Maintaining Health & Safety Standards When Using Cherry Pickers
Originally used in orchards to pick fruit, cherry pickers have become vital pieces of equipment within the construction industry. According to Health & Safety Training Limited, the top use for cherry pickers today is building maintenance.
It’s clear from this information that this type of equipment has greatly helped the construction industry; however, using cherry pickers for maintenance work does come with great risks. In fact, the Health and Safety Executive recorded that falls from a height were the most common cause of worker fatality in 2012/13, accounting for 31 per cent of deaths.
This doesn’t state whether the falls are actually because of cherry pickers, but from the examples of accidents below companies are taking strong precautions anyway to ensure none of their staff have any fatal injuries.
The most recent incident to reach the press was the accident involving Nicholas Chenery. In April 2014 the Royston Crow reported that Mr Chenery suffered a compound fracture to the left leg and three fractured vertebrae to his lower spine when falling from a cherry picker 12 metres high.
Mr Chenery was rigging three overhead lines at Chipping, on the A10 between Royston and Buntingford, when the security line he was fastened to was pulled over by a dumpster truck, causing him and the cherry picker to fall. Because his employer had failed to comply with HSE safety regulations, the company was fined £35,000.
That’s not the only incident to break the headlines. In 2013, Richard Jaeger-Fozard died when the cherry picker he was on came crashing down on to the M25 in Buckinghamshire. According to Highways Industry.com, the cause of the accident is unclear.
These accidents are causing great concern, especially since the government put the Work at Heights Regulations together in 2005 to stop incidents like this happening. These regulations are to ensure that work at a height is properly planned, organised and the risks of the work are accessed so the appropriate work equipment can be selected.
It’s clear from the statistics and previous accidents that not all companies are working alongside these regulations or using the correct equipment.
While it’s up to the company to make sure their employees follow and maintain these regulations, finding the right equipment couldn’t be easier. Nifty Lift offers trailer-mounted, self-propelled, self-drive, track-drive, static-base and vehicle-mounted cherry pickers, all with working heights ranging from 30ft to 96ft.
Different cherry pickers are used for different types of construction jobs; however, construction employees should all be familiar with The Engineering Construction Industry Association (ECIA) guide. This highlights health and safety precautions they must take to avoid trapping, crushing and falling injuries to people who are in the platform.
As well as this guide, a must among workers is a safety harness. There’s not a specific height that requires you to wear a safety harness; however, in construction, not wearing a safety harness is taken seriously, so seriously that employees can lose their job on the spot because of it.
Many companies in construction have stated that if employees are using cherry pickers, then using a harness as a restraint is the most suitable form of personal fall protection. This is because there’s a high risk of sudden movements, which can be caused by impact, ground movement, failure of a stability critical part, or overreaching.
Ensuring staff know how to wear this safety equipment properly is vital. If they’re unsure how to correctly wear a harness, here’s a picture from AFI Uplift, which is easy to understand.
Why engineers must always consider human-induced vibration
Human induced vibration, or more accurately vibrations caused by human footfall, often conjures images of Millennium Bridge-style swaying or collapsing buildings.
But in reality, the ‘damage’ caused by human-induced vibrations is less likely to ruin a structure and more likely to cause discomfort in people. Though not as dramatic as a structural failure, any good engineer wants to make sure the people using their structures, be it bridges or buildings or anything in between, can do so safely and comfortably. This is why human-induced vibration must be considered within the design process.
Resonance v Impulse
There are two ways that human-induced vibrations affect structures: resonant, and impulse or transient response. Put simply, resonance occurs when Object A vibrates at the same natural frequency as Object B.
Object B resonates and begins to vibrate too. Think singing to break a wine glass! Although the person singing isn’t touching the glass, the vibrations of their voice are resonating with the glass’s natural frequency, causing this vibration to get stronger and stronger and eventually, break the glass. In the case of a structure, resonance occurs when the pedestrian’s feet land in time with the vibration.
On the other hand, impulse or transient vibration responses can be a problem on structures where its natural frequencies are too high for resonance to occur, such as where the structure is light or stiff. Here the discomfort is caused by the initial “bounce” of the structure caused by the footstep and is a concern on light or stiff structures.
Engineers must, of course, design to reduce the vibration effects caused by either impulse or resonance.
Potential impacts from human induced vibration
Human induced vibration can lead to a number of effects upon the structure and its users. These include:
- Interfering with sensitive equipment Depending on the building’s purpose, what it houses can be affected by the vibrations of people using the building. Universities and laboratories, for example, may have sensitive equipment whose accuracy and performance could be damaged by vibrations. Even in ordinary offices the footfall vibration can wobble computer screens, upsetting the workers.
- Swaying bridges One of the most famous examples of human-induced resonance impacting a structure occurred with the Millennium Bridge. As people walked across the bridge, the footsteps caused the bridge to sway, and everybody had to walk in time with the sway because it was difficult not to. Thankfully, this feedback can only occur with horizontal vibrations so building floors are safe from it, but footbridges need careful checking to prevent it.
- Human discomfort According to research, vibrations in buildings and structures can cause depression and even motion sickness in inhabitants. Tall buildings sway in the wind and footsteps can be felt, even subconsciously by the occupants. It has been argued that modern efficient designs featuring thinner floor slabs and wider spacing in column design mean that these new builds are not as effective at dampening vibrations as older buildings are.
- Jeopardising structural integrity The build-up of constant vibrations on a structure can, eventually, lead to structural integrity being compromised. A worse-case scenario would be the complete collapse of the structure and is the reason some bridges insist that marching troops break step before crossing. Crowds jumping in time to music or in response to a goal in a stadium are also dynamic loads that might damage an under-designed structure.
How to avoid it
As mentioned, modern designs that favour thinner slabs and wider column spacing are particularly susceptible to all forms of vibration, human-induced or otherwise, but short spans can also suffer due to their low mass. Using sophisticated structural engineering software is an effective method for engineers to test for and mitigate footfall and other vibrations at the design stage.