Ex-pert Electrical Technologies

Dynamic elaboration on the Art & Science of Hazardous Area Protection

To Use… or NOT to use.. Conduits or Cables

Cable and Conduit

Conduit or Cable for Ex d or Ex de Enclosures 

The term ‘Conduits’ refer to the use of Ex-certified metallic pipes to house the insulated electrical wires for transfer of electrical current.

To use conduits or cables in a certain hazardous location depends mainly on the specifications governing the whole situation and scenario. The rule of thumb is : If the specs being followed are NEC 500 then conduits .. if the specifications belong to the NEC 505 OR IEC 60079 family of documents then CABLES will be the choice.

In principle there are three methods of providing electrical connections:

  1. Cables system with indirect cable entry, through separate Connection Boxes
  2. Cables system with direct entry
  3. Conduit Systems

Cables Systems with indirect and direct entries are specified in IEC complied systems and Conduit systems are only permitted in accordance with NEC 500.

Cable Systems:

Cable systems are mainly used in countries following IEC code. For this, high-quality cables, armored or unarmored, are laid uncovered. It is only in areas in which mechanical damage could be expected that they are laid in conduits that are open at both ends. (The ends of the conduits may require sealing for the purpose of VERMIN Proofing)

Method No.1

indirect_cable_entry

Cable is installed through Ex e / Exed  Metallic or non-metallic, certified cable glands cable grands for Ex e enclosure

Method No.2

direct_cable_entry

Method No.3  (NEC Specified )

Conduit_entry

Merits & Demerits of the three systems of connecting an Ex d or Ex de enclosure to an electrical network.

Conduit System:

  • It is strong & robust
  • Fire-proof (all metal)
  • High cost of installation
  • Time consuming installation
  • Possibility of corrosion
  • High cost of changes/augmentations (Rigid design)
  • INSTALLER is responsible for Ex Integrity (Flameproof) because all installation is carried out on site.

Direct Cable Entry

  • Flexible & thus fast installation
  • Flexible design for changes
  • Low cost of maintenance
  • Cables require protection from damages
  • INSTALLER is responsible for Ex Integrity (Flameproof) because all installation is carried out on site.

Indirect Cable Entry

  • Flexible & thus fast installation
  • Flexible design for changes
  • Low cost for maintenance
  • Cables require protection from damages
  • Manufacturer is responsible for Ex Integrity (Flameproof) .Cables are just connected into the Ex e enclosure at site

Some Important Remarks from IEC 60079-14 (Edition 5)

No. 1

Conduit Systems Remarks 1


  No.2Conduit Systems Remarks 2


The OPEN CONDUIT SYSTEM 

Conduits can be used for Mechanical Protection ONLY. Cables are drawn through the conduits and the ends of the conduits remain open . However some sort of sealing is definitely  required to prevent the :-

  • Ingress of VERMIN inside the conduit
  • Prevent the flow of rain water though the conduits

This system is in contrast to the STANDARD SYSTEM of Conduit Installation (As per NEC 500)

Open Condit Example

(Example : The cables are connected through cable glands and protected by open conduits )

Another example of OPEN CONDUITS .  (Control station is connected through non-metallic Cable Gland and connecting cable is protected through a open conduit. )

Cable or conduit Expeltec


Ex e Control Station and open conduit

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This entry was posted on October 28, 2012 by in Uncategorized and tagged , , , , , , .

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