6.1 Introduction:
Power and control cables are the nerves of any process plant in industrial segment.
Operational reliability project completion schedule of the process plant depends
upon right method of cable laying. The maintenance of cables after completion of
the project is a challenging task for an electrical and instrument engineer.
A right cable laying depends upon good cable routing and good quality of cable
tray systems. There is another aspect of plant cable engineering which makes
significant difference on following factors:
- Plant aesthetics look,
- Plant safety aspects,
- Ease in project execution,
- Fault traceability and its remedial actions,
- Protection from mechanical damages, etc.
There are two method of cable laying beyond good routing and cable tray selection
aspects. The first one is called a) OVERHEAD CABLE LAYING and second one is
called b) UNDER GROUND CABLE LAYING. The conceptual advantage and
disadvantages of two systems are described as below to understand in better way.
6.2 Type of Cable Laying Method:
There are two most popular way of cable routing which are generally followed
in most of the industrial segments. The first method is known as “Overhead Cable
Laying System” in which cable routing is decided above ground through overhead
cable galleries. The second method is known as “Under Ground Cable Laying
System” wherein cable route is decided below ground through cable trenches or
cable tunnels.
a) Overhead Cable Laying System:
Overhead cable tray systems are most popular method of cable laying in process
industries. This method is practiced in cement, power, steel, chemical, refineries,
paper etc. The cables are routed above the ground using fabricated structures,
building structures, cable galleries, conveyor belts structures, cement structures
etc. Generally, cable galleries are exclusively designed for cable routing in the
plant but some time cable can be routed along with air pipe line, water pipe line
structures for the benefit of cost economy.
The key features of this cable routing are as under:
i. This cable routing is preferred in normal course for general areas due to
easy access for laying as well as maintenance.
ii. This method is most suitable where chances of fire are more like handling of
fine coal dust, oil and gas refineries, flammable chemical industries etc. The
initiation of fire can be easy detected and controlled without any significant
damages.