A.IV Cable Transits

 The maximum and minimum sizes (in terms of both the height and the width) of each type of cable transit for which approval is sought should be tested in both vertical and horizontal orientation.

  2.2.1 A bulkhead which includes the cable transit should be constructed in accordance with 2.1.1 of the recommendation and should be insulated to class A-60 on the stiffened face, which should be the face which is not exposed to the heating conditions of the test. A deck which includes the cable transit should be constructed in accordance with 2.2.1 of the recommendation and should be insulated to class A-60 on the stiffened face, which should be the face which is exposed to the heating conditions of the test.

  2.2.2 The cable transits should be positioned only in the top half of a bulkhead but should not be closer than 200 mm from the edges of a bulkhead or a deck. Where more than one cable transit is to be tested simultaneously in a division, the separation between adjacent transits should not be less than 200 mm. Both measurements should relate to the distance to the nearest part of the transit system, including any insulation which is part of the system.

  2.2.3 Notwithstanding the above, the distance between transits should be sufficient to ensure that the transits do not influence each other during the test, except that this requirement does not apply to multi-transits which are intended to be positioned adjacent to one another.

  2.2.4 The cables should project 500 ± 50 mm beyond the transit on the exposed side of the division and 500 ± 50 mm on the unexposed side.

  2.2.5 Cable transits should be welded or bolted into the bulkhead or deck. The cables and sealing compounds or blocks should be incorporated into the transits with the bulkhead and deck panels placed respectively in vertical and horizontal positions. Any insulation should be applied to the panels and transits with the panels in the same respective positions.

  2.2.6 The transit(s) should be tested incorporating a range of different types of cables (e.g. in terms of number and type of conductor, type of sheathing, type of insulation material, size) and should provide an assembly which represents a practical situation which may be found on ships. An individual Administration may have its own specification for a "standard" configuration of penetrating cables which it may use as a basis of its approvals.

The test results obtained from a given configuration are generally valid for the tested types of cables of size equal to or smaller than tested.

  2.2.7 No more than 40% of the inside cross-sectional area of each transit should be occupied by cables and the distances between adjacent cables and between the cables and the inside of the transit should be the minimum which is allowable for the actual penetration sealing system.

 For each uninsulated cable transit, thermocouples should be fixed on the unexposed face at each of the following locations:

• at two positions on the surface of the outer perimeter of the frame, box or coaming at a distance of 25 mm from the unexposed surface of the division;
• at two positions at the end of the transit, on the face of the sealant system or material at a distance of 25 mm from a cable; and
• on the surface of each type of cable included in the cable transit, at a distance of 25 mm from the face of the sealant system or material. In case of a group or bunch of cables the group should be treated as a single cable. In case of horizontal cables the thermocouples should be mounted on the uppermost surface of the cables.

 For those thermocouples placed on the outer perimeter of the frame, box or coaming, one thermocouple should be fixed on each of two opposite faces, which in the case of bulkheads should be the top and bottom faces.

 For each partially insulated or fully insulated cable transit, thermocouples should be fixed on the unexposed face at equivalent positions to those specified for an uninsulated transit as illustrated in Figure A2.

Figure A2 Cable transits: position of unexposed-face thermocouples (shown for bulkhead)

 Additional thermocouples may be required to be fixed, dependent upon the complexity of the cable transit.

 When fixing thermocouples to the unexposed surface of the cables, the copper disc and the insulating pad should be formed over the surface to provide good contact with the surface of the cable. The copper disc and the pad should be retained in position by some mechanical means, e.g. wiring or spring clips, such that they do not become detached during the test. The mechanical retention should not provide any significant heat-sink effect to the unexposed face of the thermocouple.

 The performance of cable transits may be related to their ability to satisfy both the requirements for insulation and integrity or may be related only to the requirements for integrity, depending on the requirements of the Administration.

 Since the cable transit is a local weakness in the division it should be capable of preventing a temperature rise at any point on the surface not exceeding 180°C above the initial temperature. The average temperature rise is not relevant.