GB2045385A

GB2045385A - Pipeline unit made of glass with an outer surface covered with metal

Info

Publication number: GB2045385A
Application number: GB8008001A
Authority: GB
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1979-03-13
Filing date: 1980-03-10
Publication date: 1980-10-29
Also published as: DE7906967U1; FR2451537A1; JPS55123073A

Abstract

A glass tube 1 having end surfaces 3 for sealing connection with other glass tubes to form a pipeline has a metallic coating 2 directly outer on its peripheral surface. The metallic coating 2 is most preferably of nickel and is provided by electrolytic depositing of the metal directly onto the glass surface to produce a thin strengthening layer or layers. <IMAGE>

Description

SPECIFICATION Pipeline unit made of glass with an outer surface covered with metal The present invention concerns pipe units made of glass which in order to increase their mechanical strength are provided with a metallic coating on their outer surface, preferably one of nickel.

Glass is a material which has very good chemical stability. For this reason, it is used for the building of apparatus and pipelines in chemical plants. However, glass has the disadvantage of low tensile strength, which is further reduced by damage in the glass surface. Since the material is brittle, flow, which could reduce stress peaks, does not take place. For this reason it is advantageous to cover the glass part with a coating which protects the glass surface from damage, such as from impact or scratches, and which in addition, in the case of a glass fracture, withstands the excess pressure prevailing within the glass component part, keeps the glass part together in its form and thus prevents a flowing out of the piped medium from within the piped medium into the surrounding area.

Different coatings are already known to protect glass surfaces and to hold the framents together.

They are as follows: 1. Those where the protective layer consists of plastics of a certain thickness, which, in order to increase the tensile strength, are filled with glass fibers or other materials. These layers have the disadvantages that they must be relatively thick in order to fulfill the above described tasks of the coating, that in the case of an overstressing, however, they behave like a brittle material and break without a preceding flow phenomenon, and that in the long run they are not resistant to high temperatures as is frequently required in glass apparatus and pipeline construction. Another disadvantage is its high linear coefficient of thermal expansion, which causes shearing along and separation from the glass surface, whereby forces can occur which produce damage to the glass surface.Finally, it is disadvantageous that the relatively large layer thickness increases the outside diameter of the glass flange in such a way that unlayered glass component parts used for connecting elements no longer fit and instead of them, special parts must be used.

2. Those where the layering consists of a metallic material which is deposited on the glass surface from the gas phase. The metallic material has a higher mechnical strength and is therefore sufficient in relatively thin layers; it has a high continuous temperature resistance and exhibits a much lower length expansion coefficient.

However, deposition from the gas phase has the disadvantages that a direct deposit of the metals on the glass surface leads to breakage of the latter and therefore first a thin layer made of nonmetallic material must be applied, which separates the surfaces of glass and metallic layer from each other. On the other hand, the metal containing gases and the exhaust gases developed for metal deposition are highly toxic and/or combustible. For this reason, the deposition can be undertaken only in a completely closed installation, which makes the work processes more difficult.

These described disadvantages are avoided by the present invention.

The pipeline construction units according to the present invention are made of glass and are characterized by the fact that their outer surfaces are provided with a coating which lies directly on the glass and which is made of an electrolyticallyapplied metallic coating.

The coating of the outer surface of the glass units thus consists of one or more metallic materials which are electrolytically precipitated from a galvanic bath liquid.

The metal coating is effected in such a way that its inner surfaces lies directly on the outer surface of the glass part. Its wall thickness is dimensioned in such a way that it at least resists the inner excess pressure prevailing in the glass tube. This coating serves the following purposes: 1. It protects the surface of the glass part from mechanical damage, e.g. impacts and scratches such as can occur during transport, storage or assembly, or in the installed state. Notches in the brittle material represent damage to the glass surface on which tensile stress peaks occur which can lead to fracture if the glass part is subjected to more than permissible mechanical and thermal stresses in use. The safety factor is greatly reduced compared with an undamaged glass surface.

2. It embraces the glass part in such a way that in the case of breakage of the glass part-from what ever cause-the number of fragments is kept small and the fragments are held together so that the crack cannot widen.

The following metals are named as suitable according to the present innovation for layering pipeline parts: nickel, chromium, aluminium and silver.

Due to their differing chemical resistance and different mechanical strength, and because all metals do not deposit equally well, the abovenamed metals are not equally suited for use according to the present invention.

By far the most preferred metal is nickel.

The electrolytic deposition of metals from a bath on a substrate (galvanizing) is known and can be done without current as well as with the use of a direct current. Bath solutions, which contain suitable compounds of the concerned metal in solution, are obtainable on the market.

The innovation is explained in more detail in the drawing which is a longitudinal section through one embodiment of pipe unit according to the present invention. The drawing shows a tube length 1 of borosilicate glass with a wall thickness of 2 to 25mm, whose outer peripheral surface is coated with a 100 to 3000 FL thick layer 2 made of a metallic material, which is precipitated electrolytically. It is important not to coat end surfaces 3 of the tube 1 since these are sealing surfaces. The sealing surfaces can consist of any one of the three known design forms: sphericalconvex (ball), sperical-concave (ladle) or planar (as shown). The form of the pipe pieces can have any of the shapes which can be manufactured in glass apparatus and pipeline building.

Claims

1. A pipe unit made of glass with a coating made of metallic material applied to its outer surface, characterized in that the metallic coating lies directly on the glass surface.

2. A pipe unit according to Claim 1, characterized in that the metallic coating consists of two or more different metals, which lie on one another in layers.

3. A pipe unit according to Claim 1 or 2, characterized in that the metallic coating is applied electrolytically.

4. A pipe unit according to any preceding Claim characterized in that the metallic coating consists of nickel.

5. A pipe unit according to any preceding claim characterized in that it has uncoated end surfaces.

6. A pipe unit substantially as hereinbefore described with reference to the accompanying drawings.