Incident Investigations – Key Concepts
Case Study
Tower Crane Collapse
Incident Summary,
Root Cause Analysis, Lessons Learnt &
Corrective Actions
Incident Photo Storyboard
What happened
Location where workers
were fatally struck - they
were within 5 m of each
other
Standard mast
section
Jib
Waterproofing
blanket
Incident Photo Storyboard
(cont’d)
Crane top
A-frame
Operator’s cab
Jib
Standard mast
section
Balancing
arm
Climbing
frame
Connecting Pins
Cleat on swivel section
that connects with
climber using 40mm dia
pin
Eight high tensile Bolts connect mast to
swivel section. Bolts were removed to
swivel section
Nature of Incident: Two workers received
fatal injuries when hit by falling jib of
crane
WHO?
Male, Married, 3 Children, Age : 57
General labourer
Years of service: ~ 1 month
Time in current position: 20 days
Female, Divorced, 0 Children, Age : 30
General labourer
Years of Service: ~ 2.5 years
Time in current position: 11 days
Both deceased are employees of General Contractor
WHO? - Contractual Relationships
Client
Project Manager
Construction GC
Tower Crane Supplier
Crane Installation Company
(Install, Maintain, Operate, Dismantle Tower
Cranes #1,2,3,4)
Erection
Crew
What Happened
General Description of Incident – Preceding Events



Nov.

the Construction Manager, visits tower crane supplier to select the cranes to be used at
site.

4 tower cranes were specified (QTZ80 x 3; QTZ40 x 1) in the supply Contract between
GC and tower crane supplier.

The tower crane supplier appointed the crane installation company for installation,
operation, maintenance and dismantling of the 4 cranes.
Early Dec.

The Crane Installation crew (same crew that would install Tower crane #2) attended site
induction training as well as tower crane training and reviewed the safe work method
statement (SWMS) before installation of Tower Crane #3.

The first crane (Tower crane #3, a QTZ80) is installed and passes inspection by National
Inspection Center.

The other cranes were not installed because the site was not yet ready. One of the
cranes (QTZ80A) selected was leased to another client by tower crane supplier.
Mid Dec. (up to 17)

Tower crane #1 (QTZ80) & #4 (QTZ40) were installed by crew and passed by the
government inspection agency.

Tower crane #2 (QTZ63A or TC5510), (manufactured in December), was delivered to
the site with some components missing. Crane delivery was rejected.
What Happened
General Description of Incident – Preceding Events


Dec. 19

Missing components for crane #2 arrive - GC accept the crane, (which was not the one
ordered + copy of manufacturer’s test result report was for the ordered crane, not the
one actually received by the GC).

The manufacturer’s manual for TC5510 (the actual crane on site) was provided with the
crane.

GC apply for a Work Permit to use a mobile crane to install tower crane #2. PM approve
permit.
Dec. 20

The erection crew start to install tower crane #2 on site (same crew that installed the
other 3 cranes on site). An exclusion zone around the installation area is created.

The crane was erected to about 9 meters high (3 of the 10 standard mast sections)
other 7 sections placed on the ground 25 meters from base of the tower crane #2.

The installation was stopped by PM because it was getting dark. Pending tasks
included: jib installation; (2) Climbing frame connection to the swivel (note: the 4 pins
used to secure the climbing frame to the swivel were not put in place); (3) filling
hydraulic oil tank for climbing frame (2 drums of oil (90 liters) placed about 20 meters
from the base of the tower crane #2).

The crew and GC planned to install the jib in the early morning of December 22, 2006
as the government inspection had been scheduled for December 22, 2006.
What Happened
General Description of Incident – Preceding Events



Dec. 21

The installation of tower crane #2 continued without application for a new Permit
(even though the mobile crane was still required).

The jib was installed in the morning with the two other pending tasks still incomplete.

Tower crane #2 was inspected by National Inspection Center (SCMIC).
Dec. 22

PM safety leader states that a Permit to Work is needed daily for use tower cranes same form for approval of mobile crane use. This new requirement was
communicated between PM safety team and the GC safety team verbally.
Dec. 23

Pass Certificate and inspection report, issued by authorities – with 2 action items: (1)
the earthing for the crane was exposed; (2) the power panel for the crane was not
separated from the crane. Report noted that the climbing frame was not connected to
the swivel.

The report also stated that the bolts connecting the installed 3 standard mast sections
were tightened to specification, but it was found during the investigation that these
bolts were only hand-tight.

The crew leader only half filled the climbing frame hydraulic oil tank as he ran out of
oil.
What Happened
General Description of Incident – Preceding Events

Dec. 24
7:00 a.m.

The crew leader used tower crane #2 –to lift and move 5 rolls of water-proofing
material without a permit to use the tower crane.
8:00 a.m.

GC safety engineer initiated an application for a work permit for lifting of waterproofing material (not crane climbing) using tower crane #2.
9:00 a.m. – 9:30 a.m.



The form was returned back to GC without any rejection or approval comments on
the form. Verbal rejection was based on the earthing issues previously identified.
GC submits a copy of the Pass Certificate and Authority Inspection Report to PM.
Crane Erection crew leave site due to lack of work and return to dormitory
Throughout the day, brickwork was being performed on the footings of the
basement slab.
What Happened
General Description of Incident – Preceding Events
Dec. 24 (continued)
12:00 p.m.

The tower crane installation ltd supervisor/manager delivers 2 additional walkie-talkies
to site then visits the crane crew during lunch at their dormitory and tells the crew
leader to jack up tower crane #2 to a height of 17 meters (3 more standard mast
sections).
12:30 p.m.

The crew leader starts to prepare tower crane #2 for the jacking operation - attempts
to move the climbing frame up to connect the frame to the swivel, but fails because
there was an inadequate amount of hydraulic oil in the tank of the climbing frame. He
then lifted and moved 4 of the 7 standard mast sections on the ground closer to the
base of the crane and kept one standard mast section lifted hanging in the air when he
left the cab.
1:00 p.m.

The crew leader and flagman hand-lifted one drum of hydraulic oil to the work
platform which was attached to the climbing frame, and started to fill the hydraulic oil
tank.
1:30 p.m.

The crew leader instructs the crane operator to loosen the 8 bolts securing the top
mast section to the slewing ring support. The crew leader then finds that the hydraulic
oil tank was still under pressured to climb. The crew leader and operator #2 went over
to tower crane #4 and extracted about one drum of hydraulic oil from the tank of
crane #4
What Happened
General Description of Incident –
Preceding Events Dec. 24 (continued)
2:00 p.m.

Operator #1 loosens and removes the 8 bolts connecting the swivel and the mast, leaving
one mast section hanging in the air to keep balance.

PM’s entire site team started an accident investigation training class in site trailer.

Hydraulic oil tank of climbing frame of crane #2 filled – climbing frame operational.
3:00 p.m

The crew leader instructs tower crane Operator #1 to climb up to the operator’s cab to
move the hanging standard mast section onto the working platform.

Operator #1 pulled the hanging standard mast section towards the climbing frame
platform. The jib of the crane tilted upwards and the counter-jib tilted downwards. The jib
and crane top sections lost their balance and toppled from the mast..

Workers in the excavation area including the flagman (Op. #2) panicked and started to run
in different directions to avoid being hit. Female worker was struck on her head and male
worker was struck on his body by the tie-line of the jib.

Operator #1 stayed in cab by holding onto the window frame - received minor injuries to
his forearm.
What Happened
General Description of Incident – Incident Events
Dec. 24 (continued)
3:12 p.m.


Workers & site engineers heard the collapse and responded to the scene
of the injured. Some went to the site’s First Aid station.
Some engineers/workers phoned for an ambulance from the Public First
Aid Center.
3:15 p.m.

The site First Aid responder arrived at the scene of the injured. PM and
GC project teams were alerted and went to the scene.
3:20 p.m.

The first ambulance arrived. Wang BH was carried onto the ambulance by
the workers. He was still conscious. A call for a second ambulance was
made.
4:00 p.m.

Female worker was pronounced dead.
5:55 p.m.

Male worker was pronounced dead during surgery.
What Happened
Relevant Issues:







Both GC and PM were NOT informed of the climbing task before hand.
The Safe Work Method Statements (SWMS) for crane installation, operation,
maintenance and dismantling does not specify the process of jacking up a crane
The SWMS was not updated for installation of tower cranes #4, #1 or #2, nor
was it communicated to the crew before the installation of #4, #1 and #2.
No procedure specifically requires a work permit for crane jacking, although
there is a general requirement in the Task Hazard Analysis process.
The crew leader is certified for crane operating, signaling, installation and
dismantling. The 2 operators and 1 flagman are certified for crane operating and
signaling only, not installation or dismantling.
Operator #1 who is the nephew and trainee of the crew leader, is about 20 years
old with about 1.5 years experience of crane operation (amount of operating
hours unknown). This was his first time to operating crane type TC5510.
It was also found that he had been on duty for 15 hours operating tower crane
#3 on Dec. 25, 2006, one day before the incident. (rest time unknown)
What Happened
- Relevant Issues





Before removing the swivel bolts, Operator #1 states that he saw the 4
connection pins of the climbing section lying on the platform, but did not
verbalize this to the crew leader.
During interviews, the crew leader having seen the pins states that he did not
remember that swivel had not been connected to the climbing frame.
Operator #1 stated that he understood the direction from the crew leader for
“loosen” as “loosen and remove” the bolts.
Crew Supervisor did not remember that the swivel was NOT connected to the
climbing frame (4 pins not placed in), and the 8 bolts connecting the swivel to
the installed mast were all removed. No checks were made on this safety critical
issue.
No exclusion zone around the crane is created, however, flagman states that he
attempted to direct 4 workers who were doing soil backfilling to leave the area.
Two of them left and the other 2 refused to go. (Unable to verify if the request
was made and if the workers that remained in the area were those fatally
injured.)
Root Cause Analysis Exercise
In Small Groups (each table)…..
 Analyse the evidence in the case study
 Identify the critical factors and their immediate causes
 Using the ‘5 whys’ approach identify the causes of each
critical factor
 Identify the term from the underlying factors
terminology which best describes the key underlying
cause(s) of each critical factor (if time allows - produce
a summary diagram of the key underlying factors from
the ‘5 whys’ analysis identifying the root causes).
 Identify the key corrective actions and Lessons Learnt
Investigation Findings
Root Causes Analysis
Incident Summary








Four tower cranes mobilized on a construction project site
Tower crane #2 (last crane to mobilize) collapses
Crane climbing operation commenced without following
proper procedures
PM site project operations team unaware of work activity
No exclusion zone established during jacking operation workers associated with basement construction activities
are working near tower crane #2
Crane manufacturers’ erection procedures not followed
Unsecured tower crane jib becomes unbalanced and topples
over
Two workers involved in basement construction are fatally
injured when struck by the falling crane jib
Root Causes Analysis – Summary of Critical Factors &
Underlying Causes for Crane Jib Collapse Incident
Crew Leader
Instructs Driver To
Remove Head Bolts
Crew Leader Forgot
Pins Missing
Inexperienced Driver
Saw Pins Missingbut said nothing
No Checking
Procedure before
removing bolts etc
Competence
PF1
Crew
Supervision
JF3
Perception of
Risk
PF8
Culture: Face
- Crew Leader
= Uncle
Operation not observed
PM staff in training - GF
on leave
Work conducted
without PM permit or
notification to GC &
no exclusion zone
Poor SWMS did not deal with
climbing process
Crane operation
subcontractor – no
formal H&S system
GC Did Not
Pick Up Issue
GC did not conduct
H&S pre-qual nor
follow H&S reqs
PM Review
Did Not Pick
Up Issue
PM Permit system
lacks clarity - only for
crane operation but not
for erection/jacking JF1
Critical
Factors
PM did not check that
GC did the pre-qual
nor approve GCs sub
Inadequate THA RA
SWMS, Task
Planning, process
JF1 JF2
Communication and
Change
Management
Org F6 and F8
Contractor
Management
Org F1
PM Safety
Management
System Org F7
Resources to
implement safety
standards
Org F11
Immediate and Root Causes
Immediate Causes
Root Causes Factors Identified
1.
2.
3.
4.
Securing pins to attach
climbing frame to slewing
ring support not installed
High tensile bolts
removed from slewing
ring
Mast section trolleyed in
moving jib out of balance
causing crane to topple
over
No exclusion zone
established allowing
workers to be hit by falling
jib
Personal
Factors
Job / Process/
Procedure
Factors
Organizational
Factors
Low level of crane
operator
competence
Non-compliance with
aspects of Safety
Management System
Poor Contractor
Management
PM Resources
Poor supervision of
crane crew activities
RA, SWMS, THA, permit
process was not
adequately implemented
Lack process for control of
crane erection, climbing &
dismantling
Lack of
Communication &
Work supervision
Corrective Action
Corrective and preventative action plans
developed to address:



Project re-start
Root cause and other causes of the accident
EHS program implementation follow-up
Preventative Action
1) Operator Competence


FINDING: Inadequate experience and level of training of crane operators. Cannot
assume that crane operators with a license certified by the government are competent.
ACTIONS:
 Introduce screening of operator’s experience during induction
 Introduce crane operator testing
 Introduce minimum experience requirements for personnel involved in high risk
tasks (5 yrs for crane operators)
2) Supervision


FINDING: Inadequate supervision of crane crew operations
ACTIONS:
 Replace crane crew subcontractor
 Test competence of supervisor
 Brief supervisor on PM requirements inc weekly safety meetings and following PtW
 Implement supervisor skills workshop for GC and Subcontractor Supervisors and
additional safety induction for crew leaders
Preventative Action
3) Non-Compliance with risk safety management system

FINDING: Risk Assessment, Safe Work Method Statement, Task Hazard Analysis and Permit

ACTIONS:
to Work procedures were not completely implemented








PM to review risk assessment for missing high risk operations
Implement a look-ahead process for HROs - update project risk assessment monthly
Implement a process in addition to SWMS for all high risk operations
Add rigor in identifying risks, preparing and reviewing of SWMS - critically review all
current SWMS for level of detail and robustness
PM to conduct regional peer review of current and future SWMS prior to approval
PM to employ a crane specialist (other high risk specialists as needed)
New permit process specific for crane erection, climbing, & dimsantling
Train PM, GC, and Subcontractors on high risk operation requirements, and permit-towork process and requirements
Preventative Action
4) Poor Contractor Management
Subcontractor Pre-qualification – Process established but not followed


FINDINGS: GC did not use their described process and PM did not do verification checks
ACTIONS:







PM to maintain master list of all approved contractors cleared to enter the site
PM to prepare list of subs that will perform high risk work activities
PM to pre-qualify sub-tier contractors for all contractors involved in high risk
operations
PM to verify Contractor pre-qualification by GC
PM to spot-check subcontractor pre-qualifications for non-high-risk contractors
PM to review recommendations of Subcontractors
Retrain entire PM team in project pre-qualification requirements
Preventative Action
4) Lack of Contractor Management cont.
FINDING: Contractor & Subcontractor Oversight needs enhancement

ACTIONS:
 Restructure PM & GC Project Teams
 All PM staff & contractor supervisors are to be re-inducted about revised procedures
 Crew and supervisor sign-off on Safe Work Method Statements (SWMS) and Task Hazard
Analysis (THA)
 Improve PM auditing & review of site safety management systems
 PM to always have site personnel in the field overseeing contractors working
 PM to create minimum EHS standards for all Subcontractor safety personnel
 All project safety personnel reviewed and approved by PM onsite safety leader and PM
regional safety manager
5) Resources


FINDING: Resources inadequate to ensure contractor control and full operation of SMS
ACTIONS:
 Ensure that proposed and accepted resources are in place
 Add EHS Program Manager & change Site Safety Manager
 Ensure back-up resources are in place for team member vacations
Preventative Action
6) Communication & Change Management


FINDING: There is a lack of communication between PM and Contractors
ACTIONS: PM to be involved in GC-Subcontractor interface








Hold daily schedule coordination meetings (PM, GC, & Subs) – include EHS
Worker safety briefing at the commencement of each shift
Weekly safety meetings for PM
Weekly safety meeting with PM, GC & subs in attendance
Weekly Coordination team meeting (PM, GC, Subs)
Conduct a look ahead of high risk operations and communicate the information among site
team – monthly (PM, GC, Subs)
Establish work permit board at the site office to note all work permits issued (Permits issued
to whom, for what operations and the location of the work)
Establish monthly Safety Leadership Team calls (Senior leadership GE, PM, GC & Subs)
Lessons Learnt –
PM Global EHS Actions
1.
2.
3.
4.
Issued Global Crane Safety Alert to introduce new policy and
procedures, including permit system for controlling crane erection,
climbing & dismantling operations;
Use incident investigation analysis as a case study in H&S
management systems and root cause analysis training workshops.
Three planned in next two months to train around 50 staff.
Improve process of contactor pre-qualification, selection and
management (including communications and change
management).
Consider more carefully resource issues and client demands before
taking on projects
Accident Investigation –
Key Concepts
Review of issues covered
 Accident - Meanings & Paradigms
 Accident causation theories
 What is an investigation and why do it?
 Interviewing witnesses
 Analytical Methods
 Case study