TOWER CRANE SAFETY GUIDELINES

Tower cranes and lifting operations

Tower cranes with fixed jib are commonly used in building sites. Accidents involving tower cranes as well as mobile cranes are not uncommon. Following the

introduction to amendment legislation and code of practice in recent years, coupled with considerable effort in education, training, publicity, and certification of workers, the number of fatal accidents has decreased sharply.

The causes of tower crane and mobile crane accidents are quite varied. Most tower crane accidents happened during the erection, climbing (up and down) and

dismantling. The term “climbing” with respect to tower cranes is the process

whereby an entire crane is raised on or within/outside a structure that is under

construction. It generally refers to changing the height (up or down) of fixed tower cranes. Climbing of tower crane is more accident-prone.

Mobile crane accidents are mainly due to overturning, failing of jib as a result of

unauthorized assembly or modification of the lattice not according to the

manufacturer’s specifications or misuse by crane personnel or operator, e.g. using the crane’s counterweight instead of a vibrator to pull sheet piles, thus causing the mobile crane to tip forward.

Another common cause is overloading due to unauthorized defeat or alteration of the automatic load sensing device. In March 1999, a newly commissioned heavy-duty truck-mounted hydraulic crane at a marine base suddenly overturned while in operation, leading to the death of a marine police officer.

Accidents can happen to mobile cranes engaged in large-scale foundation work as a result of the collision of jibs resulting in the cranes overturning.

Statutory requirements on the tower and mobile cranes are clearly laid.The purpose is to assist duty holders to comply with the provisions of the Construction Sites (Safety)

Regulations and the Factories and Industrial Undertakings (Lifting Appliances and

Lifting Gear) Regulations. These guides provide guidance on the safe application

and operation of mobile cranes and tower cranes to ensure the safety of employees working at or in close proximity to a moving crane.

Apart from the general requirement of a safe system of work which should cater for the safe lifting operation and the safety of non-operators, the Code also provides guidelines regarding the safe distance between the crane in operation and other non-operators in different situations.

The Code addresses in detail the following issues –

▪ Management of the lifting operation

▪ Planning of the lifting operation

▪ Responsibilities/requirements of personnel

▪ Selection of tower cranes

▪ Markings and documentation

▪ Operation features of tower cranes

▪ Siting of tower cranes

▪ Erection and dismantling

▪ Procedures and precautions

▪ Safe working loads and operating conditions

▪ Maintenance

▪ Inspection, examination, and testing

▪ Securing of loads before lifting

▪ Recommended hand signals

▪ Frequency of test, thorough examination, and inspection of tower cranes

under LALGR

Apart from statutory requirement and the Code, the industry has in recent years

successfully developed a number of good safety practices to enhance the safe use of tower cranes and lifting operations:

Adjustment and maintenance

For adjustment or maintenance to be performed safely, some improvements have

been devised (apart from the standard design by the manufacturer) on access

walkways, handholds, footholds, safety lines, or other safeguards as necessary to

eliminate the hazard of falling from a crane.

Safety devices and signaling aids.

The development and implementation of additional active systems which prevent

cranes from exceeding their safe performance envelope have contributed to

significant decreases in the number and severity of crane accidents by minimizing the opportunity for human errors. These safety devices include CCTV, anti-collision device (to prevent overlapping loads and collision of jibs of cranes), wind speed detection device, visual warning devices, audible signals and automatic stops, which operate in relation to rated loads, limit devices, and constant pressure control devices

Characteristic of the system:

▪ The system capacity is up to 20 cranes on a single site with 5 cranes

operating in the same working area works. It works with a pre-set working

zone for each tower crane

▪ Defines restricted zones e.g. above site office, bridges or roads

▪ Allows operation at maximum safe speed with smooth stoppage

▪ Computerized indicator in cabin can show approach of other cranes

▪ Radio communication can be wired or wireless.

General Safety hints for cranes and lifting operation:

▪ Plant and equipment in good condition

▪ Daily safety inspection procedures/checklists

▪ Fault reporting/rectification system in use

▪ Operators trained and licensed

Warning and instructions displayed

▪ Warning lights operational

▪ Reversing alarm operational

▪ Satisfactory operating practices

▪ Fire extinguisher

▪ Tyres in place working satisfactorily

▪ Safe Working Load of lifting or carrying equipment displayed

▪ Permit to work or lifting certificate for heavy and/or complicated operation

(practiced in West Rail Projects and projects with extensive heavy lifting or

civil works)

SAFETY MEASURES OF SHORING IN CONSTRUCTION SITES

Shoring

Shoring uses structures such as a metal hydraulic, mechanical or timber shoring

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system that supports the sides of an excavation. It is designed to prevent cave-ins.

In fact, sheet piles are also a form of shoring. After the excavations are completed, take special precautions to prevent injury from cave-ins in the area between the excavation wall and the foundation wall:

▪ Protect the depth of excavation against cave-ins.

▪ Keep the horizontal width of the excavation to make sure that work activity

would not vibrate the soil while workers are in the trench.

▪ Plan the foundation work to minimize the number of workers in the trench and

the length of time they spend there.

▪ Inspect the trench regularly for changes in the stability of the earth (water,

cracks, vibrations, spoils pile).

▪ Stop work if any potential for cave-in develops and fix the problem before

work starts again.

For safe trench excavation, adequate support must be installed ahead of excavation as far as is practicable.

“The contractor responsible for any construction site at which excavating or

Earth working operations are being carried on shall cause a structure made of suitable timber or other suitable material to be erected in connection with the operations as soon as may be necessary after their commencement so as to prevent workmen employed on the site from being endangered by a fall or displacement of earth, rock, or other material (including waste material and debris) adjacent to or forming the side of the excavation or earthwork.”

Specific design with details of shoring complete with drawings should be prepared for excavations with particular attention to:

▪ the depth of the excavation, and

▪ possible effects affecting roads, buildings, structures, slopes, services of

adjourning areas, from the base of the excavation to the ground surface, and should be carried out by a professionally qualified engineer who is competent

in carrying out a proper shoring design.

General precaution for safe excavations

▪ Shoring in place and in sound condition

▪ Excavation well secured

▪ Signage displayed

▪ Banks battered correctly and spoiled away from edge

▪ Clear and safe access to excavation

▪ Separate access and egress points from excavation

▪ Safe work procedure in place

Points to discuss at the initial planning meeting:

▪ Find the location of all underground utilities by contacting the local utility

companies to identify and locate the services before digging.

▪ Keep workers away from digging equipment and never allow workers in an

excavation when equipment is in use.

▪ Keep workers away from space between equipment in use and other

obstacles and machinery that can cause crushing hazards.

▪ Keep equipment and the excavated dirt (spoils pile) back 2 feet from the edge

of the excavation

▪ Have a competent person conduct daily inspections and correct any hazards

before workers enter a trench or excavation.

▪ Provide workers with a way to get into and out of a trench or excavation such

as ladders and ramps. They must be within a reasonable distance from the

workers.

▪ For deeper excavations and utility trenches, use shoring, shields (trench

boxes), benching, or slope back the sides. Refer to the result of soil analysis

to determine the earth’s safe slope angle.

▪ Keep water out of trenches with a pump or drainage system, and inspect the area for soil movement and potential cave-ins.

▪ Keep drivers in the cab and workers away from dump trucks when dirt and

other debris is being loaded into them.

▪ Don’t allow workers stay under any load and train them to stay clear of the

back of vehicles.

The statutory requirements on the use of excavators in construction work are clearly laid down in the ‘Code of Practice - Safe Use of Excavators’ issued by the

Commissioner for Labour.It covers details on the safe use and operation of

excavators for excavation and earth moving operations, including the safe use of bucket attachment. 

Access/egress

Proper planning of access and egress, including rescue in case of emergency, is very

important. Access to the surface should be by means of:

▪ ladders;

▪ stairways; or

▪ ramps.

In trenches, access ladders should be spread out at intervals and at locations workers

are working and near the trench.

Normal access routes used within an excavation should, whenever practicable, permit

workers to pass along without bumping into obstructions or being hit by debris.

Walking in an excavation should be made possible by secure footing without risk of

falling.

In situations where an excavation or trench is heavily timbered and where headroom

is limited, access to and from work should be along well-defined routes which can be

protected more readily and the use of other routes should not be permitted.

Separation of traffic Wherever practicable, the route used to bring out excavated material should be separated from that used by the workers. In a small shaft or drive where it is not possible to provide separate routes for the two kinds of traffic, the movement of workers should be forbidden while excavated material or plant is being

moved and vice versa.

In shafts shallow enough for workers on top to see and talk to the workers below, no difficulty should arise, but in shafts of intermediate depth, in which the

workers have to climb up and down the ladders, there is need for an effective signaling system and there may be a requirement for automatic locking of winding gear while workers are moving. Where mechanical haulage is used in small drives, manholes or refuges should be excavated into the side of the drive to provide shelter from passing

traffic. Such refuges should be of a reasonable size and appropriately spaced on the same side of the drive.

Secure footing

This is essential for safe access. Loose stones and large rock projections should be removed and in some cases it may be necessary to provide a timbered walkway to ensure safe walking. Accumulations of mud should be prevented and sloping walkways should be cleared or otherwise made slip-proof.

Adequate lighting

Where daylight is insufficient shafts, drives, trenches and open excavation should be provided with adequate lighting. Glare should be guarded against because contrasted with a deficiency of light, it increases considerably the risk of falls from slipping

or tripping.

Protection from falls

Where there is a risk of any person falling from an access way, a handrail, and sometimes an intermediate rail or a toe board, should be provided to enable persons to pass more easily and to prevent falls. At any landing, the ladder below should be

offset from the ladder above so that it is not possible for a person or articles to fall past the landing. Landing platforms should be fitted with guard rails and toe boards.

SAFETY MEASURES IN CONSTRUCTION FOUNDATION.

Foundation work often involves massive operations in earthwork such as excavation

or digging large holes in the ground, or where the face of the earth, rock, sand, soil or

other materials are removed.

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Typical examples are:

▪ a trench, ditch, shaft well, tunnel, pier hole, cutting, caisson or cofferdam

▪ a hole drilled into the earth

Cave-ins are the most feared hazard in earthworks like excavation and trench work.

But other potentially fatal hazards exist, including asphyxiation due to the lack of

oxygen in a confined space, inhalation of toxic fumes, drowning, etc. Electrocution or

explosions can occur when workers are in contact with exposed underground utilities.

Caisson

For many years, hand-dug caissons had gone through a disturbing history of high 

accident rate and health hazards. The Building Authority in 1995 banned the use of

hand-dug caissons mainly to minimize workers from:

▪ being struck by an object falling into the excavation

▪ being trapped by the collapse of an excavation (all depths)

▪ falling into the excavation

▪ asphyxiations, inhaling, or otherwise being exposed to, carbon monoxide or

other impurities in the air in the vicinity of the excavation

▪ drowning/burying when overcome by sudden in-flush of water

▪ other hazards including noise, silica dust, explosive or flammable gases, such

as methaneExemption may be granted only if an architect or structural engineer can demonstrate

to the satisfaction of the Building Authority that the following circumstances exist:

▪ the depth of the hand-dug caisson does not exceed 3 meters and the

diameter of the inscribed circle of the hand-dug caisson is not less than 1.5

meters; or

▪ for the site concerned:

􀃠 the use of a hand-dug caisson is the only practical construction method; or

􀃠 there is no other safe engineering alternative.

Examples of these are: narrow or steep sloping sites where difficult access or

insufficient working space makes it not possible or not safe to use machine tools.

In these exceptional circumstances, the authorized person/registered structural

the engineer must specify stringent safety requirements in the method statement for the

building works and ensure that the registered contractor is fully aware of and complies

with all safety requirements. In this respect, the provisions of the Construction Site

(Safety) Regulations administered by the Commissioner for Labour should be

observed.

In all caisson operations, including complex foundation work, a risk assessment

should always be conducted in the early planning stages.

Risk assessment 

▪ Assess the risks that may result because of the

hazards

▪ Decide on control measures to prevent or minimize

the level of the risks

▪ Implement the control measures

▪ Monitor and review the effectiveness of the control

measures 

Person being trapped by the collapse of an excavation (all depths)

▪ do as much work as possible from outside the

excavation

▪ backfill excavation as soon as possible

▪ batter, bench or shore sides of excavation

▪ place excavated materials, equipment and other materials at a distance from the edge of the

excavation so that the force exerted on the edge of the excavation does not lead to the collapse of the

excavation

▪ limit the approach of vehicles and plant by erecting a barrier, such as a wheel buffer

 Person being trapped by the collapse of a trench more than 1.5 m deep

▪ shore all sides of the trench; or

▪ bench all sides of the trench; or

▪ batter all sides of the trench; or

▪ obtain written approval from a geotechnical engineer that all sides of the trench are safe from

collapse; or

▪ use a combination of the above measures 

Person being struck by an object falling into the excavation

▪ do not lift or suspend loads over any person working in the excavation

▪ use excavators and cranes with controlled descent valves on the hydraulics fitted to the boom or

dipper arm to prevent the boom or load from falling onto the workers in the event of hydraulic hose

failure

▪ evict persons from the excavation when lifting and placing loads in the excavation

▪ use plant fitted with suitable overhead protection to protect against falling objects

▪ the erect barrier along the edge of the excavation to prevent objects falling into the excavation

▪ use wheel buffers 

Person falling into the excavation

▪ backfill excavation as soon as possible

▪ secure a cover over the excavation

▪ provide safe access to and from the excavation

Person inhaling, or otherwise being exposed to, carbon monoxide or another impurity

of the air in the excavation

▪ as part of the risk assessment process - determine the likelihood of airborne and soil contaminants

being present and the need to undertake formal air monitoring in the excavation

▪ implement control measures necessary for entering and working in a confined space

▪ do not expose persons to a hazardous substance at a level exceeding the international exposure

standard for that substance

▪ monitor the level of any airborne contaminant in the excavation

▪ monitor for explosive gases or vapours

▪ ensure there is adequate ventilation provided to the excavation

▪ use extractor fans to remove airborne contaminants and explosive gases from the

excavation

▪ position vehicles, plant and machinery away from the excavation

▪ provide and use appropriate personal protective equipment, such as respiratory equipment,

protective clothing, safety gloves

▪ remove all sources of ignition if explosive gases are present.

Sheet piling

Sheet piles are commonly used to support excavations in foundation work.

Traditionally, these operations are performed without proper planning especially

during the pre-work stage. Training and information provided to workers also vary in

standards. Sheet piling in the past had a poor record of high accidents, often

resulted in the fatality.

The cause of fatal accidents pertaining to sheet piling was due to one or a

combination of the following failures in ensuring:

▪ adequate depth for interlock of sheet piles or the correct penetration depth.

▪ deviations and leaning (transverse or longitudinal) of sheet piles within

tolerance limit.

It is common in the piling industry to use a cage to lift workers, also called “top man” or

“pile monkey”, onto the top of sheet piles to carry out the aligning or interlocking by

hand. This working process by alternative methods by some contractors can avoid

such hazards.

Depending on the nature of work and site conditions, two alternative methods have

been introduced by using:

▪ threaders and shackle release device

▪ sheet pile trestle

The crane is lifting the sheet pile, interlocking manually in an exposed dangerous position by

the top man.

Workers working at the top of the pile and on the horizontal guide beam

Workers staying on top frame the level can be hit or trapped in between

Threaders and shackle release device:

Proprietary systems used elsewhere have been imported to offer a safer alternative to

this particular process. Some contractors are also beginning to use local-made

models to cut cost. The basic principle of these proprietary systems is to use a

pile-threader and a shackle release device. All the necessary operating procedures

can be done on the ground.

The sheet pile threader is designed for safe and rapid sheet pile interlocking when

sheet piles are being pitched in panels. It replaces the “top man” or “pile monkey” who

normally carries out the interlocking by hand.

The basic method of operation using a universal pile treader is as follows:

The threader is pre-loaded by pulling the pull wires and vice block against spring

pressure and cocking.

The pile to be pitched is lifted until the bottom is at about 1m (3ft) above ground level.

The threader is then clamped onto the pile with the vice. The relative position of the

pile is governed by a stop plate to suit the pile section being used.

With the threader attached, the pile is then lifted by the crane to the end-pile of the

panel.

 By means of the rollers, the lower part of the threader is then clamped to the

last pile in the panel so that the interlocks are adjacent to each other. The clamping

operation is designed to permit free movement of the pile and the threader in a vertical

direction but prevents movement in any other direction. This attachment is normally

done at the top frame level. The cocking device inside the vice slide tubes is then

released.

The crane lifts the pile to be pitched until its bottom edge is above the previous pile in

the panel. The spring pressure on the vice block forces the pile across into the

interlocking position. As the pile is lowered, it interlocks.

 The threader is then unclamped at the top frame level.

Ground release shackle device

The use of these shackles complements the “feet on the ground” approach to piling.

When used in conjunction with the sheet pile threader, there is no need for site operatives

 to go above the safety of top frame level for interlocking sheet piles or releasing the 

lifting shackles

Ratchet release shackles

The ‘shackle release’ is used for lifting steel piles from ground level to some safe vertical

position at any height. It enables these steel elements to be subsequently disconnected safely

and efficiently from a remote location. For pitching steel sheet piles, a sheet pile threader is used

for automatic remote interlocking of adjacent sheets

Another method using a Universal Sheet Pile Threader:

This threader that comes in two pieces can be manhandled and readily operated by

typical site personnel. The unit can be adjusted to suit whatever pile section is being

used on the job site without the need for additional items. The standard threader

requires a different set of guide Rollers for each pile section. When threading single

piles, the threader will readily switch from threading on the left hand to the right hand,

thanks to its unique two-piece design. This means that only one unit is required on the

job site. The threader requires two units for fast threading of single sheet piles – one

set to the left and the other to the right

Universal Sheet Pile Threader

The unit is adjusted to suit the particular pile section being threaded

A different type of threader

Another method using a guide frame fixed with suitable platforms for workers at

intermediate levels

In the past, there had been accidents involving workers falling from the man-cage.

The man-cage had to be lifted up by cranes and attached onto the top of the sheet

piles. When the hooking device of the man-cage failed, the worker fell to the ground

together with the cage. Another case involved a crane. 

When lifting the loaded man-cage, the cage fell during the journey, resulting in the

fatal injury of workers. The safety walkway above provides a safe place of work for workers.

Accidents also occurred in the past when sheet piles are being extracted, which is

rather common locally, after the excavation work is over. Common errors are: buckling

of the jib of the crane or/and overturning of the crane. In fact, tipping of the crane is also a very common scene. This situation happens from time to time, causing repeated overloading of the crane and increasing the chance of overturning.

Advantages of employing a threader:

▪ The sheet pile threader replaces the dangerous, manual operation performed

by a top man climbing or being hoisted up to the top of the piles and

interlocking the piles.

▪ Interlocking piles with the pile threader is faster than any other safe method of

working.

▪ The sheet pile threader makes it possible for piling work to be done under

more severe weather conditions as interlocking can take place even under

high winds.

Safe sheet piling operation depends on good working conditions. The health and

safety arrangements should be periodically inspected and maintained:

Safe storage and handling of sheet piles, struts, king piles, bracing beams and walers.

▪ Proper handling and maintenance of piling hammer/extractor.

▪ Boring machines are in working condition if pre-boring is required.

▪ Lifting cranes are of sufficient capacity, and boom length and bearing capacity

check to ensure safety.

▪ Proper means of transport of excavated materials (No excavated materials

are to be placed near to the pit), as this will affect the well-planned sheet pile

wall operation.

▪ Pumps are in good working condition.

▪ All welding and cutting equipment are in good working order, with proper PPE

in use and the workers involved suitably trained.