Arrange devices in zones of differing disturbance climates

Zones of differing disturbances climates must be defined within the plant in which devices are arranged according to their sensitivity or potential for interference.

These include fundamentally different zones:

• Process

• Control system

• Data processing with computer work stations

PLC system

Separation of the PLC system is enabled by being installed in cabinets or on machine chassis. The guidelines for cabinet setups can be found in Guidelines for Arranging the Device in the Cabinet or a Machine.

Process

The processing plant with interfering components forms its own zone.

Sensitive cables and devices for process data acquisition and control (that are always in this zone) must be shielded.

Strong interference affects high current equipment above all through their magnetic fields, such as:

• High current equipment in energy supply company systems

• Melting in chemical plants

• Transformers

• Energy distribution from manufacturing plants

Computer work stations

Computer work stations should be placed in separate, shielded rooms that are equipped with close-mesh equipotential bonding in the floor, see Guidelines for the Grounding System in Buildings.

In reality, it is often necessary to install computer work stations near the production line. Monitors near high current equipment can have such large problems with interference that work is no longer possible with them.

If the magnetic fields present exceed the values recommended for monitor use, counter measures must be taken such as:

• Increase the distance from the source of the interference

• Shielding of the source of interference

• Use of plasma monitors

• Shielding of monitor screens