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FWB (Edinburgh) Ltd 22/12/2015
Dangerous Substances &
Explosive Atmospheres
Eric Bertram
FWB (Edinburgh) Ltd 2
22/12/2015
DSEAR
DSEAR covers workplaces where there are
dangerous substances present that can potentially
create an explosive atmosphere during normal
operations or as an abnormal occurrence
FWB (Edinburgh) Ltd 22/12/2015
Categories of Explosive Atmospheres
DSEAR covers two categories of explosive atmospheres:
1 Explosive atmospheres that involve gases,
vapours or mists
2 Explosive atmospheres that involves a dust or
dusts
FWB (Edinburgh) Ltd 22/12/2015
Zones
Zones 0, 1 & 2 for gases, mists and vapours
Zones 20, 21 & 22 for dusts
Zones 0 & 20 are the highest risk atmospheres and
require the greatest control
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DSEAR Experience
Combustion processes:
• Steam Boilers
• Combined Heat & Power (CHP)
• Turbines
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22/12/2015
Case Study
• HSE visited a customer’s site
• Recycling waste paper
• There was an issue with the accumulation of combustible dusts
• While on site the inspector took the opportunity to visit the
boilerhouse where we were responsible the operation of the site’s
steam boilers and requested the DSEAR risk assessment
• No DSEAR risk assessment
• Fire risk assessment – stated there was a negligible, if any, risk of
explosion and no further action was required
• Not accepted by the inspector – found to be in breach of regulation
5 of DSEAR – failure to carry out a DSEAR risk assessment
FWB (Edinburgh) Ltd 22/12/2015
Case Study
• Operated energy plant on more than 400 sites
• Inspector chose to take this issue up with the operator not the
owner
• 1 month to put a plan together and 6 months for completion
The inspector’s interpretation of DSEAR was:
‘If a building has a gas line with a joint on it there is a potential
for a gas leak and therefore a risk of explosion and requires
compliance with DSEAR.’
FWB (Edinburgh) Ltd 22/12/2015
Case Study
This interpretation is not quite correct
100mm Ø 100mbar
100mm Ø 100mbar
Steam
Hot Water Less than
1050C
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Assessment Process
Vz = 0.1m3
NE = Negligible Extent
i.e. Zone 0 NE, Zone 1 NE & Zone 2 NE
FWB (Edinburgh) Ltd 22/12/2015
Risk Assessment
Site: Location: Contract No: Reference:
Activity:
Gases, Vapours, Mists Y Combustible Dusts Source of Ignition Flammability
Present or frequently present during
normal operations
Present or frequently present
during normal operations
Electricity Y Tools Extremely Flammable Y
Present occasionally during normal
operations
Present occasionally during normal
operations
Hot Works Y Sparks Y Highly Flammable
Not normally present during normal
operation but if it does occur will only
persist for a short period
Y Not normally present during normal
operation but if it does occur will
only persist for a short period
Naked Flame Y Clothing Flammable (G, V, M) Y
Hot Surface Y Static Y Flammable (Dusts)
Risk Evaluation – based on numerical values 1 to 5 on likelihood & severity, where 1 is low and 5 high, 1/6 low – 8/15 medium – 16/25 high
Description of Hazard
Persons at Risk
Existing Control Measures
L
S
R
Additional Control Measures
L
S
R
Action by
Prevent
• Control
• Mitigate
Add an Introduction, Scope and Conclusion
FWB (Edinburgh) Ltd
h2
h3
22/12/2015
Assessment
Building Volume
Equipment Volume
Free Volume
Wind Direction and Average Wind Speed
h
Surface Area of
Ventilation (m2)
Gas Pressure
Ambient Temperature
Location of Ventilation
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Calculation
There are a number of ways to calculate Vz
BS EN 60079-10-1:2009
HSL – Quadvent Software (Accurate up to 10 bar gas
pressure)
A Vz of 0.1m3 or less does not necessarily mean there
is no risk of explosion. There can be areas within the
plantroom that has a gas line with a flange or other
type of joint which may not have suitable ventilation.
FWB (Edinburgh) Ltd 22/12/2015
25000 mm
55
00
mm
3 of 4m x 1m low level vents
10500 mm
36
00
mm
1700 mm
12500 mm
1 of 4m x 1m low level vent
36
00
mm
15500 mm
Mains Gas
Ventilation Louvre free volume 50% of ventilation area
LV - 16/2 = 8 m2 (0 m from floor)
HL – 16/2 = 8 m2 (4.5 m from floor) No fly mesh fitted Vz calculated using HSL Quadvent Vz calculated to be 0.00m3 Plantroom designated to be Zone 2NE
4 of 4m x 1m high level vents
SW prominent wind direction at an average wind speed of 5 m/s
Volume of Plantroom = 1090 m3
Volume of Equipment = 200 m3
Free Volume = 1890 m3
Gas Pressure = 250 mbar
Plantroom Schematic
Not to Scale
FWB (Edinburgh) Ltd 22/12/2015
M
Gas Meter Station
M M M
200mm Ø – Below floor level
10
0m
m Ø
10
0m
m Ø
10
0m
m Ø
10
0m
m Ø
M
Gas Train
Gas Drop Valve
Vent Line
Gas Meter
Sample Points Zone 2 Zone 1 Zone 1 – 0.5m radius Zone 2 – 6.5m radius
Boiler 1 Boiler 2 Boiler 3 Boiler 4
Pipeline Schematic
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Signage
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Equipment
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Institution of Gas Engineers & Managers (IGEM)
IGEM/UP/2 (Edition 3) – Installation of Pipework on
Industrial and Commercial Premises
IGEM/SR/25 (Edition2) – Hazardous Area Classification
of Natural Gas Installations
IGEM/SR/23 – Venting of Natural Gas
FWB (Edinburgh) Ltd 22/12/2015
British Standards
BS EN 60079-10-1: 2009 – Explosive Atmospheres
BS EN 1775: 2007 – Gas Supply – Gas Pipework for Buildings
– Maximum Operating Pressure less than or equal to 5 bar
BS EN 1127-1: 2011 – Explosive Atmospheres – Explosion
Prevention & Protection
BS EN 15001-1: 2009 – Gas Infrastructure Gas Installation
Pipework with a Gas operating Pressure of Greater than 0.5
bar for Industrial Installations and Greater than 5 bar for
Industrial and Non Industrial Installations
BS EN ISO 12100: 2010 – Safety of Machinery – General
Principles for Design. Risk Assessment and Risk Reduction.
FWB (Edinburgh) Ltd 22/12/2015
Thank You
The End