03 Accidents Case Studies on ProBE Area 2009.pdf

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Silas Sng

Director

Occupational Safety & Health Inspectorate (OSHI)

ProBE 2009ProBE 2009Accident Case StudiesAccident Case Studies


Incident

RealityIdeal

Hazard

Swiss Cheese Model of Defence




Incident

Hazard

Latent Failures:Latent Failures:Organisation conditions (often aresult of managerial policies and

actions) in which its effect are notimmediately apparent and may liedormant for a considerable time

Active Failures:Active Failures:These are errors orviolations (unsafe acts)

that have an immediateadverse effect. Theseunsafe act are typicallyassociated withoperational personnel.


Cases aim to highlight the connection betweenthe lapses that eventually led to the accident.

Confined Space / Use of Chemicals Working at Height Cranes

If any layer of protection had worked, theincident could have been averted.

OverviewOverview




Case Studies:Case Studies:

Confined Space / Use of ChemicalsConfined Space / Use of Chemicals


Case: Synopsis of AccidentCase: Synopsis of Accident A worker was carrying out a visual inspection of the

isotank interior to ensure that the tank was clean and freefrom residue

He was found unconscious inside the tank

Co-worker found the victimlying face up at the bottomof the tank and attempted torescue him

He was pronounced deadon the spot




Observations and FindingsObservations and Findings

N2 was used to expel chemical di-octyl-phthalate(DOP) from ISO tank

No fresh air purging in the tank, hence atmospherein tank remained N2 rich.

Lack of Oxygen in ISO tank, i.e. volume of oxygenis below 19.5% - not sufficient to support life

Before the Deceased entered tank:

No ventilation of tank was done

No air monitoring

Cause of death: asphyxiationCause of death: asphyxiation


FatalFatalAccidentAccident

SWP developedbut was not

briefed toworkers

“Buddy” Systemwas not practicedduring the time of

accident

Workers were nottrained on the usageof gas meters to testfor the oxygen levelinside the confined

space

No PTWimplemented forconfined space

work

Where were the gaps?Where were the gaps?Permit

to Work

Safe Work

Procedures

“Buddy”

system

Training of

workers




Synopsis: Incident occurred at the bow thruster compartment of a container

vessel undergoing repair work at shipyard

Workers carried out chemical cleaning work of the bow thruster motorhousing and rotor shaft as part of the overhauling jobs

NonNon--fatal case:fatal case: Use of ChemicalsUse of Chemicals

After cleaning, 2 workers went into thecompartment to check the work, butexperienced dizziness and collapsed

3 workers attempted rescue but succumbed tothe vapours

Workers were subsequently rescued by theship crew who wore breathing apparatus.

Workers were diagnosed with PCE poisoning


The chemical cleaning involved freeing the shafts, insulation, housing,etc. of dirt/grease using a chemical, Redox Motor Cleaner, to bedischarged via a manual spray gun.

99.9% PerchloroethylenePerchloroethylene (PCE)(PCE)

Chemical useChemical use

“Like many chlorinated hydrocarbons,tetrachloroethene is a central nervous systemdepressant, and inhaling its vapors (particularly in

closed, poorly ventilated areas) can causedizziness, headache, sleepiness, confusion,nausea, difficulty in speaking and walking,

unconsciousness, and death.”




4th Deck

Tween Deck

Triggering event:Triggering event:One of the workers

went into the 2nd

deck withoutchanging to the airline respirator

8m

2m 5m

6m

4m

2.5m

4.7m

2.5m

3.5m

3.7m

5.5m

5.5m

10m

9.5m

10m

1st Deck

2nd Deck

3rd Deck

BowThruster

Motorfoundation

2 stage entry

Workers towear cartridge

respirator

Workers to wearair line

respirator

What happened?What happened?


WorkersWorkers

overcomeovercome

by PCEby PCE

Ventilationactually

circulated thePCE to entirecompartment(diff decks)

Worker did notwear air-line

respirator

Not fit tested

Not conducted todetermine

concentration ofPCE

Decision madeto clean in-situ

Where were the gaps?Where were the gaps?

Latent Failure: Did not

recognise the work space

as a Confined Space and

apply the nec control

measuresGas Checks

PPE

ForcedVentilation

Designated areafor such cleaning(reducing risk@source)

Active

Failure




CommentsComments

The yard had relied on the provision of cartridgerespirators to workers to gain access into thecompartment without knowing the concentration ofthe cleaning solvent (PCE) vapour in thecompartment

cartridge respirators may not effective if the

concentration was high.

The air fed mask was only available in the 2nd deckof the compartment. This meant that workersneed to don the cartridge respirators to enter thecompartment and make their way to 2nd deckbefore they could access to the air fed mask.

Such practice put workers in grave dangers asthere was no proper assessment of the actualconcentration of PCE vapour in thecompartment.


CommentsComments If the compartment were deemed as a confined space, entry into the

compartment for inspection would require the application of aconfined space entry permit.

Gas checks such as testing the level of oxygen, theconcentration of flammable gas and the presence of hazardoussubstances and assessment of the compartment for effectiveness ofventilation would have been carried out prior to entry. This is toensure that the atmosphere of the compartment is safe for entry.

Without classifying the compartment as a confined

space and subjected it to the above assessment, itwould put any workers gaining access into thecompartment in grave danger, even they wereprovided with gas cartridge respirators.




• One crew killed when enteringinto the cargo hold to retrieveequipment

• Two injured when attempted torescue him

• Non-compliance to simpleprocedure for entry intoconfined space

• Despite gas meter and blowerbeing available onboard theship

• Cargo hold was closed forweeks prior to the entry

Another caseAnother case……


Side View of Vessel

Main deck

Blower 1Blower 2

Air hose 1

Air hose 2

Manholeopening

Yet another caseYet another case ……

• Workers were tasked to set upair hoses onboard a Vessel, toprepare for forced ventilation.

• The ship crew had earlierdetected toxic gases, mainlyHydrogen Sulphide (H2S).

• 3 of the workers who werepreparing the air hosesentered the tank and were

overcome by the toxic gases.• Two of the workers died as a

result of H2S poisoning.

• Injured suffered toxic burns tohis respiratory system.




Key Learning Points with regards toKey Learning Points with regards to

Confined Space / Use of ChemicalsConfined Space / Use of ChemicalsLack of

awareness?“looks safe what?”

Complacency?“just a while, I can hold my breath…”

Cannot control worker?“kong buay tia…”

“they dun follow procedure..”

Taking risk?“never mind, faster to do it this way…”


Control MeasuresControl Measures--Confined Space / Use of ChemicalsConfined Space / Use of Chemicals

Typical Control Measures forConfined Space

1. Permit to Work System

2. Ventilation

3. Gas Check (prior to entry plusperiodic monitoring)

4. No entry signages

5. PPE

6. Explosive-proof equipment

7. Standby-personnel e.g. firewatchman

8. Emergency response

Typical Control Measures forTypical Control Measures for

Confined SpaceConfined Space

1. Permit to Work System

2. Ventilation

3. Gas Check (prior to entry plusperiodic monitoring)

4. No entry signages

5. PPE

6. Explosive-proof equipment

7. Standby-personnel e.g. firewatchman

8. Emergency response

Don’t be a Hero!

Never assume that you cancarry out rescue operation onyour own without equipment.

Be conscious of where the

fumes are discharge to.

Do not simply blow the fumesfrom one compartment into

another closed compartment




Control MeasuresControl Measures--

Confined Space / Use of ChemicalsConfined Space / Use of ChemicalsTypical Control Measures for

Use of Chemicals

1. Handled only by CompetentPersonnel

2. Safety Data Sheet (SDS)

3. Proper labelling of chemical

4. PPE

5. Eye-wash, overhead shower

6. Separate incompatible substances

7. Proper storage facilities

Typical Control Measures forTypical Control Measures for

Use of ChemicalsUse of Chemicals

1. Handled only by CompetentPersonnel

2. Safety Data Sheet (SDS)

3. Proper labelling of chemical

4. PPE

5. Eye-wash, overhead shower

6. Separate incompatible substances

7. Proper storage facilitiesYour prayers may not help!

Be conscious to locate prayingaltars from flammable

substances.

Its not one size fits all!

Masks comes in different typeand sizes, use the correct one


Take away pointsTake away points……

Assumptions:

1. Always assumed that the confined space is not safe for entryuntil proven otherwise.

2. Always assumed that the chemical is dangerous (not to bedisturbed or inhaled) until proven otherwise.

Assumptions:Assumptions:

1. Always assumed that the confined space is not safe for entryuntil proven otherwise.

2. Always assumed that the chemical is dangerous (not to bedisturbed or inhaled) until proven otherwise.




Case Studies:Case Studies: Working at HeightWorking at Height


Is it just about belt, harness & barricades?Is it just about belt, harness & barricades?

Worker fellWorker fell

fromfrom

heightheight

WorkerWorker

working atworking at

heightheight

Not provided with harness / belt ,

Or provided but not wearing,Or wearing but not hook on

No barricades / access

-Employer did not install

-Other workers removed it

Are there deeperAre there deeper

factors at play?factors at play?

AnsAns: Yes: Yes

Worker not careful,slipped and fall

Worker’sbehaviour

PPE

Barricades / Access

A typical setting:A typical setting:






FindingsFindings

Workers faced difficulty in hacking theexisting slab, i.e. they had to hack ina bending position

The steel mesh of the new slab wascut away to facilitate the hacking ofthe existing slab

900mm

The timber runners werenot secured to the

concrete slab


Worker fellWorker fell

fromfrom

heightheight

Built-in-safety

Intrinsically safe design

(wire-mesh) was nullified

Alternative barriers

Alternative – timber runners were placed haphazardly

Where were the gaps?Where were the gaps?




Legal ActionLegal Action

Occupier was charged under Section 11(a) of the WSH Act forfailure to put in place effective measures to prevent a personfrom falling through the slab opening in the lift motor room

Fined $80,000

Supervisor who was responsible for ensuring that the openingwas effectively barricaded or covered was charged underSection 15(1)(b) for failure to co-operate with his employer tothe extend of ensuring that they provided the deceased andother workers a safe place of work

Fined $1000


Control MeasuresControl Measures--Working at HeightsWorking at Heights

Typical Control Measuresfor Working at Heights

1. Guardrail systems

2. Safety net systems

3. Personal fall arrest systems

4. Warning line systems

5. Controlled access zones

6. Safety monitoring systems7. Covers

Typical Control MeasuresTypical Control Measures

for Working at Heightsfor Working at Heights

1. Guardrail systems

2. Safety net systems

3. Personal fall arrest systems

4. Warning line systems

5. Controlled access zones

6. Safety monitoring systems

7. Covers

Proper anchorages

A harness is only effective in so far as itis properly anchored to a secured point




Cranes AccidentsCranes Accidents


A quick summary of typical causesA quick summary of typical causes

CraneCrane

AccidentsAccidents

Structural failure of load bearing partse.g. wire ropes

HumanFailures /

OperationalErrors

Overloading

Soft ground

By passing ofsafety devices

Outriggers notextended / not

evenly extended

Incorrect riggingmethods

Unclearcommunications

Treat every lifting operation with respectTreat every lifting operation with respect

(regardless of the load / routine or non(regardless of the load / routine or non--routine lift)routine lift)

Lifting zone notcleared /

Inadequatesupervision




Case Study:Case Study:

Synopsis of AccidentSynopsis of Accident

• The crane operator was operating the mobile crane

lifting the bundle of C-channels from a trailer

• The C-channels was unloaded onto a platform located atthe 2nd storey of the dwelling house

• While the crane operator was positioning the bundle of C-channels onto the platform at the 2nd storey, the mobile

crane began to vibrate and topple to its right side

• The C-channels which was hoisted were dislodged fromthe crane’s hook


• Three of the outriggerswere found to be fullyextended on theconcrete ground. As thefourth outrigger wasobstructed by a tree, itwas partially extendedand rested upon 4

timber blocks placed ontop of the soil


Outrigger obstructed




Synopsis of AccidentSynopsis of Accident

Boom extended to about24.7 m

• The mobile crane wasprovided with a telescopicboom with a full extensionof 32 metres.

• At the time of the incident,the boom was extended toa length of about 24.7metres



C-channels

• The total weight of theC-channels and liftinggears were 3.15 tons

• Safe Working Load of

the crane @ 24.7mwas 2.85 tons

Overloading!




Conclusion…

Do your Risk AssessmentDo your Risk Assessment

But alsoBut alsoRecogniseRecognise the gaps within yourthe gaps within your

layers of protection.layers of protection.

Incident

RealityIdeal

Hazard

Documents

03 Accidents Case Studies on ProBE Area 2009.pdf