244 HANDBOOK OF ELECTRICAL ENGINEERING
which is also satisfactory.
Hence the requirements of IEC60364 are satisfied.9.5 Cables with Enhanced Performance
Sub-sections 9.1 and 9.2 described the materials and designs for cables that are intended for general
use. The oil industry has additional requirements for cables that may be routed in normal hot sur-
roundings, in areas where a fire situation must be tolerated and for the emergency control of critical
safety circuits and systems. Examples of these situations are,
a) Normally hot surroundings.
Cables for ignition and control circuits at the burner face of boilers and furnaces.
Cables routed close up against hot vessels and pipes.b) Fire situations
Cables routed near to wellhead equipment.
Cables routed in hazardous areas.
Cables installed in offshore living quarters.c) Emergency control and power.
Cables associated with emergency power supplies and control systems.
Cables that must function as long as possible in safety control systems e.g., fire and gas detection
systems, ventilation damper control and power systems, UPS, public address and communication
systems, intrinsically safe systems.There are three important factors regarding the above requirements,
- Fire retardance.
- Fire resistance.
- Emission of toxic gases and smoke.
Fire retardance or reduced flame propagation is described in IEC60331 and fire resistance in
IEC60332 (3 parts).
9.5.1 Fire retardance
The early editions of IEC60332 mainly concerned definitions and testing single lengths of cables.
This is useful for making a comparison between one cable and another.
Practical installations more often than not have several or many cables bunched together by
cleats on a rack, or in close proximity to each other due to the close spacing of tiered racks. In this
respect the IEC60332 Part 3 is more useful and relevant.
The standard describes various testing regimes in which the cable is set in a vertical test rig.
A naked flame is applied at the base of the cable. The flame is applied for a given period of time.
The extent of burning of the cable is measured from the base. The lower the measured amount of