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Presented by: Dr Goh Yang MiangPresented by: Dr Goh Yang Miang

Assistant Director, Investigations Branch, Assistant Director, Investigations Branch,

OSH Inspectorate,OSH Inspectorate,

OSHD, MOMOSHD, MOM

Accident Case Studies

on

Lifting Equipment

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Purpose and Scope of Presentation

• To share accident case studies so as to:

– highlight possible hazards and incident sequences;

– highlight reasonably practicable measures that could have been done to prevent the accidents

• These case studies are presented for learning

and educational purposes. The case studies

must not be used in any legal proceedings.

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3Not drawn to scale

Some common types of incidents during lifting operations

Lifting gear

Load

Lifting Machine

4Not drawn to scale

Lifting machine collapse/

overturn/ failure

Person struck by

falling object

Some common types of incidents during lifting operations

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5Not drawn to scale

Person struck by

falling object

Load fall

from height

Some common types of incidents during lifting operations

6Not drawn to scale

Person caught in-between

lifting machine and other

objects

Some common types of incidents during lifting operations

Or struck by lifting machine

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7Not drawn to scale

Person

struck by

object

Load struck

object

Some common types of incidents during lifting operations

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Situation – Lifting Operation

Load fall off

Common Incident Sequences

Lifting machine overturn

Person hit by lifting machine/ load (no

overturn)

Struck persons/ properties

Struck persons/ properties

Load struck

object

Object fall off

Struck persons/ properties

MajorMinor Moderate

Severity

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Case Studies

• Case Study 1 – Truck-mounted crane overturned

• Case Study 2 – Crawler crane overturned

• Case Study 3 – Load fall from height

• Case Study 4 – Person caught in-between

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6

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Fly jib = 16m at 5º to boom

Load = 1.2-1.3 ton

Initial boom angle = 60º

Crane collapsed when boom angle = 50º to 52º

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7

13

Right front outrigger

Right rear outrigger

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Breakdown Event(BE)

Conse-Quences

(CSQ)

Incident Sequence

Situation

Lifting of debris using

mobile cranePossible Direct Causes

Crane

overturn

Crane

struck

property

Why?

Accident AnalysisAccident Analysis

Overloaded

Ground failure

Wind

Sudden dynamic load

Boom structure failure

Lifting gear failure

Improper maneuvering

Load entangled

Hoist rope failure

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Actual load =

1.2-1.3 ton

Boom

Angle

60º

53º

Allowable load = 1.06 ton Allowable load = 0.55 ton

5º tilt16m jib

Initial angle

Just before collapse

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Rear quadrant usually has higher Factor of Safety for stability than side quadrants

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Breakdown Event(BE)

Conse-Quences

(CSQ)

Incident Sequence

Situation

Lifting of debris using

mobile crane Causation

Crane

overturn

Crane

struck

property

Accident AnalysisAccident Analysis

Overloaded

Why? Operator over-

relied on moment limiter

Operator continued operation even though overload alarm sounded

Moment

limiter not properly

calibrated (?)

Actual

condition deviated from

calibration condition, e.g.

out-of-level (?)

Moment limiter did not perform

as expected Unsafe habit not

identified and corrected

No system to identify and correct unsafe habit

No lifting plan/ dry rehearsal

Why?

Why?

Why?Why?

Why?

Why?

Why?Momentum too high –cut-off too late (?)

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Incident Sequence

Situation

Lifting of debris using

mobile crane

Crane

overturn

Crane

struck

property

Possible Risk ControlsPossible Risk Controls

Overloaded

Why?

• Require pre-lifting risk assessment and planning (run through key lifting parameters) • Conduct briefing, additional test or on-

the-job observations to ensure operator

is competent and has safe habits

• Conduct frequent check on crane

condition (incl. safety devices)

Employer/

Principal

Persons-

at-work

Supplier/

Manufacturer

Occupier

• Highlight limitations of safety devices to

users

• Assist users in basic maintenance of

crane

Please note that the risk control measures mentioned here are provided for the benefit of enhancing workplace safety and health. Stakeholders should review their own

workplace and determine what measures need to be taken.

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Vertical Main Boom = 33m

Luffing jib = 25m

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Deceased

was struck by

the boom here

Precast staircase that was lifted

Precast staircase =

6900kgHook Block = 250kg

Total Load = 7,150kg

Safe working load

based on load chart = 7,600kg

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3 Steel plates provided to ensure level and stable ground

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Crawler was

moved out of the steel plate

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Initial condition

Steel plates

Cabin

Boom Truss

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Before Accident

Steel plates

Cabin

Boom Truss

Fulcrum shifted

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Breakdown Event(BE)

Conse-Quences

(CSQ)

Incident Sequence

Situation

Lifting of staircase using

crawler crane Causation

Crane

overturn

Crane

struck

worker

Accident AnalysisAccident Analysis

Crawler moved

out of steel plate

Why?

Crane

struck

worker

Contact Event(CE)

Crane moved to gain better

view

Signaller not available (walking

to position)

Operator failed

to wait

Operator unaware

No alarm or demarcation to

alert operator

Reckless? Negligent?

No risk assessment &

lifting plan

Why?

Why? Why?

Why?

Why?

Why?

Why?

Work

pressure?

Why?

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Incident Sequence

Situation

Lifting of staircase using crawler crane

Possible Risk ControlsPossible Risk Controls

• Require pre-lifting risk assessment and planning• Ensure that crane are on stable grounds –

e.g. simple flag markers to highlight to operator

edge of steel plate

Employer/

Principal

Persons-

at-work

Supplier/

Manufacturer

Occupier

• Highlight common causes of

overturning to users

• Engineering Control - Develop

new devices to control risk of

overturning (ground condition

detector? Edge detector?)

Breakdown Event(BE)

Conse-Quences

(CSQ)

Crane

overturn

Crane

struck

worker

Crane

struck

worker

Contact Event(CE)

• Follow SWPs and highlight

hazards to employers

• Participate in identifying risk

controls

Please note that the risk control measures mentioned here are provided for the benefit of enhancing workplace safety and health. Stakeholders should

review their own workplace and determine what measures need to be taken.

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Scrap DB

(119kg)

Chain slings

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Gap widened

With safety latch

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Hook can come

out easily

Chain sling

becomes vertical

during lifting

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Breakdown Event(BE)

Conse-Quences

(CSQ)

Incident Sequence

Situation

Lifting of scrap DB using

lorry crane and chain

sling Causation

Object fall

from height

Object

struck

worker

Why?

Accident AnalysisAccident Analysis

Chain sling unhooked

Contact Event(CE)

Fatality +

commercial

losses

Gap of hook too wide (no

latch)

Lack of maintenance and

check by Authorised

Examiner (AE)

Decision to use defective

lifting gear

Lack of competency

Gap of hook facing the wrong side

Lack of training

Why?

Why?Why?

Why?

Why?

Why?

No maintenance regime

Lack of supervision

Why?

Why?

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Breakdown Event(BE)

Conse-Quences

(CSQ)

Incident Sequence

Situation

Lifting of scrap DB using

lorry crane and chain

sling Causation

Object fall

from height

Object

struck

worker

Why?

Accident AnalysisAccident Analysis

Worker too near to load

Contact Event(CE)

Fatality +

commercial

losses

Failure to clear

away during lifting

Lack of training

& supervisionWhy?

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Breakdown Event(BE)

Conse-Quences

(CSQ)

Incident Sequence

Situation

Lifting of scrap DB using

lorry crane and chain

sling

Object fall

from height

Object

struck

worker

Possible Risk ControlsPossible Risk Controls

Contact Event(CE)

Fatality +

commercial

losses

Employer/

Principal

Persons-

at-work

Occupier

• Provide training to workers that are expected

to be involved in lifting work (rigger, signaller

etc)

• Ensure that the training is effective and worker

practise what they are taught – on-going

supervision and briefing

• Practise according to SWP or

training

Supplier/

Manufacturer

• Recommend basic checks to

determine if lifting gear is

serviceable

• Ensure that all lifting gears are

individually identified and checked

by AE

Please note that the risk control measures mentioned here are provided for the benefit of enhancing workplace safety and health. Stakeholders should to review their own workplace and determine what measures need to be taken.

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Steel mould

Motor housing

Deceased

caught in-

between here

(gap of about

5mm)

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Emergency button

cover not present

�Investigation

revealed that

button still working

�Operator should

have clear view of

deceased

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Conse-Quences

(CSQ)

Incident Sequence

Situation

Operating gantry crane

in precast yardCausation

Worker

caught in-

between

motor and

mould

Why?

Accident AnalysisAccident Analysis

Worker working too near to motor and

mould

Contact Event(CE)

Fatality +

commercial

losses

Clearance between motor and mould too

small

No risk assessment

Operator failed to stop crane

Why?

Why?

Operator

reckless/ negligent

Poor risk perception

(?)

No measures to improve risk

perception

Why?

Why?

Why? Why?

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Incident Sequence

Situation

Operating gantry crane

in precast yard

Possible Risk ControlsPossible Risk Controls

Employer/

Principal

Persons-

at-work

Occupier

• Conduct risk assessment

• Erect barrier to ensure no one gets near to

motor

• Yellow line to demarcate stacking zone

• Inspection by supervisors

• Briefing and training on possible hazards

• Don’t take chances – Look, Think,

Do

Supplier/

Manufacturer

• Highlight inherent hazards of

crane components – recommend

clearance from motor housing

Conse-Quences

(CSQ)

Worker

caught in-

between

motor and

mould

Contact Event(CE)

Fatality +

commercial

lossesPlease note that the risk control measures mentioned here are provided for the benefit of enhancing workplace safety and health. Stakeholders should to

review their own workplace and determine what measures need to be taken.

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Common Issues with Lifting Equipment Accidents

• Altering of accident scene is an offence!!

• Poor planning– Inadequate knowledge of hazards – poor risk

assessment

– No lifting plan/ dry rehearsal

• Inadequate supervision of lifting works

• Competency/ habits of operators

– Over-reliance on overload alarm

– Unable to read load chart (load chart in foreign language)

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“Duty to take, so far as is reasonably

practicable, such measures as are necessary to

ensure workplace safety and health”

Occ

upiers

Emplo

yers

Self-e

mplo

yed

Man

ufact

urers

/

Suppliers

Perso

ns at

work

Princi

pals

Conclusion…

Workplace Safety and Health Act

All stakeholders should use risk management as the basic tool to help improve safety and health at workplaces.

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Thank You!Thank You!