Armoured Cable - week 3 & 4

Week 3 and 4
Topic: Armoured Cable
Specific Objectives: By the end of the lesson, student should be able to
1. Define armoured cable
2. Mention main two types of armoured cable
3. State areas armoured cables can be applied
4. state four precaution to be taken when terminating PVC armoured cable
5. State two advantages of armouring cable over conduit
Armoured cable
Armoured cables are used where there is likelihood of mechanical damage to the conductor or insulation e.g underground cable run
Types of armoured cable
There are two main types of armoured cable: PILCSWA and PVC armoured (a) Lead covered paper insulated steel wire armoured cable (PILCWA).
It consists of the following parts.
1. An inner heart of jute used to keep the cable circular
2. Copper or aluminum, conductor insulated with mineral oil impregnated paper
3. A lead sheath which contain the insulation and is also used as an earth continuity conductor.
4. Jute bedding tape impregnated with bitumen used to protect the lead against the armouring
5. Galvanized steel wire
6. Bitumen impregnated jute serving.

Termination of PILCSWA cable procedure
1. Place binder 1 meter from end of cable
2. Remove servicing (ie water proof serving)
3. Bend steel wire armouring back until it is dear of lead sheet
4. Remove approximately 12cm of lead sheath and clean remainder
5. Place brass gland on cable leaving approximately 10cm of lead sheat showing
6. Plump joint using plumer metals
7. Clean galvanized wire over plumb
8. Clamp wires to gland and bolt gland to sealing chamber
9. Cut back paper insulation on conductor and make through joint to V.R.I conductive using weak back ferules
10. Assemble sealing chamber and pour in hot bitumen to seal oil impregnated paper insulation against moisture.
P.V.C Armoured cable
This is made of PVC insulated core packed with PVC to give a circular cross-section. An outer PVC sheath covers the galvanized steel wire.
PVC armoured cable may be terminated and jointed as the type of cast iron boxes used for PILCSWA armoured cable although plastic boxes are often used. Its temperature limit is 00 to 650C.
Precaution when terminating PVC armoured Cable
1. PVC insulation must be protected against heat (e.g with cloth or tape)
2. PVC tapes should be used for insulating the conductor
3. Particular care must be taken with the clearing and clamping of the galvanized wire armouring as it often the sole earth continuity conductor.
4. Compound temperature: The temperature of the powering compound should be such that it does not melt the PVC insulation of the conductors.

Evaluation
1. Define armoured cable
2. Mention two main types of armoured cable
3. State four precaution when terminating PVC armoured cable
Area of application of armoured cable (Week 4)
Armoured cable can be used in the following area because they can withstand chemical and mechanical damage
1. Boiler house
2. Filling station
3. Industries
4. Airport
5. Transmission/distribution lines
Materials used for armoured cable sheath are
1. Lead alloy eg paper-insulated cable
2. Tough rubber eg tough rubber cable
3. Metal eg mineral insulated conductor
4. Aluminum eg Aluminum conductor
5. Polychloropreneeg pipe cable
6. Polyving/chloride (PVC)
Types of armouring material
1. Galvanize steel wiring armouring
2. Galvanize steel tape armouring
3. Aluminumstrip armouring
Important of armouring
1. To protect against mechanical danger
2. Secondly, the armouringmaterials is also used as earth continuity conductor.
Advantages of armouring cable over conduit or trunking
1. It is more convenient for long single runs of heaver current supplies
2. It can be shaped into position quite easily
IEEE regulation for armoured cable
1. Single core armoured cable must not be used for AC
2. Termination and joints should be made by using correctly designed joint boxes, these can be filled with compound to prevent the ingress of moisture.
3. The radiesof any bends made in the cable should not be less than 2 times the overall diameter of the cable
4. When cables are installed underground they should be installed at a depth of at least 18 inches (0.6m)
Evaluation
1. State four areas where armoured cable can be applied
2. State two advantages of armouring cable

Assignment
Draw and label an armoured cable