US3614073A

US3614073A - Fired heater construction

Info

Publication number: US3614073A
Application number: US885894A
Authority: US
Inventors: Sidney Born
Original assignee: BORN ENGINEERING CO
Current assignee: BORN ENGINEERING Co
Priority date: 1969-12-17
Filing date: 1969-12-17
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19
Also published as: GB1325158A; FR2075881A1; FR2075881B1

Abstract

A direct fired heater having a furnace chamber and a plurality of vertical tubes disposed therein which are extended through a sliding seal in the chamber floor and are engaged by a plurality of spring loaded legs mounted on swingable cradles. Beneath the chamber, each vertical tube has a small connector tube which is attached to an outlet manifold supported on legs extended upwardly from swingable manifold cradles. Each outlet manifold is connected to a centrally disposed collector conduit which is suspended from a transverse structural member by a plurality of sliding anchor supports.

Description

United States Patent 72 Inventor Sidney Born 1,647,570 11/1927 Kling 563/20 Tulsa, Okla. 3,476,519 11/1969 Decaux 165/145 X [21] P 885894 Primary Examiner-John J. Camby [22] Filed Dec. 17,1969 A" S E m K S fi ld&L we 45 Patented on. 19, 1971 6 [73] Assignee Born Engineering Company Tulsa, Okla.

54 FIRED HEATER CONSTRUCTION ABSTRACT: A direct fired heater having a furnace chamber 7 Claims, 8 Drawing Figs and a plural1ty of vertical tubes disposed therein wh1ch are extended through a sliding seal in the chamber floor and are en- [52] U.S. Cl 263/20 gaged b a plurality of spring loaded legs mounted on swinga- [51] Cl F23115/04 ble cradles. Beneath the chamber, each vertical tube has a [50] Field of Search 263/20; small connector tube which is attached to an outlet manifold l65/145 supported on legs extended upwardly from swingable manifold cradles. Each outlet manifold is connected to a cen- [56] References cued trally disposed collector conduit which is suspended from a UNITED STATES PATENTS transverse structural member by a plurality of sliding anchor 1,574,547 2/1926 Bell 263/20 supports.

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FIRED HEATER CONSTRUCTION BACKGROUND OF THE INVENTION The art of supplying heat to a substance to produce a chemical transformation, known as pyrolysis," and supplying heat to reactants to produce a chemical reaction has long been practiced. To meet the need of the chemical and petroleum industries to produce large quantities of products by a pyrolytic or endothermic reaction, devices known as direct fired heaters are employed to continuously supply radiant and convective heat to process materials.

A design obstacle of major importance in such heaters is the thermal expansion of various members produced by the high temperature at which these heaters must operate.

A typical configuration of a direct fired heater includes a furnace chamber in which hot gases are introduced or formed and a plurality of elongated tubes which are vertically disposed in parallel rows within the chamber. The vertical tubes extend through the top or roof of the chamber where small flexible tubes are attached to deliver process material to each vertical tube from an inlet manifold. Preferably, many vertical tubes are employed in order to increase the surface area of the process materials available for heat transfer and, depending upon the particular substance or reactants to be heated, the tubes are filled with a catalyst to enhance the reaction rate.

The tubes are supported from a gantry structure located above the furnace chamber by a counterweight suspension apparatus. This permits any longitudinal expansion of the vertical tubes, caused by heating, to be primarily in an upward direction.

At their lower ends, the vertical tubes terminate within the furnace chamber and have associated small connector tubes to deliver material to an outlet manifold which extends from the chamber and is connected to auxiliary piping to deliver the products to additional process equipment.

In the lower furnace region, the thermal expansion problem is particularly acute. The outlet manifold expands longitudinally in a direction perpendicular to the vertical tubes and, through the small connector tubes, tends to spread apart the vertical tubes, thus putting shear stress in the connector tubes.

U.S. Pat. No. 3,267,915 teaches that the stress in the connector tubes can be eliminated by interconnecting the vertical tubes in a row with a bar which expands at the same rate as the outlet manifold. As the outlet manifold expands, the vertical tubes are spread apart by the expansion of the bar so that each vertical tube retains its same position relative to the manifold, thus eliminating stress in the connector tubes. This configuration, however, necessitates additional structural material which must be subjected to a high temperature and from the standpoint of safety and maintenance, is not satisfactory in the event repair to any of the various connections is required.

SUMMARY OF THE INVENTION The primary object of this invention is to provide a direct fired heater of improved construction wherein the lower portions of the vertical tubes, the small connector tubes, and the outlet manifolds are all located outside the furnace chamber. Since the manifolds are not exposed to the hot flue gases within the furnace chamber, the thermal expansion of the manifold at a lower temperature is greatly reduced. This, in turn, results in less horizontal displacement of the vertical tubes and minimizes the stress in the connector tubes.

From the standpoint of maintenance and safety, there are a multiplicity of advantages in locating the outlet manifolds and connections to the vertical tubes remote from the furnace chamber. Routine inspection, as well as minor repair, of the vertical tube connections, which in other fired heaters is impossible, is now possible. In addition, the undesirable possibility of process material leaking from the various connections into the furnace chamber is virtually eliminated. Since only a straight section of the vertical tube is exposed to the hot flue gases, the heater can be operated at higher temperatures without damage to the welds or the connector tubes necessary to deliver material from the vertical tubes to the outlet manifolds.

Another object of the invention is to provide a direct fired heater of improved construction wherein the furnace chamber includes a slidable floor seal through which a plurality of vertical tubes are extended. When the vertical tubes are spread apart in a horizontal direction by the thermal expansion of the outlet manifold, the floor seal is operable to slide with the displacement of the vertical tubes. The floor seal is also operable to support loose refractory material which fills in any gaps in the furnace floor to prevent heat leak when the vertical tubes and seal are horizontally displaced.

Another object of the invention is to provide a direct fired heater of improved construction wherein the outlet manifolds and lower portions of the vertical tubes are located beneath the floor of the furnace chamber and are supported by swingable cradles. The cradles are operable to swing outwardly in order to minimize shear stress in the small tubes connecting the vertical tubes and the outlet manifolds when the latter members thermally expand. Counterweights attached to the top of the vertical tubes collectively aid in relieving stress in the connector tubes when the cradles supporting the outlet manifolds and the cradles supporting the vertical tubes swing outwardly in an upward arc.

An additional object of the invention is to provide a direct fired heater of the character described wherein spring loaded support legs are mounted on the swingable cradles and are extended upwardly therefrom to engage the vertical tubes. The support legs are spring relieved to assist the counterweights in preventing stress in the small connector tubes and to compensate for the variation in the deflection profile of the manifold cradles compared to the deflection profile of the vertical tube cradles.

A further object of the invention is to provide a direct fired heater of the character described wherein the outlet manifolds are connected to a collector conduit which is suspended from a transverse structural member by a plurality of sliding anchor supports. One end of the conduit is closed and the other end is connected to piping which delivers the products from the furnace chamber to additional process equipment. The sliding anchor supports permit the conduit to thermally expand only in a direction away from the piping-conduit connection.

Other and further objects of the invention, together with features of novelty appurtenant thereto, will appear in the course of the following description.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith, and in which like reference numerals indicate like parts in the various views:

FIG. 1 is a sectional elevational view of a direct fired heater constructed in accordance with a preferred embodiment of the invention;

FIG. 2 is a plan view generally along line 22 of FIG. I in the direction of the arrows;

FIG. 3 is a fragmentary plan view along line 3-3 of FIG. 1 in the direction of the arrows;

FIG. 4 is an enlarged, detailed sectional view of the lower portion of the fired heater;

FIG. 5 is a side view of the collector conduit generally along line 5-5 of FIG. 2 in the direction of the arrows;

FIG. 6 is a sectional view along line 6-6 of FIG. 5 in the direction of the arrows;

FIG. 7 is a sectional view along line 7-7 of FIG. 5 in the direction of the arrows; and

FIG. 8 is a fragmentary plan view along line 8-8 of FIG. 4 in the direction of the arrows.

Referring again to FIG. 1 which is a partly schematic, sectional view of the fired heater, a frame structure 10 mounted above the ground 11 on piers 12 provides the basic rigidity of the heater and in the preferred embodiment of the invention is constructed of l-beam members. A furnace chamber 13 in section is in the shape of an isosceles trapezoid and is defined by

beam members

14 and 15 supported on the piers 12 and sloped inwardly from bottom to top, upper horizontal members 16 joined to the ends of the sloped

members

14 and 15, and lower horizontal members 17 joined respectively to the sloped

members

14 and 15 above the piers 12.

Surrnounting the furnace chamber 13 is a gantry structure 18 having

upright members

19 and 20 journaled to the ends of the sloped

members

14 and 15 and to the upper horizontal members 16. Upper gantry members 21 are connected to the ends of the

upright members

19 and 20.

A suitable sheeting (not shown) is attached to the inner surfaces of the I-beam members defining the furnace chamber 13 to form the roof 13a, floor 13b,

sidewalls

13c and 13d, and end wall closures (not shown). The interior of the furnace chamber 13 enclosed by the sheeting is lined with a refractory material 22 and additional sheeting may be attached to the outer surfaces of the I-beam members to'provide a dead airspace as additional insulation.

Schematically shown in the floor 13b of the furnace chamber are nozzles 23 which may be conventional burners to form combustion gases within the chamber or inlet ports for delivering hot gases into the chamber and which can be provided at any convenient location within the furnace chamber 13, such as in the sidewalls, end walls, or roof. The hot gases so formed or introduced are discharged near the upper end of the chamber 13 through a flue gas outlet 24.

In the roof 13a and substantially continuous throughout the length of the chamber 13 is an elongated slot 25. Aligned with the slot 25 is an elongated continuous slot 26 in the floor 13b of the chamber which is structurally defined by

longitudinal members

27 and 28 attached to the lower horizontal members 17. Slot 26 is continuous throughout the length of the fired heater save for the lower horizontal members 17 which are traversely located at opposed piers 12. Received by the

slots

25 and 26 are a plurality of vertical tubes 29 which, as best viewed in FIG. 2, are arranged in two parallel rows and are &- set in order that each tube in one row is adjacent the space between two tubes in the other row. Altemately, a single row of tubes may be employed, but either arrangement allows uniform heat transfer to the surface area of each tube 29.

The upper portion of each vertical tube 29 extends through the slot 25 into the interior of the gantry structure 18 where one end of a cable 30 is connected to the end cap 31 of the tube. The other end of the cable 30 is attached to a lever arm 32 which is supported at a pivot attachment 33 by a cable 34 from longitudinal members (not shown) of the gantry structure 18. A counterweight 35 is connected by a cable 36 to the opposite end of the lever arm 32. Each vertical tube 29 may have an individual counterweight apparatus as described or a single counterweight apparatus may be employed for a plurality of vertical tubes 29.

Throughout the length of the furnace chamber 13 is an inlet manifold 37 supported within the gantry structure 18 by cantilever posts 38 attached to the inside surfaces of the vertical members 20. A plurality of pigtail tubes 39 are connected along the inlet manifold 37 and each pigtail tube 39 is connected to one of the'vertical tubes 29.

A roof seal 40 having holes through which the vertical tubes 29 are received is preferably fabricated from a refractory material and provides a closure for the continuous slot 25.

The lower portion of each vertical tube 29 extends beneath the furnace floor 13b through the slot 26 and is closed by an end cap 41. Associated with the

longitudinal members

27 and 28 are a plurality of J-bolts 42 which receive the upper eyelet loops 43 of hanger rods 44. One hanger rod 44 on each side of the vertical tubes 29 is connected to a skewed horizontal cradle member 45 by a J-bolt 46 receiving the lower eyelet loop 47 of the hanger rod 44. Extended upwardly from each cradle member 45 is a plurality of spring loaded support legs 48, later to be described in detail, each of which engage. the end cap 41 of a vertical tube 29. As best viewed in FIG. 2, the cradle members 45 are oriented at an angle in order to support one vertical tube 29 in each row of parallel tubes.

Above the end cap 41, but beneath the furnace chamber 13, horizontally disposed connector tubes 49 extend outwardly from each vertical tube 29 and are joined to an outlet manifold 50. In the preferred embodiment of the invention an outlet manifold 50 is provided for each rowof parallel tubes 29. However, a single outlet manifold 50 can be connected to two rows of tubes 29 by passing the connector tubes 49 from the manifold to the far row of tubes through the spaces between the tubes 29 in the near row. This alternate arrangement may also be duplicated to increase the heater capacity by employing four parallel rows of tubes.

Associated with the lower horizontal members 17 toward the outer ends of the outlet manifolds 50 are a plurality of 1- bolts 51 which receive the upper eyelet loops 52 of hanger rods 53. One hanger rod 53 on each side of an outlet manifold 50 is connected to a manifold cradle 54 by a .l-bolt 55 receiving the lower eyelet loop 56 of the hanger rod 53. A support leg 57 extends upwardly from each manifold cradle 54 toward the outlet manifold 50 where it is received by a tubular extension 58 and secured thereto by a plurality of bolts 59.

As viewed in FIG. 2, the outer end of each outlet manifold 50 is closed by a pipe cap 60 and the opposite, inner ends are connected through

cross fittings

61 and 62 to a collector conduit 63 which is located at the transverse center line of the heater. Pipe cap 64 closes one end of the collector conduit 63 and the other end is connected to auxiliary piping (not shown) at a tight anchor" (that is, a piping connection which is not displaced by thermal expansion of the collector conduit 63) in order to deliver products from the fired heater to additional process equipment.

The collector conduit 63 is mounted beneath the furnace chamber 13 on the center lower horizontal member 17 by a plurality of anchor supports 65 and 66 best viewed in FIGS. 5, 6 and 7. A support bracket 67 is attached to the member 17 to provide a substantially flat surface on which the upper surface of an inverted U-shaped pipe hanger 68 is rigidly attached. A pair of struts 69 project inwardly from the lower ends of the pipe hanger 68. A pipe support member 70, as viewed in FIG. 7, is attached to the exterior surface of the collector conduit 63 and has diametrically opposed channels 71 which receive in slidable engagement the struts 69 of the inverted U-shaped pipe hanger 68. t

In FIG. 5 and also in FIG. 2, there is shown a frustoconical fitting 72 which provides a transition to a double pipe configuration in which the annulus 73 between pipe jacket 74 and conduit 63 is filled with insulation 75. The anchor support 66 is similar to support 65 as described but large enough to accommodate the pipe jacket 74 connected to the frustoconical fitting 72. Support 66 includes a support bracket 76, pipe hanger 77, struts 78, pipe support member 79, and opposed channels 80.

Referring once again to the vertical tubes 29 which project beneath the furnace chamber 13, a slidable seal 81 closes the open space around the vertical tubes 29 received by the elongated slot 26 in the furnace floor 13b. As best viewed in FIG. 3, the sliding floor seal 81 includes a plurality of parallelogram shaped members 82 having semicircular recesses 83 which circumferentially engage the vertical tubes 29. In the preferred embodiment of the invention, the parallelogram shaped members 82 are fabricated from asbestos millboard, the outer edges of which rest on

runners

84 and 85 attached respectively to the

longitudinal members

27 and 28. The members 82 support loose refractory material 86, shown in FIG. 4, which fills the slot 26 and provides a level interior floor in the chamber 13.

Referring more particularly to FIG. 4, which is an enlarged view of the lower region of the fired heater to show additional details of construction, the lower ends of the vertical tubes 29 extended beneath the furnace fioor 131:, the connector tubes 49, and outlet manifolds 50 are wrapped with suitable insulation material 87.

As previously mentioned, each vertical tube 29 is engaged by a support leg 48, now to be described in detail, extended upwardly from a cradle member 45. Securely attached to the end cap 41 of the vertical tube 29 is a vertically oriented, tubular extension 88 which receives a plunger 89 connected thereto by a plurality of bolts 90. The plunger 89 extends downwardly and is received by a sleeve 91 which is connected by a baseplate 92 and bolt 93 to the cradle member 45. Oblong holes 94 on a diameter of the sleeve 9'] are aligned with a hole 95 through the plunger 89 to receive a guide bolt 96 having an associated nut 97. The lowermost end of the plunger 89 bears on a helical spring 98 within the sleeve 91 communicating between the plunger 89 and the baseplate 92.

The engaging surfaces of the plunger 89 and the sleeve 91 are polished and coated with a suitable lubricant to allow free slippage of the plunger 89 within the sleeve 91 through a distance corresponding to the length of the oblong holes 94. In the preferred embodiment of the invention, the oblong holes 94 are :5 inch in length in'order to allow the plunger 89 to move within the sleeve 91 a distance of his inch. Characteristically, each tube 29 filled with catalyst weighs approximately 2,100 pounds of which 1,575 pounds is supported from the gantry structure 18 by the previously described counter weight apparatus. The helical spring 98 is designed to support the remaining 525 pounds without deflection and to support 623 pounds with a z-inch deflection.

As previously mentioned and now to be described in detail, a plurality of J-bolts 42 are associated with the

longitudinal members

27 and 28 and a plurality of .l-bolts 51 are associated with lower horizontal members 17. As viewed in FIG. 4, each J-bolt 51 includes a .l-shaped rod 51a which receives the upper eyelet loop 52 of hanger rod 53 and extends upwardly through holes in the lower surfaces of horizontal members 17. The longer leg of the .l-shaped rod 51a receives a tubular sleeve 51b and threadably receives a nut 510 which engages the upper end of the tubular sleeve 51b. By tightening or backing off nut 51c, the J-shaped rod 51a can be adjusted upwardly or downwardly with respect to its associated horizontal member 17. Likewise, the J-bolts 42 correspond to J-bolts 51 and include J-shaped rods 42a, tubular sleeves 42b, and nut 42c.

Each J-bolt 55 associated with manifold cradles 54 includes an inverted J-shaped rod 55a received by a tubular sleeve 55b which is securely attached to the end of the manifold cradle 54, and an associated nut 550 which adjusts the inverted J- shaped rod 550 with respect to the manifold cradle 54. The J- bolts 46 associated with the cradle members 45 are similar to .l-bolts 55 and correspondingly include inverted J-shaped rods 46a, tubular sleeves 46b, and associated nut 460.

In operation, the direct fired heater is utilized in the manner to be described.

Process material to be heated is delivered to the inlet manifold 37 from which it flows to one of the many vertical tubes 29 through the pigtail tubes 39. The process material then flows downwardly through the vertical tubes 29 to the connector tubes 49 through which it is delivered to the outlet manifolds 50. From the outlet manifolds 50, the material passes into the collector conduit 63 by way of the

cross fittings

61 and 62 and is discharged to auxiliary piping to be delivered to additional process equipment.

As process material flows through the heater in the manner described, hot combustion gases are formed or introduced in the furnace chamber 13 through the nozzles 23. The gases rise through the furnace chamber 13 transferring heat to the vertical tubes 29 and are then exhausted through outlet port 24.

Since the thermal expansion of the various members is greatest during the startup or that period when the heater is first put in operation, for purposes of the following discussion it will be assumed that the members are being heated from an ambient temperature. The thermal expansion of the vertical tubes 29 is primarily in an upward direction due to the counterweight apparatus suspended from the gantry structure 18. As each vertical tube 29 expands upwardly, the end of the pigtail tube 39 connected to the vertical tube 29 likewise is displaced in an upwardly direction.

As the hot process material is delivered from the vertical tubes 29 to the outlet manifolds 50, the latter tend to longitudinally expand away from the collector conduit 63. As the outlet manifolds 50 expand outwardly, the manifold cradles 54 likewise are displaced outwardly in arcuate movement.

With the expansion of the outlet manifolds 50 acting on the connector tubes 49, the vertical tubes 29 move outwardly from the collector conduit 63. As the vertical tubes 29 move outwardly from the collector conduit 63, the cradle members 45 swing outwardly in upward arcuate movement. Since the expansion of the outlet manifolds 50 is substantially uniform, the displacement of the vertical tubes 29 caused by the expansion of the outlet manifolds 50 is cumulative in effect. That is, the vertical tube 29 furthest from the collector conduit 63 is displaced a greater distance than the vertical tube 29 closest the collector conduit 63. Since the horizontal displacement of the vertical tubes 29 also results in an upward displacement through the arcuate movement of the cradle members 45, the counterweight apparatus suspended from the gantry structure 18 likewise compensates for this upward displacement of the vertical tubes 29.

Due to the fact that the deflection curve of the manifold cradles 54 departs slightly from the deflection curve passing through the plurality of cradle members 45, the support legs 48 are spring relieved in the manner described to assist the counterweights 35 in preventing stress in the small connector tubes 49. When a vertical tube 29 would tend to lift the outlet manifold 50, thus putting stress in the connector tube 49, the spring 98 within the support leg 48 is compressed. On the other hand, when the outlet manifold 50 would tend to lift the vertical tube 29, the spring 98 is extended to alleviate the stress in the connector tube 49.

Because the outlet manifolds 50 are provided with cradles 54 separate from the cradles 45 supporting the vertical tubes 29, the outlet manifolds 50 can swing away from the vertical tubes 29 when the connector tubes 49 thermally expand.

As the collector conduit 63 heats up, it also thermally expands, but in a direction away from the tight anchor connection (that is, to the right in FIGS. 2 and 5). Expansion in this manner is achieved because the

pipe support members

70 and 79 supporting the collector conduit 63 slide along the struts 69 and 78 of the

pipe hangers

68 and 77.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombina tions are of utility and may be employed without reference to other features and subcombinations.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A direct fired heater comprising:

a furnace chamber,

means for providing hot gases within said furnace chamber,

a plurality of vertical tubes arranged in at least one row within said furnace chamber, a lower portion of each of said tubes extending beneath said furnace chamber,

a plurality of swingable cradles mounted beneath said furnace chamber to supportingly receive said vertical tubes, an inlet piping system connected to said vertical tubes to deliver thereto process material to be heated by said hot gases, and an outlet piping system located beneath said furnace chamber and connected to said lower portions of the vertical tubes to receive process material therefrom.

2. The heater as in claim 1, said vertical tubes arranged in two parallel rows, one said row offset with respect to the other said row, and said cradles horizontally disposed in skewed fashion in order that one said cradle supportingly receives one said vertical tube in each row of said tubes.

3. A direct fired heater comprising:

a furnace chamber,

means for providing hot gases within said furnace chamber, a plurality of vertical tubes arranged in at least one row within said furnace chamber, a lower portion of each of ble cradles which are mounted beneath said furnace chamber and on which are connected said spring loaded support legs.

5. A direct fired heater comprising:

a furnace chamber,

means for providing hot gases within said furnace chamber,

a plurality of vertical tubes arranged in at least one row within said furnace chamber, a bwer portion of each of said tubes extending beneath said furnace chamber,

an inlet piping system connected to said vertical tubes to deliver thereto process material to be heated by said hot gases, and

an outlet piping system located beneath said furnace chamber and connected to said lower portions of the vertical tubes to receive process material therefrom, said outlet piping system including a plurality of connector tubes attached to said lower portions of the vertical tubes, at least one horizontally disposed outlet manifold attached to said connector tubes, and at least one swingable manifold cradle mounted beneath said furnace chamber to support said one outlet manifold.

6. The heater as in claim 5, said outlet piping system including a plurality of horizontally disposed outlet manifolds attached to said connector tubes, a plurality of swingable manifold cradles mounted beneath said furnace chamber to support said outlet manifolds, and a collector conduit attached to said outlet manifolds to deliver process material from said manifolds to auxiliary piping.

7. The heater as in claim 6, said collector conduit transversely mounted beneath said furnace chamber by a plurality of sliding anchors operable to permit thermal displacement of said conduit away from said auxiliary piping.

Claims

1. A direct fired heater comprising: a furnace chamber, means for providing hot gases within said furnace chamber, a plurality of vertical tubes arranged in at least one row within said furnace chamber, a lower portion of each of said tubes extending beneath said furnace chamber, a plurality of swingable cradles mounted beneath said furnace chamber to supportingly receive said vertical tubes, an inlet piping system connected to said vertical tubes to deliver thereto process material to be heated by said hot gases, and an outlet piping system located beneath said furnace chamber and connected to said lower portions of the vertical tubes to receive process material therefrom.

3. A direct fired heater comprising: a furnace chamber, means for providing hot gases within said furnace chamber, a plurality of vertical tubes arranged in at least one row within said furnace chamber, a lower portion of each of said tubes extending beneath said furnace chamber, a plurality of spring loaded support legs which engage the lowermost ends of said vertical tubes, an inlet piping system connected to said vertical tubes to deliver thereto process material to be heated by said hot gases, and an outlet piping system located beneath said furnace chamber and connected to said lower portions of the vertical tubes to receive process material therefrom.

4. The heater as in claim 3, including a plurality of swingable cradles which are mounted beneath said furnace chamber and on which are connected said spring loaded support legs.

5. A direct fired heater comprising: a furnace chamber, means for providing hot gases within said furnace chamber, a plurality of vertical tubes arranged in at least one row within said furnace chamber, a lower portion of each of said tubes extending beneath said furnace chamber, an inlet piping system connected to said vertical tubes to deliver thereto process material to be heated by said hot gases, and an outlet piping system located beneath said furnace chamber and connected to said lower portions of the vertical tubes to receive process material therefrom, said outlet piping system including a plurality of connector tubes attached to said lower portions of the vertical tubes, at least one horizontally disposed outlet manIfold attached to said connector tubes, and at least one swingable manifold cradle mounted beneath said furnace chamber to support said one outlet manifold.