RU51703U1 - PIPE HEAT INSULATION - Google Patents

Abstract

The utility model is aimed at increasing the mechanical strength of the heat-insulating coating of pipes while maintaining its elasticity and flexibility, reducing the weight of the coating, increasing its service life. The technical result is achieved by the fact that the design of the pipe insulation is fixed on the outer surface of the pipe and between each other layers of elastic heat-insulating material, in which refractory adhesive is used as a fixing material. The coating can be created from one or more layers of thermal insulation material. It is advisable to use a fibrous refractory material with an apparent density of not more than 200 kg / m ³ as an elastic thermal insulation material. 2 zpf

Description

The utility model relates to heat engineering, to pipe insulation devices, in particular, can be used for thermal insulation of metal pipes in methodical heating furnaces of rolling production.

In methodological furnaces, where the preforms are heated before rolling, metal water-cooled pipes are used, through which the heated preforms are moved through the furnace using a pusher (pusher furnaces), or by mechanical movement of individual sections from the hearth pipes (walking beam furnaces). The uniformity of metal heating substantially depends on the effective thermal insulation of the hearth pipes through which the steam-water mixture circulates.

The prior art thermal insulation of hearth pipes made of dense refractory materials, for example, thermoblocks obtained from concrete of various compositions and having a significant mass.

The disadvantages of such thermal insulation structures include the difficult use of blocks for lining complex structures having bends and crosshairs. In addition, thermal blocks are installed on the pipes by welding metal mortgages located in the blocks. Such thermal insulation reduces the mechanical strength of glide pipes as a result of the use of electric welding. The disadvantage of using thermoblocks is also the rapid oxidation of metal mortgages, resulting in the formation of cracks in the mortar when it shrinks under the influence of high temperatures and vibration during operation of the furnace, which leads to collapse of the blocks and exposure of pipes. Such coatings continue to be used at a number of domestic metallurgical plants.

At present, thermal insulation coatings made of ceramic-fiber refractory materials are also used, which combine such properties as high heat resistance, low heat conductivity, low weight, elasticity, flexibility and vibration resistance, but they have low mechanical strength. In the article of V.M. Krylov et al. “The Efficiency of Using Fibrous Materials and Products in the Heat Barriers of Ovens” (New Refractories Magazine, M., Intermet, No. 4, 2003, p.22-25) described

thermal insulation using ceramic fiber, which is attached to the pipes by means of heat-resistant wire. Such insulation is quite simple, has a small mass and high vibration resistance, but has a small service life due to damage due to gas flows, crumbling scale and oxidation of the wire.

Thermal insulating coatings from a soft inner layer adjacent to the protected surface of the pipe and a dense outer layer through which the pipe is in contact with the environment are widely used.

Two-layer thermal insulation is most widespread. There are several varieties of such insulation, in which ceramic-fiber materials are used as the inner layer, and the outer layer is made of refractory products of a special shape from various concrete. Moreover, the methods of fastening dense products are diverse. As fastening material, anchors, studs, bolts, pins of various metals are used, which are welded to the hearth pipes and enter grooves or holes in the refractory blocks (see French Patent No. 2239166, F 27 D 3/02, 5/00, C 21 D 9/70, publ. 31.05.75; US Patent No. 3941169, F 27 D 3/02, F 16 L 9/16, 9/22, publ. 02.03.76).

The disadvantages of these designs include:

1) The shrinkage and subsequent sealing of the ceramic-fiber gasket between the pipe and dense refractory products, which leads to the formation of cracks and oxidation (destruction) of the fasteners, and, as a result, the collapse of the thermal insulation of the pipes.

2) A large mass of dense refractory products of various shapes, which increases the load on the hearth pipes, reduces their mechanical strength, especially in high temperature zones, and contributes to a more rapid collapse of refractory products during oxidation of metal fasteners.

3) The use of electric welding to connect metal fasteners with pipes, which helps to reduce the mechanical strength of the pipes in which the steam-water mixture is located at high temperature and pressure.

4) The destruction of the thermal insulation of the outer layer under the influence of vibration and shock loads, since the refractory products and the binder have a large mass and, moreover, during the operation of the furnace turn

in solid monolithic material with very low impact strength. This is most evident in pusher type furnaces.

The technical solution described in British Patent No. 1318352, F 27 D 5/00, F 16 L 59/02, publ. 05/31/73. It describes the Insulok thermal insulation and its variant Skidlock of Morgan Refractoris, which consists of Sipamul shaped products manufactured by vibration casting. This insulation is used in metallurgical plants in Europe and Japan. The service life, depending on the conditions in the furnace, is 6-24 months (Fryatt I. - Steel Times, 1975, v.203, No. 5). The advantage of such insulation is the absence of any binders during the assembly of insulation, as a result of which it can withstand vibration loads. However, this insulation cannot withstand mechanical stress. In addition, it should be noted that the prototype has all the other disadvantages listed above of other analogues.

The objective of the new utility model is the creation of pipe insulation, which is able to provide:

- increase the mechanical strength of the insulating coating while maintaining its elasticity and flexibility;

- the exclusion of the use of various kinds of metal fasteners;

- increase the service life of thermal insulation;

- regulation of heat loss in the zones of the heating furnace through the use of various thicknesses (number of layers) of the used elastic material (ceramic fiber) in the respective pipe sections;

- effective reduction of gas consumption for heating the steam-water mixture in the bottom tubes of the methodical heating furnaces.

The technical result is achieved by manufacturing a thermal insulation structure, which is layers of heat-insulating elastic material fixed on the outer surface of the pipe and between each other, in which refractory adhesive is used as the fastening material. It is advisable to use an affordable ceramic fiber material that provides long-term reliable insulation of structures of complex configuration, eliminating the influence of the compaction process and shrinkage of the heat-insulating material on the formation of cracks during operation of the furnace, reducing

the mass of the coating with its sufficiently high heat resistance, shock and vibration resistance by original fixing the main heat-insulating coating on the pipe using refractory glue.

The coating can be made of glued layers of fibrous refractory material with an apparent density of not more than 200 kg / m ³ , and the refractory adhesive is used, for example, sodium aluminosilicate system. On top of the ceramic fiber refractory material, it is possible to apply an additional, protective layer of refractory adhesive, which, when dried, forms a dense outer coating.

In accordance with the task, based on the results of thermal calculations, the coating can be made of one or more layers of heat-insulating material glued to each other using refractory glue.

For gluing the first layer of fibrous refractory material to the pipe, it is advisable to use glue with a lower working temperature with respect to subsequent gluing operations of other coating layers, as well as for forming an outer protective layer.

In the proposed thermal insulation of the hearth pipes, a fibrous refractory material with an apparent density of 200 kg / m ^{3 is used} , which is most preferable for solving the problem in the claimed combination of essential features. Known ceramic fiber web material with the specified characteristic on density, which is manufactured industrially under the brand name MKRV-200 (manufacturer - OAO Sukholozhsky Refractory Plant, GOST 23619-79 with amendment 1, 2). The properties of such a material make it possible to create a reliable coating that eliminates the destruction of insulation due to scale falling off from heated products, as well as as a result of vibrations and shocks to which pipes are exposed, especially in pusher-type furnaces. Roll material MKRV-200 provides the insulation of the most complex designs of hearth pipes directly at the facility without the manufacture of special shaped products. Materials with a higher density, for example, mullite-siliceous chromium-containing felt MKRBH-250 (GOST 23619-79) and mullite-siliceous heat-insulating cardboard flexible MKRKG-400 (TU 14-8-537-93), do not have sufficient flexibility and the ability to fit snugly to metal bottom pipe designs, all the more complex configuration, i.e. in this case excluded

the possibility of reliable bonding of flexible heat-insulating materials to insulated surfaces, which dramatically reduces the lining life.

The use of refractory glue provides special comfort in creating a reliable heat-insulating coating with high thermal insulation properties in almost all respects.

It is advisable to use sodium aluminosilicate glue with a working temperature of 1200 ° C and 1400 ° C. Refractory adhesive with the necessary properties can be prepared on the basis of liquid glass when included in the composition of electrocorundum, refractory clay and kaolin. Such glue is a solid basis for holding the internal refractory coating of ceramic fiber on the pipe surface, and also provides reliable protection of the external surface of ceramic fiber from destruction under the influence of gas flows and falling scale from a heated metal. In general, the design of thermal insulation is quite simple and technologically advanced in all required parameters.

The utility model is illustrated by drawings, which depict heat insulation schemes for hearth pipes with a two-layer coating.

Figure 1 shows a cross section of a longitudinal hearth (glide) pipe with a heat-insulating coating applied, where: 1 - a pipe, 2 - the first layer of refractory adhesive applied to the pipe surface, 3 - the first inner layer of elastic heat-insulating material, on which a layer 4 of refractory is applied glue, 5 - the second layer of heat-insulating material glued with refractory glue. The number 6 denotes a racer fixed from a longitudinal pipe 1 along its entire working length, along which metal workpieces heated in the furnace move.

Figure 2 shows a cross-section of the supporting transverse hearth pipe, in which the raters are not used and on which the glide pipes are supported.

Thermal insulation of metal (hearth) pipes using the proposed utility model is as follows. Before lining the metal surfaces of pipes, they are cleaned of foreign materials, rust and rinsed with water. A refractory adhesive layer 2 is applied to the cleaned outer surface of each pipe 1. Pre-prepared webs of mulit-siliceous refractory felt MKRV-200 with a thickness of 15-20 mm, a width of up to 600 mm and a length of up to 2000 mm are coated with a layer of refractory glue and the webs are pressed tightly to the pipe 1,

thus forming the first layer 2 of the inner coating. Depending on the required degree of heating of the steam-water mixture in the pipes, one more, two or more layers are glued to the first inner layer of ceramic fiber 2. The choice of the number of additional layers of ceramic fiber is carried out on the basis of thermal calculation.

As can be seen in the drawings, the sections of the hearth pipes located along the furnace and across it are distinguished by an additional structural element in the form of a reiter 6 on the longitudinal pipe (Figure 1), which usually makes up a small part of the total section of the longitudinal pipe. Figure 1 shows two layers 3 and 5 of a fibrous coating reaching the side surface of the reiter 6.

In Fig.2, the cross-section of the transverse pipe has an even heat-insulating coating over the entire surface.

The resulting coating creates a good heat-insulating effect for the hearth pipes and does not collapse under the influence of vibrations and shocks to which the hearth pipes are exposed (this is especially true for pusher-type furnaces), since soft ceramic-fiber material is used. The refractory protective adhesive layer allows you to increase the operating temperature in the furnace up to 1350 ° C without destroying the fiber. In this case, in the case of applying an additional protective adhesive layer when the glue dries, such a layer is a dense ceramic refractory material having a small mass and forms a framework that prevents the MKRV-200 from breaking under the action of high-speed gas sweats and scale falling from the heated metal.

Refractory adhesives are used in two types, which differ in maximum application temperatures, which is due to the temperature interval between the baking pipes and heating gases in the furnace (approximately 200 ° C to 1350 ° C).

Thermal calculations showed that the gas flow rate for heating the steam-water mixture when using the proposed thermal insulation compared to uninsulated pipes or insulated using thermal blocks is less by 14.2 and 4.3 times, respectively.

The proposed design of pipe insulation was tested in heating furnaces of the mill 900/680 of CJSC Petrostal, a subsidiary of Kirovsky Zavod OJSC, St. Petersburg. Tests have shown that there is a decrease in gas consumption for heating the metal. At the same time, more uniform heating of the workpieces was noted, eliminating the appearance of “black marks” on

heated metal and an increase in the life of the lining compared to previously used thermal insulation using thermal blocks.

Such a thermal insulation design can be used for any pipes where it is necessary to use flexible thermal insulation in accordance with specific environmental and operating conditions.

Claims (3)

1. The design of the thermal insulation of the pipe, which is one or more layers of elastic thermal insulation material fixed by refractory adhesive to the outer surface of the pipe. 2. The pipe insulation design according to claim 1, in which the layers of the insulating material are made of fibrous refractory material with an apparent density of not higher than 200 kg / m ³ . 3. The design of the pipe insulation according to claim 1, in which the layers of insulation material are interconnected by refractory adhesive.