Elevating Work Platform Safety in the Workplace
Elevating work platforms (EWP) are hydraulically, electrically, or mechanically controlled devices used to elevate workers or materials. These include scissor lifts, articulated boom lifts, individual personnel lifts, self-propelled lifts, manual “push-around” lifts, elevating rolling work platforms, self-propelled elevating work platforms, boom-type elevating work platforms, vehicle-mounted aerial devices, and aerial work platforms.
There are two basic types of elevating work platforms – boom and scissor. Both types share three major components: base, lifting mechanism, and platform assembly. Both types come in:
• On-Slab Models for use on smooth hard surfaces such as concrete or pavement
• Rough-Terrain Models for use on firm, level surfaces such as graded and compacted soil or gravel.
These are raised and lowered by hydraulic pistons and an expanding scissor mechanism. Platforms are available in various configurations with different capabilities for extension and movement. Some have extendable platforms or platforms that can rotate. Extendable platforms should be retracted before raising or lowering the device. Scissor-type machines range in capacity from 500 to several thousand pounds. They are available with platform heights often reaching 15 metres (50 feet) and beyond. Scissor-type machines must be set up on stable level ground, even with outriggers deployed. A slight imbalance or instability is amplified when the machine is raised.
• Not designed for uneven or sloping ground
• Normally have solid rubber tires
• Generally powered by rechargeable dc battery
• Some powered by internal combustion engine, either gasoline or propane
• Most have “pothole protection”—a metal plate lowered close to the ground
• Similar in design to on-slab machines, built to handle rigorous off-slab challenges
• Normally have wider wheelbases, larger wheels, and pneumatic tires
• Some fitted with outriggers for extra stability
• Usually powered by internal combustion engines, gasoline, diesel, propane, or DC
• Lifting mechanism is hydraulic.
Self-Propelled Boom-Supported Platforms
• Normally fitted with rough-terrain undercarriages
• Some smaller on-slab units
• Platforms have lifting capacity of about 227 kg (500 pounds) or two workers
• Lack capacity of scissor-type machines; not intended for lifting materials
• Usually powered by an internal combustion engine, gasoline, diesel, or propane.
• Telescopic, articulating, or combination of both
• Raised and extended by hydraulic cylinders
• Can reach up to 45 metres (150 feet)
• Can extend well beyond the wheelbase.
Non-Self-Propelled or Push-Arounds
As the name indicates, these units are not self-propelled and must be transported from one location to another with an independent power source or manually in the case of the smaller devices. The machines are intended primarily for use on smooth, level, hard surfaces, or on-slab conditions. Some trailer-mounted units are available. Many of these devices can fold up to pass through a standard door and can be transported by pick-up truck. As a result, they are suitable for maintenance or renovation work.
• Raising mechanism powered by gas or propane engine or by electric motors, AC or DC
• Normally raised and lowered by hydraulic cylinders
• Platform capacities vary from 300 to 1000 pounds or more but are generally less than 500 pounds
• As platform is raised, risk of overturning increases
• Extra care required when operating at maximum height
Elevating work platforms are designed for different uses. It is essential to select the right machine for the job. Typical mistakes include:
• Using an on-slab machine on rough terrain
• Using a unit undersized with respect to height, reach, and lifting capacity
• Extending the platform with planks, ladders, or other devices because the machine can’t reach the required height
• Failing to assess the job needs before starting and using the wrong machine or not ordering the right machine to do the job
Factors to Consider
• Capacity – Does the machine have the lifting capacity, the reach, and the height to complete the task?
• Surface conditions – Are the surface conditions hard or soft, sloped or level? Will the ground influence the type of machine selected?
• Platform size and configuration – Do you need a regular or extendable platform? Is rotation required? Are there space restrictions to consider?
• Mobility – Is a boom type better suited than a scissor lift to the task at hand?
• Material to be lifted – Will the machine be able to lift the size and weight of material required for the job?
• Access – Will the machine be able to travel around the workplace safely? Are there obstructions or depressions that will restrict the use of certain machines?
• Operator skill or training – Are the people on site competent to operate the machine? If a propane-powered engine is used, has the operator received propane training?
• Work environment – If the work is to be done indoors or in a poorly ventilated area, will an electrically powered machine be required?
Machine Tipping or Overturning
Many factors cause instability—sudden stops, depressions, drop-offs, overreaching, overloading, etc. Overturning and tipping result in many fatalities and injuries.
Overriding Safety Features
Disarming features such as the tilt or level warning and the Deadman switch can prevent operators from knowing when they are in a dangerous situation. Overriding the dead man switch and malfunction of the tilt warning has resulted in a fatality.
Working near overhead wires can result in electrocution. This can happen when using any type of machine.
When the machine can’t reach the working height desired, don’t compensate by using scaffold planks, ladders, blocks of wood, or other makeshift arrangements. Such practices lead to falls and machine instability.
Overloading the Platform
EWPs overloaded or loaded unevenly can become unstable and fail. Boom-type machines are especially sensitive to overloading. Always stay within the operating range specified by the manufacturer.
Failure to Cordon Off
EWPs have been struck by other construction equipment or oncoming traffic when the work area is not properly marked or cordoned off. Workers can be injured if they inadvertently enter an unmarked area and are struck by falling material, tools, or debris. In unmarked areas, workers can be injured by swinging booms and pinched by scissor mechanisms.
Moving the machine or platform may cause contact with workers or with obstacles. Use a designated signaler on the ground to guide the operator when the path of travel isn’t clear, or access is tight.
Improper Maintenance or Modifications
EWPs should be maintained by competent workers in accordance with manufacturer’s instructions. No modifications should be made to the machine without the manufacturer’s approval.
Improper Blocking During Maintenance
Failing to block, or improperly blocking the machine, boom, or platform can cause serious crushing injuries and property damage.
Don’t access the platform by climbing the scissors or the boom. Don’t use extension ladders to gain access. Ladders exert lateral loads on the platform that can cause overturning. For the safest access, lower the machine completely.
Moving with Platform Raised
Lower the platform before moving the machine unless the machine is designed to move with platform raised and the supporting surface is smooth and level. Slight dips and drops are amplified when the platform is raised and can cause the machine to overturn.
Workers must be competent to exchange propane cylinders or handle liquid fuels or batteries. Cautions are also required to prevent spills and sparks.
Clothing, fingers, and hands can get caught in scissor mechanisms. As platforms are raised, machines may sway. Workers can be pinched between guardrails and the structure. Position the platform so that work takes place above guardrail height.
Regulations and Responsibilities
The construction regulation (Ontario Regulation 213/91) includes the following requirements:
• Elevating work platforms must be engineered and tested to meet the relevant standard for that equipment [section 144(1)(a)]. Standards include:
o CSA B354.1: non-self-propelled elevating work platforms
o CSA B354.2: self-propelled elevating work platforms
o CSA B354.4: boom-type elevating work platforms.
• The devices must be checked each day before use by a trained worker [section 144(3)(b)].
• The owner or supplier must keep a log of all inspections, tests, repairs, modifications, and maintenance [section 145(2)].
• The log must be kept up to date and include names and signatures of persons who performed inspections and other work [section 145(3)].
• A maintenance and inspection tag must be attached near the operator’s station and include the date of the last maintenance and inspection and the name and signature of the person who performed the work [section 146].
• Workers must be given oral and written instruction before using the platform for the first time. Instruction must include items to be checked daily before use [section 147].
• All workers on the platform must wear a full-body harness or a safety belt attached to the platform while the platform is being moved [section 148(e)].
The health and safety responsibilities of all parties on a construction site are outlined in the “Green Book”—the Occupational Health and Safety Act and Regulations for Construction Projects. Because elevating work platforms are often rented from an equipment supplier, there is confusion as to the responsibilities of the parties involved.
The owner or supplier must ensure that the machine:
• Is in good condition
• Complies with regulations
• Is maintained in good condition
• Conforms to the appropriate CSA standard
• Includes the correct load rating charts if required.
The employer and supervisor on the project must:
• Ensure that the operator is competent
• Ensure that the machine has the correct load rating capacity for the job
• Maintain the equipment and all its protective devices
• Maintain a logbook for each platform
• Ensure that workers use appropriate personal protective equipment
• Keep the manufacturer’s operating manual on site
• Train workers on each class of equipment being used.
The worker or operator of the equipment must:
• Receive adequate training to be fully competent
• Only operate the machine when competent
• Operate the machine in a safe manner and as prescribed by the manufacturer and the company’s health and safety policy
• Inspect the equipment daily before use
• Perform function tests before use
• Report any defects to the supervisor
• Read, understand, and obey the manufacturers safety rules, including the operating manual and warning decals.
When a defect is reported to the supervisor, the equipment must be taken out of service until the repairs are completed and the equipment is inspected and approved for use.
Stability and Tipping
In general, EWPs are well manufactured and are safe to use within their specific limitations. As with any equipment or tool, there are dos and don’ts to follow. One of the most dangerous hazards in operating EWPs is tipping over. This can be caused by one or several of the following factors:
• Sudden movement of the unit or parts of the unit when elevated
• Sudden stopping when elevated
• Overloading or uneven loading of the platform
• Travelling or operating on a slope or uneven terrain
• Changing the weight distribution of the machine by adding attachments not approved by the Manufacturer
• Holes or drop-offs in the floor surface causing one wheel to drop suddenly
• Operating the equipment in windy conditions.
It is important that users understand what makes a platform stable and what causes it to overturn. To understand stability, one must understand the concept of centre of gravity, tipping axis (or tipping point), and forces that shift the centre of gravity. Stability is resistance against tipping over. Stability depends on the location of the centre of gravity in relation to the tipping axis.
Centre of Gravity
Every object has a centre of gravity. It is the point where the objects weight would be evenly distributed or balanced. If a support is placed under that point, the object would be perfectly balanced. The centre of gravity is usually located where the mass is mostly concentrated. However, the location doesn’t always remain the same. Any action that changes the machines configuration—such as raising the platform, extending the boom, or travelling on a slope—can change the location of the centre of gravity.
Tipping Axis and Area of Stability
When an EWP turns over, it tips around an axis or point. This is called the tipping axis or tipping point. EWPs typically have four tipping axes – front, back, left, and right. Each EWP has its own area of stability. This varies from platform to platform and from model to model. In most cases, the area of stability is bound by the four tipping axes (or the four tires or outriggers). The platform is stable if the centre of gravity remains inside the area of stability. This is the key to safe operation.
The centre of gravity moves towards the platform but remains inside the area of stability. When the centre of gravity shifts beyond the area of stability, the machine will tip over. Some factors that can cause a shift beyond the stability area are overloading, moving on excessively sloped ground, a sudden drop of one wheel, and shock loading. Raising the platform also raises the EWPʼs centre of gravity. When a scissor lift is situated on a slope, and the platform is raised, the platforms centre of gravity will move toward the tipping axis. If the centre of gravity moves beyond the tipping axis, the platform will overturn.
Boom-supported EWPs work in the same way. When the boom is extended outward, the centre of gravity moves outwards towards the tipping axis. The EWP will overturn if the boom is extended such that the centre of gravity moves beyond the axis. Boom-type machines have an interlocking system that prevents the machine from moving into an unstable configuration.
Factors Affecting Stability
Dynamic Forces – Dynamic forces are forces generated by movement or change of movement. For example, applying the brakes suddenly or travelling too fast around corners can cause instability – as in a car or van. Sudden stops while raising or lowering the platform can also cause instability.
Travelling – Travelling the platform over rough or uneven ground can also cause instability. A tire dropping 100 mm can cause the boom to sway 600 mm. It is important to lower the platform fully or to retract telescoping sections while travelling, particularly on uneven surfaces.
Work Area Inspection
Before operating the EWP, check the work area for:
• Drop-offs or holes in the ground
• Bumps or floor obstructions
• Overhead obstructions
• Overhead wires, powerlines, or other electrical conductors
• Hazardous atmospheres
• Adequate operating surface—ground or floor
• Sufficient ground or floor support to withstand all forces imposed by the platform in every operating configuration
• Wind and weather conditions.
Personal Protective Equipment
• CSA Approved Hard Hat
• CSA Approved Grade 1 Safety Boots
• Reflective Apparel (Vest)
• Fall Protection Equipment (Safety Harness, Lanyard, Lifeline)
• Operators must be familiar with the manufacturers operating manual, the manufacturers warning and caution signs on the machine, the location of all emergency controls and emergency procedures and daily maintenance checks to perform.
• Always check for overhead powerlines before moving the machine or operating the platform. You must observe the minimum permitted distances from overhead powerlines and when the equipment operates within reach procedures must be developed and the utility de-energized by the owner.
• Allow for movement or sway of the lines as well as the platform. Be aware of overhanging tools or equipment.
• Wear a full-body harness and tie off to a designated tie-off point while the machine is moving.
• Do not leave the machine unattended without locking it or otherwise preventing unauthorized use.
• Don’t load the platform above its rated working load (RWL).
• Make sure that all controls are clearly labeled with action and direction.
• Keep guardrails in good condition and ensure that the gate is securely closed before moving the platform.
• Shut off power and insert the required blocking before maintenance or servicing.
• Deploy stabilizers or outriggers according to the manufacturer’s instructions.
• Don’t remove guardrails while the platform is raised.
• Position the boom in the direction of travel unless the manufacturer specifies differently.
• Keep ground personnel away from the machine and out from under the platform.
• Don’t access the platform by walking on the boom.
• Don’t try to push or move the machine by telescoping the boom.
• Do not use the machine as a ground for welding.
• Don’t use a boom-supported platform as a crane.
• Don’t operate the equipment in windy conditions. For safe wind speeds refer to the operator’s manual for the specific make and model you are using.
• Do not place the boom or platform against any structure to steady either the platform or the structure.
• Secure loads and tools on the platform so that machine movement won’t dislodge them.
• Make sure that extension cords are long enough for the full platform height and won’t get pinched or severed by the scissor mechanism.
• Use three-point contact and proper climbing techniques when mounting or dismounting from the machine.
• Never operate equipment on which you have not been trained or which you are not comfortable operating.