GB2115238A

GB2115238A - Electrical lead through device

Info

Publication number: GB2115238A
Application number: GB08303534A
Authority: GB
Inventors: Hans Olof Oborg
Original assignee: Lyckeaborgs Bruk AB
Current assignee: Lyckeaborgs Bruk AB
Priority date: 1982-02-12
Filing date: 1983-02-09
Publication date: 1983-09-01
Also published as: GB2115238B; FR2521765A1; GB8303534D0; NO159689C; SE430191B; SE8200851L; NO159689B; NO830462L

Abstract

A device for leading insulated conductors (1) through the wall (2) of a pressurised vessel comprises a tubular lead-through housing (3) and a sealing body (4) with stepped holes (5), through which the partially bared conductors (1) are inserted. Further sealing is achieved by a thermosetting material (9), a pressure plate (7), a polyurethane filled pressure ring (6) and ceramic (11). <IMAGE>

Description

SPECIFICATION Electrical lead through device The present invention relates to a longitudinally pressure-tight lead-through for disposition of an electric cable containing insulated conductors through an opening in a pressure-tightwall which on the outside (the pressure side) is in contact with, in addition to the lead-through, a liquid or gas under comparatively high pressure, there being a comparatively low pressure on the opposite side, said lead-through comprising a tubular metal lead through housing fixed to the wall and a sealing body consisting of insulating material, which longitudinally seals a portion ofthe interior of the housing and is provided with through-holes through individual ones ofwhich each ofthe insulated conductors is inserted.

Such a lead-through is intended to be used in vessels which can be subjected to high pressure and are therefore provided with pressurised hulls, through which electrical conductors must pass for various purposes. Designs known upto now have however either been very complicated and bulky and thus difficultto handle or have not functioned with sufficient reliability, so that there is leakage resulting in electrical over conduction or even short-circuit between the different conductors in the cable. This was primarily a result ofthe cable itself not being pressure-tight longitudinally. The same is also true of the conductors and their insulation, between which it is possible for liquid or gas to penetrate.

Therefore the invention seeks to provide a leadthrough which is tight upto high pressures, is compact and is comparatively simple to manufacture.

Accordingly the invention provides an electrical lead-through device for the wall of a pressurised vessel, adapted to receive an insulated conductor or conduuctors, and comprising a generally tubular housing adaptedforconnection to an aperture in the wall ofthe vessel, and an insulating plug assembly addapted to fit in the housing and having an axial bore for each ofthe conductors to be introduced into vessel,theoreach said bore having one internal portion of a diameter equal to the diameter ofthe conductor without its insulation, and at least one portion having a diameter equal to that of the conductor with its insulation, the conductor being located in the plug assembly with a portion of its insulation removed over a length of at least equal to the axial length ofthe said internal portion, so as to provide effective sealing between the plug and the conductor.

A preferred arrangement of the invention comprises an electrical lead-through device for disposition of an electric cable containing insulated conductors through an opening in a pressure tight wall which on the outside (the pressure side) is in contact with, in addition to the lead-through, a liquid or gas under comparatively high pressure; there being a comparatively low pressure on the opposite inside, said lead-through comprising a tubular metal leadthrough housing fixed to the wall and a sealing body consisting of insulating material, which longitudinal ly seals a portion ofthe interior of the housing and is provided with through-holes through individual ones of which each of the insulated connductors is inserted, characterised in that each conductor is bare along a portion from a pointinsidethesealing body spaced from the surface ofthe body closest to the pressure side of the housing to a point outside and in the vicinity of the opposite surface ofthe body closest to the inside of the wall, against said opposite surface there being in contact a thermosetting sealing material with high fluidity which penetrates into the capillary spaces between the bare conductor portions andthewalls ofthe holes in the sealing body, and that a press ring and a pressure plate press an elastic sealing material against the surfaces ofthe sealing body facing the pressure side and into the holes in the body.

In the preferred arrangement of the invention, in which there is an elastic sealing material on the pressure side, which is subjected to compression forces and completely seals the conductors and the associated holes in the sea ling body, and athermo- setting sealing material with high fluidity on the opposite side ofthe body, which penetrates into the narrow spaces between the walls of these holes and the bare conductor portions, the lead-through can be used atpressures iupto about 300 bar and at temperatures between -40 C and + 1 50"C.

In a particularly suitable embodiment of the lead-through, each opening in the sealing body is conically bevelled at its opening facing the pressure side. This allowsthe elastic sealing material to effectively seal between the opening and the conductor insulation.

The invention will be described in more detail belowintheformofanexamplewith referencetothe accompanying drawing, which shows a cross-sec tionalviewofa lead-th roug h according to the invention, mounted in awall of a pressure vessel.

According to the Figure, the lead-through comprises a tubular lead-through housing 3, which is made of metal such as steel and is mounted on a pressuretightwall 2 of the same material by means of bolts or the like. The outside or pressure side of the wall 2 and the housing 3 is to the left in the Figure and is in contactwithagas or liquid which can be water and can be under a high pressure ofthe magnitude mentioned above, while a comparatively low pressure, such as atmospheric pressure, prevails on the opposite inside of the wall to the right in the Figure.

An electric cable (not described in more detail here) with insulated condutors 1 isto be inserted pressuretight through an opening in the wall 2.

Forthis purpose in the interiorofthe housing 3 there is a sealing body4which seals a portion ofthis interior longitudinally and is provided with through holes 5 with essentially the same diameter as the insulated conductors 1. The body 4 is made of fabric bakelita or another insulating material with similar mechanical properties. When the interior has a circular cylindrical shape, the holes 5 can be suitably arranged along concentric circles.The insulated conductors 1 are inserted through the holes 5 in the body 4 and are bare along a portion 1 awhich extends from a point spaced from the surface ofthe body 4 facing the pressure side to a point outside and in the vicinity of the opposide side ofthe body 4facing the inside, so that the conductors 1 thereafter extend insulated through the portion ofthe interior notfilled by the body 4, closestto the inside of the wall 2.

Into this portion of the interior, a thermosetting sealing material 9 with high fluidity is introduced which penetrates into the capillary-like spaces between the base conductors 1 a and the walls of the holes 5 in the body4, and furthermore into the space between the body 4 and the innerwall of the cavity.

The material 9 can be epoxy resin for example, with low temperature expansion coefficient and high fluidity, so that it has a good penetrating ability.

On the pressure side of the sealing body4, there is an elastic sealing 8which covers the entire pressure side surface of the body and is subjected to such compressive forces that it penetrates into the holes 5 and sealingly closes the same about the insulated conductors 1. To facilitate this penetration, each hole 5 in the body 4 is conically bevelled at its opening towards the pressure side, as shown in the Figure.

This sealing material 8 should have high compressibility and elasticity but low settling and stress relaxation; it can be silicone rubber for example.

To achieve the pressure on the material 8, a pressure plate 7 abuts against it and is provided with openings corresponding to the holes Sin the sealing body 4 and consists of metal or similar rigid material.

Against the pressure plate 7 a press ring 6 presses, which is provided with external threads which cooperate with corresponding threads on the inside of the cavity. By turning the ring 6, the pressure exerted on the plate 7 and thus on the material 8 can be adjusted, Inside the ring 6, there is a filler material 10 such as polyurethane to keep the ring in the set positioned, while a ceramic material 11 fills out the rest of the interior of the housing 3 and has a reinforcing effect.

Fortightconnection of the cable to the leadthrough there are special sealing devices, which do not affect the invention and therefore not shown or described in more detail.

Claims

1. An electrical lead-through device for the wall of a pressurised vessel, adapted to receive an insulated conductor or conductors and comprising a generally tubular housing adapted for connection to an apertureinthewall ofthevesseland an insulating plug assembly adapted to fit in the housing and having an axial bore for each of the conductors to be introduced into the vessel,the or each said bore having one internal portion of a diameter equal to the diameter of the conductor without its insulation, and at least one portion having a diameter equal to that of the conductor with its insulation, the conductor being located in the plug assembly with a portion of its insulation removed over a length corresponding to the axial length of the said internal portion, so as to provide effective sealing between the plug and the conductor.

2. A lead-through device according to claim 1 and which the plug assembly includes a sealing body having respective counterbores on its high pressure side to receive the insulated portions of the conductors, and an elastic sealing member urged into engagement with the said high pressure side by a retaining ring which is threaded into the said housing.

3. A lead-through device according to claim 2 further comprising a body ofthermosetting sealing material which is applied to the low pressure side of the sealing body in a fluid state so as to penetrate the capillary spaces between uninsulated portions of the conductors and the bores of the sealing body.

4. An electrical lead-through device for disposition of an electric cable containing insulated conductorsthrough an opening in a pressure tight wall which on the outside (the pressure side) is in contact with, in addition to the lead-through, a liquid or gas under comparatively high pressure, there being a comparatively low pressure on the opposite inside, said lead-through comprising atubular metal leadthrough housing fixed to the wall and a sealing body consisting of insulating material, which longitudinally seals a portion of the interior of the housing and is provided with through-holes through individual ones ofwhich each of the insulated conductors is inserted, characterised in that each conductor is bare along a portion from a point inside the sealing body spaced from the surface of the body closest to the pressure side ofthe housing to a point outside and in the vicinity ofthe opposite surface of the body closestto the inside of the wall, against said opposite surface there being in contact a thermosetting sealing material with high fluidity which penetrated into the capillary spaces between the base conductor portions and the walls ofthe holes in the sealing body, andthata press ring and a pressure plate press an elastic sealing material againstthe surfaces of the sealing bodyfacing the pressure side and into the holes in the body.

5. An electrical lead-through device according to any of claims 2 to 4, characterised in that each hole in the sealing body is conically bevelled at its opening facing the pressure side.

6. An electrical lead-through device according to any of claims 3 to 5, characterised in that the thermosetting sealing material is an epoxy resin with a thermosetting sealing material is an epoxy resin with a lowcoeffeicientoftemperature expansion.

7. An electrical lead-through device substantially as herein described with reference to the accompanying drawing.