GB2125926A

GB2125926A - Insulating sheaths for horizontal pipes in furnace installations

Info

Publication number: GB2125926A
Application number: GB08321447A
Authority: GB
Inventors: Hans Steinborn; Werner Thomas
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1982-08-26
Filing date: 1983-08-09
Publication date: 1984-03-14
Also published as: SE8304587D0; FR2532399A1; DE3231736C2; GB2125926B; JPS5958298A; DE3231736A1; FR2532399B1; IT8348876A0; BE897590A; IT1170448B; SE8304587L; GB8321447D0

Abstract

An insulating sheath for a horizontal pipe in a furnace installation includes "lower portion" 13, 14 made of moulded ceramic fibre material and adapted to extend around the lower part of the pipe and an upper portion 4, 5 made of a highly stable ceramic material and adapted to extend around the upper part of the pipe. The upper portion completely covers the lower portion from above and thus protects it from slag and cinder attacks. <IMAGE>

Description

SPECIFICATION Insulating sheaths for horizontal pipes in furnace installations The invention relates to insulating sheaths for substantially horizontal pipes in furnace installations, in particular slide support or transverse pipes, and is concerned with radially divided sheaths in which the component members are adapted to be secured to the pipe and each cover a proportion of the periphery of a pipe.

The disposition of the necessary support and transport structures in fireboxes, combustion chambers, heating zones and exhaust gas flues of furnace installations of various types generally necessitates a forced cooling of the structural members by air, water or steam. Thus, for instance the hearths of bottom and top heated warming furnaces of the type used in the steel industry (e.g.

a walking beam furnace, an end pusher furnace, or the like) are formed from round or rectangular pipes which are designated slide, support or transverse pipes when they are horizontal, and standing pipes when they are vertical. To cool these pipes one can use cold or hot cooling, for which purpose either water or hot steam is passed through the entire pipe system.

In order to reduce the high heat losses from the furnace resulting from the cooling and thus to increase the furnace efficiency and also to prevent a deleterious effect being exerted by the cooling of the pipe on the material to be warmed (e.g. slabs, blocks, billets, wire bars and the like), the pipes must in general be sheathed, i.e. insulated. In this connection it must be born in mind that in addition to the thermal stresses which occur there are also mechanical stresses resulting from cinder or slag attacks or from expansion, bending and vibration of the pipe system. On the other hand, it is desirable for the thickness of the pipe insulation to be as thin as possible, particularly in the case of support and slide pipes, so that the shaded area of the heated underside of the material to be heated is limited to a minimum.

Insulating shaped member together constituting a sheath are described in U.S. Patents Nos. 2 693 352 and 3 781 167, German Patent No. 2 125 885 and Austrian Patent Application No. OE 552/1 979. The shaped members comprise dense refractory compositions in which steel reinforcement is embedded. These shaped members have low thermal insulation values as a result of the high thermal conductivity of dense refractory compositions. Furthermore shocks emanating from the pipe system which are transmitted to the steel reinforcement frequently lead to the breakage of the rigidly jointed inelastic shaped bodies.

To improve the thermal insulation values it has been attempted to use an insulating sheath comprising shaped members made from a ceramic fibre mat. Thin mats as an intermediate layer between the pipe and the rigid shaped body result, however, in a weakening of the solid shaped bodies and lead also to an increase in the size of the shaded area on the material to be warmed.

The use of mats of ceramic fibres alone does not result in a satisfactory strength and vibrational stability.

It is an object of the invention to provide an insulating sheath of the type referred to above which may be disposed in the individual peripheral zones of the pipe in accordance with the requirements at those points and can be simply assembled and disassembled.

According to the present invention an insulating sheath for a horizontal pipe in a furnace installation includes a first portion comprising ceramic fibre material and adapted to extend around the lower part of the pipe and a second portion comprising a stable ceramic material and adapted to extend around the upper part of the pipe and constructed so as, in use, to cover the top of the first portion. The upper portion is preferably radially divided into two or more upper bodies, more preferably two symmetrical bodies, and the lower portion is preferably similarly divided.

The lower portion of the sheath thus inherently has a low thermal conductivity, a low thermal storage capacity, a high resistance to thermal shock and a low weight and thus produces a high degree of thermal insulation. Furthermore their structure is not totally rigid but has a certain flexibility and they are therefore substantially insensitive to vibrations of the pipe. ~, Tire upper portion which is made from a highly stable ceramic material is resistant to cinder and slag attacks and protects the lower portion against such attacks. The upper portion preferably comprises refractory materials based on aluminosilicate, silicon carbide, magnesite and the like.

In a preferred embodiment of the invention the lower bodies are shaped to extend over more than 1800 but less than 2700, preferably about 240 , of the periphery of the pipe and the upper portion is shaped to extend to the vertical tangents of the lower bodies. In this embodiment the lower bodies of the sheath, which constitute particularly effective thermal insulation, extend around a major proportion of the pipe and are protected against cinder and slag attacks by the upper portion of the sheath which completely covers them.

In one embodiment of the invention ribs are formed on the inner surface of the upper portion and when in position on a pipe the thermal insulation of the upper portion may be improved by positioning ceramic fibre strips between the ribs and between the upper portion and the pipe.

The upper portion of the sheath is preferably constructed in the form of a gable roof in order substantially to prevent the risk of damage by articles in the furnace and by baked-on slag.

The lower portion of the sheath may be vacuum moulded from ceramic fibre material, in which case it is preferably tempered subsequent to its moulding or alternatively it may be formed from a plurality of ceramic fibre strips.

The lower portion is preferably provided with a metal reinforcement whilst the upper portion preferably has no such reinforcement.

The invention also embraces a substantially horizontal pipe in a furnace installation surrounded by such an insulating sheath. It is preferred that brackets project from the pipe, e.g. are welded thereto, which act as supports for the upper portion of the sheath which results in the upper portion not exerting any load on the lower portion and the ability of the two portions to be exchanged independently.

The lower portion of the sheath may be connected to the pipe with the aid of adhesive or cold setting fireproof mortar or alternatively by means of mounting clips secured to the pipe. In the case in which the lower portion of the sheath has reinforcements embedded therein, it is preferred that these afford hooks which engage straps secured to the pipe to hold the lower portion onto the pipe. It will be appreciated that the connection between the pipe and the lower portion of the sheath must bear the entire weight of the lower portion.

Further features and details of the invention will be apparent from the following description of certain specific embodiments which is given by way of example with reference to the accompanying drawings, in which.~ Figure 1 is a partially sectioned perspective view of a pipe carrying an insulating sheath in accordance with the invention; Figure 2 is an underplan view of the upper insulating bodies of the sheath viewed in the direction of the arrow A in Figure 3; Figure 3 is a transverse section through the upper insulating bodies; Figure 4 is a perspective view of a vacuum formed lower insulating body; Figure 5 shows a moulded body similar to that of Figure 4 with a reinforcement insert; Figure 6 is a view similar to Figure 4 of a lower insulating body composed of strips of ceramic fibre material;; Figure 7 shows a lower insulating body similar to that of Figure 6 with a different orientation of the strips and reinforcement inserts; Figure 8 shows one way of securing a lower insulating body to a pipe; Figure 9 shows a way of securing a lower insulating body with a reinforcement insert to a pipe: Figure 10 is a view of the securing device of Figure 9 on an elongated scale; and Figure 11 shows a further way of securing a lower insulating body in particular of the type shown in Figure 7, to a pipe.

Referring first to Figure 1, a pipe 1 extending horizontally in a firebox has rider) 2 for supporting material to be warmed. A cooling medium flows through the pipe 1.

Radial brackets 3 are secured to the exterior of the pipe 1, each of which lies on the pipe 1 at an angle W of about 300 above the horizontal plane of symmetry of the pipe. Upper insulating bodies 4 and 5 rest on the brackets 3 and together form a gable roof-shaped cover (see Figure 3). In the region of the riders 2 the bodies 4. 5 are provided with recesses 6 and 7 (see Figure 2) through which the riders extend. The upper bodies 4 and 5 carry spaced ribs 8. 9 and 1 0, 11 respectively on their interior surface. Between the pairs of ribs there is an insulating layer 12 of ceramic fibre strips (see Figure 1).

The upper bodies 4 and 5 are made of dense, highly mechanically stable, abrasion-resistant refractory material based on alumino-silicate, silicon carbide, magnesite or the like.

In addition to the upper bodies, the pipe is also partially surrounded by two lower insulating bodies 13 and 14 which are manufactured from a ceramic fibre material. In comparison to the bodies 4 and 5 the lower bodies, therefore, have a particularly low thermal conductivity and a small thermal storage capacity.

The lower bodies 13 and 14 are each manufactured in one piece in a vacuum moulding process and subsequently tempered and are provided on their outer stressed surface with a protective coating (see Figures 4 and 5). The protective coating can be based on silicon carbide fillers or on alumina fillers or on other fillers. In each case it is cold setting.

The lower bodies 13 and 14 can alternatively be prefabricated from individual ceramic fibre strips 15 (see Figures 6 and 7). In this case the tempering is unnecessary. The outer stressed surfaces are provided with a protective layer of the type described.

The lower bodies 13 and 14 engage one another along a parting line 16 and the upper bodies 4 and 5 respectively along respective parting lines 17 and 18. In order to maintain the parting lines 17 and 18 as narrow as possible, the lower bodies 13 and 14 afford steps 19 and 20 to receive the brackets 3.

In order completely to cover the lower bodies 13 and 14 from above, the edges 4' and 5' of the upper bodies 4 and 5 are projected to the vertical tangents T of the lower bodies 1 3 and 14.

The parting line 16 and the ridge line 21 between the two upper bodies 4 and 5 and also the joints formed between the recesses 6 and 7 and the riders 2 and the butt joints between adjacent insulating bodies in the longitudinal direction of the pipe are filled with a refractory mortar. The length of the individual insulating bodies 4, 5, 1 3, 14 is preferably so selected that for each metre of pipe three of each insulating body are used.

To increase the stability of the lower insulating bodies 13 and 14 metal reinforcements 22 are set in them in the specific embodiments of Figures 1,5,7.

The lower bodies 13 and 14 can be glued directly to the pipe 1 by means of a cold setting adhesive. They can however also be secured to the pipe 1 by means of mechanical fasteners.

Such fasteners are illustrated in Figures 8 to 11.

In the specific embodiments of Figures 8 to 10 fastening clips 23 are welded to the pipe 1 into which a limb of an angle bracket 24 can be inserted.

In the embodiment of Figure 8 the angle bracket 24 includes clips 25, 26 which extend in the longitudinal direction of the pipe. Clips 25 and 26 are pushed into the material of the lower insulating bodies 13 and 14. Each angle bracket 24 thus holds two insulating bodies 13, 14 at their abutting ends. The movability of the angle brackets 24 in their securing clips 23 results in a compensation for length tolerances.

In the embodiment of Figures 9 and 10 a pipe socket 27 is secured to a limb of the angle bracket 24 and extends on both sides beyond the latter in the longitudinal direction of the pipe. The pipe socket 27 is so constructed that reinforcing rods 22 of abutting insulating bodies 13 and 14 engage in it from both sides. This form of anchoring is advantageous primarily when the insulating members are subjected to particularly powerful shocks.

In the embodiment of Figure 11 hooks 28 are arranged on the exterior of the pipe 1. The insulating bodies 13 and 14 have on their inner surface a metal backing of substantially rigid expanded metal 29, perforated metal sheet or the like which is used to connect the insulating bodies to the hooks.

The upper bodies 4 and 5 and the lower bodies 13 and 14 can be exchanged independently of one another when they are worn. The upper bodies 4 and 5 exert no force on the lower bodies 13 and 14 but are held in position by the brackets 3. They can thus be lifted up from the brackets 3 and exchanged without removing the lower bodies 13 and 14. Similarly the lower bodies 13 and 14 may be separately exchanged.

The upper bodies 4 and 5 are extremely resistant to slag attacks and protect the lower bodies 13 and 14 from such attacks. The lower bodies 13 and 14 are predominantly responsible for the thermal insulation of the pipe 1.

Claims

1. An insulating sheath for a horizontal pipe in a furnace installation including a first portion comprising ceramic fibre material and adapted to extend around the lower part of the pipe and a second portion comprising a stable ceramic material and adapted to extend around the upper part of the pipe and constructed so as, in use, to cover the top of the first portion.

2. A sheath as claimed in Claim 1 in which the upper portion is radially dividied into two or more upper bodies.

3. A sheath as claimed in Claim 2 in which the upper portion comprises two symmetrical bodies.

4. A sheath as claimed in any one of the preceding claims in which the lower portion is radially divided into two or more lower bodies.

5. A sheath as claimed in Claim 4 in which the lower portion comprises two symmetrical bodies.

6. A sheath as claimed in Claim 4 or Claim 5 in which the lower bodies are shaped to extend over more than 1800 but less than 2700 of the periphery of the pipe and the upper portion is shaped to extend to the vertical tangents of the lower bodies.

7. A sheath as claimed in any one of the preceding claims in which the upper portion has no steel reinforcement.

8. A sheath as claimed in any one of the preceding claims in which ribs are formed on the inner surface of the upper portion.

9. A sheath as claimed in any one of the preceding claims in which the upper portion is constructed in the shape of a gable roof.

10. A sheath as claimed in any one of the preceding claims in which the lower portion is vacuum moulded from ceramic fibre material.

11. A sheath as claimed in Claim 10 in which the lower portion is tempered subsequent to its moulding.

12. A sheath as claimed in any one of Claims 1 to 9 in which the lower portion is composed of ceramic fibre strips.

13. A sheath as claimed in any one of the preceding claims in which the lower portion is provided with a metal reinforcement.

14. An insulating sheath for a horizontal pipe in a furnace installation substantially as specifically herein described with reference to Figures 1 to 3 alone or in combination with one of Figures 4 to 11.

15. A horizontal pipe in a furnace installation surrounded by an insulating sheath as claimed in any one of the preceding claims.

16. A pipe as claimed in Claim 15 when dependent on Claim 8 including strips of ceramic fibre material disposed between the ribs and between the upper portion and the pipe.

17. A pipe as claimed in Claim 15 or Claim 16 in which brackets project from the pipe which act as supports for the upper portion.

18. A pipe as claimed in any one of Claims 15 to 17 when dependent on Claim 13 in which securing means are arranged on the pipe which engage the metal reinforcement of the lower portion.

19. A pipe as claimed in any one of Claims 1 5 to 17 in which the lower portion is secured to the pipe by adhesive.

20. A pipe as claimed in any one of Claims 15 to 17 in which the lower portion is secured to the pipe by means of clips secured to the latter.