Refractory application process and method

Abstract

A refractory insulation on boiler tubes using studs circular in cross-section and having shoulders intermediate their ends with washers frictionally engaged on the studs sandwiching a mesh therebetween. The shoulder restrains movement of the first washer and mesh toward the substrate and the second washer retains the mesh from movement away from the substrate. A first insulation is applied to the substrate through the mesh and a second insulation layer is applied over the mesh to a predetermined thickness determined by the height of the studs above the shoulders. Pins can be welded to the tops of the studs and used to impale fibrous insulation.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a non-provisional patent application based upon provisional patent application having Serial No. 60/336,266, filed Nov. 2, 2001, and which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable

BACKGROUND OF THE INVENTION

[0003] This invention is applicable to the field of refractory application and in particular to the application of refractory to boiler tubes. The invention also concerns a novel stud for stud welding which has a shoulder spaced intermediate the ends of the stud to accommodate washers used to position the mesh commonly used to reinforce the refractory applied to the boiler tubes. The invention specifically involves a process for applying a refractory coating to boiler tubes using a stud which is circular in cross-section and has a shoulder to locate a reinforcing mesh a predetermined distance from the tube surface.

[0004] The preferred stud is cylindrical and has a base leg which is attached at one end to the outside of the boiler tube and a shoulder located on the other end of the base leg. The shoulder is rounded on the top to mate with the inner surface of a washer which is positioned over the free end of an upper arm of the stud. The upper arm extends upwardly from the shoulder and is aligned with the leg. The top end of the arm preferably is chamfered or rounded to facilitate application of the washers. The preferred stud also has a completely rounded shoulder in the form of a sphere to facilitate fabrication of the stud.

[0005] This invention has particular application to coal or gas fired electrical generation plants in which steam heat is used to drive generating turbines. The outer surfaces of the boiler tubes are covered with an insulating refractory composition which is sprayed (gunned) or troweled into place. To support the refractory, studs are welded onto the tubes and an expanded metal mesh is placed onto the studs a predetermined distance from the tubes. A finish coat of insulation then is troweled over the mesh to a predetermined thickness.

[0006] Studs presently used for this purpose are rectangular and difficult to firmly weld to a boiler surface which may be partly corroded or uneven. These studs are long and require the free end to be bent over the clip by hammering which often results in breaking the weld.

[0007] Pointed studs also have been used, but the clips used to locate the mesh tend to slide down the pin toward the boiler tube when the outer layer of refractory is applied.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0008] The objects of the invention are achieved as set forth in the illustrative embodiments shown in the drawings which form a part of the specification.

[0009] FIG. 1 is a fragmentary vertical sectional view of the present invention applied to a boiler tube;

[0010] FIG. 2 is a diagrammative drawing of the stud applied to a boiler tube;

[0011] FIG. 3 is an elevational view of the stud;

[0012] FIG. 3a is a plan view of the mesh used in this invention;

[0013] FIGS. 4a-d are elevational views of modifications of the stud; and

[0014] FIG. 5 is a fragmentary vertical sectional view of another modification of the invention applied to a boiler tube.

[0015] Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF INVENTION

[0016] The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what I presently believe is the best mode of carrying out the invention. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

[0017] FIG. 1 shows the application of the invention to a boiler tube 10. The studs 111 are stud welded to the tube 10 using conventional stud welding techniques. The stud 111 is shown in more detail in FIGS. 2 and 3 and comprises a leg portion 12 whose lower end 13 is welded to the outer surface of the boiler 10. The leg 12 is circular in cross-section and preferably is cylindrical in shape. The lower end 13 can be chamfered 13a or flat and has a flux load 14. A shoulder 15 is connected to the other end of the leg 12 and preferably is rounded to have a spherical surface 16 for simplicity of fabrication. A top arm 17 is aligned with the leg 12 and is connected at one end to the shoulder 15 and has a free top end 18 which preferably is chamfered 18a or rounded for ease of applying washers 30, as will be explained in detail hereinafter. The arm 17 is circular in cross-section and preferably is cylindrical in shape.

[0018] In the application process, the outer surfaces of the boiler tubes usually are first cleaned and the studs 11 are welded on. After the studs 11 are welded to the boiler tube 10, a washer 30 is passed over the stud end 18 and engages the top of the shoulder 15. The washer 30 can be of any shape so long as it is sufficiently large so it will retain the mesh 31 which also is passed over the stud 11. The washer 30 has a center opening 32 which is sized to frictionally slide over the stud arm 17 and resist movement on the arm 17. The opening 32 can be in the form of an “X” cut in the washer 30. The washer 30 preferably has a concave undersurface 33 around the opening 32 to mate with the stud shoulder surface 16 to keep the washer 30 from moving past the top of the shoulder 15.

[0019] After the first washer 30 is applied to the stud 11, the mesh 31 is positioned over the stud 11 and into engagement with the stud 30. A retainer washer 30a identical to the washer 30 is then passed over the stud 11 and into engagement with the mesh 31 The top washer 30a frictionally engages the stud arm 17 to retain the mesh 31 on the stud 11.

[0020] Refractory insulation 40 is then sprayed (gunned) or troweled onto the tube 10 through the mesh 31. A final layer of refractory 41 may then be troweled onto the top of the mesh 31. The layer 41 can be of a less dense, higher insulating refractory material. The thickness or “stand-off” of the refractory layers 40 and 41 are as defined by the design engineer. Thus, the stud 11 preferably is fabricated so the height of the leg 12 and the shoulder 15 (plus the amount of the stud consumed in the weld) equal the desired thickness of the first refractory layer 40 and the height of the stud arm 17 equals the desired thickness of the top refractory layer 41. The person applying the refractory can use the tops of the studs 11 as reference points in applying the top layer of refractory 41 to insure it is of the specified thickness, thus avoiding excess, which adds to the cost of the installation, or a too thin layer which could result in failure of the refractory in use.

[0021] FIGS. 4a-d show other forms of the stud. FIGS. 4a-c show a flat shoulder 50 whereas FIG. 4d shows a stud having a shoulder 51 with only the top surface 52 rounded. All of the studs shown in FIGS. 4a-d are round in diameter.

[0022] Typical dimensions for the stud length A is 1¼″; the arm B is ⅜″; the height of the leg and shoulder C is ⅞″; the diameter D of the stud arm is {fraction (3/16)}″ (0.1877″ 0.250″; and the diameter B of the stud leg is {fraction (5/16)}″ (0.250″ 0.3125″).

[0023] FIG. 5 shows the application of pins 55 which are welded to the top of the studs 11 and used to impale a fibrous insulation 58 over the outer surface of the refractory 41. Speed clips 56 are positioned on the pins 55 at the free ends to retain the fibrous insulation 58. A metallic top sheeting 57 can be applied over the insulation 58 to protect it. The top sheeting 57 may be fastened to the tops of the pins 55.

[0024] In view of the above, it will be seen that the several objects and advantages of the present invention have been achieved and other advantageous results have been obtained. REFRACTORY APPLICATION PROCESS AND METHOD (Our File TSF 81761U) 1 Parts List 10. boiler 11. studs 12. leg of studs 13. lower end of studs 13a chamfered 14. flux load 15. shoulder 16. spherical surface of 15 17. top arm 18. free top end of 17 18 chamfered 19. 20. 21. 22. 23. 24. 25. 30. washers 30a top washer 31. mesh 32. center opening of 30 33. concave under surface of 30 34. 35. 40. refractory insulation 41. top refractory layer 42. 43. 44. 45. 50. flat shoulder 51. shoulder 52. rounded surgface of 51 53. 54. 55. pins 56. speed clips 57. top cover 58. fibrous insulation

Claims

1. A stud for applying refractory to a substrate comprising a leg having a first free end adapted to be stud welded to said substrate, a shoulder attached to a second end of said leg, and an arm having a free first end and a second end attached to said shoulder and aligned with said leg.

2. The stud of claim 1 wherein the arm and leg are circular in cross-section.

3. The stud of claim 1 wherein the shoulder is rounded on the top.

4. The stud of claim 3 wherein the shoulder has a spherical outer surface.

5. The stud of claim 1 wherein the free end is chamfered or rounded.

6. The stud of claim 1 wherein the leg and shoulder have a predetermined length equal to the desired thickness of a first layer of refractory adapted to be gunned or trowled onto the substrate plus the amount of stud consumed by the weld, and the stud arm has a predetermined length equal to the thickness of a top layer of refractory adapted to be trowled onto the substrate.

7. A refractory installation comprising:

a substrate,

a plurality of studs welded to said substrate, said studs having a shoulder intermediate their ends,

first washers frictionally positioned on the studs and restrained from movement toward the substrate by the shoulders,

a mesh positioned on the studs and restrained from movement toward the substrate by the first washers,

second washers frictionally positioned on the studs and restraining the mesh from movement away from the substrate, and

refractory positioned between the mesh and the substrate.

8. The installation of claim 7 including a second layer of refractory positioned over the mesh and having a thickness substantially the distance between the shoulders and the free ends of the studs.

9. The installation of claim 8 including pins positioned on the free ends of the studs and insulation impaled on the pins and retained thereon.

10. The installation of claim 9 including a protective cover over the impaled insulation and fastened to the pins.

11. The installation of claim 8 wherein the studs are circular in cross-section.

12. The installation of claim 8 wherein the stud shoulders are rounded on the top.

13. The installation of claim 12 wherein the first washers have concave under surfaces which mate with the stud shoulder rounds.

14. The installation of claim 11 wherein the free ends of the studs are chamfered or rounded to facilitate passage of the washers.

15. The installation of claim 8 wherein the stud leg and shoulder have a predertermined length equal to the desired thickness of the first layer of refractory on the substrate plus the amount of stud consumed by the weld, and the stud arms have predetermined lengths equal to the thickness of the top layer of refractory.

16. The installation of claim 8 wherein the substrate is boiler tubes.

17. A method of applying insulation to a substrate including the steps of welding the studs of claim 1 to the substrate,

frictionally engaging first washers onto the studs against the shoulders,

positioning mesh onto the studs whereby the first washers restrain the mesh from movement toward the substrate,

frictionally engaging second washers onto the studs over the mesh to restrain the mesh from movement away from the substrate,

applying a first layers of insulting material to the substrate to a thickness of the mesh, and

applying a second insulating layer to the first insulating layer to a thickness defined by the free ends of the studs.

18. The method of claim 17 including the steps of positioning pins on the free ends of the studs, impaling fibrous installation onto the pins and restraining the fibrous insulation on the pins.

19. The method of claim 17 wherein the substrate is boiler tubes.