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Engineering: Hazards, Protection Methods & Functional Safety
Transcript of Engineering: Hazards, Protection Methods & Functional Safety
21% in Air
Removed by smothering a fire
With some fires water can be used to reduce heat.
Turn of electricity in electrical fires removes heat source.
When all fuel is used the fire stops.
Remove fuel if possible.
Energy required to ignite a combustible vapour or gas.
Measured in Joules.
MIE - Minimum Ignition Energy.
Air/Fuel ratio changed Minimum Ignition Energy.
Hydrogen has very low MIE.
LEL - Lower Explosive Limit
UEL - Upper Explosive Limit
Flammable range is between LEL and UEL
Below LEL is Lean mixture
Above UEL is Rich mixture
Oxygen in air - 21%
Above 21% is oxygen enriched environment.
Increased Oxygen causes
Slight increase in LEL
Large increase in UEL
Increase in flammable range = more dangerous gas
Sources of Ignition
Can you think of more?
Hazardous Area Classification
Gas, vapour or mist present continuously or for long periods or frequently.
Gas, Vapour or mist is likely to occur in normal operation occasionally.
Gas, Vapour or mist is not likely to occur in normal operation but, if it does occur, persists for short periods only
No gas present
Surface Industries Gas
Surface Industries Dust
Maximum surface temperature of electrical equipment
T1 - 450°C
T2 - 300°C
T3 - 200°C
T4 - 135°C
T5 - 100°C
T6 - 85°C
T6 is the best as it will not exceed 85°C
Dispersal of Gases
Less dense than air will rise
More dense than air will fall
Inside or outside
Spread gases to other area
Remove gas safely
Reduce Energy - Normal and Fault conditions
Reduces the possibility of spark
Low voltage not harmful
Lower surface temperature
Live maintenance is possible
Barrier in the non-hazardous area
Types of Barriers