CONSTRUCTION & PERFORMANCE STANDARDS

National Cable Gland standards may exist that determine the construction and performance requirements for cable glands. During the formative years of the rapidly expanding power generation industry in the United Kingdom, the acute need for a common standard reference document that could address cable gland requirements was recognised, and from this GDCD 190 was created.

The original goal was later met by the British Standard BS 4121, when the industry had developed further and with more sophistication. Latterly in the 1970’s BS 4121 was superseded by BS 6121 with the introduction of the metric system of measurement across Europe.

Although it does not replace the full scope of the BS 6121 construction requirements, today there is a European Standard EN 50262, which offers manufacturers the opportunity of meeting its requirements by degrees of performance. It should be noted that whilst products that have been designed to comply with BS 6121 will quite comfortably meet the requirements of EN 50262, it does not automatically follow that cable glands designed to EN 50262 would also be able to comply with the requirements of BS 6121.

At the time of writing a new draft IEC standard for cable glands, IEC 62444 is being reviewed and will be published in due course.

It is the user’s responsibility to ensure that the cable gland selected is of the correct size and type to suit the type of cable being terminated.

The information provided below is intended to assist users in ensuring that the correct cable gland is selected. The European Cable Gland Standard EN 50262 : 1999 requires cable glands to be classified in accordance with their properties and performance. Users should therefore be aware that if they intend to select or specify cable gland products according to EN 50262 they must also stipulate clearly what classification from EN 50262 they require. Without such a clear definition the likelihood of the wrong product being obtained is increased.

For information purposes, here is a summary of the basic requirements of EN 50262
  1. Material : Metallic, Non-metallic or a combination of both
  2. Mechanical Properties :
    1. For Cables without Armour -Anchorage Category (A or B)
    2. Impact Level
    3. For Cables with Armour – Retention Class (A or B)
  3. Electrical Properties
  4. Resistance to External Influences

These can be further explained as follows :-
  1. Material : See Material & Thread for CMP specification
  2. Mechanical Properties :
    1. For Cables without Armour - Anchorage Category (A or B)
      Values taken from EN 50262:1999   Nearest CMP Cable
      Gland Size
      Cable
      Diameter
      Cable Retention
      (Newtons)
      Cable Anchorage
      Type A (N)
      Cable Anchorage
      Type B (N)
      Up to 4 5 - - -
      > 4 to 8 10 30 75 16
      > 8 to 11 15 42 120 20S
      > 11 to 16 20 55 130 20
      > 16 to 23 25 70 140 25
      > 23 to 31 30 80 250 32
      > 31 to 43 45 90 350 40
      > 43 to 55 55 100 400 50
      > 55 70 115 450 63

      The actual Performance Capability for the CMP metallic cable gland range intended for unarmoured cables far exceeds the requirements of EN 50262 : 1999 Category B

    2. Impact Level
      Values taken from EN 50262:1999   Nearest CMP Cable
      Gland Size
      Cable
      Diameter
      Cable Retention
      (Newtons)
      Cable Anchorage
      Type A (N)
      Cable Anchorage
      Type B (N)
      Up to 4 5 - - -
      > 4 to 8 10 30 75 16
      > 8 to 11 15 42 120 20S
      > 11 to 16 20 55 130 20
      > 16 to 23 25 70 140 25
      > 23 to 31 30 80 250 32
      > 31 to 43 45 90 350 40
      > 43 to 55 55 100 400 50
      > 55 70 115 450 63

      Please note that all CMP cable gland types meet the 20J (20Nm) impact resistance test (level 8).

    3. For Cables with Armour – Retention Class (A or B)
      EN 50262:1999 Values Nearest CMP
      Cable Gland Size
      Cable
      Diameter
      Cable Retention
      Class A (N)
      Cable Retention
      Class B (N)
      > 4 to 8 75 640 16
      > 8 to 11 120 880 20S
      > 11 to 16 130 1280 20
      > 16 to 23 140 1840 25
      > 23 to 31 250 2480 32
      > 31 to 43 350 3440 40
      > 43 to 55 400 4400 50
      > 55 450 5600 63

      The actual Performance Capability for the CMP metallic cable gland range intended for armoured cables far exceeds the requirements of EN 50262 : 1999 Category A & B

  3. Electrical Properties - Protective Connection to Earth (Category A, B or C).
    Cable Diamater Rms current (kA) Nearest CMP
    Cable Gland Size (Metric)
    Category A – Cable
    Gland only
    Category B – with an
    Earth Tag attached
    Category C – with a heavy duty integral Earth Lug
    > 4 to 8 0.5 3.1 10.0 16
    > 8 to 11 0.5 3.1 13.1 20S
    > 11 to 16 0.5 3.1 13.1 20
    > 16 to 23 0.5 4 13.1 25
    > 23 to 31 0.5 5.4 13.1 32
    > 31 to 43 1.8 7.2 43.0 40
    > 43 to 55 2.3 10.4 43.0 50
    > 55 2.8 10.4 43.0 63
    Note: Category A, is the minimum requirement which may apply in cases where the cable armouring (other than steel wire) is the limiting factor & where the cable gland is screwed into a threaded hole in the metallic equipment enclosure.

    Category B, is the medium requirement which may apply in cases where steel wire / metallic sheathed armoured cable is used and the system includes a high sensitivity method of secondary protection against fault currents and where earth tags are used with the cable gland.

    Category C, is the highest requirement, which may apply in cases where steel wire / metallic sheathed armoured cable is used and the system relies on a low sensitivity method of secondary protection against fault currents and where integral earth lugs (e.g. CMP CIEL) are incorporated into the cable gland. (See: Safe Earthing Systems).
  4. Resistance to external influences -
    1. Ingress Protection Minimum of IP54
    2. Salt & sulphur laden atmospheres.
In respect of 4) i. above CMP Products can confirm that its minimum Ingress Protection rating is IP66 to IEC 60529. Please see individual cable gland catalogue pages for further information.

To meet the requirements of 4) ii. above CMP would recommend electroless nickel plating when cable glands are required to be installed in salt laden atmospheres. In addition stainless steel or copper free aluminium cable glands are recommended for use in sulphur atmospheres and stainless steel with a minimum grade 316 for use in H2S atmospheres.

For comparison purposes only, set out below are some of the key differences between BS6121:1989 and EN50262:1999.

Test BS 6121 EN 50262
Cable Gland Type Designation Specified as per Cable Sealing Concept Not Specified
Cable Gland Construction Across Flats & Lengths Specified for each Cable Gland Size Not Specified, Manufacturer must state cable acceptance range in it literature
Cable Acceptance Specified for both Inner and Outer Sheaths for each  Cable Gland Size Not Specified, Manufacturer must state cable acceptance range in its literature
Ingress Protection Rating (only applicable to glands with seals) Must be Minimum of IP66 Must be Minimum of IP54
Armoured Cable Pull Out Specified but varies with Cable Gland Size, Minimum 2.7kN to Maximum 8.83kN Varies with Cable Diameter not Cable Gland Size, Minimum 75 Newtons to Maximum 450 Newtons
Unarmoured Cable Pull Out Specified but varies with Cable Gland Size, Minimum 2.7kN to Maximum 8.83kN Varies with Cable Diameter not Cable Gland Size, Minimum 4 Newtons to Maximum 70 Newtons
Twist Test Not Specified Torque applied which varies with Cable Size, Minimum 0.1 Newtons to Maximum 1.2 Newtons
Impact Level Not Specified (Due to Torque & Construction being so detailed) 8 Categories Specified, Minimum 0.2J to Maximum 20J
Proof Torque Specified but varies with Cable Gland Size, Minimum 2.7 kN to Maximum 8.83kN 50% above the manufacturers stated Installation Torque
Electrical Resistance Cable to Gland Two Tests, Not more than 10% difference is allowed Specified 0.1 Ohm allowed
Earth Fault Rating Not Specified due to to high cable pull out resistance Specified Categories A, B, or C, Minimum 1.0 kA to Maximum 43.0 kA
Temperature Range Not Specified, Dependant upon the Seal Material Specified minimum range of -25º to +65º C
Seal Compression Test After Conditioning, No more than 25% variation Not Specified
Seal Ageing / Hardness Test After Conditioning, No more than 15% variation Not Specified