Software Development Life Cycle By Team Orange (Dept. of Pharmacy)
4072721.ppt
1. Safety Talk 17 / 2
Why discuss flare and overhead systems ?
Workplace safety depends on people !
Discussions like this are essential:
• To maintain awareness
• To learn the lessons from past accidents
• To hear your local knowledge and experiences
Flares and overhead systems present many and
varied hazards. Accidents continue to happen to
experienced people, who repeat previous mistakes,
and fail to learn the lessons. It is often in common
systems like the flare where problems occur.
Ownership and extra vigilance are needed
2. Safety Talk 17 / 3
What are the risks ?
• Fire and explosion
– air ingress, ignition sources
• Toxic
– hydrogen sulphide, asphyxiation, pyrophoric and
chemical deposits
• Environmental
– smoke, glare, noise, smell
• Leakage / rupture
– corrosion, embrittlement, vibration / hammer
– overpressure, restriction or blockage
• Critical equipment or locations
– flare area, incinerators, working at height
• Critical tasks
– draining liquid, lighting pilots, hot work
• The unexpected
– unexpected physical and / or chemical combinations
3. Safety Talk 17 / 4
Managing the risks
• Plan and think through the work in advance
• Identify and assess the risks
– what are the risks ?
– what can go wrong ?
– how likely ?
– what consequences ?
• Apply the appropriate controls to the extent
warranted by the risks
– use a safer method, time or location
– reduce the risk
– procedural controls, work permits
– training, including contractors
4. Safety Talk 17 / 5
Risks – air ingress
leading to explosion
risks • Vacuum systems
• Pump suctions
• Draught
• Drawn in through water
seals, blanketting systems
• During work
• Purging air to flare
Where else can air be pulled in ?
5. Safety Talk 17 / 6
Risks – Fire and explosion
• Hydrocarbon leaks and spills
– failures due to corrosion, vibration
– liquid carryover, blowdown
– flare puking, grass and ditch fires
– cold work, breaking containment
• Ignition sources
– flare tip / flashback, incinerators,
furnaces / stacks
– pyrophoric scale
– hot work
• Explosion
– liquid carryover to incinerator,
stack, sulphur plant
– hot oil in contact with water
eg. in K.O. / Blowdown drums
7. Safety Talk 17 / 8
Risks – Overloading or restriction
• Overloading
– inadequate design, modifications
or additions
– simultaneous relieving
eg. during power failure
– unit upset
• Restriction (or complete blockage)
– closed valves or broken fittings
– blockage of flame arrestors or
molecular seals
– ice hydrate, heavy oils /
wax, hydrates
– liquid accumulation
8. Safety Talk 17 / 9
Risks – Leakage or rupture
• Corrosion
– water is often present in flare and overheads systems
– the aqueous phase is usually acidic
– chemical injections eg. ammonia
• Metal embrittlement
– low temperature eg. during depressuring
• Vibration
– liquid slugging (and solids eg. ice)
– water/steam hammer
– RV chatter
• Water injection
– local corrosion / erosion
10. Safety Talk 17 / 11
Risks – Critical tasks, equipment, locations
• Critical tasks
– draining liquid (toxic and flammable)
– lighting flare
• Critical equipment
– incinerators, explosions
• Critical locations
– flare area, radiation (flare and sun),
several hundred feet long
– work at height eg. from platform,
on flare stack
11. Safety Talk 17 / 12
Risks – The unexpected
Change is one of the greatest risks
If you are surprised, you and/or the plant are at risk
• Unblocked drain
• Unexpected substance
• Unusual pressure, temperature, level, flow
• Unusual operating mode
eg. plant floating on flare
• Internal heat exchanger leaks
Any other surprises ?
12. Safety Talk 17 / 13
Controls – Air ingress
• Prevent air ingress using molecular seals,
purge gas, water seals (check)
• Address the hazards of air in start up and
shutdown procedures eg. break vacuums
with adequate gas or nitrogen
• Monitor oxygen content at strategic locations
13. Safety Talk 17 / 14
Controls – Fire & explosion
• Ignition sources
– beware adjacent ignition sources
including pilots and adjacent flares
– remove and/or wet down
pyrophorics
– use the hot work permit system
• Flare area
– keep flare areas clean,
free from vegetation,
and under observation
(by TV)
14. Safety Talk 17 / 15
Controls – Breaking containment
• Use work permits for all work on flare systems
– assume all valves will pass
– use positive pressure face mask BA
– drain liquid at all low points
– assume H2S and pyrophorics
will be present
• Detailed planning and procedures,
and senior staff authorisation for
high risk work
• Carry out work when refinery is steady,
and allow no process changes during work
15. Safety Talk 17 / 16
Controls – Toxic
• Consider what may be present, and assess the risks
• Can the risk be reduced ?
• Prepare procedures for critical tasks
• PPE must be worn to provide adequate protection
• When exposure to flare gas is possible, use positive
pressure face mask BA
• Identify equipment containing H2S (>0.5%) with
yellow bands
16. Safety Talk 17 / 17
Controls – Overloading or restriction
• Overloading
– clear responsibility for the flare system
– carry out Hazops
– prepare contingency plans
– flare system alarms to be handled
independently of the DCS
– trips to reduce amount flared
– trips to prevent liquid disposal to flare
– venting directly to atmosphere
• Restriction
– block valves must be locked open
– drain liquid regularly
– tackle root causes of restrictions & blockages
17. Safety Talk 17 / 18
Controls – Leakage or rupture
• Corrosion
– monitoring and inspection
– pH control, chemical injection
• Embrittlement
– segregation of wet and dry (cold) streams
– material selection eg. stainless steel
• Liquid slugging
– liquid knockout eg. on units
– grading and low point drains
• Water hammer
– dewatering eg. reflux drums, pumps
• Inspection and maintenance priority for the flare system
18. Safety Talk 17 / 19
Controls – Environmental
• Low level (ground) flare for normal / low flows
(but safety implications)
• Height of stack to dilute / disperse emissions
• Tip design and maintenance
• Steam injection for clean burning
• Liquid knockout
• Community relations programme
• Environmental initiatives
eg. landscaping,
tree planting
19. Safety Talk 17 / 20
Controls – Critical tasks, equipment, locations
• Critical tasks
– work permits, procedures and training
– PPE, including positive pressure BA
– standby / rescue personnel
• Critical equipment
– operating instructions and technical guidance
– inspection and maintenance schedules for critical equipment
– relief valve removal needs proper technical approval
– high priority must be given to completing work and re-installing
• Flare area
– restrictions on entry to flare area, for what tasks, length of time,
precautions needed etc.
20. Safety Talk 17 / 21
Fire due to liquid carryover
A fire occurred when
hydrocarbons were carried
over into a crude unit stack.
The acid gas KO pot was
designed for water but not
hydrocarbon.
21. Safety Talk 17 / 22
Explosion at flarestack
Beware ignition sources
including pilots, pyrophorics,
adjacent flares
During decommissioning
of a flare, a steam purge was
replaced with nitrogen. As a
spectacle blind was being removed
there was an explosion
which blew a worker to the
ground killing him.
22. Safety Talk 17 / 23
Fire during flare valve removal
A flare main valve was being
removed by contractors working
on a temporary platform. There was
a release of hydrocarbon liquid,
which vaporised and ignited.
2 men died and 2 suffered
serious burns.
23. Safety Talk 17 / 24
Flare valve removal
• Install flare valves ‘upside-down’
• Survey flare line topography for low points
• Initial break near drain valves
• Spade isolation
• Investigate use of hydraulic devices to split
flanges remotely
• Venting points to inject inert gas
• Nitrogen purging and wetting of work surfaces
• Location and protection of machinery
• More senior staff involvement / written procedure
• Carry out work only when refinery is steady,
and allow no process changes during work
24. Safety Talk 17 / 25
Ditch fire near flarestack
During clean-up of drainage
ditches, burning liquid fell from the
flare tip and ignited oil in the ditch
The fire spread quickly beneath
crude and propane pipelines
25. Safety Talk 17 / 26
• No work permit was in force
• The fitters began their work
without informing anyone
• The plant flare was not
isolated from the refinery
flare main because other
equipment within the plant
was ‘live’
• The Refinery Fire Service
were notified 13 minutes
after the Medical Centre
Fatal gassing while replacing RV
A fitter replacing a RV
on a plant flare main was killed
when a large emission of gas containing
H2S occurred. He was wearing a ‘demand’
BA set – where the pressure inside the face
mask drops below atmospheric.
A second fitter and 2 rescuers
(without BA) also collapsed.
26. Safety Talk 17 / 27
Fatal gassing
• Work on a live flare system requires detailed risk assessment,
preparation and precautions, with authorisation by senior
management
• Technical guidance should be available
• Work permit systems need regular reinforcement and auditing
• BA should have a positive pressure face mask with no in-leakage
• First action in an emergency is to raise
the alarm and call for the appropriate
emergency services
• Only fully trained and equipped personnel
may attempt rescue
27. Safety Talk 17 / 28
Flare gas backs into unit
• Remember that the flare can be a source of gas when equipment is depressured
• Positive isolation from the flare must be defined in operating procedures
7 people were overcome
by flare gas entering via a
pressure control valve during
spade swinging on a
Cat. Cracker start-up.
A fire was prolonged by
flare gas entering via a RV
bypass following an emergency
depressurisation. A fire occurred
on an ESV bonnet that had not
been isolated from flare.
28. Safety Talk 17 / 29
Unexpected outcome ?
A fitter received chemical
burns during the swinging
of a spade in a flare line.
He was off work for 1 day.
If you think work through and ask “what if?”
you should never be surprised - and you
will be much safer
29. Safety Talk 17 / 30
Mis-use of flare system
Clay treaters on a MEROX
plant were being water washed
via the RV bypass, using the
flare K.O. drum as a pump out vessel.
An undetected valving error routed
kerosene into the flare for 8 hours.
The flare stack water seal overflowed,
contaminating ground water
and the river.
30. Safety Talk 17 / 31
Overhead vent failure
A 2 inch vent located on
the top of a horizontal 10 inch
line completely failed, releasing a
large vapour cloud which
fortunately did not ignite.
31. Safety Talk 17 / 32
Disastrous accumulation of liquid
During a lightening
storm a RV lifted and disposed liquid
to flare. A second RV lifted 5 hours later,
and 2-phase flow created mechanical shocks
leading to a 30 inch corroded elbow failing.
The resulting explosion and fire injured
24 people, damaged 2 units, and caused
structural damage to buildings
2 miles away.
32. Safety Talk 17 / 33
Blocked flare
During an upset, a cat. reformer
relieved into a 42 inch flare stack that
was blocked by ice. Temperature was
about - 18°C, which was normal.
Fortunately the crude unit was cracked
open to flare, and this allowed the
crude column to act as a
pressure buffer.
33. Safety Talk 17 / 34
Optional quiz
1. Name 5 general risk areas associated with flare systems
2. How can air find its way into the flare ? (5 ways)
3. List 5 ignition sources found in flare and / or overhead systems
4. List hazardous substances found in the flare (5)
5. What precautions should be taken when draining flare drums / pots ? (4)
6. Which of your critical tasks are associated with flare / overhead systems (5)
7. What specific precautions should be taken when breaking into a flare line ?
8. What can cause blockages in flare / overhead systems (5)
9. Give 5 examples from this Safety Talk of incidents involving flare systems (5)
10. Give 2 more examples from your experience.(4)
