US1791244A

US1791244A - Furnace wall

Info

Publication number: US1791244A
Application number: US286128A
Authority: US
Inventors: Nygaard Oscar
Original assignee: Individual
Current assignee: Individual
Priority date: 1928-06-18
Filing date: 1928-06-18
Publication date: 1931-02-03
Anticipated expiration: 1948-02-03

Description

Feb. 3, 1931. o. NYGAARD 1,79%24 FURNACE WALDL 7 Filed June 18. 1928 4 Sheets-Sheet 1 lg J w T wg 0' NYGAARD Feb. 3, 1931.

FURNACE WALL Filed June 18. 1928 4 Sheets-Sheet. 2

O. NYGAARD Feb 3, 1931.

FURNACE WALL Filed June 18. 1928 4 Sheets-Sheet 3 IN VEN TOR Feb. 3, 1931. Q, NYGAARD 1,791,244

FURNACE WALL Filed June 18, 1928 4'Sheets-Sheet 4 Patented 3, 1931 PATENT I OFFICE oscan new, orsavsus, msgcnusn'r'rs rumuc'nwm Appllcatlon fled June 18, 1928. Serial in. 286,128.

' This invention relates to furnace wallsand more es ciallyto those furnace walls which are sub ected to high temperatures for long periods of time, -as for example, those in pul:

, verized fuel furnaces used in large plants for 'the generation of steam.

The temperaturescre'ated in furnaces of this type are so high and the operating periods are so long sustain ed that it has been found necessary to cool the wallsin some manner in order to prevent a very rapid destruction of them. For this purpose, provision has been made for cooling the walls by air, and such walls are now used quite gen erally. More recently walls having tubes embedded in them and conducting steam or water have come into use, the water or steam fiowingthrough the tubes serving to carry away the heat at a sufficient rate to maintain g the temperature of the wall below a dangerous point. This arrangement also has theadvantage of making use of the excessive heat transmitted to the wall.

The present invention relates to the latter type of wall and it aims to improve such walls with a view to reducing the manufacturing expense, simplifying the construction, and facilitating the making of repairs, while at the same time providing a superior wall structure. 'It is contemplated, however, that some features of the invention will be used in other types of walls.

At the present time one of the chief objections to water cooled walls is the very high 3 Initial expense. The fact that when repairs to such a Wall are required it is necessary to tear down a considerable section of the wall, beginning at the back or rear side thereof, is also a very .serious practical objection. 49 The present invention provides a practical solution for both of these problems. It al so provides a novel brick for furnace wall construction. I

The nature of the invention willbe readily understood from the following description when read in connection with the accompanying drawings, and the novel features. w1ll be particularly pointed out in the ap-' pended claims. I

In the drawings,

- Figure 1 is a'perspective view of the cor ner portion of a furnace wall looking at the inside of the wall Fig. 2 is a front elevation of a portion of the wall shown in Fig. 1;

Fig. 3 is a perspective view showin certain details of the upper part of the wa 1 section shown in Fig. 2; I

Fig. 4 is a similar view of aportion of the lower part of the wall section shown in Fig. 2;

Fig. 5 is a perspective view of one of the l1j1rick2s in thelower part of the wall shown in Fig. 6 is a vertical sectional view of the wall shown in Fi 2;

Fig. 7 is a horizontal cross-sectional view of the wall shown in Fig. 2; g Fig. 8 is a horizontal cross-sectional view of the wall shown in Fig. 1;

Fig. 9 is a perspective view of one of the corner bricks of the wall section shown in Figs. 1 and 8, illustrating means for anchoring the brick in place;

Fig. 10 is a perspective view illustrating a modified construction of brick; and

Fig. 11 is a sectional View somewhat diagrammatic of a stoker furnace showing the invention applied to an arch. I

Referring first to Figs. 1 to 5, inclusive, it will be observed that the wall construction illustrated comprises a series of substantially upright pipes or tubes 2 designed to conduct water or steam. For example, these tubes may be used to heat feed water or they may be connected into and form a part of the cir-. culating system of the boiler. Back of these tubes is a rear wall section, and the tubes themselves are embedded in and protected byaa front-wall section or lining composed chiefly of bricks or blocks 3.- As shown in 00 Figs. 1 and 2, the bricks are arranged in vertical rows, each row including two series of bricks. Referring, for example, to the two left-hand tubes 2 in Fig. 1, it will be seen that these tubes are rotected for a distance by a row of bricks lymg between the points a and b. The bricks of one series are indicated at 3 while those of the other series are indicated at 3". Fig. 2 shows these bricks on a somewhat lar er scale. The

bricks

3 and 3" are exactly ali e in construction.

Referring to Fig. 3, it will be observed that each brick is of approximately rectangular outline when viewed from one side, and that it has a flat end face 0' which is exposed at the fire side of the wall. This forms the front face or fire face of the brick. One side of the brick for its entire height is grooved, as shown at d, to receive the tube 2, the brick thus fitting partly around the tube, as shown somewhat more clearly in Fig. 7, with the greater or body portion of the brick located in front of the groove and the tube. The side of the brick opposite to the grooved surface isaprovided with a tapered enlargement e, and the upper and lower surfaces, respectiyely, of this enlargement are laterally inclined, in this particular instance at an angle of approximately 45 to the main body of the brick and to the groove d. It will be clear from an inspection of Fig. 2'that the projection 6 from each brick of one series fits between the inclined faces of the two abutting bricks of the opposite series. In other words, the bricks are arranged in staggered relationship to each other. It will also be evident that the bricks of each series tend to slide on the inclined faces of the bricks of the other series due to the action of gravity, and that this tendency results in the crowding of the bricks against their respective tubes. (3on sidering, for example, the uppermost brick of the series 3" in Fig. 2, it will be evident that gravity will urge this brick downwardly, and that any downward movement of it will cause its inclined face 9 to slide on the 1nclined face f of the next lower brick of theseries 3'. Such movement necessarily will result in crowding or wedging the uppermost brick 3 between its tube 2' and the next lower brick 3. The same action will occur in the case of each brick of both series, so

that in this wall lining or front wall section the bricks are held in their operative relationwall by vibration of the tubes since any movement of a brick to free it from its respective tube necessarily results in raising the brick somewhat and such a movement, therefore, is

resisted by gravity. It will thus be seen that each brick, when in its normal position, is

locked against movement except in a direction parallel to the tubes.

That portion of the wall shown in the lower part of Fig. 2 is made up of bricks whichdifier slightly from the bricks shown in the upper part of said wall, and the detailed constructionof the former bricks is clearlyillustrated in Figs. 4 and 5. These

bricks

3 and 3 are like those shown in Fig. 3 except that the inclined faces f and g on the projection 6 of each brick are provided with tongues h and grooves Preferably the tongues-h are formed on that portion of the inclined wall which adjoins the main body of the brick,

while the grooves j are formed inalinement with and at the ends of the tongues. Each in tion with reference to the other.

bricks with each other, and it makes it neces sary to move each brick vertically through a greater distance in order to free it from the next adjacent brick against which it abuts.-

.At the same time this construction is devoid of partswhich are 'fragile and the brick is not likely to crack or break due to uneven expansion and contraction causedby changes 1 in temperature.

As the furnace wall heats uporcools ofi the tubes expand as well as the bricks and the wall constructions illustrated permit the very slight movement of the bricks upon each other which occurs during such expansion and contraction and which is very desirable. It may here be noted, however, that j the clearances between adjacent bricks are shown considerably exaggerated in the drawings in order better to illustrate the outlines of individual bricks. In practice the bricks fit quite closely together and the excessive clearances illustrated in the drawings arev not present.

The weight of the wall is supported chiefly or entirely by the tubes but some of the weight may be taken by pipes, such asthose shown at 5, Figs. 6 and 7, which are located immediately back of the tubes. Horizontal brackets6 of angle iron are held spaced at suitable intervals by these pipes, the horizontal flanges of the angle ironsbeing supported between nuts 77 on the pipes 5. The ver-. tical flanges of the angle irons 6 carry .a series of U-bolts 8, each one of which encircles one of the tubes 2, as clearly shown in Figs. ti I and 7, the ends of the bolts being drawn, back tightly by nuts 9. A vertical series ofblocks rests on each ill-bolt, the height of each series depending'upon the vertical spacing of the U-bolts. The lowermost block in each series which rests directly on the U-bolt is recessed or cut away to receive the bolt, as clearly shown in Fig. 6. The pipes 5 act as spacers for the brackets.

In order to facilitate the making of repairs the wall is divided into sections, and such division is made naturally by the construction of the bricks themselves. That is, the upright row of bricks between two adjacent tubes is independent of the next adjacent row. Advantage is taken of this fact and of the means for supporting the weight of the bricks to divide each row-into sections substantially at the points of support,'or in other words,

approximately at the U-bolts 8. As above stated, each brick which rests on a U-bolt' is cut out to receive the U bolt and inthis respect is a special brick. A si'milarbrick,

.but placed with the cut-out on its upper side,

is located immediately belowthe U-bolt. This arrangement is shown in Fig. 6 in which the brick immediately above the U-bolt isin; dicated at 3 and that immediately below the U-bolt at 3". Preferably the U-bolts arranged in horizontal alinement with each other are. located only on alternate pipes 2, Fig. 2, so that the brick which cooperates with or fits between the two

bricks

3 and 3", Fig. 6, will be a regular brick. The vertical rows of bricks are interrupted just below the special bricks to divide the row into sections by means of key blocks 10, and short sections 12, Fig. 6, of packing or cement. As shown in Fig. 6 the key brick has a lower face which is inclined backwardly so that it is of greater height at its rearward edge than at its front edge and thus is keyed in the wall. On its upper surface it is provided with grooves 13, F ig. 6, to receive the packing 12 and lock it in position. Usually a packing of asbestos,

magnesia or the like is used, although cement may be substituted for it. A similar key block 10 and packing 12 is used atthe upper end of each section.

It will thus be seen that whenever it is necessary to repair a section of the wall due to a broken brick or for any other reason, it is simply necessary to dig out the packing and then to remove the key block 10, after which as many of the bricks as desired in that. particular section can be lifted out of place and removed bodily from the wall. The damaged brick or bricks can thus be removed and perfect bricks substituted for them, and the bricks previously removed can then be replaced and a new packing substituted-for that which has been dug out at'the beginning of the repairing operation. Attention is hind the bricks 3. This not only saveslabor and materials, but it is of particular advantage in reducing the length of time that the boiler must be shut down. It is, therefore, an important practical consideration.

.While the walls'sliown in Figs. 2 and 6 include-two different designs of brick, one having tongues and grooves in the inclined surfaces, while the other does not, it will be understood that it is the more usual practice to make the wall of one form of brick only. At the same time the two designs can be combincd,"as shown, when that is desirable for any reason.

Where two walls meet toform a corner, as shown in Figs. 1 and 8-, I prefer to use special corner blocks or'bricks 14 to close the space at the fireside of the wall. The detailed constructionlof these corner bricks will be clear from an inspection of Fig. 9. It will be ob. served that each brick has a lug or enlargement 15 at the rearward side thereof," the vertical edges of the lug being grooved to re ceive tie rods or

bolts

16 and 17, respectively,

that project through the rear'section of the wall and serve to hold the corner bricks firmly in position. These bricks are placed one upon the other, as shown in Fig. 1, and they partly overlap thead'jacent margins ot'the two wall sections so that they effectually close the corner of the furnace.

- Due to the expansion and contraction of the horizontal headers. to which the tubes are secured at the top. and bottom, it is necessary to provide an expansion space or joint at the opposite ends of the wall "to permit this lateral expansion; The corner construction illustrated in Figs. 1 and 8 provides for such an expansion and contraction, the bricks or blocks which are slightly overlapped by the example, by being interlocked with the rear or outer section of the wall instead of being. held in positionby anchor bolts. Essentially the same construction can also be used at the edge of a water cooled wall where it adjoin-s'a wall of another construction, and whether or not it is in a corner.

Any suitable construction may be the rearward side of the tubes 2 and their protecting bricks 3. This rear section of the wall has been indicated at 18 andmay consist simply of clay bricks properly set. Preferused at llu ablythis rear wall section also includes backing plates 19 which cover the entire rear surface of the wall and prevent any substantial amount of air leakage through the wall. Y

Angle irons 20, or other plates of suitable form, close-the-joints between adjacent plates 19-19."Ad ditional angle irons or channel construction is desirable mechanical strength or the ability to withpieces 21 are located in an upright position and secured to the wall at intervals to hold the plates 19 securely in position. This rear section of the wall should be made sufiiciently thick and of such construction as to afford the desired degree of heat insulation as well as preventing any substantial air leakage through the wall.

Usually both the tube protecting bricks or blocks 3 and the corner bricks 14 are made of some hard, refractory, nonmetallic material, such" as silicon carbide, or carborundum. Under some circumstances, however, these bricks or blocks may be'made of cast iron, or of other suitable materials. The cast iron where greater stand abrasion is'needed, or where a low first cost is an important consideration.

Instead of providing the bricks or blocks 3 with tongues 72. and grooves j, the bricks may be constructed as shown at 3 in Fig. 10, the inclined surfaces of the tapered projecting portion of each brick being provided with sockets 70-4; to receive short pins which may enter corresponding sockets in the abutting bricks. These pins preferably are made of some highly refractory material such as silicon carbide.

In addition to using the bricks in a wall cooled by Water or steam, as above described, they can also be used in an arch, as illustrated in Fig.11, where the bricks 3 are like those shown in Figs. 1 and 2 and coopei-ate with the tubes 23 in substantially the same manner as in the constructions above described. At the bends bricks or blocks of the same general design above described may be used, but the groove in the side of each block for receiving the tube will have a longitudinal curvature agreeing substantially with that of the tube. Also, the ends of the blocks will not run parallel to each other but will lie in planes which converge and intersect approximately at the center of the radius of the bend.

In this connection it may also be pointed out that the elimination of clamping means for securing the bricks to-the tubes is an especially important advantage at the bends. In prior constructions it has been necessary to use special and relatively expensive clamps at these points. They must be screwed-up tightly, which stifi'ens the bent portions of the tubes and necessarily increases very greatly the strains to which the tubes, clamps and blocks are subjected as the tubes expand and contract. Serious breakage frequently These difiiculties, however, are entirely eliminated in the present construction since it provides for a limited freedom of movementbetween the tubes and the blocks and between the blocks themselves. All rigid clamping means has been eliminated.

isomer It will now be appreciated that this invention provides an extremely simple form of water cooled or steam cooled wall construction. Iron clamps for holding the bricks or blocks to the tubes have been eliminated, the blocks being in their operative positions by their weight. When used on horizontal tubes in either a wall or arch they are simply pushed together and locked in place by key blocks in essentially the manner above described. They are free to expand and contract with changes in temperature, and their construction and relationship to each other and to the tubes are such that a good contact is always provided beween the tubes and the blocks. This ensures a high rate of heat transfer from the blocks to the tubes.- The construction of the blocks is such that they are economical of material and they substantially eliminate any danger from cracking while in use due to unequal expansion or contraction. Such walls'as those illustrated can be manufactured very economically, and when repairs are necessary they can be made with a minimum of time, labor and materials.

and consequently reducing the difliculties,

which have been found in prior constructions to result from this cause. Thisreduction in weight is realized partly by the elimination of meta-1 clamps for securing the blocks to the tubes, and partly, also, by the design of the blocks or bricks themselves. The wall structure also is exceptionally satisfactory from any operating standpoint.

Essentially the same wall construction can be used to advantage in gas generators, the circulating fluid in the tubes consisting of air, steam, or water, depending upon the design of the particular installation in which the wall is used. It is obvious, however, that so far as the bricks or blocks are concerned the tubes are simply supports for them, and that other supports can be substituted for the tubes as equivalents for them.

In determining the shape of the blocks or bricks particular attention has been given. to the problems of eliminating cracking or breaking of the blocks due to unequal expansion and contraction and to economy in mai'iufacture. The first of these considerations is important from an operating stand-- point, while the second assumes considerable importance when the bricks are made of expensive materials, such as silicon carbide. It will be seen from an inspection of Figs. 4, 5, 6 and 7 that the rearward part of each block is bevelled on one side, the bevel beginning at a point somewhat forward ofthe center line of the tubes. This construction increases the clearance between each block and the next adjacent tube and therefore faciliever, is the fact that it provides a construction in which the thickness of the block decreases gradually from a central portion toward the rearward edge and avoids the presence of thin section of material between two thicker sections. It should be noted that the maximum thickness of the block is in its central part and that it tapers toward its upper, lower and rearward edges, thus minimizing any tendency for failure due to unequal expansion andcontraction. \Vhile the foregoing description refers to a preferred embodiment of brick, a practical job can also be made with blocks which are not provided with a bevelled surface at the rear. Such a structure would represent a full equivalent of the bevelled blocks, insofar as the features of mounting same in a wall are concerned.

While I have herein shown and described a referred embodiment of my invention, it Will be understood that the invention may be embodied in other forms without departing from the spirit or scope thereof.

Having thus described my invention, what I desire to claim as new is":

1. In a furnace Wall, the combination of' a series of supports and bricks substantially covering theentire' widths of'said supports at the fire side of the wall to protect the supports, said bricks each having a groove extending substantially the length of the brick and shaped to contact with a support over a substantial portion of the groovelsurface, said bricks having an interlocking engagement with each other and with'said supports and being held in their operative'positions by said engagement.

2. In a furnace wall, the combination of a series of tubes and bricks substantially covering the entire widths of said tubes at the fire side of the wall toprotect the tubes, said bricks fitting partly around the tubes and being interlocked with each other and with the tubes to prevent removal of any-individual brick from the wall except in a direction longitudinally of the tubes.

3; In a furnace wall, the'combination of a series of upwardly extending supports spaced apart, and a wall facing comprising bricks having parts extending between. said supports and interlocked with the supports and additional parts lying in front of said supports and jointly operative to cover substantially the entire widths of the fire sides of the supports, said bricks being grooved longitudinally to fit against the supports and having inclined surfaces on their sides op-.

posite to said grooves to fit against other bricks, said inclined surfaces serving to cause the bricks to slide one upon the other substantially in the plane of the facing into firm engagement with said supports.

4. In a furnace wall, the combination of a series of upwardly extending tubes, and bricks substantially covering the fire sides of said tubes for considerable portions of their lengths to protect them from the heat generated in the furnace, said bricks having parts extending between the tubes and body portions lying in front of the tubes and forming part'of the fire face of the wall, the bricks also having laterally inclined surfaces serving to cause the bricks to slide one upon the other substantially in the plane of the wall into contact with the tubes.

5. In a furnace wall, the combination of a plurality of tubes, and bricks arranged-in rows between adjacent tubes and havingparts extending in front of the tubes and jointly effective to cover substantially the entire widths of the fire sides of the tubes to protect them, the bricks in each row being in- I terlocked with the two tubes between which the row is located, and having inclined sur- "faces adapted to slide on each other during entire widths of the fire sides of the tubes to protect them, each row including two series of bricks abutting, respectively, against the tubes between which they are located, the bricks in each series being arranged end to end and also having laterally inclined faces bearing against similar faces of the bricks in the other series and causing the bricks to wedge against each other and thereby to crowd them against the tubes.

7 In a furnace wall, the combination ofa plurality of tubes, and bricks arranged 1n rows between adjacent tubes and having parts extending in front of the tubes and jointly effective to cover substantially the entire widths of the fire sides of the tubes to protect them, each row including two series of bricks abutting, respectively, against the tubes between which they are located, the individual bricks of one series having inclined faces fitting between those of the bricks of the other series and each brick fitting partly around a tube.

8. In a furnace wall, the combination of a plurality of tubes, and bricks arranged in rows between adjacent tubes and having parts extending in front of the tubes and jointly efiective to cover substantially the entire widths of the fire sides of the tubes to protect them, each row including two series of bricks abutting, respectively, against the tubes between which they are located, the individual bricks of one series being arranged end to end and being staggered with reference to and fitting between adjacent bricks of the other series, each brick fitting partly around a tube, the bricks of the two series having laterally inclined faces serving to cause any sliding movement downwardly of the bricks along the tubes to wedge them one upon the other against the tubes.

9. In a furnace wall, the combination of a plurality of tubes, and bricks arranged in rows between adjacent tubes and having parts extending in front of the tubes and jointly efi'ective to cover substantially the entire widths of the fire sides of the tubes to protect them, each row including two series of a bricks abutting, respectively, against the tubes between which they are located, the bricks of one series being arranged end to end and each having a tapered projection fitting into a tapered recess between two adjacent bricks of the opposite series, and the walls of said recess and projection being inclined and serving to cause the bricks to crowd against the tubes as the inclined face of one brick tends to slide on the correspond 3c ing surface of an abutting brick.

10. In a furnace wall, the combination of a plurality of tubes and bricks arranged in rows between adjacent tubes and having parts extending in front of the tubes and jointly effective to cover substantially the entire widths of the fire sides of the tubes to protect them, each row including two series of bricks abutting, respectively, against the tubes between which they are located, the individual bricks of one series being staggered with reference to and fitting between adjacent bricks of the other series, each brick fitting partly around a tube, the bricks of the two series having laterally inclined; faces serving to cause any sliding movement downwardly of the bricks along the tubes to wedge them one upon the other against the tubes, and said inclined surfaces of adjacent bricks being tongued and grooved to interlock with each other.

11. lln a furnace wall, the combination of a series of tubes, a facing for said wall comprising bricks cooperating with said tubes to protect them, said facing being removable from the fire side of the wall and divided into sections each including a series of bricks, and brackets fastened to said tubes and supporting the sections, the bricks of each section being held in cooperative relationship to the tubes by their engagement with each other and with the tubes, but the brackets supporting at least a part of the weight of the bricks. 12. In a furnace wall, the combination of a seriesof tubes, bricks located on the fire 65 side of the tubes and cooperating with said till actate tubes to protect them, said wall being divided into sections each including a series of bricks, brackets on which said sections rest, and structural members behind the tubes for holding said brackets spaced apart.

13. In a furnace wall, the combination of a series of tubes, bricks cooperating with said tubes to protect them, said wall being divided into sections each including a series of bricks located at the tire face of the wall, brackets on which said sections rest, means for holding said brackets in cooperative relationship to said tubes, the bricks of each section being held in their operative positions by their interlocking engagement with each other and with the tubes but being relatively movable to release one from the other and thereafter being removable from the wall at the fire side of the wall, and key bricks locking the bricks of each section against movement out of interlocking relationship to each other.

14. In a furnace wall, the combination of a plurality of tubes, and bricks covering substantially the entire widths of said tubes to protect them at the [ire side of the wall, said bricks being shaped to be wedged by gravity against each other to hold them in contact with the tubes, and being free to move slightly with reference to each other as they expand and contract with changes in temperature.

15. In a furnace wall, the combination of wall sections having tubes therein and meeting at an angle to form a corner, corner bricks mounted one upon another in said corner at the fire side of the wall and overlapping the adjacent margins of said wall sections whereby they serve to close the corner, and means for securing said corner bricks in position with their edges abutting against said margins.

16. A brick for furnace wall construction having a groove formed therein to receive a tube and provided with a face to lie in front of and cover substantially one-half of the front of the tube, to protect said tube at the fire side of the wall, said brick having an en largement projecting at one side thereof and provided with an inclined face disposed at an angle to said groove, said inclined face being adapted to abut against and rest on an adjacent brick.

17. A. brick for furnace wall construction having a fire face at one end thereof, said brick having a groove in one side thereof to receive a tube whereby the brick will partially fit around the tube to cover substantially onehalf of the width of the tire side of said tube, said brick including a tapered projection extending at the side thereof opposite said groove and having laterally inclined faces at the top and bottom of said projection.

18. A brick for furnace wall construction having a fire face at one end thereof, said brick having a groove in one side thereoi to receive a tube whereby the brick will partially fit around the tube to cover substantially onehalf of the-width of the fire side of said tube, said brick having a tapered enlargement extending from the side thereof opposite said groove and provided with a laterally inclined face, and said face having a tongue extending in the, direction of the height of the brick 'along that portion of the incline adjacent to the body of the brick and having a groove in line with said tongue and approximately at the end of the tongue to receive a similar tongueof an adj acent brick.

19. In a furnace wall, the combination of a series of upwardly extending tubes for con? ducting a fluid medium, and bricks covering substantially the entire widths of said tubes at the fire side of the wall to protect the tubes, said bricks each including a body portion located at the fire side of one of said tubes and having an extension projecting backwardly between adjacent tubes, said bricks each having a groove extending substantially the length of the brick, and shaped to contact with a tube over a substantial portion of the groove surface, said bricks cooperating with each other and with said tubes to hold the bricks in their operative positions in thewall.

20. In a furnace wall, the combination of a series of upwardly extending tubes for conducting a fluid medium, and bricks covering substantially the entire widths of said tubes at the fire side of the wall to protect the tubes,

said bricks each including a body'portion shaped to fit around one of said tubes from one lateral edge of the tube to approximately the center of the side of the tube toward the fire side of the wall, said bricks also having parts located between adjacent tubes and each having a groove extending substantially the length of the brick, shaped to contact with a tube over a substantial portion of the groove surface, and said bricks being mounted to cooperate with the tubes and with each other to hold the bricks in their operative positions inthe wall.

21. A furnace wall comprising a rear wall section, tubes at the forward side of said section for conducting a fluid medium, and a facing removablefrom the fire side for protecting said tubes at the fire side 'of the wall,

said facing comprising bricks closely associated with said tubes and having ortions covering substantially the entire widths of the fire sides of the tubes, and held in their operative positions independently of said rear wallsection but by their engagement with each other and with said tubes.

' 22. A furnace wall comprising a rear wall section, tubes at the forward side of said section for conducting a fluid medium, and a facing removable from the fire side for protecting said tubes at the fire side of the wall,

said facing comprisingbricks closely .associ- "ated with said tubes and having portions covering substantially theieintire widths of the fire sides of the tubes, and held in their operative positions independently of said rear wall section but being removable at the fire side of the wall without disturbing said rear wall section.

23. A furnace wall comprising a rear wall section, tubes at the forward side of said section for conducting a fluid medium, and a facing removable from the fire side for protecting said tubes on the fire side of the wall, said facing comprising bricks closely associated with said tubes and having portions covering substantially the entire widths of the fire sides of the tubes, and held in their operative positions independently of said rear wall section but being removable at the fire side of the wall without disturbing said rear wall section, and key bricks cooperating with the other bricks of said facing to hold the latter bricks nonnally against removal from the wall.

24. A furnace wallcomprising a rear wall section, upwardly extending tubes at the forward side of said section for conducting a fluid medium, and a removable facing for protecting said tubes at the fireside of the wall, said facing comprising bricks closely associated with said tubes and having main body portions located at the fire sides of said tubes, said bricks each having a groove extending the length of the brick, shaped to contact with a tube over a substantial portion of the groove surface, said bricks beingheld in their operative positions independently of said rear wall section and by their engagement with each other and with the tubes, but being removable from the Wall at the fire side thereof without disturbing said rear wall section or said tubes.

25. In a furnace wall, the combination of a series of upwardly extending supports spaced apart, and a wall facing interlocked with said supports and comprising bricks having body portions covering substantially the entire widths of the front faces of the supports and protecting them from the heat generated in the furnace, said bricks also being provided with grooved surfaces to engage said supports and with inclined surfaces located between the supports and abutting against similarly inclined faces of other bricks to cause the force of gravity to wedgethe bricks against the supports.

26. A brick for furnace wall construction having a groove in one side thereof to receive a support and provided with a face portionto lie in front of and to cover substantially half the width of the front face of the support to protectit at the fire side of the wall, the side of said brick opposite to said groove-being provided with a face laterally inclined with reference to said groove to abut against an adjacent brick.

2'1. In a furnace wall, the combination of a menaee series of upwardly extending tubes for c0nducting a fluid medium, and a facing for said Wall comprising bricks interlocked with said tubes and having body portions covering sub stantially the entire width of the front faces of the tubes and protecting the tubes from the heat generated in the furnace, said bricks having laterally inclined surfaces located between adjacent tubes and abutting against each other to cause theforce of gravity to wedge the bricks laterally against the tubes.

OSCAR NYGAARD.