BACKGROUND OF THE INVENTION Oil refineries and petrochemical plants commonly use large-scale, fired heaters to heat oil, water and other fluids. Figure I illustrates a typical fired heater 10.

The fluid to be heated enters the heater 10 at a first location 11, flows around a flame at the center of the heater until it reaches an elevated temperature, then exits the heater at a second location 12. The heated fluid then flows at a desired temperature to a subsequent piece of equipment (not shown). One or more large-scale heaters 10 can simultaneously operate at various locations within the plant. For the plant to use the heated fluids efficiently, the heaters 10 typically are located near other pieces of process equipment.

Fired heaters 10 are generally fabricated with a shell 13, a burner 14, a plenum chamber 15. and a heater tube 16. The shell 13 is typically a hollow right cylinder fabricated from sheet steel. Depending on the capacity of the heater, the cylinder can measure 40 or more feet in diameter and 100 or more feet along its radial axis. During use, the radial axis of the cylinder is commonly oriented vertically, with one end of the cylinder mounted to a foundation 17.

Fired heaters 10 burn fuel, such as natural gas. oil or coal. which is ignited within the plenum chamber 15 to heat the fluid. The burner 14 is located at the bottom of the heater 10, with the plenum chamber 15 located directly above the burner.

The burner 14 discharges fuel at a controlled rate to create a flame of the proper size to heat the process fluid to the desired temperature.

The fluid to be heated flows through the heater tube 16 around the perimeter of the plenum chamber 15. where the flame generally is the hottest. 1 lle heater tube 16 enters the plenum chamber 15 at the first location I I in the shell 13. As

the fluid flows through the heater tube 16 in the presence of the burning fuel, the temperature of the fluid increases. In order to heat the fluid efficiently, the heater tube 16 is routed as densely as possible around the plenum chamber 15. The heater tube 16 accordingly follows a tight, alternating pattern up and down the inner wall of the shell 13 and around the perimeter of the plenum chamber 15. Near the top and bottom of the shell 13, the fluid flows through a 180 degree bend and changes direction. The heater tube 16 follows this pattern around substantially the entire perimeter of the shell 13, at which point it leaves the plenum chamber 15 at the second location 12 in the shell.

The top of the heater 10 often carries a significant amount of equipment to use and discharge the burner's exhaust. A stack 18 for discharging exhaust is mounted to the top of the heater 10. In addition. other process equipment, such as a hot air bypass duct, a convection section or a transition, is commonly mounted to the top of the heater.

As the heater 10 ages, the heater tube 16 corrodes, causing the wall of the heater tube to become thinner. If the wall of the heater tube 16 becomes too thin, the heater tube can leak or burst from the pressure of the fluid being heated. In such a case, heated oil or other flammable liquid can discharge directly onto the flame at the center of the heater. This can result in the heater 10 exploding, which is extremely dangerous, as well as expensive and time-consuming to repair. To lessen the likelihood of such an event, the heater tube 16 is replaced regularly. Each day the heater 10 is down for repair, however, translates into significant costs for the plant. It is therefore desired that such repairs be completed as quickly as possible.

Replacing heater tubes 16 in the traditional manner is a costly and time- consuming project. Traditionally, the equipment on top of the heater 10 is first removed to provide access the inside of the heater and the heater tube 16. A large and often expensive crane is typically used to remove the stack 18. hot air by pass duct, convection section and transition due to the size and weight of this equipment. Also. because other equipment often surrounds the heater 10. the removed equipment must be moved to a remote parking lot or storage area. Each of these additional steps can add to

length, cost and complexity of the project, and to the cost of the equipment required for the project.

SUMMARY OF THE INVENTION The present invention is directed toward apparatus and methods for guiding a section of a heater tube to or from a mounting position along a wall of a fired heater while, for example, re-tubing the heater. In one embodiment, an apparatus incorporates an elongated member having a first end configured to be removably, rotatably and pivotally coupled inside the heater, and a second end spaced apart from the first end and configured to be coupled to a selected section of the heater tube. The elongated member can be rotated centrally within the heater about an axis of rotation aligned to intersect a central plenum section of the heater, and can be independently pivoted with respect to the heater about a pivoting axis non-parallel with the axis of rotation. The elongated member can rotate to position the second end of the elongated member radially inward of the selected section of the heater tube in its mounting position. The elongated member can pivot between a first position in which the second end of the elongated member approaches the selected section of heater tube and a second position in which the second end of the elongated member is spaced apart from the heater tube. When the elongated member is in the first position, the selected section of heater tube can be attached to or released from the second end of the elongated member. When the elongated member is in the second position, the apparatus can rotate within the heater about the axis of rotation to align the second end of the elongated member radially inward of the respective mounting position. The apparatus thus can sequentially replace every section of heater tube without removing any equipment from the top of the heater.

In another embodiment, the apparatus incorporates a central member configured to be removably, rotatably coupled inside the heater to rotate about the axis of rotation. In this particular embodiment, an elongated member is pivotally coupled to the central member to rotate therewith and to independently pivot about the pivoting axis between the first and second positions.

BRIEF DESCRIPTION OF THE DRAWINGS Figure I is an isometric view of a fired heater and related equipment according to the prior art.

Figure 2 is a sectional view of a fired heater and a portion of a heating tube for the fired heater and, positioned within the heater, an elevation view of an apparatus for re-tubing the heater according to an embodiment of the present invention.

Figure 3 is an enlarged elevation view schematically illustrating the apparatus for re-tubing the heater of Figure 2.

Figure 4 is a side elevation view of a central member of the apparatus for re-tubin, the heater of Figure 3.

Figure 5 is a side elevation view of an elongated member of the apparatus for re-tubing the heater of Figure 3, Figure 6 is a plan view of the apparatus for re-tubing the heater positioned for operation within the fired heater of Figure.

DETAILED DESCRIPTION OF THE INVENTION The present detailed description is generally directed toward apparatus and methods for re-tubing a fired heater. Many specific details of certain embodiments of the invention are set forth in the following description and in Figures-6 to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the invention may be practiced without several of the details described in the following description.

Figure 2 illustrates an apparatus For for removing or replacing a heater tube 21 in a fired heater'^ according, to an embodiment of the present invention. The apparatus 20 includes a mast 24 and a boom 26 pivotally attached thereto. In the illustrated embodiment, the boom 6 is attached to a point near a bottom of the mast 24, The boom 26, however, can be attached to other suitable locations along the mast 24.

The illustrated mast 24 is an elongated member aligned with a radial axis of the heater 22 during use. The mast 24 extends from a base 28 of the heater 2 to a point within the heater 22 near a top 40 of the heater. The mast 24 has a first rotating coupling 30 removably anchored to the base 28 of the heater 22. The mast 4 rotates about its longitudinal axis within the first rotating coupling 30. In the illustrated embodiment, the longitudinal axis of the mast 24 is collinear with both an axis of rotation R of the mast and the radial axis of the heater 22. The illustrated mast 24 is fabricated from multiple sections of steel pipe connected together by mast flanges 38.

The mast 24 can instead be fabricated as a single unitary body, or can be fabricated from other suitable materials, such as alloy metals or composites.

The illustrated apparatus 20 also has a second rotating coupling 32 located on the mast 24 opposite the first rotating coupling 30. The second rotating coupling 32 is attached by mounting cables 34 to a wall 36 of the heater 22. The mounting cables 34 are adjustable to plumb or retain the mast 24 in a desired orientation with respect to the heater 22. The second rotating coupling 32 retains the mast 24 in the proper alignment, and the mast rotates within the second rotating coupling about the axis of rotation R within the heater 22. The second rotating coupling 32 can instead be attached directly to the top 40 of the heater 22. or the mast 24 can be free standing. In either case, the stiffness of the mast 24 or a structure attaching the mast to the base 28 of the heater 22 can be designed to withstand the forces created during operation.

The boom 26 is pivotally coupled to the mast 24 by a pin 42. In the illustrated embodiment, the boom 26 and the mast 24 are coplanar, and the boom 26 can pivot toward and away from the mast within a plane defined by the two members. The boom 26 is coupled to the mast 24 at a point on the mast above the first rotating coupling 30. The boom 26 accordingly rotates with the mast 24 about the axis of rotation R. The boom 26 independently pivots with respect to the mast 24 between a closed position in which the boom is generally aligned with and adjacent to the mast. and an open position in which an upper end 46 of the boom approaches the wall 36 of the heater 22 (see. e.g., Figure 3). The illustrated boom 26 is fabricated from multiple

sections of steel pipe connected together by boom flanges 44. The boom 26 can instead be fabricated as a single unitary body. or can be fabricated from other suitable materials, such as alloy metals or composites.

Figures 3-5 illustrate the apparatus 20 and its primary elements. In Figure 3, the boom 26 in the open position is designated in solid lines and the boom 26' in the closed position is designated in broken lines. A section of the heater tube 21 is suspended from the upper end 46 of the boom 26.

A tube control cable 48 releasably connects the section of heater tube 21 to the boom 26. The tube control cable 48 is configured to be securely connected to the heater tube 21, but to be quickly and easily connected thereto and disconnected therefrom. In the illustrated embodiment, the tube control cable 48 extends from the heater tube 2 1, over a top boom pulley 50, and terminates at a boom winch 52. One or more intermediate pulleys can be situated along the length of the boom 26 to guide the tube control cable 48. In the illustrated embodiment, the boom winch 52 is located near a lower end 54 of the boom 26, and can be controlled by an individual standing on the base 28 of the heater 22 (Figure 2). The illustrated boom winch 52 is powered by a boom winch motor 56 and controlled by a boom winch control 58. The boom winch control 58 controls the boom winch motor 56 to selectively lower or raise the heater tube 21 when suspended from the upper end 46 of the boom 26. The apparatus 20 can similarly use a manual winch, a chain drive or other known linkages for controlling the position of the heater tube 21 with respect to the upper end 46 of the boom 26.

A boom control cable 60 connects the upper end 46 of the boom 26 to an upper end 62 of the mast 24. In the illustrated embodiment, the boom control cable 60 extends from the upper end 46 of the boom 26, through the upper end 62 of the mast 24, and over a top mast pulley 64, and terminates in a mast which 66. One or more intermediate pulleys can be situated along the length of the boom control cable 60 to guide the boom control cable or to adjust the forces acting on the mast 24 and the boom 26. The illustrated mast winch 66 is located near a lower end 68 of the mast 24, and can be controlled by an individual standing on the base @ 28 of the heater 22 (Figure 2).

'the mast winch 66. and similarly the boom winch 52, can instead be mounted at other

locations along the length of the mast 24. elsewhere on the apparatus 20, or to the wall 36 of the heater 22. and can be controlled remotely. The illustrated mast winch 66 is powered by a mast winch motor 70 and controlled by a mast winch control 72. The mast winch control 72 controls the mast winch motor 70 to selectively move the boom '6 between the first and second positions. The apparatus 20 can similarly use a manual winch, a chain drive or other known linkages for controlling the position of the boom 26 with respect to the mast 24 and the heater 22.

Figure 4 provides a more detailed view of the mast 24. The first rotating coupling 30 at the extreme lower end 68 of the mast 24 has a first flange 74 and a first bearing 76. The first flange 74 can be removably attached to the base 28 of the heater 22 (Figure ?) The first bearing 76 is positioned between the first flange 74 and the mast 24. The second rotating coupling 32 at the extreme upper end 62 of the mast 24 similarly has a second flange 78 and a second bearing 80. The second flange 78 can have openings or other fasteners to attach the mounting cables 34 to the mast 24. The mast 24 thus rotates between the first and second rotating coupling 30/33.

An extension arm 82 is mounted to the lower end 68 of the mast 24, and projects outward from the mast. One or more additional extension arms can also be mounted about the perimeter of the apparatus 20. The extension arm 82 is rigidly attached to the mast 24, and can be used by an operator to rotate the mast about the axis of rotation R.

A pair of opposing first hinge members 84 are mounted on either side of the lower end 68 of the mast 24, Each first hinge member 84 has a first opening 86 for receiving the pin 42. The size. shape and location of the first hinge members 84 and the first openings 86 can vary based on the size or shape of the heater, the configuration of the heater tube, or other factors.

Figure 5 provides a more detailed view of the boom 26, A pair of opposing second hinge members 88 are attached on either side of the lower end 54 of the boom 26. The second hinge members 88 are sized and shaped to complement the first hinge members 84. Each second hinge member 88 has a second opening 0 positioned to align with the first openings 86 during use. The pin 42 accordingly

extends through the first and second openings 86/90 in the first and second hinge members 84/88 to pivotally attach the boom 26 to the mast 24.

Figure 6 illustrates the heater 22 and the apparatus 20 in various configurations during operation. Prior to assembling the apparatus 20, an access opening 92 is cut in the top 40 of the heater 22 at a location selected to avoid interference with overhead equipment. The access opening 92 is considerably smaller than the top 40 of the heater 2, but sufficiently large to allow the mast 24. the boom 26 and the heater tube 21 to pass longitudinally therethrough. After the access opening 92 is cut, the mast 24, boom 26 and other parts of the apparatus 20 are inserted into the heater 22 through the access opening 92, and the apparatus is assembled inside the heater.

The assembled apparatus 20 is then positioned to remove the heater tube 21 from the heater 22. An operator draws the boom control cable 60 into the mast winch 66 (Figure 3) to pivot the boom 26 about the pivoting axis P to the closed position (designated by distance C in Figure 6). In the closed position C, the boom 26 is free to rotate with the mast 24 within the heater 22 about the axis of rotation R. The operator rotates the mast 24 with the extension arm 82 (Figure 4) until the boom 26 is aligned radially inward of the section of heater tube 21 to be removed. The boom control cable 60 is then let out from the mast winch 66 to pivot the boom 26 about the pivoting axis P to the open position (designated by distance O in Figure 6). In the open position O, the upper end 46 of the boom 26 contacts or is above the heater tube 21, The upper end 46 of the boom 26 is then attached to the section of heater tube 21. An individual on a mobile work platform (not shown). such as a Spider platform, suspended from a fixed point on the upper end 46 of the boom 26 attaches the tube control cable 48 projecting from the upper end 46 of the boom 26 to the heater tube 2 1. By suspending the Spider platform from the upper end 46 of the boom 26, the individual moves with the boom. This can make it more efficient for the individual to connect and disconnect the heater tube 21 and the tube @ control cable 48. The individual could similarly work from a ladder, or from lines suspended from the top 40 of the

heater 22. The operator on the ground then uses the boom winch 52 to take the slack out of the tube control cable 48.

The heater tube 21 can then be removed, section by section. from the heater 22, The heater tube 21 is cut to allow sections of it to be removed from the heater 22. The size of the section of heater tube 21 removed is based on the height of the heater 22, the schedule of the heater tube e 21 and the size of the apparatus 20. Once the heater tube 21 is cut, the operator releases or cuts one or more fasteners 94 attaching the heater tube 21 to the wall 36 of the heater 22. The section of heater tube 21 is now suspended solely from the apparatus 20.

The operator then pivots the boom 26 toward the closed position C to permit the upper end 46 of the boom 26 and the removed section of heater tube 21 to rotate inside the remaining sections of heater tube. and rotates the mast 24 and boom 26 to radially align the boom with the access opening 92. The boom 26 is then pivoted to position the removed section of heater tube 21 directly under the access opening 92. and the heater tube 21 is raised with the boom winch 52 to a height near the upper end 46 of the boom 26. Workers outside the access opening 92 can attach the removed section of heater tube 21 to an external crane 96. The heater tube 21 can then be released from the tube control cable 48 and the heater tube can be removed from the heater 22 by the external crane 96.

The mast 24 is then rotated to align the boom 26 with the next section of heater tube 21 to be removed, and the steps repeated until the entire heater tube is removed from the heater 22, Installation of a new heater tube 91 is done in the reverse order.

Embodiments of the present invention have a number of advantages over the traditional apparatus and methods of re-tubing a fired heater. The apparatus is portable and eliminates the need for a heavy-duty crane'I'he illustrated embodiment. for example can be assembled and disassembled on site. and breaks down to a size convenient for being transported by truck and stored on site when not in use. The apparatus can be hoisted in parts into the heater using a small crane. The apparatus further can be used without removing the crossover hot air duct. cold air duct. stack.

stack transition, or other heavy equipment from the top of the heater. Traditionally. many of these functions were performed using a heavy-duty crane. The apparatus and methods of the invention consequently may be more efficient and less expensive than traditional methods.

The apparatus is also quicker and easier to use than traditional equipment and methods. The apparatus can be controlled from the ground by one or a few individuals, and requires only one individual on an elevated platform to connect and disconnect the heater tube from the apparatus. The apparatus consequently may be quicker than traditional methods and apparatus.

Example An example of a method for fabricating the apparatus of the present invention in a particular heater, using the apparatus to remove and replace the heater tubes from that heater, and remove the apparatus from the heater is summarized below.

The exact methods used in other situations will vary depending upon, among other factors, the size and shape of the heater, the configuration of platforms, the shape of the transition, etc. Other variations and details can be found in Provisional Application No.

60/105106. incorporated herein by this reference. This description accordingly is offered by way of illustration and not by way of limitation.

A track consisting of two I beams with side rails is set on top of the plywood floor to mount"Multi ton"or"Hillman"rollers on. This track is set in line with the opening in the roof or transition. extending over and beyond the center of the furnace. This is how the bottom or lower end of the lifting device is supported and transferred from the outside of the furnace to the center.

At the top of the straight side of the furnace shell, on the outside where the transition begins, to the underside of the convection section. 4 individual sheave assemblies are mounted in 90 segments. These sheave assemblies will accept 5/8"guy lines extending from the top of the lifting device and are the top end support for the device. In a horizontal line with the groove on top of the sheave, drill a 1"hole straight into the transition on a level plane with the sheave.

The sheaves is mounted in such a manner that when the cable passes over the sheave it clears the top angle on the straight portion of the vertical shell and also clears any other interferences that exist on or down the shell of the furnace. At the outside lower catwalk, equally spaced in line with the sheaves at the top of the shell, attachment brackets with 2 previously drilledz 3/4"holes are welded. The inside hole is for a turnbuckle and the outside hole is for a shackle.

Pre-position four guy lines cut to a dimension approximately equal to double the vertical shell height. Take the guy lines to the top platform and feed the end of each guy line through the hole in line with the sheaves until the line reaches the floor of the furnace. Through the access opening in the transition, drop four independent 3/4"manilla ropes to the floor of the furnace keeping the other end secured at the opening. Tie each rope to one guy line and haul each line up through the access opening securing them at the opening. These guy lines will be attached to the top of the lifting device mast when it is in position.

The center support of the plenum chamber is reinforced to take the added weight of the lifting device and the weight of the tubes to be lifted. This is accomplished, in most cases, by adding !/2"x 3"cs. flatcar to the full length on four sides of the support pipe.

In order to install the lifting device and remove/install tubes, an opening is cut in the roof or transition of the heater. The size of the opening will be determined by the overall size of the lifting device's largest dimension.

The tubes can be removed either one at a time or two at a time. Two at a time (hairpin assembly) is preferable. This determination will provide the maximum load capacity for the lifting device. Once the load capacity is determined the lifting device can be engineered.

Prior to cutting the access hole in the roof or transition the opening is re- reinforced. This is accomplished by welding 1/2" x 6" es flatcar around the proposed cut staying back far enough to allow the use of arc gouges and a demolition saw (6"is usually sufficient).

A bearing housing for the lifting device is installed in the center of the inside floor of the furnace. This housing will be mounted on a 30"diameter, 1/2"thick, cs plate which is welded to the floor of the furnace.'I here is usually at least a 36" diameter opening that the refractory can be chipped out in order to make this weld.

The burner nose tile typically protrudes above the castable refractory floor anywhere from 2 to 6 inches. This requires a false floor consisting of 3/4" plywood laid flat and nailed or screwed into place on either cribbing or beams. The outside diameter of the floor should be at least 4 ft. smaller in diameter than the inside face diameter of the tubes. This will leave enough room to work between the outside edge of the floor and the face of the tubes.

The lifting device is designed to pick the maximum weight of the tube assemblies being removed or installed. It will consist of a"mast"and a"boom" constructed of at least three pipe sections depending on the height of the furnace. The mast has a bearing at the top and the bottom that allows the mast to rotate 360°. At the top of the mast is a plate with four equally spaced holes in which shackles are attached and accept four 5/8"guy wires. Near the bottom of the mast are two mounting brackets for tugger support bases. On the back side of the mast a 2000 lb. IR lufting tugger is mounted. This lufting tugger, requires approximately 300'of 3/8"cable. The cable runs up the back side of the mast, through the mast and over a sheave which is built into the mast just under the top bearing. The cable is attached to a block and two parted with the dead end coming back to the top of the mast just under the bearing. This is rigged up in advance and enough slack (c. g.. the radius of the heater plus a little) is taped off to the mast so it can be raised to the vertical position without dangling off to the side. The excess cable is to be coiled up and secured at the lower end of the mast.

It is to be spooled onto the luffing winch at a later time. There is also a 3/4"safety line that attaches to the mast just under the topping sheave in its own padeye. This line is also taped off to the mast before raising the mast to the upright position.

Once all the rigging has been completed and inspected. the mast is ready to be set into the furnace. I he mast is lifted at a single 1-1/4"eye bolt attached to the top center. The mast weight will be a function of the dimensions of the furnace and the

weight of the tube assemblies. For example ; in a furnace 30 ft. in diameter by 84 ft. high with 80 ft. long, 6"schedule 80 tubes, the weight of the derrick consisting of the mast and boom would be approximately 11, 000 pounds. The mast will weigh approximately 5000 pounds and the boom will weigh approximately 6000 pounds.

Rigging and moving the mast to the center of the heater is probably the most difficult task of the entire process. The mast is lowered into the heater and is placed on the rollers and track assembly already positioned. At the base of the mast is a collar that is wider than the mast itself. This collar allows the mast to sit in the rollers.

A 1/ 2"cable choker is fixed around the base of two tubes in the direction of the move to the center of the furnace. Attach either a 1-ton chainfall or come-a- long to this choker and attach the other end to the base of the mast and draw it tight. Do the same in the opposite direction as a hold back. As the one pulls towards the center of the furnace the opposing one acts as a brake and vice versa.

The four guy lines that were previously secured by ropes at the access hole are now made up to the collar ring at the top of the mast. This collar ring has four equally spaced holes 90'apart. The guy lines protrude from the furnace through four holes spaced at 90'intervals around the furnace. Each guy line is to be connected to a corresponding hole in the mast with 3/4"shackles. A fifth guy line is attached to the lifting eye on the top the mast. This guy line is woven through a sheave welded to a bracket at the access hole inside the furnace, opposite the line of travel. Another (the fifth) bracket is welded at a lower elevation in line with the bracket welded at the access opening. The five guy lines now are attached to the top of the mast, through the holes in the transition and laid in the sheaves, dropped alongside the heater down to the lower platform (Make sure there is enough excess cable For the guy lines). Five. 5/8"chokers, 10 feet long are attached to each guy line. The two in the direction of travel are clamped at least the distance of travel required to the center of the furnace. Hence, if the mast is to travel 15 feet to reach the center of the heater then the eye of the choker is at least 17 to 20 feet up from the bracket to which the guy line will finally be attached.

Chainfalls are now attached to each choker and the previously installed attachment bracket. The two chainfalls opposite the direction of travel will only need to be

attached to the cable at a point low enough to be able to work the chainfalls because they will be letting line out. The chainfatt attached to the 5th guy wire is the one that works in conjunction with the two pulling chainfalls. As the two pulling chaiIllalls are taken up the no. 5 chainfall is let off just enough to keep the two pulling chainfalls tight.

When the five guy wires with chokers and chainfalls are in place the mast is ready to be maneuvered to the center of the furnace. Workers are positioned in the furnace at the base of the mast while others are positioned around the furnace, at the outside. These workers will maneuver the mast to the center of the furnace keeping it vertical to within 4 in. from bottom to top. The guy lines attached to the top of the mast should be kept tight enough to keep out slack but should not put strain on the mast at all.

Upon reaching the center of the furnace, when the base is directly over the bearing all four guy lines from the top of the mast are made up to turnbuckles attached to the second hole in the attachment bracket. The four main guy wires are drawn tight and the mast is plumbed vertical.

Two hydraulic porta-powers are set on the plate on the outside of the bearing (inside the tracks) under the mast collar and the mast is raised up until the rollers become loose enough to remove. Remove the rollers and track and then lower the machined base of the mast into the bearing. This completes the setting and moving of the mast.

Mount the two tugger bases and the tuggers. The previously installed lufting tugger cable is now spooled onto the tutting lugger. It will be needed as soon as the boom is pinned into place. Also bolt on the two seismic or anti-sway braces for the boom.

Set the"Spider"into the furnace pulling it off to the side out of the way of work. Run off enough of its cable to reach the top of the heater. drop a line from the opening and draw the"Spider"cable up through the access opening and secure it until the boom is towered into the furnace.

The boom has a single sheave at the top with a hole for a 3/4"shackle in the cheek plate. This is where the dead end of the 1/2"cable will be clamped to make

two parts on the hook block. Run off enough cable (three times the length of the furnace shell) to make up the two-part block. Coil up the remainder and secure it to the base of the boom. At the top of the boom are two separate padeyes, one for the "Spider"cable connection and the other for a safety line connection for the people working out of the"Spider". The boom also will have two separate tugger bases that will be set into place after the boom is fixed into its final position. On the very top of the boom is a padeye for lifting. Once the boom is assembled and rigged, it is ready for standing and setting into the furnace. Upon lowering the boom into the furnace, stop when the boom tip is accessible to the people at the top of the access opening. This is when the lufting block is attached to the upper padeye on the top backside of the boom and the safety line is attached to the padeye below it. Also connect the"Spider"cable to its padeye and the two safety lines to their padeyes. The two anti-sway cables are also attached to their connection points. After these two lines are made up, lower the boom down until the point (pin) is just above its connection point on the mast. Connect a cable choker around the mast and one around the boom, each at the same elevation.

Hook a 1-1/2 ton come-a-long and draw the boom over to the mast. Align the connection points and insert the boom pin. Take up on the lufting tugger at this time and run it up and down a few times. Connect the two anti-sway cables and tighten the turnbuckles. The anti-sway arms are used for turning the device. Now the large tugger is ready to spool on the cable. Run the"Spider"cable up until you lift it off the floor.

The lifting device is now ready to test.

The first tubes to be removed are the ones directly under the access opening in the transition. A person in a full body harness with a lanyard, gets into the "Spider", and climbs to the predetermined point on the tubes the rigging is to be attached. This point will be somewhere below the"horseshoe"or keepers.

Using a single nylon choker, each eye of the choker is double wrapped around one tube of the hairpin and shackled to itself, this nylon choker should be at least 20 feet long. Once both ends of the choker are connected. the person in the "Spider"attaches the hook block in the bight of the choker, this insures the weight will be evenly distributed even if the eyes or connection points are not exactly at the same

elevation. The person in the"Spider"now calls to the main tugger operator to take up just enough to make the rigging snug. The point of the boom is to be lying against the tubes. (There is a bar on the cheek plates of the top sheave that prevents the sheave from nesting between the tubes). Once the rigging is taut, the person in the"Spider" moves up to the"horse shoes"and removes the pins from the"horse shoes"to the"T" bars. Once this is accomplished the two tubes or"hairpin"is now ready to be cut off at the lower ends with power hacksaws. These two cuts can be partially made before the rigging is attached but not while the person in the"Spider"is working over head. The person in the"Spider"does not have to come to the floor, they let themselves down to about the choke elevation and wait for the cuts to be completed. When the cuts are completed the tubes usually have to be lifted a little, the configuration of the lifting device automatically keeps pressure against the rtw bar. The tubes will hang vertically and the lifting device will now need to be boomed up just enough to clear the"T"bars.

Swing the lifting device to the opening and lift the hairpin high enough so the people on the outside platform can put a choker (basket hitch) on the 180'return bend. The outside crane then lifts the hairpin until the rigging on the lifting device is slack, at this time the person in the"Spider"removes the shackles from the nylon sling. Boom up the lifting device to clear the load being lifted. At this time the device can be turned to the next set of tubes and the process started all over again until the furnace is completely void of all the tubes.

To install the tubes the procedure is reversed.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. For example, the diameter and height of the heater and the diameter and schedule of the heater tubes will affect the overall size or configuration of the apparatus and the size and structure of its elements. Accordingly, the invention is not limited except as by the appended claims.