Introduction to Process

Safety

Introduction to Process

Safety

Topic 1.

In Memories…

3

In Memories: Bhopal, 1984

• Release of Toxic Gas

– 40 tons Methyl Isocynate escape from Union

Carbide Plant

– Immediate cause : 500L seepage

– Erupts and release fumes

• Aftermath

– 3000 died : respiratory failure

– Thousands more died in weeks that followed

– 500,000 suffer

– USD470mil spent

In Memories : PEMEX, 1984

• Pemex is a liquid petroleum gas ( LPG) distribution plant.

• Pemex is located a few km. north of Mexico City (Pop = 16MM).

• Plant was 25 years old and built to 1950 API standards of the U.S.

• 15 of 48 Vessels BLEVE In Domino Fashion

• 550 people killed., 2,000 people receive severe burns, 7,231

people classed as injured.

In Memories: Chernobyl, 1986

• 26 April 1986 at the Chernobyl Nuclear Reactor, Ukrain

• Large area of Russia, Ukraine and Belarus evacuated, 336,000

people resettled.

• Fewer than 50 direct death but, thousands of cancer related

cases

• Severe damage to the environment

6

In Memories: Piper Alpha, 1988

World’s most famous oil rig disaster in North Sea 1988

167 out of 229 people died

initial explosion followed by a fierce fire which, in turn, triggered off a further series of explosions

“Jump and try or fry and die.”

Flames could be seen 100km away

Cause of death 109 out of 137 recovered bodies inhalation of smoke & fire. Few died of burns.

In our backyards: Bright

Sparklers, 1991

• On 7 May 1991 at about 3.45 p.m.

fire ignited from product testing

activities.

• Fire spread, causing an explosion,

which caused the rockets to fly

everywhere, spreading the fire to

other places and buildings

• The fire and explosion destroyed

the entire factory.

• 23 people lost their lives and 103

others sustained injuries

More Recent: BP Texas City Refinery (2005)

• Vapour Cloud Explosion

• March 23, 2005, killing 15 workers and injuring more

than 170 others • On October 30, 2009 the OSHA imposed an $87 million fine on the

company for failing to correct safety hazards revealed in the 2005

explosion. The fine was the largest in OSHA's history, and BP announced

that it would challenge the fine

More Recent: Imperial Sugar, Georgia, USA, (2008)

• February 7, 2008

• Sugar dust explosion

• 14 deaths and injuring 38 others, including 14

with serious and life-threatening burns.

More Recent: Deepwater Horizon, USA (2010)

• Deepwater Horizon was an ultra-deepwater, dynamically

positioned submersible offshore oil drilling rig, owned

by transocean, built by Hyundai, leased to BP

• April 20, 2010, blowout turned fireball, killed 11

• Sank on April 20. Oil gushing into the sea causing

massive pollution

More Recent: Fukushima Daiichi, Japan (2011)

• March 11, 2011. Nuclear meltdown following

earthquake and Tsunami

• 6 reactors designed by GE

• Full meltdown of reactor 1,2,3

• No immediate deaths due to direct radiation

• at least six workers exceeded lifetime legal limits for

radiation

• more than 300 received significant radiation doses

• Impacted Japan’s Energy Policy

More Recent: Thai Petrochemical (2012)

• May 12, 2012

• Explosion when workers were cleaning chemical tank

at a synthetic rubber plant

• 12 dead, more than 100 injured

More Recent: Iran Petrochemical (2012)

• Friday August 3, 2012

• Fire at Imam Khomeini Petrochemical Complex,

Southwestern City Mahshahr

• At least 6 dead, dozens injured

• Gas Leak

In Our backyard: Petronas Gas (2012)

• Explosion at PETRONAS Plant in Paka

– May 10, 2012, Gas Processing Plant, GPP3 area 2.

– 2 dead 23 injured

• Suspected gas leak to storm water drain

In our backyard: Petronas Carigali (2012)

• Fire at Tukau B Drilling Platform, 31 nautical

miles from Miri.

• June 12, 2012, 9.20 am

• 16 people were working, 5 injured (various

degree of burn). Living quarters in Tukau A

In Our Backyard: MISC (2012)

• MV Bunga Alpinia 3, Ship carrying Ammonia in filling

operations at Petronas Methanol, Labuan

• 26th July 2012, Early morning Explosion

• Source of ignition: suspect lightning strike during

thunderstorm, 2.30 am.

• 29 crews, 5 dead (1 immediately found, 2 found dead

the next day, 5th body found dead 30/7.)

So much for statistics !!!

What shall we do about it ???

Introduction to Process

Safety

Topic 2.

Hazard in Process Industries

Hazards in Process Industries

• There are Three Major Hazards: Fire,

Explosion, Toxic Release

• Fire

– Impacts on plant, people and environment

– May also followed by toxic release

• Explosion

– Same as fire but more severe

• Toxic Release

– Impacts of people and environment. e.g. Bhopal

The Fire Triangle

Ignition

Source

2. Oxidizers* (the molecule contain oxygen atoms)

• Gases - oxygen, nitrous oxide (N2O)

• Liquids - hydrogen peroxide (H2O2), nitric acid (HNO3)

• Solids - ammonium nitrate (NH4NO3).

1. Fuels

• Liquids - gasoline, acetone, ether, pentane;

• Solids - plastics, wood dusts, fibers, metal particles, flour;

• Gases - acetylene, propane, carbon monoxide, H2

3. Ignition Sources

• Sparks, flames, static electricity, heat.

Distance of Effect Comparison

1

2

5

10

20

50

100

200

500

1000

INVENTORY

(tons)

18

36

60

90

130

200

280

400

600

820

BLEVE

120

150

200

250

310

420

530

670

900

1150

UVCE

20

30

36

50

60

100

130

FIRE

Distance

in Meters

Pool Fire

• Liquid spilled onto the ground

spreads out to form a pool.

• Volatile liquid (e.g. petrol)

evaporate to atmosphere and

soon form flammable mixture

with air.

• Upon ignition, a fire will burn

over the pool.

• The heat vaporizes more fuel

and air is drawn in round to the

side to support combustion.

• Danger to people is by direct

thermal radiation and burn.

Jet Fire

• High pressure release of gas from a vessel or pipeline ignites

almost immediately.

• This give rises to a giant burner of flame length tens of meters.

• Danger from thermal radiation and also impingement on adjacent

pressurized vessel, such as LPG vessel, heating the content

followed by pressure build up causing ‘boiling liquid expanding

vapor explosion’ (BLEVE).

• Sometimes called Torch Fire

Flash Fire

• Fire due to vapour cloud below explosive limit

• Resulting from spillage of relatively volatile (e.g.

propane, butane, LPG) material due to rapid

evaporation

• People at risk from thermal radiation effects.

• Usually unexpected event and short duration

Vapor Cloud Explosion

• Cloud will spread from too rich, through flammable range to too lean.

• Edges start to burn through deflagration (steady state combustion).

• Cloud will disperse through natural convection.

• Flame velocity will increase with containment and turbulence.

• If velocity is high enough cloud will detonate.

• If cloud is small enough with little confinement it cannot explode.

Factors Favoring Overpressures of Vapor Cloud

1. Confinement

– Prevents combustion products escaping, giving higher local

pressures even with deflagration.

– Creates turbulence, a precursor for detonation.

2. Cloud composition

– Highly unsaturated molecules are bad due to high flammable

range, low ignition energy, high flame speed etc.

3. Weather

– Stable atmospheres lead to large clouds.

– Low wind speed encourages large clouds.

4. Vapor Cloud Size impacts on:

– probability of finding ignition source

– likelihood of generating any overpressure

– magnitude of overpressure

5. Source

– flashing liquids seem to give high overpressure

– vapor systems need very large failures to cause UVCE

– slow leaks give time for cloud to disperse naturally without

finding an ignition source

– high pressure gives premixing required for large combustion

– equipment failures where leak is not vertically upwards

increases likelihood of large cloud

Factors Favoring Overpressures of Vapor Cloud

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Flixborough, England

• Company: Flixborough Works of Nypro Limited.

• June 1974.

• Product: cyclohexane – highly flammable

• 6 reactors in series, total capacity 120 tons.

• Fire and explosion – over than 10 days

• 28 people died & 36 others were injured.

• 53 civilians were reported injury

• Damage: entire plant, 1821 nearby houses &

167 shops and factories.

Phillips Pasadena, USA

• 23rd Oct. 1989, Vapour Cloud explosion

• 23 Deaths 130 Injuries, Loss US$ 500 Millions

BLEVE (Boiling Liquid Expanding Vapour

Explosion)

• When BLEVE is initiated, the liquid boils off rapidly producing a reaction which turns parts of the ruptured vessel into rockets which can travel 2500 ft or more.

• The liquid can take fire if it is flammable and burning material can spread over a large area. If the gas or liquid mixes with air a vapour cloud explosion can occur.

The Tragedy Of San Juanico,

PEMEX, Mexico City, 19 Nov 84

• Pemex is a liquid

petroleum gas ( LPG)

distribution plant.

• Pemex is located a few

km. north of Mexico

City (Pop = 16MM).

• Plant was 25 years old

and built to 1950 API

standards of the U.S.

• LPG gas is used for

heating and cooking in

almost every

household.

• 15 of 48 Vessels BLEVE in domino

fashion

• 550 people killed.

• 2,000 people receive severe burns.

• 7,231 people classed as injured.

Impact

Bullet Tank Area

Spherical Tank Failure (F4) Cylindrical tank flew as missiles

Nearby Houses

CAUSES OF

DUST

EXPLOSION

Combustible dust

Dust is suspended in

the air at a proper

concentration

There is an

ignition source The dust is

confined

There is an

oxidant (typically

atmospheric

oxygen)

*If any of these five conditions is missing there can be no dust

explosion

Dust Explosion

Imperial Sugar Explosion

February 7, 2008 in Port Wenworth, Georgia, USA. 13 people killed and 42 injured

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Hazard from Toxic Substances

• Source of Toxicants

– Toxic Release

– Fire and Explosion leading to release of toxicants

• Route of Entry

– Injection: through cuts or hypodermic needles into the

skin, usually cause highest blood level concentration.

– Inhalation: through mouth/nose into the lungs

– Ingestion: through mouth into stomach and gastrointestinal

tract,

– Dermal (Skin) absorption: through skin membrane

Toxicants

• Agents

– Chemicals: organic solvent, pesticides, lead etc

– Physical (dusts, fibers, noise, and radiation) agents,

e.g. Asbestos

– Carcinogenic, terratogenic, mutagenic

• Toxicity is a property of toxicant that describe

its effect on biological organism.

– Very Toxic > Toxic > Harmful

• Toxic Effect

– Reversible vs irreversible

– Acute Vs Chronic

– Local Vs Systemic

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The Bhopal Tragedy

• 40 tons Methyl Isocynate escape

• Immediate cause : 500L seepage

• Erupts and release fumes

• 3000 died : respiratory failure

• 500,000 suffer aftermath

• USD470mil spent

Introduction to Process

Safety

Topic 3.

RISK & RISK RANKING

39

Definition of Risk

Risk = Severity x Likelihood

Severity

• Probability of Fatality

• Monetory Losses

• Environmental Impact

Likelihood

• Chance of failure

• Probability

40

Risk is expressed in as Rating

• Rating is typically – simple to use and understand

– Not require extensive knowledge to use

– Have consistent likelihood ranges that cover the full spectrum of potential scenarios

• In applying risk assessment – Clear guidance on applicability is provided

– Detailed descriptions of the consequences of concern for each consequence range should be described

– Have clearly defined tolerable and intolerable risk levels

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Example of a Severity Range Description Category Environmental, Safety and Health Result Criteria

Catastrophic I • Death, permanent total disability • Loss of exceeding $1M • Irreversible severe environmental damage that violates law or regulation

Critical II • Permanent partial disability, injuries or occupational illness that may result in hospitalization of at least 3 personnel •Loss exceeding $200K but less than $1M •Reversible environmental damage causing a violation of law or regulation

Marginal III •Injury or occupational illness resulting in one or more loss of workdays •Loss exceeding $10K but less than $200K •Mitigatible environmental damage without violation of law or regulation where restoration activities can be accomplished

Negligible IV Injury or illness not resulting in a lost work day Loss exceeding $2K but less than $10K Minimal environmental damage not violating law or regulation

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Example of Likelihood Ranges Description Level Specific Individual Item Fleet or Inventory

Frequent A Likely to occur than 10-1 in that life Continuously experienced

Probable B Will occur several times in the life on an item, with probability of occurrence less than 10-2 but greater than 10-3 in that life

Will occur frequently

Occasional C Likely to occur some time in the life of an item, with a probability of occurrence less than 10-2 but greater than 10-3 in that life

Will occur several times

Remote D Unlikely but possible to occur in the life of an item with a probability of occurrence less than 10-3 but greater than 10-6 in that life

Unlikely but can be reasonably expected to occur

Improbable So unlikely, it can be assumed occurrence may not be experienced, with a probability of occurrence less than 10-6

Unlikely but possible

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Example Risk Ranking Categories

Risk Rank Category Description

I Unacceptable Should be mitigated with engineering and/or administrative controls to a risk ranking of III or less within a specified period such as 6 months

II Undesirable Should be mitigated with engineering and/or administrative controls to a risk ranking of III or less within a specified period such as 12 months

III Acceptable with Controls

Should be verified that procedures or controls are in place

IV Acceptable as is No mitigation required

44

Sometimes presented as Risk Matrix

Risk = Probability of occurrence x Consequence of occurrence

45

Guidelines for Risk Mitigation

Risk Level Action Required

A Risk Mitigation required to risk level C or D

B Risk Mitigation required to risk level C or D

C Risk Mitigation to risk level D is optional

D No further Risk Mitigation required

Page 46

• Risk cannot be eliminated entirely.

• Every chemical process has a certain amount of

risk associated with it.

• At some point in the design stage someone needs

to decide if the risks are “tolerable".

• Each country has it owns tolerability criteria.

• One tolerability criteria in the UK is "as low as

reasonable practicable" (ALARP) concept

formalized in 1974 by United Kingdom Health and

Safety at Work Act.

Can we accept risks

A risk is Acceptable When:

• it falls below an arbitrary defined probability

• it falls below some level that is already tolerated

• it falls below an arbitrary defined attributable fraction of total

disease burden in the community

• the cost of reducing the risk would exceed the costs saved

• the cost of reducing the risk would exceed the costs saved when

the ‘costs of suffering’ are also factored in

• the opportunity costs would be better spent on other, more

pressing, public health problems

• public health professionals say it is acceptable

• the general public say it is acceptable (or more likely, do not say it

is not)

• politicians say it is acceptable.

Acceptable Risks

• 1 in 1000 as the ‘just about tolerable risk’ for any

substantial category of workers for any large part of a

working life.

– Same as dying due to road traffic accidents (1998)

• 1 in 10,000 as the ‘maximum tolerable risk’ for

members of the public from any single non-nuclear

plant.

• 1 in 100,000 as the ‘maximum tolerable risk’ for

members of the public from any new nuclear power

station.

• 1 in 1,000,000 as the level of ‘acceptable risk’ at which

no further improvements in safety need to be made.

– Same as the chance of being electrocuted at home

The Magic Number !

1 x 10 -6

Page 50

ALARP Criteria

1 X 10-6

1 X 10-3

INTOLERABLE REGION (Risk cannot be justified on any ground)

ALARP REGION (Risk is undertaken if benefit is desired)

BROADLY ACCEPTABLE REGION

TOLERABLE only if risk reduction is impracticable, or its costs is grossly disproportionate to the improvement gained.

TOLERABLE if cost of reduction would exceed the improvement gained

Reasonably Practicable

“Reasonably practicable is a narrower term than “physically possible” and

implies that a computation must be made in which the quantum of risk is

placed in one scale and the sacrifice, whether in money, time or trouble,

involved in the measures necessary to avert the risk is placed in the other;

and that, if it be shown that there is a gross disproportion between them, the

risk being insignificant in relation to the sacrifice, the person upon whom the

duty is laid discharges the burden of proving that compliance was not

reasonably practicable”

Edward Vs National Coal Board [1949]

Conclusion

• Yes, we need to do something…

• The issue is how to make the plant safe for the

workers and the surrounding community and

environmentally benign?????