With head protection taking centre stage, Graeme Lawrie looks at accident prevention systems for working in proximity to overhead powerlines, lifting over pressurised plant, hands free lifting, lifting of people, ground conditions, weather, and tandem lifting.
Probably the most important aspects of PPE in lifting and hoisting operations are head protection and foot protection. There are highly significant hazards associated with head injury, first and foremost the risk from dropped objects during lifting and hoisting operations. This can be from items falling off the load, not just the load falling in its entirety.
A properly fitting protective helmet is essential when working with lifting and hoisting equipment. Head protection also protects operators from the risk of contact with a moving load. Of course, no person should ever be underneath a slung/ moving load, but the interface with pick up and lay down can bring operators into closer proximity with loads, and this is where the protective equipment can be key – both when it comes to head protection and foot protection.
“for lifting and hoisting a helmet with lateral deformation properties is good as there is a significant risk to operators from a moving or swinging load”
The selection of protective head gear is important. Protective head gear must comply with an internationally recognised standard; examples would be as follows:
- Within the European Union – EN 397
- In the United States of America – ANSI/ISEA Z89.1-2014
Protective headwear is manufactured for specific environments such as extreme heat and extreme cold, and for specific tasks, e.g. lateral deformation and electrical insulation. It is therefore very important to review your specific requirements through your detailed risk assessment and discuss the opportunities with the manufacturing/ supplying companies. Specifically, for lifting and hoisting, a helmet with lateral deformation properties is good as there is a significant risk to operators from being ‘swiped’ on the side of the head from a moving or swinging load.
As operators are also required to look up on a regular basis to monitor the load, a helmet with a smaller brim will aid visibility without forcing the operator to keep adjusting the helmet for vision.
You raise me up
Lifting of personnel in a suspended basket or elevated forklift basket should be avoided in preference of dedicated lifting devices such as Mobile Elevated Work Platforms, cherry pickers and scissors lifts. Where personnel lifts associated with lifting appliances are unavoidable, these lifts must be managed through detailed planning and rigorous physical and administrative controls, including: regular inspection requirements, risk assessment and written authorisation by the person in control of the location.
Personnel transfer by lifting
This type of lifting operation is usually associated with ‘basket transfer’, which can be from vessel to vessel, vessel to rig/ platform, and vice versa. Basket transfer is performed with some form of proprietary basket, e.g. Billy Pugh. Historically, basket transfer has been shunned as it is considered high hazard; however, a recent increase in the number of helicopter crashes and significant improvement in both lifting devices and equipment have seen some operators move back to basket transfer as an acceptable option.
The key safety components of personnel transfer are:
- Operations are performed according to a specific personnel lift plan
- Lifted personnel are adequately secured in the device
Cranes are fitted with additional protective devices to protect against catastrophic failure and free fall, and routine/planned personnel transfer by lifting should not be performed in hours of darkness.
Lifting over live plant
Live plant is defined as equipment containing a hazardous, pressurised, energised or strategic resource. Lifting over or in close proximity to live plant is defined as any lifting operation where there is a process safety risk of the load, lifting appliances and/or lifting accessories impacting, damaging and/or rupturing live plant. This includes positioning the crane jib without a load attached. It may also include the planning and preparation phase when perhaps a piling rig may be required to construct a solid base to install the crane on to perform the operation. The introduction of the piling rig is often overlooked in this context and there have been examples where the piling rig has overturned and damaged the live plant.
Lifting over or in close proximity to live plant should be avoided if at all possible, but it is recognised that it is not always feasible to shut down a large plant to undertake one small lift. A detailed risk assessment must always be conducted. There are numerous mitigation measures that can be implemented to minimise the risk of damage to the plant. A protective platform can be constructed over the plant to minimise the risk of falling equipment or a dropped load coming into contact with the plant. There is an inflatable cushion device (often referred to as ‘bouncy castle’ because of its similarity to the children’s play version) which can also be used in the same capacity. Of course, the key considerations here are the mass and shape of the object. A heavy sharp object might easily penetrate the inflatable cushion and a very heavy dense load could break through the scaffolding platform, so risk assessment and engineering calculations must be applied to ensure risk is reduced to ALARP. A further safety consideration is to reduce the height of the load above the plant to as low as practicable, this way if the load should drop it will not gather momentum and further reduce the risk of damaging the plant underneath, again the mass, shape and material of the load will determine how feasible this mechanism might be.
“lifting of personnel in a suspended basket should be avoided in preference to dedicated lifting devicesl”
An operational contingency plan is developed for the lift, this defines the potential worst-case consequences in the event of a dropped object or catastrophic failure of the lifting equipment, documenting the mitigation measures to be taken prior to the lift and the emergency response actions required. The exclusion zone used during the lift is extended to match the requirements of the operational contingency plan.
Lifts involving two or more cranes (incl. top and tail, load transfer, multiple hooks) are complex operations requiring considerable planning. A lifting engineering expert must be engaged in the process of developing a detailed lift plan.
Hands free lifting
Lifting and hoisting contractors and operators have been focussing on methods to prevent the need for personnel to touch loads. This is typically a problem when a load is first picked up; personnel are often required to control a load to stop it swinging and damaging other plant or indeed itself. Then the reverse occurs when the load is being landed, particularly into a confined space location. Many loads have such large mass that it is not safe or practicable for a person to use their hands to try and stop the load swinging and many personnel have been injured and even some fatally injured in trying to do this. So, industry has been focussing on removing the people from the process through the use of ‘hands free lifting’. Two identified techniques that have been developed to assist in this programme: push/pull sticks and tag lines.
In order to avoid direct contact of workers with the lifted load while executing lifting operations, push pull sticks can be used to guide the load – creating a buffer zone of safety – and retrieve slings. The stick allows operators to manoeuvre loads in multiple directions to properly position them, without needing to put their hands onto the load. The stick also allows them to snag slings and shackles.
Tag lines are only used in normal operating conditions to adjust the position of a load that is stable and under full control of the crane or powered equipment operator. Again, they can be used to guide stable loads into position. Tag lines can introduce risk and are only to be used after risk assessment.
Consider the following before executing the lift:
- Personnel being struck by a dropped object when retrieving a tag line that is in close proximity to the load
- Tag line becoming tangled around the body, limb and/or hand of personnel
- Tag line becoming snagged on an adjacent fixed structure
- Length of tag line
- How tag lines will be recovered without going under suspended load
- The proximity of personnel to the load
A principal cause of lifting equipment overturning is a lack of ground bearing strength under the mobile crane. Ground surfaces can be highly deceptive; they may look solid, but there may be many underlying issues that are not immediately apparent, including:
- Setting up lifting equipment on ‘brownfield’ sites, the ground may have been disturbed, dug up and re-laid, but as a result it no longer has the ground bearing strength of the original compacted land
- Identification of underground services
- Identification of underground voids
- Effects of environmental / weather conditions such as ice, permafrost, rain, and lightning
- Proximity to excavations
It is very important to understand the ‘make up’ of the ground that you wish to position the crane on. For some heavy loads you may need to undertake piling operations to strengthen the ground to the required level. It would require a technical expert to make these calculations and assessments. For all operations involving mobile cranes, the outriggers should always be fully deployed and wooden boards placed under the outrigger pads to minimise ‘point loading’.
The effect of wind
Strong winds may swing suspended loads (panels, formworks/shutters etc) out of balance and radius, making the mobile crane unstable. If the operator feels that he cannot maintain full control of the load, it should not be lifted. The operator has the primary responsibility for making the decision, in conjunction with the person in charge of the location. The operator’s decision to take the crane out of service should not be overridden by site management under any circumstances.
During the planning of any lift it is important to determine if any part of the equipment, load line or load (including rigging and lifting accessories) could get close to a power line. It is vitally important to understand the reference here of ‘close to’ the overhead power line. Lifting equipment does not need to come into contact with the overhead lines for the current to flow. The current can arc (travel through the air) for a certain distance that is a direct relation to the voltage. The higher the voltage the greater the arcing distance. The first and preferred option is always to request the local utility owner to de-energise and ground the line, but the options are:
Option 1: De-energise and ground. Confirm from the utility owner/operator that the power line has been de-energised and visibly grounded at the worksite.
Option 2: Ensure sufficient clearance in consultation with the utility owner/ operator and in compliance with regional regulations.
Option 3: Use the table opposite to determine if any part of the equipment, load line or load (including rigging and lifting accessories), while operating up to the equipment’s maximum working radius in the work zone, could get closer than the minimum approach distance of the power line. If tag lines are used, they must be non-conductive.
Other precautions that can be taken when working in proximity to overhead powerlines are as follows.
Control the slew radius of the crane to prevent it coming into proximity with the overhead lines. This is particularly effective if the crane is to be kept in one static location. The slew radius can be set up with limit blocks to prevent it travelling beyond a certain safe radius. It can be more difficult and problematic if the crane is constantly moving and the slew radius has to be constantly changed.
A set of ‘flag’ goalposts can be used as a visual warning about the proximity to overhead lines, the cross-bar flag line indicating a maximum safe height for vehicles and equipment passing underneath.