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
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
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
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 ?
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
Safety Talk 17 / 7 Hazardous substances –hydrogen sulphide, other flare / overhead gases –benzene, PCAHs –acids, alkalis, injections eg. ammonia –additional substances from physical changes or chemical reactions –solid deposits, sludge Critical tasks –draining, venting, sampling, gas testing –cold work, breaking containment eg. spade swinging Critical locations –K.O. and blowdown drums, sumps, hotwells Risks – Toxic
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
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
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
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 ?
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
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)
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 H 2 S 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
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 H 2 S (>0.5%) with yellow bands
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
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
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
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.
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.
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.
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.
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
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
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 H 2 S 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.
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
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.
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
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.
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.
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.
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.
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)