve 76 is sized to cooperate loosely with the stud 46. The third plate washer 78 and second locking member 80 support the insulation 70 on the respective studs 46. The second locking member 80 secures the sleeve 76 between the second and third plate washers 73, 78. Each of the plate washers 72, 73, 78 is made of zinc plated steel and is about two inches in diameter and about 1/32 of an inch in thickness. Preferably, the sleeve 76 is cylindrically- shaped, made of steel, has a diameter of about % of an inch and is 1 3/4 inches m length. The second locking member 80 is substantially identical to the first locking member 50 discussed previously, and may be a nut and lockwasher or, preferably, a locknut . Preferably, the elongated portion 74 of each of the studs 46 is coated with locking compound before the sleeves 76 are positioned on the respective studs 46. An adhesive tape oint 82 may be provided between each transverse edge 84 of the insulation 70 and the elongated members 38, 39 of the structural member 32. A spacer block 86 of fiberglass insulation may be positioned on the insulation 70 to generally enclose the skin effect heaters 60 which enhances the heat transfer between the skm effect heaters 60 and the vehicle carrying portion 40 of the structural member 32. As shown m Fig. 6, the skin effect heaters 60 are generally positioned within cavities 88 formed by the insulation 70 and the spacer block 86. The adhesive tape joints 82 further seal each of the cavities 88 and help support the insulation 70 in a vertical direction. Fig. 8 shows an end view of the system 30 at an end of a run of the heating tubes or the skin effect heaters 60. At the end of the run of the skin effect heaters 60, the skm effect heaters 60 are held between the plate members 48, discussed previously, and a second set of plate members 90. The second set of plate members 90 are positioned against the second side 44 of the vehicle carrying portion 40. The second set of plate members 90 are sandwiched between the skm effect heaters 60, or heating tubes, and the second side 44 of the vehicle carrying portion 40. The skm effect heaters 60, or heating tubes, are preferably welded to the plate members 90. This design applies to the stability of the ends of the skm effect heaters 60 to counteract the forces due to thermal expansion between adjacent runs of skm effect heaters 60. The second set of plate members 90 are preferably also formed with a saddle shape to engage a top portion of the skm effect heaters 60. The first and second set of plate members 48, 90 fixedly hold the skin effect heaters 60 therebetween.

Referring again to Fig. 4, the removable physical contact of the skin effect heaters 60 with the structural member 32 eliminates the possibility of inducing fatigue cracks into the structural member 32, such as is the case with the prior art welded skin effect heating systems discussed previously. The resulting heated structural member 32 of the present invention, having the skin effect heating system 30, is an AASHTO Bridge Code Category C stress detail or less, which is preferable for bridge components as discussed previously.

Referring now to Figs. 4-9, the present invention is also a method of attaching the skin effect heaters 60 to the structural member 32. The studs 46 are secured at spaced intervals along the second side 44 of the vehicle carrying portion 40. Preferably, the studs 46 are provided as threaded studs that are welded to the second side 44 of the vehicle carrying portion 40. The plate members 48 are received on the studs 46. The removable locking members 50 are then received on the end of the studs 46 and support the plate members 48 in the vertical direction. The locking members 50 are received on the studs 46 so that spacing exists between the respective plate members 48 and the second side 44 of the vehicle carrying portion 40. The continuous skin effect heaters 60 are then guided into the spacing between the respective plate members 48 and the second side 44 of the vehicle carrying portion 40. The locking members 50 positioned at the end of the studs 46 are generally provided in the form of nuts and lockwashers or, preferably, removable locknuts. The locking members 50 are then tightened against the plate members 48 so that the plate members 48 engage the skin effect heaters 60. The locking members 50 are tightened sufficiently against the plate members 48 to maintain the skin effect heaters 60 in removable contact with the second side 44 of the vehicle carrying portion 40. In general, the locking members 50, when provided as locknuts, are tightened on the threaded studs 46 to about forty- five foot-pounds of torque. This ensures that the plate members 48 maintain the skin effect heaters 60 in contact with the second side 44 of the vehicle carrying portion 40. A source of electrical power (shown in Fig. 1) , preferably 600V AC single phase current, is supplied to the skin effect heaters 60. This is generally sufficient to heat the skin effect heaters 60, or heating tubes, to about 250°F. The heat from the skin effect heaters 60, or heating tubes, is transferred primarily by conduction to the vehicle carrying portion 40 through the physical contact between the second side 44 of the vehicle carrying portion 40 and the respective skin effect heaters 60. The now heated vehicle carrying portion 40 is heated sufficiently whereby the first side 42 of the vehicle carrying portion 40 reaches a temperature that substantially prevents the accumulation of frozen precipitation thereon. The first side 42 of the vehicle carrying portion 40 generally defines a vehicle carrying surface upon which a vehicle (not shown) will travel. A similar principle of operation is employed when the structural member 32 is a rail and the skin effect heating system 30 is attached to the top flange of the rail. Heat transfer between the skin effect heaters 60, or heating tubes, and the vehicle carrying portion 40 will also occur by convection through the air between the surfaces of the skin effect heaters 60 and the second side 44 of the vehicle carrying portion 40, especially when the skin effect heaters 60 are enclosed by insulation 70 and spacer block 86, and housed within respective cavities 88 when heat loss to the ambient environment is reduced.

If desired, insulation 70 may be installed adjacent the skin effect heaters 60 and, together with the spacer block 86, enclose the skin effect heaters 60 as shown in Fig. 6. In particular, the first and second washers 72, 73 are received on each of the studs 46. The first washer 72 is placed in contact with the locking member 50 previously positioned on each of the studs 46. The insulation 70 is then received on the elongated portion 74 of the studs 46 and held in place on each of the studs 46 by the sleeve 76, the third plate washer 78, and the second locking member 80. The third plate washer 78 and the second locking member 80 generally support the insulation 70 and the spacer block 86 in the vertical direction on the respective studs 46. The second locking member 80 secures the sleeve 76 between the second and third plate washers 73, 78 on each of the studs 46.

At the end of the run of the skin effect heaters 60, or heating tubes, the second set of plate members 90 may be positioned against the second side 44 of the vehicle carrying portion 40. The skin effect heaters 60 are held fixedly between the first set of plate members 48, discussed previously, and the second set of plate members 90. The second set of plate members 90 provide stability at the end of a run of the skin effect heaters 60. The skin effect heaters 60 are preferably provided as a coil in which the skin effect heaters 60 have a length of about fifteen hundred feet .

The present invention as described hereinabove provides a skin effect heating system for attachment to a structural member that results in a more favorable fatigue stress category for the structural member. In addition, the present invention simplifies and reduces the costs associated with the fabrication and installation of the skin effect heating system for attachment to the structural member. Furthermore, the present invention provides a skin effect heating system which affords flexibility for future changes and improvements to the system by providing removable locking members and plate members which support the skin effect heaters.

The present invention was described with reference to a preferred embodiment which is merely illustrative of the present invention and not restrictive thereof. Obvious modifications and alterations of the present invention may be made without departing from the spirit and scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereto.

Claims

WE CLAIM :

1. A skin effect heating system, comprising: a structural member adapted to carry a vehicle, the structural member having a vehicle carrying portion with a first side and a second side, with the first side defining a vehicle carrying surface upon which the vehicle travels; and a continuous skin effect heater removably attached to the second side of the vehicle carrying portion and in contact therewith.

2. The system of claim 1, wherein the continuous skin effect heater is held in removable contact with the second side of the vehicle carrying portion along substantially an entire length of the skin effect heater.

3. The system of claim 2, wherein the continuous skin effect heater has a length of about fifteen hundred feet .

4. The system of claim 1, further including a clamp attached to the second side of the vehicle carrying portion, wherein the clamp holds the skin effect heater in removable contact with the second side of the vehicle carrying portion.

5. The system of claim 4, wherein the clamp further comprises: a threaded stud secured to the second side of the vehicle carrying portion; a plate member cooperating with the stud; and a removable locking member positioned on the stud to retain the plate member on the stud member and hold the plate member in engagement with the skin effect heater such that the skin effect heater is held in removable contact with the second side of the vehicle carrying portion.

6. The system of claim 5, further comprising: a plurality of threaded studs secured at spaced intervals along the second side of the vehicle carrying portion; a plurality of plate members cooperating with the studs, respectively; and a plurality of removable locking members respectively positioned on the studs to retain the plate members on the studs and hold the plate members in engagement with the skin effect heater such that the skin effect heater is held in removable contact with the second side of the vehicle carrying portion.

7. The system of claim 6, wherein the studs are spaced at about six inch intervals along the second side of the vehicle carrying portion.

8. The system of claim 7, wherein the studs are welded to the second side of the vehicle carrying portion, and wherein the locking members are locknuts tightened on the studs to about forty-five foot-pounds of torque.

9. The system of claim 4, wherein the clamp is a saddle clamp.

10. The system of claim 6, wherein thermal insulation is supported on an elongated portion of the studs and encloses the skin effect heater.

11. In combination: a box beam adapted to carry a vehicle comprising: a first member; a second member spaced from the first member; and two elongated members connecting the first and second members, wherein the first member is a vehicle carrying portion of the box beam and includes a first side and a second side, wherein the first side of the vehicle carrying portion defines a vehicle carrying surface upon which the vehicle travels; and a continuous skin effect heater removably attached to the second side of the vehicle carrying portion of the box beam and in contact therewith.

12. The combination of claim 11, wherein the continuous skin effect heater is held in removable contact with the second side of the vehicle carrying portion along substantially an entire length of the skin effect heater.

13. The combination of claim 12, wherein the continuous skin effect heater has a length of about fifteen hundred feet .

14. The combination of claim 11, further including a clamp attached to the second side of the vehicle carrying portion, wherein the clamp holds the skin effect heater in removable contact with the second side of the vehicle carrying portion.

15. The combination of claim 14, wherein the clamp further comprises: a threaded stud secured to the second side of the vehicle carrying portion; a plate member cooperating with the stud; and a removable locking member positioned on the stud to retain the plate member on the stud member and hold the plate member in engagement with the skin effect heater such that the skin effect heater is held in removable contact with the second side of the vehicle carrying portion.

16. The combination of claim 15, wherein the stud is welded to the second side of the vehicle carrying portion, and wherein the locking member is a locknut tightened on the stud to about forty-five foot-pounds of torque .

17. The combination of claim 14, further comprising : a plurality of clamps secured at spaced intervals along the second side of the vehicle carrying portion.

18. The combination of claim 17, wherein the clamps are spaced at about six inch intervals along the second side of the vehicle carrying portion.

19. The combination of claim 14, wherein the clamp is a saddle clamp.

20. The combination of claim 15, wherein thermal insulation is supported on an elongated portion of the stud and encloses the skin effect heater.

21. The combination of claim 11, wherein the vehicle includes a plurality of spaced-apart drive wheels in contact with the first side of the vehicle carrying portion, and wherein the combination further includes a plurality of skin effect heaters removably attached to the second side of the vehicle carrying portion and in contact therewith, with the plurality of skin effect heaters positioned along the second side of the vehicle carrying portion opposite from the spaced-apart drive wheel of the vehicle.

22. A method of attaching a skin effect heater to a structural member adapted to carry a vehicle, the structural member having a vehicle carrying portion with a first side and a second side, with the first side defining a vehicle carrying surface upon which the vehicle travels, comprising the steps of: securing a plurality of studs at spaced intervals along the second side of the vehicle carrying portion; receiving a plurality of plate members on the studs, respectively; receiving a plurality of removable locking members on the studs, respectively, with the locking members retaining the plate members on the studs such that spacing exists between the respective plate members and the second side of the vehicle carrying portion; guiding a continuous skin effect heater into the spacing between the respective plate members and the second side of the vehicle carrying portion; and securing the locking members on the studs such that the respective plate members engage the skin effect heater and hold the skin effect heater in removable contact with the second side of the vehicle carrying portion.

23. The method of claim 22, wherein the studs are threaded studs and the locking members are locknuts received on the studs, and wherein the method further includes the step of tightening the locknuts on the threaded studs .

24. The method of claim 22, further including the step of connecting a source of electrical power to the continuous skin effect heater.

25. The method of claim 22, further including the step of initially providing the continuous skin effect heater as a coil prior to guiding the continuous skin effect heater into the spacing between the respective plate members and the second side of the vehicle carrying portion.