CA2534488A1 - System and apparatus for safely coupling multiple ground thawing heaters - Google Patents

Description

1 "SYSTEM AND APPARATUS FOR SAFELY COUPLING

2 MULTIPLE GROUND THAWING HEATERS"

3

4 FIELD OF THE INVENTION

The present invention relates to ground thawing apparatus and more 6 particularly to a plurality of apparatus coupled together in a safe manner and fed 7 from a minimum number of fuel supplies.

It is known to thaw frozen ground so as to ease excavation such as for 11 maintenance or repair access to buried utilities. A variety of patents discuss prior art 12 heaters including pending published application CA 2,330,214 and corresponding 13 issued US Patent 6,408,843 to Olson, U.S. Pat. No. 5,441,038 issued to Ohmann, 14 U.S. Pat. No. 5,033,452 issued to Carriere.

These prior art apparatus and others typically use propane has fuel 16 and generally use one propane tank for each heater. A multiplicity of fuel lines are 17 required and are exposed to vandalism and general damage.

18 There is still a need for a safe and effective system of ground thawing 19 heaters.

As stated in US 6,408,843 to Olson, a ground heater is used to thaw 21 ground to depths in the order of three feet during the cold winter months which will 22 allow individuals to evacuate soil from previously hard frozen earth to gain access 23 utilities.

1 Some disadvantages of the prior art heaters include convenience and 2 safety factors. Some ground heaters utilize burners which are removeably installed.
3 The live burners are easily dislodged by accidental contact with the fuel lines.
4 Multiple burners have multiple lines which add to clutter and risk of damage.
Multiple burners enhance the risk of one blowing out and discharging unburned fuel 6 while the other continues to act as an ignition source. Other heaters are poorly 7 insulated resulting in hot surfaces.

8 Further, for large areas requiring thawing, multiple heaters have been 9 provided however each being supplied with their own fuel supply, or with a header distributing a plurality of flexible lines, further elevating the risk of damage, numbers 11 of connections and access by vandals.

14 The present invention implements a system of heaters which are safe and can thaw larger areas of ground. A plurality of heaters is easily and safely 16 coupled together and can be fuelled by one or more fuel gas sources. Each heater 17 is coupled with a common main fuel line to an adjacent heater. Connections are 18 protected from abuse, accidental or intentional. A variety of sizes of heaters can be 19 provided which enable adapting to fit between utility access boxes, such as phone and electrical boxes, yet can be arranged in series and parallel to adapted to larger 21 areas as well. Examples of convenience heaters dimensions (plan view) include 1 22 foot by 6 foot which fit between most surface utility boxes and 2 foot by 6 foot which 23 cover larger areas but can still be handled by personnel. Convenient man-handling 1 chain (as shown), cable, or other handles can be provided at each end of the heater 2 housings.

3 Heaters themselves comprise an insulated housing forming a cavity 4 with an open bottom. The housing rests on the frozen ground with the open bottom facing the ground. A radiant heater tube extends through the cavity and out of each 6 end of the housing. The tube delivers heat through the cavity to the ground.
The 7 heater further comprises a main fuel line, preferably extending through the insulated 8 housing and being insulated from the cavity and not accessible from outside the 9 housing.

In a system of multiple heaters, a fuel source is coupled to a first 11 heater in a chain of heaters. The fuel source may be coupled directly coupled to the 12 first heater and to main fuel line or the fuel source can be regulated at a first 13 pressure (about 15 - 17 psig) for delivering gas at a controlled pressure to the main 14 fuel line. While a first regulator at the fuel source is not required, there is added safety should the coupling hose or main line be damaged. Each heater further 16 comprises a second unit regulator for providing fuel at a second pressure (about 8-17 12 psig) to a burner or torch which fires into a first burner end of the radiant heater 18 tube accessible at a burner end of the heater. The first burner end of the tube 19 extending about 1 inch from the housing is fit with torch, an ignition system and aspirated air inlets. A second of the tube extends from the other discharge end of 21 the housing for discharging exhaust gases. Persons of skill in the art are aware of 22 the burner requirements to support a radiant heater. An example is a length of 23 radiant heater tubing of 2-1/2" exhaust pipe tubing. The torch can be propane 1 certified brass fittings including a'/" pipe with an end cap, the end cap being drilled 2 with a propane fuel sized-orifice. Preferably the orifice is positioned deep enough in 3 the tube to fire beyond the housing insulation.

4 Adequate air ports are provided to ensure combustion, such as ports formed through the closed end of the tubing or a plurality of ports formed about the 6 circumference of the tubing adjacent the fuel orifice. A conventional igniter includes 7 a piezoelectric igniter for a barbeque. The igniter preferably extends into the tube to 8 about the end cap and orifice.

9 In more detail, the heater housing comprises an outer protective shell.
Inside the housing is an inner shell. Typically the outer and inner shells are formed 11 of galvanized steel. Between the shells is insulation. In one embodiment, the 12 insulation includes a high temperature woven fibre ceramic insulation such as 13 Cerablanket (a register trademark of Thermal Ceramics, Inc. of Augusta, GA) 14 adjacent the inner layer. A thickness of 1 inch is suitable. Outwardly, and adjacent the outer shell is a layer of mineral fiberboard insulation such as FBX
Industrial 16 Board insulation from Fibrex Insulations Inc., Sarnia, Ontario Canada. A
thickness 17 of 2 inches is suitable.

18 The heaters are joined by a length of flexible, preferably armoured, fuel 19 line coupled between the main fuel lines of each discrete heater. The main fuel lines, such as 3/ inch pipe, are safely located within the outer shell of the housing 21 and are themselves insulated with tubular woven insulation. Preferably the insulated 22 main fuel line is wholly located within a longitudinally extending cavity formed in the 23 board insulation and thus extends along the outer shell.

1 To further protect the equipment from tampering, vandalism and 2 general damage, the burner and discharge ends of each heater are fit with end caps 3 or lock boxes.

4 A lock box has an open at least one open side for coupling with the burner end or discharge end of the heater and can have an open bottom. When 6 supported from the heater by fasteners, the bottom of the lock box is spaced above 7 the ground for ease of placement of insulating mats thereunder. When installed to 8 the heater, the lock box protects fuel fittings, the torch and second regulator. The 9 top of the lock box has a locking lid or access door for enabling maintenance access thereto. When coupled with other heaters, flexible coupling hose between main fuel 11 lines of adjacent heaters enables elevation changes and rotational placement 12 therebetween. The lockboxes of adjacent heaters are only spaced enough that 13 insulating mats can be slipped under the lock boxes and insulate substantially all of 14 the ground between heaters.

17 Figure 1 is a perspective view of an embodiment of the invention 18 illustrating one of a plurality of heaters with lock boxes and surrounding side ground 19 mats. The heater has lifting chains or cables at adjacent the burner end and the discharge end. Lock boxes on each end are shown closed and locked to protect fuel 21 fittings. A propane tank is shown as a source of fuel.

22 Figure 2 is a plan view of an arrangement of a system of heater boxes, 23 each with lock boxes and ground pads surrounding each box to best retain the

5 1 generated heat in the ground under and adjacent teach heater , Each heater is 2 connected in series with the adjacent heater. Parallel arrangements and mixtures of 3 parallel and series arrangements can also be made. One propane tank is shown 4 although multiple tanks may also be used where convenient, each tank feeding one or more heaters.

6 Figure 3 is a perspective view of one heater according to the invention.

7 The burner end illustrates a flexible feed fuel line to a tee fitting which splits to the

8 main fuel line valved at the heater housing, and a line to the burner. The main line

9 extends through the heater housing, emerging at the discharge end and outfitted with an additional valve (Fig. 6). The burner line is fit with a regulator and a 11 discharge line to the burner in the fire tube. A piezoelectric ignition button and line is 12 shown at the right and extending into the fire tube.

13 Figure 4 is close up alternate view of the burner end according to Fig.
14 3.

Figure 5 is a close up view of the fittings and piping at the burner end.
16 A shutoff valve is more clearly shown between the secondary regulator and the 17 burner or torch.

18 Figure 6 is a perspective end view of the discharge end o the heater.
19 The fire tube exhaust is shown as is the main fuel line and shutoff valve.

Figure 7A is an outside end view of a heater illustrating the 21 arrangement of main valve, secondary regulator, igniter and burner extending into 22 the fire tube.

1 Figure 7B is a cross-sectional end view of the heater of Fig. 7A
2 showing the outer shell, board insulation, blanket insulation, inner shell and fire tube.
3 Figure 8A is a plan view of the heater housing.

4 Figure 8B is an underside view of the heater housing illustrating cavity hand radiant fire tube.

6 Figure 9 is a perspective view of a heater with the outer and inner 7 shells installed and the side and end walls being capped along the bottom surface 8 about the cavity.

9 Figure 10 is a perspective view of a heater with the outer and inner shells installed with some bottom capping removed from the sidewalls to show the 11 board and blanket insulation.

12 Figure 11 is another perspective view of the heater of Fig. 10 with the 13 outer and inner shells installed and with all of the bottom capping removed from the 14 sidewalls to show the board and blanket insulation.

Figure 12 is a partial cutaway side view of an embodiment of a burner.

17 Although the present invention has been described in considerable 18 detail with reference to certain preferred versions thereof, other versions are 19 possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

Claims