AU2006222543B2

AU2006222543B2 - Improved anchor for refractory linings

Info

Publication number: AU2006222543B2
Application number: AU2006222543A
Authority: AU
Inventors: Graham Millar
Original assignee: Antec Group Pty Ltd
Current assignee: Antec Group Pty Ltd
Priority date: 2005-03-09
Filing date: 2006-03-09
Publication date: 2011-05-19
Anticipated expiration: 2025-08-12
Also published as: AU2006222543A1

Description

WO 2006/094342 PCT/AU2006/000294 IMPROVED ANCHOR FOR REFRACTORY LININGS This invention relates to refractory linings for furnaces and in particular relates to the anchoring of refractory linings to the surface, and generally the inner surface, 5 of the furnace, BACKGROUND OF THE INVENTION Although the following description refers generally to the utilisation of an anchor system for anchoring a refractory lining to the surface of a furnace or the like, the anchoring device can also find utility in any situation where linings are required to i be applied to similar or other types of surfaces. Therefore, reference to refractory linings is also meant to encompass any similar material where, by suitable modification if necessary, the invention may also be utilised. Such refractory linings are used in industry for a variety of reasons including thermal insulation, abrasion resistance and general steelwork protection for vessel 1s components in a variety of process applications. Due to harsh conditions within a furnace, the linings need to be replaced as they deteriorate over time. The linings are generally affixed by means of anchors which are fitted to the internal wall surface of a furnace, for example by welding the anchor to the inner wall thereof 20 In some cases, the individual anchors are welded to the internal surface of the furnace and need to be removed and replaced when it is time to replace the lining. It has been found that it is inconvenient to remove and install the welded anchors and it would be advantageous to provide an anchor apparatus which enabled the lining to be applied and anchored more efficiently. 25 To this end, two component anchor systems have been previously developed, in which, for example, a 'V' anchor is rotated within a base nut, fixing itself into its WO 2006/094342 PCT/AU2006/000294 2 final vertical position by an interference fit between the V anchor and the base nut. Originally it was found that such a design necessitated the use of a 10mm or 3/8" thickness base nut. If the nut was thinner than 10mm it was previously found to be insufficient to create an interference bond with the V anchor. 5 It has now been found that reduced thicknesses of the base nut are possible, the interference fit relying less on the thickness of the nut itself and more on the shape of the V anchor in that region where it passes through the nut. OBJECT OF THE INVENTION The present invention has therefore been conceived out of the need to provide a 10 more economical means whereby refractory concrete type linings can be adhered to surfaces of furnaces or the like utilising an anchor system which provides less material usage in the anchor system. At the very least, the invention provides an alternative to presently known anchor systems for applying such refractory linings. DISCLOSURE OF THE INVENTION 1s According to the present invention there is provided an improved anchor system for refractory linings, said system including a V anchor and base nut, the base nut being welded to the wall of the furnace and having a thickness of less than 10mm or 3/8", one leg of the V anchor being threaded through a hole in the base, the V anchor then being rotated upwards from horizontal to vertical, whereby the base of 20 the V anchor is so shaped in that region where it passes through the hole in the base as to hold the V anchor in place therein by interference fit. Preferably the base nut is 8mm or 5/16" in thickness. Thus the present invention is significantly at variance to earlier designs in that a similar result is achieved by using for example only 80% of the previous thickness 25 of the base nut in the preferred embodiment.

WO 2006/094342 PCT/AU2006/000294 3 The two piece anchor system on which the present invention is modified, thus has improved technical, commercial and safety advantages. The anchor system of the present invention consists of two separate parts. - A base piece or nut preferably manufactured from 30 x 10 flat bar having a 5 precise shaped punched hole, and - A V anchor preferably manufactured in either 8mm or 10mm diameter wire. The separate base piece is securely welded to the furnace shell. Immediately prior to the installation of refractory castable material one leg of the V anchor top is threaded through the hole in the base piece and rotated upwards from 10 horizontal to vertical, and by virtue of the shape in that region where it passes through the hole, holds in place by interference fit. The shape of the V anchor and the size of the hole in the base have thus been calculated so that an interference fit bond occurs when the anchor top is rotated to the vertical position. No welding of the V anchor to the base is therefor required. 15 However, if the V anchor is rotated repeatedly from horizontal to vertical, the edges of the hole in the base piece will be increasingly deformed reducing the tightness of the interference fit. Since the hole in the base needs to be relatively small, a coated or capped V anchor can not be threaded through the hole as there is insufficient clearance. Therefore if 20 capping is required one leg of the V anchor can be pre-capped and the other end capped on site after threading through the hole. The merits of the present system include the following: 1. Refractory linings, such as refractory linings in rotary kilns, are subject to a small degree of movement and flexing during operation. A solid and rigid anchor 25 that has ho flexibility will resist movement of the refractory during operations, and WO 2006/094342 PCT/AU2006/000294 4 hence the anchor will be under stress to resist any movement. Additionally stress occurs in the refractory as it tries to move against a rigid inflexible anchor. A non flexible standard anchor can therefore cause stress in the castable lining contributing to cracks occurring in the refractory lining. 5 The present system was developed to tackle these problems. Whilst the base is firmly and securely welded to the furnace shell, the top V anchor has the capacity to move. Therefore the present anchor system has flexibility and can move to reduce stress in both the anchor and the refractory. As a result, the tendency for the lining to crack can be reduced and there is also a reduction in anchor breakage. 10 2. The base can be made in a range of alloys and frequently manufactured in carbon steel. When carbon steel is used and welding to a carbon steel shell, a regular carbon steel electrode is all that is required for welding. This simplifies the welding process and reduces the cost of the weld when compared to welding of higher grade stainless steel or high nickel alloy anchors. 15 In addition to reduced costs, regular carbon steel rods are more commonly available, particularly in remote areas. 3. The V anchor can be manufactured from whatever alloy the customer prefers without any concern for the cost or difficulty of welding the alloy, because no welding is required to join the V anchor top to the base. 20 4. The anchors as herein described offer trafficking and safety advantages over traditional anchors. Traditional anchors are pre-welded to the furnace shell prior to the refractory installation. These pre-welded anchors stand up from the furnace shell. The resulting forest of anchors, particularly in horizontal rotary kilns, makes it difficult for traffic in the kiln and for cleaning out of rubble before the refractory 25 is installed. It represents a safety hazard for personnel tripping over or failing on top of anchors. It is not unusual for the traditional anchors to be trodden on and flattened out. When this occurs the anchors are normally hand bent back to their WO 2006/094342 PCT/AU2006/000294 5 original shape. The re-bending significantly increases the cold working effect on the anchor with subsequent reduced life of the anchor. The anchor system as described does not have these problems. The only item that is welded to the furnace shell is the base piece or nut which is generally only s approximately 30mm high and therefore does not suffer distortion or bending from traffic in the kilns, even at reduced thicknesses. It is easy to clean rubble out prior to refractory installation and they have a much better safety feature due to their small size. 5. Similarly, for prefabricated vessels manufactured off-site, since only the 30mm 10 high bases need to be installed, it avoids a forest of anchors, simplifying transportation and erection at site without risk of damage. 6. There is also the possibility that the bases can be reused when relining the kiln, therefore considerably saving time and expense for repairs. In this event, anchors do not need to be ground off and re-welded. Whether the base is able to be reused 15 is entirely dependant on the condition of the base and how many times the V anchor has been rotated in the particular base. If the edges in the hole of the base have been too damaged from several rotations, the fit might not be tight enough and a light tack weld may be used to rigidise the V anchor in the base. In this situation the cost again would still be far less than removing and re-welding new 20 anchors to the shell. An extended base is also envisaged when the normal base is extended and made longer than the standard 30mm or 40mm high base. The extended base is utilised for dual layer refractory linings. The height of the standard base is increased by the same amount as the back up 25 lining thickness, so that the extended base protrudes through the back up lining by about 30 to 40 mm.

WO 2006/094342 PCT/AU2006/000294 6 The extended base can have an anchor welded to it to anchor the back up lining this anchor is pre-welded to the base. This reduces on site cost and time for welding of insulation anchorage to the furnace shell. The standard V anchor is used for the hot face. 5 The extended base system has all the advantages of the standard system as detailed above plus the following important advantages. 1. When installing the backup insulating refractory, the extended base is the only part of the anchor system used. The Vee anchor is only installed after the insulation is completed and when the hot face refractory is to be installed. Without 10 the hot face anchorage in place, a significantly simplified installation of the backup lining is available, giving better control. The base height gives good height gauge for lining thickness control and it is easier to trim back excess thickness of insulating lining between the short base pieces extending through the back up lining. 15 2. Historically when conventional anchors break in service, it is most often at the interface of the back up lining and the hot face lining. Differing stresses and other reasons have shown that it is crucial to consider the strength of the anchor at the interface to help reduce failure during operation. The extended base has a cross sectional area at the interface of 300mm 2 or equal to the approximate cross 20 sectional area of a 20mm diameter round bar. The extended base has proven resistant to breakage at this point due to its high strength and mass. Also as there is no cold working or bending at this interface point, there is no acceleration of thermally induced embrittlement under operating temperatures. 25 3. When repairing dual layer linings anchored with extended bases, it is only necessary to replace the hot face refractory and it is not necessary to remove the WO 2006/094342 PCT/AU2006/000294 7 insulation back up. Because the anchor system of the present invention is separable, the V anchor can be readily replaced whilst leaving the base intact. When this applies, the time saving and cost saving is of major consideration and summarised as follows, 5 * Insulation does not need to be replaced, thereby saving on demolition cost, new insulating refractory supply and reinstallation costs. " Anchors do not have to be ground off the shell. " Anchors are not needed to be re-welded to the shell. " The repair of the hot face can generally be carried out by the one trade not 10 requiring welding. (In the case of repeated rotation of the anchor bases, the edges of the hole creating the interference fit will be increasingly deformed, progressively reducing the tightness. In that case a light tack weld may be needed to give the V anchor sufficient strength to remain vertical. Even if this applies, the savings are still considerable). 15 4. The system is supplied as two separate pieces. The base may not be subject to the same temperature and operational conditions as the top or V anchor. Therefore if preferred, the base can be manufactured from a lower and less expensive alloy grade. This not only decreases supply cost, but could mean lower cost welding wire. 20 5. With a one piece conventional anchor, the entire anchor needs to be manufactured from alloy appropriate to the most demanding conditions. Stainless alloys are subject to thermally induced embrittlement when operating in temperature zone generally between approximately 6000 C and 9000 C. If a furnace temperature is say 11000 C, due to the temperature gradient through the 25 lining thickness, some section along the length of the anchor will be exposed to this undesirable embrittling effect temperature zone. Some higher grade alloys resist or WO 2006/094342 PCT/AU2006/000294 8 are immune to embrittlement in this temperature zone. Therefore because the anchor of the present invention is a two piece system, it allows the customer a choice to use a higher and more effective grade in the part of the anchor system that operates in this temperature zone. 5 BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will now be described with reference to the drawings in which: Fig. I is a side view of an anchor system according to a preferred embodiment of io the invention, Fig. 2 is an end view of the anchor system of Fig. 1, Fig. 3 is an end view of a V anchor being rotated from an insert position to an interference position, Fig. 4 is side view of an anchor system according to a second embodiment of the 15 invention having an extended base piece, and Fig. 5 is an end view of the anchor system of Fig. 4. BEST MODE OF CARRYING OUT THE INVENTION Referring generally to Figures I to 3, there is illustrated an anchor device 10 which is for use with refractory linings. The device includes a base nut 11, having a 20 thickness of less than 10mm and preferably 8mm, welded to the surface 12 of the furnace and a V anchor 13 threaded through a hole 14 in the base nut 11. An interference fit between the base 15 of the V anchor and the hole 14 causes the V anchor 13 to remain in the vertical position, ie perpendicular to the surface 12 of furnace wall. A refractory lining (not shown) is applied to the surface 12 over the 25 devices 10.

WO 2006/094342 PCT/AU2006/000294 9 Fig. 3 shows the rotation of the V anchor 13 from its horizontal position "A" after insertion, to its vertical in-use position "B", where it is held in place by interference fit as described above. Figures 4 and 5 illustrate a further embodiment where identical components to 5 those described in relation to Figures 1 to 3 utilise the same reference numerals. In this embodiment however the base nut I 11, which is again less than 10mm thick and preferably 8mm thick, is extended to allow for dual layers of lining as described above. To facilitate anchoring of the first layer (not shown) there are provided additional anchor members 16 which extend from the lower region of the lo extended base nut 11'. Otherwise the embodiment functions in an identical way as described above in relation to Figures 1 to 3, as far as the use of the V anchor 13 having an interference fit in hole 14 of the extended base nut 111 is concerned. The foregoing describes only some embodiments of the present invention, and modifications obvious to those skilled in the art can be made thereto without 15 departing from the scope of the present invention.

Claims

1. An anchor system for refractory linings, the system including a V anchor and base nut, the base nut being welded to the wall of the furnace and having a thickness of less than 10mm, one leg of the V anchor being threaded through a hole in the base, the V anchor then being rotated upwards from horizontal to vertical, whereby the base of the V anchor is so shaped in that region where it passes through the hole in the base as to hold the V anchor in place therein by interference fit.

2. An anchor system for refractory linings according to claim 1, wherein the base nut is 8mm in thickness.

3. An anchor system for refractory linings according to claim 1 or claim 2, wherein the system is a two piece anchor system which includes a base piece or nut manufactured from 30 x 10 flat bar having a precisely shaped punched hole, and a V anchor manufactured in either 8mm or 10mm diameter wire.

4. An anchor system for refractory linings according to claim 3 in which the separate base piece is securely welded to the furnace shell.

5. An anchor system for refractory linings according to any one of the preceding claims in which immediately prior to the installation of refractory castable material one leg of the V anchor top is threaded through the hole in the base piece and rotated upwards from horizontal to vertical, and by virtue of the shape in that region where it passes through the hole, holds it in place by interference fit.

6. An anchor system for refractory linings according to claim 5 wherein the shape of the V anchor and the size of the hole in the base are determined so that an interference fit bond occurs when the anchor top is rotated to the vertical position, thereby eliminating welding of the V anchor to the base.

7. An anchor system for refractory linings according to claim 6 wherein the hole in the base is relatively small, so that where a coated or capped V anchor is not able to be threaded through the hole as there is insufficient clearance, one leg of the V anchor can be pre-capped and the other end capped on site after threading through the hole, if capping is required.

8. An anchor system for refractory linings according to any one of the preceding claims in which the base is firmly and securely welded to the furnace shell, and the top V anchor has the capacity to move.

9. An anchor system for refractory linings according to claim 8, wherein the anchor system can move to reduce stress in both the anchor and the refractory lining, such that any tendency for the lining to crack is reduced and there is also a reduction in anchor breakage

10. An anchor system for refractory linings according to any one of the preceding claims wherein the base is made in from a range of alloys including carbon steel. 11

11. An anchor system for refractory linings according to any one of the preceding claims wherein the V anchor is manufactured from any suitable alloy since no welding is required to join the V anchor top to the base.

12. An anchor system for refractory linings according to any one of the preceding claims in which the only item that is welded to the furnace shell is the base piece or nut which being generally only approximately 30mm does not suffer distortion or bending from traffic in the kilns, even at reduced thicknesses.

13. An anchor system for refractory linings according to any one of the preceding claims in which the bases are reusable when relining the kiln.

14. An anchor system for refractory linings according to any one of the preceding claims wherein an extended base is utilised, the normal base being extended and made longer than the standard 30mm or 40mm high base, the extended base being utilised for dual layer refractory linings.

15. An anchor system for refractory linings according to claim 14 in which the extended base has an anchor welded to it to anchor the back up lining.

16. An anchor system for refractory linings substantially as herein described with reference to the drawings.