II - DCE FEL ČVUT v Praze

Mechanical Configuration of an Automation System with SIMATIC S7 Ex Modules
1.10 Installation Work in Hazardous Areas
1.10.1 Safety Measures
Measured for
eliminating the risk
of explosion
1-40
All possible measures which eliminate the risk of explosion must be
implemented not only when using programmable controllers in hazardous
areas but also during the installation stage.
Tools which tend to produce sparks must not be used for working in
potentially explosive systems or system sections in operation. Copperberyllium
is a suitable material for tools such as screwdrivers, pliers,
wrenches, hammers and chisels. Since this material has low wear-resistance,
the tools should be used with care.
For mechanical work, the risk of sparks capable of causing ignition is
low – when bare steel elements strike each other
possible – when steel elements collide or drop
great – when striking rusty steel
very great – when striking rusty steel with an alloy coating,
such as aluminum paint.
The possibility of creating sparks capable of causing ignition is substantially
reduced by using non-sparking tools. An exception is when the tool is harder
than the workpiece.
Safely closing off the working area, e.g. with dummy panels.
Good ventilation of the rooms.
Flushing with inert gas. Testing the effectiveness of the flushing (gas
tester). Then working with a normal tool.
If the risk of explosion at the workplace cannot be eliminated, the following
measures must be implemented:
Avoidance of collisions and dropping of steel elements.
Wearing antistatic shoes, e.g. leather shoes or using shoe grounding strips.
Avoidance of rust layers and aluminum coating at impact points.If this is
not possible, eliminating the risk of explosion locally, e.g. with inert gas.
Adequate air supply and waste air disposal.
Removing or enclosing readily flammable substances in the vicinity.
Keeping the workplace and, if applicable, floor moist.
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04