US3804585A

US3804585A - Precast furnace pipe insulation

Info

Publication number: US3804585A
Application number: US00375958A
Authority: US
Inventors: T Twort
Original assignee: Bloom Engineering Co Inc; URGUHART ENG CO Ltd
Current assignee: Bloom Engineering Co Inc; URGUHART ENG CO Ltd
Priority date: 1972-07-06
Filing date: 1973-07-02
Publication date: 1974-04-16
Anticipated expiration: 1991-04-16
Also published as: GB1441915A; DE2333695A1; FR2192694A5; IT989749B; JPS4951638A; AU5765273A

Abstract

A refractory insulative member for protecting elongate pipes in a furnace comprises a hollow refractory element into which is solidly embedded a reticulated metal structure. Openings in the refractory element at the longitudinal edges thereof expose portions of a wire rod which can be welded to the pipe to support the member. The wire rods have portions solidly embedded in the refractory element which portions are mechanically linked to the reticulated metal structure.

Description

United States Patent [1 1 Twort [451 Apr. 16, 1974 [5 PRECAST FURNACE RIPE INSULATION [75] Inventor: Thomas James Twort, Greenford,

England [73] Assignees: Urguhart Engineering Company Limited, Greenford, England; Bloom Engineering Co., Inc., Pittsburgh, Pa. Q

[22] Filed: July 2, 1973 [21] App1. No.: 375,958

[30] Foreign Application Priority Data July 6, 1.972 Great Britain 31811/72 [52] US. Cl 432/234, 138/147, 138/149, 7 v I I 432/248 [51] Int. Cl. F2711 3/02 [58] Field of Search 432/233-236,

[56] 1 References Cited UNITED STATES PATENTS 3,647,194 3/1972 Brungraber et a1 432/234 2,867,112 1/1959 Krone 4327233 3,168,297 2/1965 Brough 432/234 2,693,352 11/1954 Bloom 432/234 3,329,414 7/1967 Greaney 432/234 3,486,533 12/1969 Doherty et all... 432/234 3,282,579 11/1966 Miller, Jr. 432/248 3,226,101 Balaz et at .L 432/234 Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney, Agent, or Firm-Webb, Burden, Robinson & Webb [57] ABSTRACT A refractory insulative member for protecting elongate pipes in a furnace comprises a hollow refractory element into which is solidly embedded a reticulated metal structure. Openings in the refractory element at the longitudinal edges thereof expose portions of a wire rod which canbe welded to the pipe to support the member. The wire rods have portions solidly embedded in the refractory element: which portions are mechanically linked to the reticulated metal structure;

7 Claims, 6 Drawing Figures m-u m mPR 16 1974 (3,804,585

saw 1 0r 2 PATENTEDAFR 16 I974 SHEET 2 [IF 2 PRECAST FURNACE PIPE INSULATION This invention relates to means for insulating members mounted within high temperature furnace chambers, particularly water cooled pipes in the supporting structures for work pieces in heat treating furnaces.

A supporting structure within a furnace chamber where temperatures may be in the order of 2,000 F must be compact in order to leave sufficient combustion space in the chamber, must be strong enough to support heavy metal work pieces being treated in the furnace, and must 'be protected against injuryby the high temperature within the furnace while at the same time not seriously interfering with the efficiency and maximum temperature of a furnace. It must also be strong enough to withstand the stresses and heavy vibration set up by the movement of the heavy workpieces within the heating chamber.

A combination of small size with high strength dictates the use of metals in the supports and the necessity for cooling the metal dictates the use of hollow metal pipes through which cooling water is circulated.

If water cooled pipes with bare outer surfaces are used, however, the absorption of heat through the pipe metal to the cooling water is so great that more fuel is wasted in heating the cooling water than in heating the work pieces. Forexample, an under fired furnace having bare metal supports in its lower zone requires about three times as much fuel to heat the lower zone of the furnace as the upper zone ofthe fumace,.and no matter embedded therein with portions of the wire protruding from the refractory material such that when the section is placed against the pipe the protruding wire portions are situated adjacent opposite sides of the pipe. The protruding portions of the wire are welded tothe pipe, and a similar insulating section is then placed against the upper portion of the pipe. Each of the section's extends approximately l80 around the pipe, there being a gap between the refractory material of the sections on each side of the pipe. Wire pins or rods are inserted axially through the gaps and through the protruding wire loop portions to connect the two sections together. The insulation is completed by forcing a plastic refractory material into the gaps to fill and close the gaps; Additional sections are added in abutting end-to-end relationship as required to insulate'the length of piping.

While the above form of insulation is capable of giving very satisfactory results, it has been found that there are certain areas of potential weakness in the insulation. Because the high temperature furnace environment is usually well above that which the wire is capable of withstanding it is essential that the wire be both deeplyembedded within the refractory material and'maintained below failure temperature by being in good heat conducting contact with the piping through which the coolant is circulated. Failure of the wire is how much fuel is supplied to the lower zone it still remains distinctly cooler than the upper zone.

In an endeavour to correct this condition it has been proposed to apply refractory insulatingmaterial directly to the water cooled support pipes. However, this expedient has not proved very satisfactory because the refractory material tends to crack after some use, principally because of the difference in thermal expansion of the inner and the outer layers of the refractory mate- 4O rials and because of the difference in'the thermal expansion characteristics of the refractory materials and the metal pipe which it encloses. The movement of the supporting structuredue to the movement of the heavy work pieces within the heating chamber also contributes significantlyto the break up and loss 'of the refrac- It is therefore advantageous that the insulation be so constructed that if cracking of the refractory material does occur, movement of the piping does not result in the complete break-up and loss of the refractory material. It has been proposed, for example in U.S. Pat. No. 2,693,352, that this be accomplished by embedding in the refractory material a reticulated metal structure such as a wire fabric comprising interlocking coils of wire extending parallel to each. other and to the pipe axis to act as a reinforcement and support for the refractory material which, should damage to the refractory material occur, will hold the refractory material together andin situ round the piping thus preserving the'heat insulation. n t

To facilitate theinstallation of such an insulation on piping the insulation has conveniently been made in two or more preformed sections which are secured together circumferentially around the piping. For example, a'two-section insulation has included a preformed semi-cylindrical refractory element having wire fabric a most likely to occur in the gaps which are filled on installation with the plastic refractory material, and the securing pin or wire is also located in the gaps so that any failure of the till material will effect the connection between the sections as well as the integrity of the sections themselves. To prevent a break-down of the insulation, it is necessary thatthe wire and securing pin be adequately shielded from flame-impingement and heat radiation at all times. However, it is not alwayseasy during installation to ensure that the gaps are filled directly with the plastic refractorymaterial and that no voids are present. n

It is accordingly an object of the present invention to provide an improved pipe insulation which is not sub ject to the above drawbacks. v n

n It has also been found that the time taken to weld and pin such insulation is such as to restrict the amount of insulation which can be installed effectively during the sometimes brief periods of time. the furnaces are shut downfor repair.

It is accordingly another object of the presentinven- According to the invention there is provided a refractory insulative member for application to the outer surface of an elongate pipein a furnace to protect the pipe from the effects of furnace heat, said member comprising a body of refractory insulatingmaterial; a reticulated metal reinforcing structure wholly embedded within said body; at least one metal rod partially embedded in the refractory material and having a plurality of spaced portions wholly embedded in the refractory material and connected to the reticulated metal structure; a plurality of other portions radially offset with respect to said wholly embedded portions; and a plurality of spaced openings in said refractory insulating material, each of said spaced openings exposing a respective said offset rod portion to permit of said offset rodportions being welded to the underlying pipe for anchoring the insulative member to the pipe.

Some preferred embodiments of the present invention are illustrated by way of example in the accompanying drawings of which:

FIG. 1 is an isometric view of an insulative member according to the invention;

FIG. 2 is a side view of the metal rod incorporated in the insulative member of FIG. 1;

FIG. 3 is an end view of the rod of FIG. 2;

FIG. 4 is a side view of two of the insulative members of FIG. 1 applied to a water-cooled pipe in a heat treating furnace;

FIG. 5 is a cross-sectional view taken on the line v -v in FIG. 4 and FIG. 6 is an isometric view showing a second embodiment of insulative member according to the invention applied to a furnace pipe having a skid bar.

Referring to the drawings, a refractory insulative member 6 according to one embodiment of the invention is shown in FIG. 1. The member 6 is in the shape of a hollow semi-cylinder and comprises a cast moulded body 7 of a refractory insulating material within which there is wholly embedded a reticulated metal reinforcing structure which may take various forms but is illustrated as comprising a wire mesh fabric consisting of a plurality of interlocking coils of wire. The wire fabric is only partly depicted in the drawings wherein substantiallyonly the wire coils or loops adjacent the embedded longitudinal edges of the fabric are illustrated.

A metal wire or rod 2 is partially embedded in the refractory material 7 adjacent each longitudinal edge 8 of the member 6. The rod 2 is shaped by bending or otherwise to the form shown in FIGS. 2 and 3 and provides at intervals along its length a plurality of spaced portions 4 alternating with a plurality of radially offset por tions 5. The length of each rod 2 is substantially the same as the length of the'member 6.

Portions 40f the rods 2 are connected to the reticulated metal reinforcing structure by passing them through the wire loops 10 before the refractory insulating material is cast around the metal structure in a forming mould (not shown). In the casting operation a plurality of the offset rod portions 5 are left exposed by the use of suitable cores in the mould which prevent the refractory material from embeddingthese portions, so that the finally cast member 6 has in the wall thereof a plurality. of spaced openings 12 extending from'the radially outer face 16 to the radially inner face 14 thereof, a portions of the rod 2 being exposed within each opening 12. The openings 12 are positioned along both longitudinal edges 8 of the member 6 and are regularly spaced longitudinally of the member along each edge so that each opening 12 in one edge 8 has another opening 12 diametrically opposed thereto in the other edge 8. Each opening '12 exposes an offset rod portion 5 substantially flush with the radially inner face 14 of the member 6 and intervening portions of the metal rods 2 including the portions 4 are wholly embedded within the refractory material 7. The wall of each opening 12 is tapered in a direction radially away from surface 14 whereby the cross-sectional area of the opening 12 is greater adjacent the radially inner face 14 of the member 6 than adjacent the radially outer face 16.

FIGS. 4 and 5 show how two similar

insulative members

6 and 6 as shown in FIG. 1 are assembled onto the outer surface of 'a furnace pipe 18 to protect the pipe from the effects of furnace heat. Respective openings l2 and 12 of the two insulative members are positioned next one another to form a weld-through hole, shown more particularly in FIG. 5. Working through the hole, the exposed offset portions 5 and 5' of the rods 2 and 2' are welded to the underlying pipe surface. Thereafter the weld hole is filled with a plastic refractory material to protect the welds from deterioration in a high temperature environment. The insulative members 6 and 6' are preferably sized to leave a small axial gap 19 between the members to allow for irregularities in the pipe.

The refractory insulative members 6 and 6' described possess a number of advantages over the preformed insulating sections hitherto known. The members can be installed in a wide variety of work environments and their use is not confined to protecting horizontal pipes since they can equally be employed on riser and crossover pipes. Stockholding is simplified since all the members for a particular pipe size are similar and matched sets are therefore not required since any member can be used with any similar member. Installation is simplified and quickened with improved results. An offset rod portion 5 and 5' of each insulative memher is exposed at the single weld-through hole formed by the aligned openings 12 arid 12 which permits the rods of both members 6 and 6' to be welded to the pipe without the need for the welder to alter his position. This effectively speeds up the rate of installation. The rods 2 are preferably thicker than the wire 'of the reinforcing mesh fabric including loops 10 which makes the welding easier and affords less risk of burn through.

' Longer welds are possible on the rods than on mesh so the installation is more secure and is more resistant to shock. The welding can be inspected while being done and the use of the taper-sided openings 12 not only exposes a greater length of rod for welding than would a parallel-sided opening but promotes easier access to the weld site for both welding and inspection and also is effective to retain the refractory filler material in situ which is an important factor in extending the installed life of the insulation as it prevents loss of the filler material which would expose the welds to high tempera ture furnace environment and lead to rapid deterioration of the welds.

In additiomthe rods 2 act as part of the reinforcement for the cast refractory body 7 both by being partially embedded therein and due to'the mechanical connection of the embedded rod portions to the wire loops 10 a substantial improvement in overall strength and support is achieved.

The water-cooled pipes in a furnace which support the actual workpieces being treated are usually provided with a skid bar welded to the upper surface of the pipe and on which the workpieces bear. An embodiment of a refractory insulative member designed for application to a pipe having a skid bar and possessing also the advantages of the invention enumerated abov is shown in FIG. 6 of the drawings. i

As shown in FIG. 6 a water-cooled pipe 20 has a skid bar 22 extending longitudinally the length of the pipe. The presence of the skid bar and the proximity of work pieces moving along the bar dictates that the insulation on the pipe can only extend approximately round twothirds of the pipe circumference. The refractory insulative member 26 in this embodiment comprises two integral parts 26' and 26" hingedly connected by a bottom hinge pin 28. Each part 26' and 26" has a longitudinal edge 8 providedwith a plurality of spaced openings 12 at which are exposed offset rod portions 5 as already discussed in connection with FIGS. 1 to 5. Member 26 is installed by opening the preformed integral parts 26' and 26" up around hinge pin 28 and placing it around the pipe 20. Each-offset portion 5 of the wire rods 2 incorporated in the parts 26' and 26" is then welded to the pipe adjacent a respective side of the skid bar 22 and a plastic refractory material is then trowelled'over the exposed welds in the openings 12 and in the hinge joint to complete the installation.

It will, of course, be appreciated that the invention is not restricted to the particular preferred embodiments described but maybe otherwise embodied within the scope of the appended claims. For example, instead of providing the members 6 in the shape of hollow semicylinders as described they may be of lesser partannular extent and, for example, three-members may be used to surround the full circumference of a pipe.

I claim: V

1. A refractory insulative member for application to the outer surface of an elongate pipe in .a furnace to protect the pipe from the effects of furnace heat, said member comprising a body of refractory insulating material having an inner face; a reticulated metal reinforcing structurewholly embedded within said'body; at least one metal rod partially embedded in the, refractory material and having a plurality of spaced portions whollyembedded'in the refractory material and connectedto the reticulated metal structure; a plurality of other portions radially offset with respect to said wholly embedded portions and substantially flush with the inner face;.and a plurality of spaced openings in said refractory insulating material, each of said spaced openings exposing a respective said offset rod portion to permit of said offset rod portions being welded to the underlying pipe for anchoring the insulative member to the pipe.

2. A refractory insulative member according to claim 1, wherein said reticulated metal structure includes wire loop portions and said wholly embedded rod portions are connected to the reticulated metal structure by passing them through said wire loop portions.

3. A refractory insulative member according to claim 2, wherein said metal rod is thicker than the wire comprising said wire loop portions.

4. A refractory insulative member according to claim 2, wherein said spaced openings are positioned along at least one longitudinal edge of the insulative member.

5. A refractory insulative member according to claim 4, wherein said openings are regularly spaced longitudinally of the insulative member.

a 6. A refractory insulative member according to claim l 5, wherein each said opening is tapered so that its cross-sectional area is greater adjacent the inner face of the member opposed to the outer surface of the pipe than adjacent the outer face of the member.

pipe adjacent a respective side of the skid bar.

Claims

1. A refractory insulative member for application to the outer surface of an elongate pipe in a furnace to protect the pipe from the effects of furnace heat, said member comprising a body of refractory insulating material having an inner face; a reticulated metal reinforcing structure wholly embedded within said body; at least one metal rod partially embedded in the refractory material and having a plurality of spaced portions wholly embedded in the refractory material and connected to the reticulated metal structure; a plurality of other portions radially offset with respect to said wholly embedded portions and substantially flush with the inner face; and a plurality of spaced openings in said refractory insulating material, each of said spaced openings exposing a respective said offset rod portion to permit of said offset rod portions being welded to the underlying pipe for anchoring the insulative member to the pipe.

6. A refractory insulative member according to claim 5, wherein each said opening is tapered so that its cross-sectional area is greater adjacent the inner face of the member opposed to the outer surface of the pipe than adjacent the outer face of the member.

7. A refractory insulative member according to claim 2, wherein for application to a pipe having a skid bar said member is constructed of two hingedly connected integral parts and each said part possesses a longitudinal edge provided with a said plurality of spaced openings and exposed offset rod portions for welding to the pipe adjacent a respective side of the skid bar.