Safe high level inspection and maintenance
09 April 2010
In hazardous industries there is a good chance that pipes, pumps, valves and electrical equipment will be elevated and access will at best be awkward and often difficult. Working at height represents one of the most serious potential risks in the workplace and safety should always be a priority. Employers have a duty of care to their staff and have to provide the appropriate equipment to ensure inspection and maintenance can be carried out safely and efficiently.
Safe high level inspection and maintenance
The HSE recommends that working at height should be avoided if at all possible. But for many inspection and maintenance tasks it is simply impossible to do the job properly without getting close to the working area. So the question then comes how can this be done in the safest and most efficient way?
Contrary to popular belief the HSE has not banned ladders from the workplace. For simple one off jobs at low levels these are still an ideal access tool. However, where the task is longer term or the area being accessed higher, then a semi-permanent access platform such as a portable access tower or scaffold might be more appropriate. Any sensible risk assessment should highlight when a ladder is not suitable and a tower or scaffold becomes the better option.
While towers and scaffold provide good access to many applications there are plenty of drawbacks. They are generally more appropriate for working up against a wall but by their very nature they can also obstruct access to some of the working area if a strut or spar gets in the way. They take time to erect and take down which limits their efficiency and they can obstruct other activities in the area. The weather, especially strong winds, can cause instability outdoors, especially when relatively tall structures are involved and even in calm conditions and indoors there can be the flexing or swaying that can help make people at the top unsteady on their feet. And with the best will in the world with any temporary construction that it taken apart and put together regularly there is an increased chance of mistakes being made that can cause sudden failures and accidents.
Fortunately there are a number of options when it comes to mobile access platforms. These can broadly be placed into three categories: low level indoor access; medium level access for indoor and outdoor applications; higher level outdoor access. The first two are probably of most interest as the very tallest applications are likely to be provided by specialist contractors who will do the job themselves or hire their machinery out with a trained operator who will accompany a local maintenance engineer in the platform to manage the safe control of the equipment.
There has been quite a growth in the range of low level mobile access platforms in the past couple of years. These machines typically offer maximum working heights of up to around 10 metres, often much less, and are a simple and affordable option to buy or rent. In general terms these devices can be moved around a factory or warehouse floor and parked into position before the operator enters the platform basket and uses mains or battery power to raise themselves to the correct working height.
For the very tallest applications, to heights of 100m or more, it is likely that the sort of mobile access platform will be rented in for very short periods or operated by a contractor. The baskets on the very biggest machines not only reach the upper levels of some of the tallest industrial and residential structures but also have the capacity to carry two or more people and a good payload of tools and equipment.
Things get more interesting in the medium access range where there is a wider choice of equipment that can be hired or purchased on a "self-drive" basis or hired with a specialist operator. Broadly the choice of these platforms will come down to self-propelled, vehicle mounted and track mounted. Each has its advantages. Self propelled platforms, usually with wheels, are designed to provide easy mobile access on reasonably level surfaces. Vehicle mounted platforms offer greater versatility because they can be driven on the road, and are therefore very mobile, and can offer much higher maximum working heights depending on the design and chassis. Track mounted access platforms offer the added dimension of being able to operate over rougher terrain such as building sites, uneven indoor surfaces, park and woodland. They generally have a lower overall weight than other self-propelled platforms which, with the tracks spreading the load, means they can operate on more types of floor. Whatever the choice the chassis should provide a stable and solid base for the main access platform mechanism, boom and the basket.
Vehicle mounted platforms that weigh less than 7.5 tonnes in total can be driven by anyone with a standard "Category B" car driving license, including younger and newly-qualified drivers. Proper training to use the equipment itself is still required, of course, but this versatility helps to explain why this type of vehicle is increasingly popular in the hire and owner-operator markets.
It is important to think about the application before selecting the access platform. Some platforms have a simple boom that simply extends and retracts in a straight line to achieve the required working height. These are good for many straightforward applications but not all. A boom that can fold or articulate offers much better versatility when accessing the working area. It can, for example, usually take up a configuration like a concertina and fold up or down to provide access to almost any point within what is known as the working envelope, that is the volume defined by the maximum safe outreach, working height and rotation of the platform. For even greater versatility a fly-jib on the end of the boom will enable a configuration similar to an inverted V(Λ) which allows the basket to reach points up and over obstructions. Booms which only extend straight out cannot do this and may also have points inside the working envelope which they cannot easily access.
The combination of boom and chassis is the basis for safe working at height and should ensure the basket and its occupants do not move or sway unexpectedly. This stability is vital to safety. The hydraulic and electrical services passing from the base of the platform to the basket should ideally be housed neatly and tidily inside the boom sections to offer protection from accidental damage to vital components and eliminate the risk of snagging on external structures.
Overload protection and safety cut-outs are another consideration. Ideally the overload protection should prevent the maximum working load from being exceeded, stop the platform operating outside its design envelope and only allow movements that bring it back inside safe parameters. Other safety cut outs should, for example, prevent operation of the platform until any required stabiliser legs or outriggers are properly deployed and the equipment level and secure.
The design of the basket itself is important. Use of composite materials, rather than metal, offers some protection against electrical shock. The basket should be self-levelling to the elevation and inclination of the boom. By law all access platforms baskets must have guard fences at a specified height and toe rails to help prevent the risk of falls. Controlled side-to-side rotation of the basket will allow precise positioning at the working face without having to move the entire boom. Some tracked machines allow the basket to be detached quickly to allow the machine to enter a goods lift or pass through the narrowest possible doorways and gates.
Controls should be simple, smooth and proportional to prevent jerky or unexpected movements that can be disconcerting when working at height. Most access platforms will allow the entire machine to be operated from the basket. An override at ground level is required but this should be configured to prevent both sets of controls being used at the same time to avoid conflicting commands being issued to the equipment.
Most of the safety considerations for mobile and vehicle mounted platforms also apply to tracked machines. With these a "wander lead" umbilical remote control allows the operator to stand safely clear when the machine is being loaded and unloaded from transportation and manoeuvred into position. Suitably compact dimensions and low overall weight can allow these units to pass through standard internal doors and be carried on conventional plant trailers or inside light commercial vehicles for added hiring potential. A mains electric power option, in addition to a diesel engine as the primary power source, is worth considering if the platform is to be used indoors or in areas where quiet operation is desirable.
The choice of access platform for inspection and maintenance tasks can be a little daunting. But with a little planning and forethought of the operational, training and safety considerations, the decision will become a little clearer. And of course any reputable supplier of these machines should be able to advise on the most appropriate equipment.
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