GB2186649A

GB2186649A - Electrically separated connection piece for gas conduits

Info

Publication number: GB2186649A
Application number: GB08629430A
Authority: GB
Inventors: Karl-Heinz Haense; Eduard Kolbe
Original assignee: SEPPELFRICKE GEB GmbH
Current assignee: SEPPELFRICKE GEB GmbH
Priority date: 1986-02-19
Filing date: 1986-12-09
Publication date: 1987-08-19
Also published as: BE1000937A5; DE3605251C2; GB8629430D0; IT8719321A0; IT8720794V0; IT1202505B; DE3605251A1; GB2186649B

Abstract

An electrically separated connection piece for gas conduits consists of a tubular housing (1), a tubular insert (3) surrounded by and spaced from the housing (1) and a synthetic plastics material sleeve (4) occupying the space for the electrical insulation and rotation-fast connection of housing (1) and insert (3). Annular washers (5,6) of a refractory inorganic fibre material lie on the two axial end faces of the insert (3). The tubular insert (3) and the two annular washers (4,5) are clamped axial)y in between an inner axial abutment shoulder (8) of the housing (1) and a threaded ring (9) screwed into the housing (1). <IMAGE>

Description

SPECIFICATION Electrically separated connection piece for gas conduits The invention relates to an electrically separated connection piece for gas conduits, consisting of a tubular housing, a tubular insert surrounded by and spaced from the housing and a synthetic plastics sleeve occupying the space between the housing and insert, for the electrical insulation and rotation-fast connection of housing and insert.

Connection pieces of the above-stated kind are used for connecting gas appliances which contain an electric drive to a gas supply conduit without electrically conductive connection.

The usual connection pieces known for example from Federal German P.S. 1,429,101, have an external threading on one end of the tubular housing and an internal threading in the tubular insert for the screwing of the connection piece with the existing screw threadings on the one hand to the gas supply conduit and on the other to the gas appliance or a connection pipe of the gas appliance. Housing and insert are mostly also made polygonal in any desired manner at their mutually opposite circumferential surfaces for connection with one another by the insulating filling, in order to obtain high twist strength or security against turning of the connection piece.The filling between housing and insert must not only fulfil the required electric dielectric strength values, it must also be able to withstand the impact or shear stresses or the like forces which occur especially in the fitting of the connection piece between housing and insert, and for this purpose possess the required adequate mechanical strength.For this purpose synthetic plastics materials such as for example polyamides have hitherto possessed the best and most suitable properties and mechanical properties in order to connect and insulate the housing and insert electrically, to secure against rotation and to secure against twisting with one another and in order to fill the cavity between the housing and the insert of polygonal external and internal circumferences in such a way that after the hardening of the synthetic plastics filling the housing and insert are also gas-tightly connected with one another.It is increasingly required of fittings for gas conduits which contain non-metallic seals between metallic fitting parts, that the fitting is fire-proof for example in the case of burning of the building and that after heating to a test temperature of 6500C it still possesses an adequate sealing quality.

However as yet there is no synthetic plastics material which still remains undamaged at 6500C and so being suitable as a component of a connection piece of the initially stated kind which could fulfil the fire safety requirements. It has been proposed that metallic conduit parts fitted one into the other and connected with one another be electrically separated from one another by a refractory interlayer of porcelain or enamel material. These materials however have proved unsuitable and unusable for use in a connection piece of the initially stated kind in place of the conventional and usual synthetic plastics material layer.

They are too brittle and fragile to be able to take up the mechanical forces and stresses occurring between housing and insert. Crack formations also endanger the gas-tightness and dielectric strength.

The problem to be solved by the invention is that of forming a connection piece of the initially stated kind so that despite the use of the usual, preferred and especially suitable synthetic plastics layer for the electrically insulating, twist-resistant and gas-tight connection of housing and insert, the requirements of fire safety can be fulfilled.

This problem is solved in accordance with the invention in that annular washers of a refractory inorganic fibre material rest on the two axial end faces of the insert and in that the insert and the two annular washers are clamped axially in between an inner axial abutment shoulder of the housing and a threaded ring screwed into the housing. Refractory materials of inorganic mineral fibres with for example an organic binding agent usable for the annular washers are known per se in practice. The annular washers of the inorganic fibre material electrically insulate both end faces of the insert in relation to the housing abutment shoulder and the threaded ring.

Since the two annular washers are subjected only to axial compression, the mechanical strength values of the refractory inorganic fibre material, which would not be suitable as filling of the polygonal cavity between housing and insert, are completely satisfactory for the annular washers. On a heating of the connection piece for example to the test temperature of 6500C the synthetic plastics layer of sleeve form between housing and insert burns away and in fact the organic binding agent in the annular washers also burns away; however the refractory fibre substance of the annular washers is retained and the insert with the two annular washers abutting on the end faces of the insert remains clamped in between the housing abutment shoulder and the threaded ring, so that a gas-tightness fulfilling the fire safety requirements is maintained between housing and insert.

An example of an embodiment of the connection piece according to the invention is represented in axial longitudinal section in the drawing.

The connection piece contains a tubular housing 1 with an externally threaded extension piece 2 for the screwing of the housing into a gas supply conduit. The housing 1 surrounds and is radially spaced from a tubular insert 3 which possesses an internal threading onto which the connection piece or connection pipe of a gas appliance can be screwed. The spacing or interspace between housing 1 and insert 3 is filled with a synthetic plastics layer 4 in sleeve form which electrically insulates the housing and the insert is secured against rotation and is also gas-tight through their mutually opposite circumferential surfaces. These mutually opposite circumferential surfaces of housing and insert are formed for example as a dodecahedron or with another profiling to increase the resistance and security against twisting.On the two axial end faces of the insert 3 there rest annular washers 5 and 6 which consists of an electrically non-conductive and at the same time refractory inorganic fibre material. By way of example ceramic fibres containing an organic binder, known per se, are suitable. The axial length of the synthetic plastics layer 4 of sleeve form, consisting for example of polyamide, is suitably equal to the axial length of the insert 3, so that the annular washers 5 and 6 can also extend in contacting manner along the edges of the synthetic plastics filler layer 4. The edge of the insert 3 facing the annular washer 5 is preferably formed with a radially outward protruding widening 7 in order to enlarge the surface of the contact between insert 3 and annular washer 5. With the synthetic plastics layer 4 the insert 3 and the two annular washers 5 and 6 are clamped axially in between an inner axial abutment shoulder 8 of the housing 1 and a threaded ring 9 screwed into the housing. Thus above all, the annular washer 6 lying in the interior of the connection piece is also pressed in sealing manner against the abutment should 8 of the housing 1. In the case of burning away of the synthetic plastics layer 4 of sleeve form which under normal conditions also effects the seal between housing 1 and insert 3, due to the action of heat, the insert 3 with the two annular washers 5 and 6 remains clamped in between the housing abutment shoulder 8 and the threaded ring 9 and mainly the annular washer 6 and additionally the annular washer 5 still guarantee a gas-tightness between housing 1 and insert 3 satisfying fire safety requirements.

Claims

1. An electrically separated connection piece for gas conduits, comprising a tubular housing, a tubular insert surrounded by and spaced from the housing and a sleeve of synthetic plastics material occupying the space between the housing and the insert for the electrical insulation and rotation-fast connection of the housing and the insert, in which annular washers of a refractory inorganic fibre material rest on the two axial end faces of the insert and in which the insert and the two annular washers are clamped axially between an inner axial abutment shoulder of the housing and a threaded ring screwed into the housing.

2. A connection piece according to claim 1 in which the mutually opposite circumferential surfaces of the housing and insert are formed as dodecahedron.

3. A connection piece according to either of claims 1 and 2 in which the synthetic plastics material is polyamide.

4. A connection piece according to any one of the preceding claims in which the edge of the insert facing the annular washer adjacent to the threaded ring has a radially outward protruding widening.

5. A connection piece according to claim 1 substantially as hereinbefore described with reference to the drawings.