BN-DS-E06 Electrical Design Conduits for Cables

Details
  1. All cables shall be protected by conduits or other means when they emerge from underground to above ground level and when mechanical damage is likely.
  2. Protection is required up to 20 cm max. above floor level.
  3. Conduits may be used for guiding or protection of the overhead cables.

    3.1 Conduits are also applied for:

    - pipe ducts,

    - spare conduits in trenches, crossing roads or dikes,

    - routing from trench to equipment.

    See standard BN-DS-E3.

  4. No conduits are allowed where overhead cables have to pass from a dangerous area to a less dangerous - or safe area (or reverse).

    In these cases cable transits or sand boxes shall be applied.
  5. Conduits to be made of heavy galvanized steel or of rigid non metallic material if its chemical resistance permits the application.
  6. Before final installation of any conduit, approval of the Electrical field engineer has to be obtained.
  7. The max. filling percentage of a conduit is 40% of the internal conduit cross-section.

  8. When conduits are required the following shall be observed:

    a. Provide for each continuous loaded cable a separate conduit.

    b. Several normally unloaded cables such as control-and lighting subcircuit cables, may be run in one conduit.

    c. Cables for special purposes i.e. communication, electronics, etc., shall always be pulled in separate conduits.

    d. For single core cables and earth wires exclusively non-metallic conduits shall be used.

  9. Where several cables are pulled in a common conduit, all cables shall be pulled-in simultaneously. Care shall be taken not to allow twists to occur during pulling-in.

    Only the use of French chalk is permitted to assist the pulling of cables.
  10. Care shall be taken that adequate distances are allowed between the conduit end and the cable connection box to provide for an easy handling of the cable without exceeding its min. bending radius.
  11. Bending of conduits should be avoided as much as possible, but in any case the number of bends shall be limited to three in one pipe length.
  12. In between successive conduits adequate pulling space shall be provided.
  13. Steel conduits:

    a. Have to be reamed at both ends, and in principle shall not contain connections.

    b. If connections have to be made this will be subject to approval of the Engineer and threaded couplings shall be used.

    c. Bends shall have a radius of at least 15 times the largest cable diameter in the conduit or 5 times the conduit diameter whichever is the greatest.

    Preferable bending radius is for 1” = 50 cm

    2” = 50 cm

    3” = 60 cm

    4” =100 cm

    5” =150 cm

  14. Non metallic conduits: e.g. polyethylene (PE)

    a. Min. wall thickness shall be 3 mm.
    b. Up to and incl. 50 mm outside diameter the conduits can be completely handled locally.

    Bending radius by cold bending is 8 D for conduit diam. up to 32 mm.

    D for conduit diam. up to 50 mm.

    Note: those bends must be positively secured during pouring in concrete, to prevent stretching of the bend.

    c. Over 50 mm outside diameter the conduits shall be used for straight runs only.
  15. Sealing

    15.1 During construction all conduits and after cable pulling the spare conduits must be sealed at both ends with caps or suchlike, to prevent entering of filth.

    15.2 Where cables leave a vertical portion of a conduit, the top end of the conduit shall be sealed with a plastic adhesive compound or with a suitable end cap to prevent entering of liquids or filth.

    15.3 When a conduit can conduct fluids from one area to another, it has to be sealed off at the possible fluid entrance.
  16. Where and when conduits are cast in concrete Contractor shall make an electrician available to be present during pouring.