GB2510427A

GB2510427A - Encapsulating a plurality of cables passing through a conduit

Info

Publication number: GB2510427A
Application number: GB1302010.2A
Authority: GB
Inventors: Gary Martin Edward Traill
Original assignee: Flakt Woods Ltd
Current assignee: Flakt Woods Ltd
Priority date: 2013-02-05
Filing date: 2013-02-05
Publication date: 2014-08-06
Anticipated expiration: 2033-02-05
Also published as: GB201302010D0; GB2510427B

Abstract

A method of encapsulating a plurality of cables 11 passing through a conduit comprises the steps of: packing a settable potting compound 12 in the spaces between the cables 11 and the conduit (or a coupling of the conduit); passing the cables through respective holes of a packing member (e.g. a thin disc 13) that is dimensioned to cover the open end 9 of the conduit; packing the potting compound 12 around the cables 11 and in the conduit until it projects out of the conduit; then pushing the packing member 13 towards the conduit to press the potting compound 12 into the conduit to completely close and seal the spaces between the cables 11 and the conduit. The potting compound 12 is then allowed to set. The holes of the packing member 13 may be dimensioned to accommodate a particular cable and hold the cables 11 in a predetermined, spaced apart position. The cables 11 may be encapsulated in a conduit coupling 8 through which the cables pass and which is connected to a main conduit. A packing member 13 may be mounted on the cables 11 on both sides of the coupling 8 to enable the potting compound 12 to be pushed into the coupling 8 from both directions.

Description

I

A method and apparatus for encapsulating cables The present invention relates to a method and apparatus for encapsulating a pluraUty of cables passing through a condua, particularly but not exclusively, for use in ventilation or air movement ducting which contain a fan or fans for driving the air powered by an electric motor located in the ducting.

In operation, electric motors, generate sparks or transient electrical discharges during operation and in certain situations such discharges can give rise to extremely hazardous situations, This is a particular problem in industrial atmospheres containing dust and or volathe gases where such discharges can give rise to explosions. In a typical installation, the supply of electricity to an electric motor takes place through cables leading through. a conduit extending from the electric motor to the exterior of the ducting.

It has been found that such electric discharges can track through the conduit in the spaces between the cables and the conduit to the exterior of the ducting. Furthermore, in situations where volatile gases are in the air, such gases can enter the conduit and pass through into the electric motor where sparks from the electric motor can instigate an explosion.

To prevent such tracking and the passage of volatile gases through the conduit it is a known practice to assemble the cables to a conduit, or a connecting coupling for the conduit, and to manually pack the end of the conduit or the coupling with a setlable compound in order to seai the gaps between the cables and the conduit wall to nearby prevent the transmission of electricai discharges through the conduit. As the settable compound takes typically several hours to cure and set during which the cables cannot be moved, it is a standard practice at the end of the day tar the installers to manually pack the ends of the conduit is for the conduit that they will need for the next day, leaving the compound to cure overnight. It has been found that such a practice is not entirely foolproof because it relies on the dexterity and thoroughness of the installer. The fact that this operation is usually carried out at the end of the working day when workers are inevitably tired is also not an ideal solution. Furthermore, the more cables there are z passing through the conduit, the more difficult it is for the operator to guarantee that these setting compound is packed completely round aD of the cables.

The present invention seeks to provide a solution to this problem.

According to the present invention there is provided a method of encapsulating a pluraUty of cables passing through a conduit comprising the steps of, packing a settable potting compound in the spaces between the cables and the conduit or a coupling thereof, providing at least one packing member having a plurality of holes each adapted to receive one of said cables, the packing member being dimensioned to cover the open end of the conduit, passing the cabies through the packing member, packing the compound around the cables and in the conduit until it projects out of the conduit, and then pushing the packing member towards the conduit so as to press the polling compound into the conduit to completely close and seal the spaces between the cables and the conduit and thereafter allowing the compound to set.

PreFerably, the packing member has an associated hole for each one of the cables, the holes being dimensioned to accommodate only the associated cable and to hold the cables in a predetermined position relative to each other and the conduit. Preferably, the packing member comprises a disc having a diameter substantially the same as the conduit or coupling so that when pushing the potting compound into the conduit, the disc can be aligned with the conduit to maintain the cables in a required position in the conduit.

Preferably the cables are encapsulated in a conduit coupling through which the cables pass and which is adapted to be connected to a main conduit. In this arrangement, a packing member can be provided around the cables on each side of the coupling to push the potting compound into the coupling from both directions.

The present invention also provides a packing member for use in carrying out a method, comprising a disc having therein a predetermined number of holes dimensioned and positioned to hold a predetermined set of cables in a predetermined spaced relationship.

In a preferred embodiment the packing member or members are frangible so as to be removable from the cables after the compound has set.

A preferred embodiment of the present invention wHI now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a perspective view of the fan located in a ducting with a conduit for electrical cables leading to the exterior of the ducting, Figure 2 shows a cross-secton through a coupling of the conduit, and, Figure 3 shows a view of the disc having 3 spaced holes each dimensioned to receive a particular size of cable, Referring now to Figure 1 there is shown a fan and motor unit contained in a duct section I for incorporation in a ventilation duct which typically is suspended from the roof or ceiling of a building. The duct section 1 has a casing with flanges 2 by which the unit is incorporated in the ventilation duct. The duct section includes an axial air movement fan 3 powered by an electric motor 4. The supply of electricity to the motor 4 takes place through a conduit 5 which extends from a control box 6 on the electric motor 4 through the casing to a junction box 7 mounted on the exterior of the casing. The conduit 5 contains aD of the power and control cables necessary to power and control the electric motor 4. In a simple installation, only 3 electric cables may be necessary but up to 6 cables are necessary in some installations.

With an electric motor in operation, it is inevitable that sparks or transient electrical discharge spikes may be generated and it has been found that these discharges can travel through the conduit 5 and thus out of the ducting into the open, In certain industrial instaflations dust and volatile substances are frequently present and the transient discharges can cause an explosion. There is therefore a serious safety issue.

Referring now to Figure 2, there is shown an exploded view of part of a conduit 5 through which 3 electrical cables pass. As shown, there is a coupling 8 adapted to be secured to the electric motor control box or housing and through which power and control cables, in this embodiment of 3 cables reference 11 pass to the electric motor. The coupling is adapted to be connected to a screw threaded coupling unit 10 to which the end 9 of the conduit is fastened, thus connecting the conduit 5 to the couphng 8 secured to the electric motor control box 6. The coupng unit 10 is filed with a settable potting compound 12 to completely close the air space between the coupling 8 and the conduit 5 itself so that transient discharges cannot enter the conduit.

To ensure that the settable potting compound 12 completely closes the air space in the coupling unit 10 a packing member in the form of a thin disc 13 is provided. The disc, as shown in Figure 3, contains 3 holes which are each dimensioned to accommodate a particular cable and spaced apart so that the cables are kept in a preferred spaced position from each other and from the peripheral wall of the coupling unit 10 and hence the conduit. The disc 13 has a diameter substantially the same as the conduit or coupling, the method including the step of ensuring that the disc 13 is aligned with the conduit 5 to maintain the cables in a required position in the conduit when pushing the potting compound into the conduit 5. The space between the coupling unit 10 is first packed manually by hand until the potting compound protrudes from the unit as shown in Figure 2. Thereupon, the disc 13 is pressed down manuafly to push the potting compound down into the unit 10. Since the disc 13 presses the entire area of the potting compound into the unit, the potting compound is pressed into every space. More compound can be put into the unit by withdrawing the disc slightly repacking the compound and then pressing the disc onto the compound and repeating this until no more compound can be pushed into the unit. At this point there would be some spilling of the compound outwardly from the end of the unit 10. To achieve the best possible pressure on the compound, the disc should be the same diameter as the coupling unit or, 85 shown in Figure 2, slightly larger. The potting compound is then allowed to cure and set.

Where the arrangement is such that the conduit 5 itself is screwed onto the coupling unit 10, it is possible for a further disc to be threaded onto the cables before the coupling unit is placed over the wires and in this way pressure can be applied to the potting compound from both sides of the unit 10.

hi some nstaUations ft would be possible to eave the disc 13 in piece but in others it. wifl need to be removed To this end, the disc 13 is made frangible sø it can be broken up and removed or it may incorporate tear fines, between the ho'es for the cables for example to enable it te be easy torn apart and removed.

Claims

CLAIMS1. A method of encapsulating a plurality of cables passing through a conduft comprising the steps of, packing a settable potting compound in the spaces between the cables and the conduit or a coupling thereof, providing at least one packing member having a plurality of holes each adapted to receive ore of said cables, the packing member being dimensioned to cover the open end of the conduit, passing the cables through the packing member, packing the compound around the cables and in the conduit until it projects out of the conduit, and then pushing the packing member towards the conduit so as to press the potting compound into the conduit to completely dose and seal the spaces between the cables and the condut, and thereafter allowing the compound to set.
2. A method according to claim I wherein the packing member has an associated hole for each one of the cables, the method including the step of feeding the cables through the associated hole, the holes being dimensioned to accommodate only the associated cable and to hold the cables in a predetermined position relative to each other and the conduit.
3. A method according to claim 1 or 2 wherein the packing member comprises a disc having a diameter substantially the same as the conduit or coupling, the method including the step of ensuring that the disc is aligned with the conduit to maintain the cables in a required position in the conduit when pushing the pothng compound into the conduit.

*
4. A method according to claim 1, 2 or 3, wherein the cables are encapsulated in a conduit coupling through which the cables pass and which is adapted to be connected to a main conduit.
5. A method according to claim 4, including the step of providing a packing member mounted on the cables on both sides of the coupling to enable the potting compound to be pushed into the coupling from both directions B. A packing member for ue n carñng out the method according to any one of daWns I to 4. compd&ng a diw having therein a predetermned number of hoS thmensioned and positioned to hold a predetermined set of cables in a predetermined spaced rSationship 7. A packing member according to otaim 8, wherein th packing member is frangible: so as to be removabe from the cab'es after the compound has set.8, A method of encapsulating a pluraity of cables passing through a conduit, substantiaUy as described herein with reference to, and as iilusflted in the accpmpanyiflg drawings.