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Engineering: Hazards, Protection Methods & Functional Safety

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by

Richard Reid

on 3 September 2013

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Transcript of Engineering: Hazards, Protection Methods & Functional Safety

Engineering: Hazards, Protection Methods & Functional Safety
Fire Triangle
OXYGEN
HEAT
FUEL
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.
Ignition Energy
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.
Flammable Levels
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
Tutorial Time
Oxygen Enrichment
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
Electrostatic Sparks
Mechanical Friction
Stray Currents
Electromagnetic Fields
Naked Flames
Can you think of more?
Hazardous Area Classification
Safe area
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
Gas Groups
Group I
Group II
Group III
Mining
Surface Industries Gas
Surface Industries Dust
IIA
IIB
IIC
IIIA
IIIB
IIIC
Propane
Ethylene
Hydrogen
Combustible
Flyings
Non-Conductive
Dust
Conductive
Dust
Temperature Classification
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
Vapour Density

Location

Ventilation

Temperature
Less dense than air will rise
More dense than air will fall
Inside or outside
Spread gases to other area
Remove gas safely
Affects density
Intrinsically Safe
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
Zener
Galvanic
Isolation
Capacitive
Inductive
Full transcript