DE202013100713U1 - Jacket tube heater for use under corrosive conditions - Google Patents

Abstract

Jacket tube heater, comprising a heating conductor (3), a jacket tube (1) and insulator material (2), wherein the heating conductor (3) at a distance from the jacket tube (1) in the interior of the jacket tube (1) is arranged and the space between the jacket tube (1 ) and heating conductor (3) with insulator material (2) is filled, characterized in that further at least one corrosion-resistant secondary casing (4) is arranged.

Description

The invention relates to a jacket tube heater, which is particularly suitable for use under corrosive conditions.

Jacket tube heaters are very widely used for heating media and materials. The electrical energy for operating the jacket tube heaters is usually converted into thermal energy in an electrical resistance wire and thermally dissipated via an electrical insulator to the outside. The electrical insulator often consists of a refractory ceramic material, which is in powder form prior to the production of the jacket tube heater. The heat reaches the outer shell (jacket tube) in this way and is then released to the environment usually by heat conduction, convection and radiation.

• 1. Durchfädeln des Heizleiters in das Mantelrohr,
• 2. Füllen des Mantelrohrs mit dem Isolatormaterial,
• 3. Walzen und Pressen des Mantelrohrs, um einen mechanisch festen Mantelrohrheizer zu bekommen,
• 4. Ein- oder mehrfaches Biegen und Glühen des Mantelrohrheizers, um die gewünschte Form zu erhalten, und dabei die mechanischen Spannungen an den Biegestellen abzubauen.

The insulator is often made of MgO, SiO2 or / and other high-melting ceramic materials. In the production of the jacket tube heater, there are usually the following basic steps:

• 1. threading the heat conductor into the jacket tube,
• 2. filling the jacket tube with the insulator material,
• 3. rolling and pressing the jacket tube to get a mechanically strong jacket tube heater
• 4. Single or multiple bending and annealing of the jacket tube heater to obtain the desired shape, thereby reducing the mechanical stresses at the bending points.

As a material of the jacket tube often come from manufacturing reasons commercially accessible tubes made of materials based on nickel, such as 1.4828 u. a. for use.

The jacket tube heater produced in this way is used inter alia in substrate treatment systems, for example vacuum coating systems and the like. In this case, aggressive substances can act on the jacket tube. Such aggressive substances may vary depending on the technology e.g. Sulfur, selenium, tellurium, cadmium and others. If the service temperature of the jacket tube heater is high, increased corrosion of the jacket tube of nickel-based alloys, which may be caused by z.T. very high nickel content is due to take place. Nickel forms with selenium, tellurium and sulfur corresponding compounds that can form eutectics with the nickel content of the material of the jacket tube. These eutectics have relatively low melting temperatures and can not build up a protective layer on the cladding tube material, as is the case with oxides and nickel-base alloys. As a result, the chemical attack progresses rapidly and the jacket tube is quickly corroded in the hottest places. The jacket tube crumbles locally and in the same place also the insulator slowly crumbles, because there is no wall anymore.

As soon as a sufficient amount of the insulator material is missing, a short circuit between the heating element and the jacket tube takes place and the jacket tube heater fails.

Such jacket tube heaters usually fail during ongoing production, which is accompanied by a demolition of production. The unwanted failures could be kept to a minimum at predetermined intervals by a preventive replacement of the jacket tube heaters. In any case, they represent a significant cost factor.

Jacket tube heaters of the type described are for example made DE 10 2009 038 341 A1 in which a heating device for a substrate treatment device is described which comprises a jacket tube heater having straight sections and bent sections, straight sections being arranged parallel to one another in a main plane and straight sections being interconnected by bent sections, and at least a portion of the curved sections Sections is oriented inclined relative to the main plane.

It is an object of the present invention to improve known jacket tube heaters in such a way that an extension of the service life to failure by short circuit is achieved.

According to the invention the object is achieved by a jacket tube heater with the features of claim 1. Advantageous embodiments and further developments are described in the dependent claims.

The solution consists in a construction of the jacket tube heater, which makes a short circuit between heat conductor and jacket tube less likely by action against the falling out of the insulator are used.

The measure consists of adding to the known components of jacket tube heaters a corrosion-resistant secondary jacket, for example a hose, which encloses the insulator and continues to fulfill this function after the disintegration of the metallic jacket tube, so that the insulator can not fall out. The task of the secondary sheath is thus to hold the insulator to prevent short circuits.

In a corrosion-induced breakthrough of the jacket tube so the powdered insulator in the corrosion-resistant secondary shell, For example, a hose, stay and thus prevent the electrical contact between the heating element and jacket tube.

If the corrosion-resistant secondary casing itself is made of an electrically insulating ceramic or ceramic fibers, it should also prevent short circuits between heating conductor and casing pipe itself.

As corrosion of the jacket tube progresses, the metallic and electrically conductive parts of the jacket tube continuously disappear from the vicinity of the aperture. In the limiting case, the entire heated area of the jacket tube will crumble due to the corrosion.

The failure of the jacket tube heater by short circuit is either completely prevented by the secondary jacket, or is clearly delayed.

Of course, the heating element itself must not be attacked or only slightly chemically attacked. As a heat conductor therefore come here both the ordinary alloys NiCr2080 into consideration, as well as special alloys and metals, which are commercially available as a wire. The choice of the correct material of the heating element should take into account the corrosion resistance at the high temperature of the heating element during operation, in the presence of aggressive media.

In a first variant, the jacket tube heater may have the following features.

The outer jacket tube may be made of a commercially available alloy commonly used by the manufacturer of the jacket tubes, e.g. 1.4828, 1.4841, Inconel 600 u. a.

The secondary jacket, which is significantly more resistant to corrosive attack, should also be sufficiently high temperature resistant so that its function of retaining the insulator material satisfies, if the jacket tube is locally damaged, sufficiently heat-conducting so that the heat transfer from the heating conductor to the outside is not is impermissibly impeded (MgO, for example, 11 W / (m K) at 500 ° C), and be mechanically flexible, so that the production process of the jacket tube heater is not affected.

The secondary shell can be designed, for example, as a mesh, knitted or knitted fabric, which prevents the particles of the insulator material from falling out. Such materials may for example be made of metallic and / or ceramic fibers. Furthermore, the secondary shell can be made seamlessly tubular or tubular.

In addition, the secondary shell can be constructed in one or more layers, wherein all layers of the same material or different layers of different materials can be made.

For this purpose, for the secondary coat, e.g. Braids made of metal or ceramic fibers in tube form into consideration. These materials should be sufficiently resistant to corrosion in the expected working conditions of the jacket tube heater, so as not to be attacked yourself chemically.

The insulating material must be located between the heating element and the secondary casing when the secondary casing is located inside the casing tube. By contrast, if the secondary jacket is arranged on the outside of the jacket tube, the insulation material must be located between the heating conductor and the jacket tube.

If the secondary shell is metallic, its geometry must be chosen so that no short circuits with the heating element occur during the manufacturing process.

As insulator material is for example a filling of MgO and / or another refractory ceramic material into consideration. The heating conductor (heating coil / heating wire) can be made, for example, from NiCr8020 or other suitable material which is attacked at process conditions in the presence of aggressive media much less or only slightly chemical or corrosive than conventional jacket pipes.

As with known jacket tube heaters, a mechanically strong jacket tube heater can be obtained by rolling and pressing the jacket tube. Single or multiple bending and annealing of the jacket tube heater can be used to obtain the desired shape and relieve the mechanical stresses at the bending points.

When rolling and pressing the jacket tube heater, the secondary jacket remains intact. When bending the jacket tube heater, however, there is a risk that the secondary jacket in the outer fiber of the bent portion is stretched too much and ruptures. When selecting the ceramic or metallic fiber material, therefore, it should be checked which material can be stretched to what degree to select the appropriate material and, if appropriate, the appropriate shape of the braid, knitted fabric or knit.

In a first embodiment (variant 1), which in 1 is shown, the secondary shell is first 4 in the jacket tube 1 threaded and then the heating conductor 3 and the insulator material 2 introduced, so that the secondary coat 4 between the insulator material 2 and the jacket tube 1 is arranged.

In a second embodiment (variant 2), the in 2 is the, as conventionally produced, in a jacket tube 1 a heating conductor 3 and insulator material 2 containing, rolled and pressed jacket tube heaters in an outer secondary shell 4 threaded, which should have a suitable inner diameter in this case, so that the jacket tube 1 fits. Then the jacket tube heater including the jacket tube 1 enclosing secondary coat 4 bent and annealed. When bending, the tools should be adjusted so that the secondary shell 4 not damaged.

In a third embodiment (variant 3), an outer secondary shell is mounted only after bending the jacket tube heater.

In a fourth embodiment (variant 4), which in 3 is shown, a jacket tube heater with an inner secondary jacket 4 after the first variant additionally with an outer secondary coat 4 coated according to the method of the second variant.

In a fifth embodiment (variant 5), which is also the representation of 3 corresponds, is a jacket tube heater with an inner secondary jacket 4 after the first variant additionally with an outer secondary coat 4 coated according to the method of the third variant.

In particular, in the variants 2 to 5 with an outer secondary shell of the outer secondary shell should be sufficiently tight against the jacket tube, so that the stop function for falling out of insulator material can be met. In a sixth embodiment (variant 6), an alternative to a (as described in variants 1 to 5) prefabricated and threaded into the casing tube (inner) and / or striped over the casing tube (outer) secondary casing is proposed:
A secondary jacket (inside or outside or both) is made of a material that is created by applying a coating and annealing the jacket tube heater at a given temperature. Such material may be, for example, a ceramic coating. The secondary jacket thus formed should be resistant and self-supporting under corrosive conditions, ie when the metallic casing of the jacket tube heater is corrosively attacked and destroyed, the secondary shell should remain intact and prevent falling out of the internal ceramic insulator material and thus the life of the jacket tube heater among the corrosive Extend conditions by preventing the short circuit.

The jacket tube heaters should generally have a possibility to connect a thermocouple. This is no problem in variant 1, since the components for the thermocouple attachment are welded after rolling and pressing. In the variants 2-5, the components are to be welded only after the application of the outer secondary sheath. This is preferably done by producing suitable cutouts in the secondary casing at the intended locations and by welding the corresponding components there as usual on the casing pipe.

LIST OF REFERENCE NUMBERS

1

casing pipe

2

insulator material

3

heating conductor

4

secondary coat

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009038341 A1 [0008]

Claims (6)

Jacket tube heater, comprising a heating conductor ( 3 ), a jacket tube ( 1 ) and insulator material ( 2 ), wherein the heating conductor ( 3 ) with a distance to the jacket tube ( 1 ) in the interior of the jacket tube ( 1 ) is arranged and the space between the jacket tube ( 1 ) and heating conductors ( 3 ) with insulator material ( 2 ), characterized in that furthermore at least one corrosion-resistant secondary jacket ( 4 ) is arranged. Jacket tube heater according to claim 1, characterized in that at least one inner secondary jacket ( 4 ) in the interior of the jacket tube ( 1 ) between jacket pipe ( 1 ) and insulator material ( 2 ) is arranged. Jacket tube heater according to claim 1 or 2, characterized in that at least one outer secondary jacket ( 4 ) on the outside of the jacket tube ( 1 ) is arranged. Jacket tube heater according to one of claims 1 to 3, characterized in that at least one secondary jacket ( 4 ) is designed as a braid, knitted or knitted fabric of ceramic and / or metallic fibers. Jacket tube heater according to one of claims 1 to 4, characterized in that at least one secondary jacket ( 4 ) by melting a corrosion-resistant material as a closed coating of the inside or the outside of the jacket tube ( 1 ) is made. Jacket tube heater according to one of claims 1 to 5, characterized in that the secondary jacket ( 4 ) is seamlessly tubular or tubular.

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