Rope access or BMUs — which technology is safer?
Original article by Gordon Cadzow, secretary of the Australian Working at Heights Association (WAHA) found online here.
Rope access or BMUs — which technology is safer?
Recent falls from height on building facade work have been recorded from both rope access applications and from the use of building maintenance units (BMUs). These incidents have again raised discussions on which is the safer of the two technologies.
Let us start by considering who is responsible for safety — both in a new building and in an older, existing building.
The OHS/WHS Act places an obligation on designers of buildings and structures to design a workplace for the facade maintenance workers that is safe and without risk to the workers’ health, so far as is reasonably practicable. This includes managing risks associated with falls and includes requirements for emergency and rescue procedures. However, on older buildings prior to the OHS/WHS Act, there is no designer duty. The persons who exercise management and control of the workers and their workplace on these buildings have similar duties to provide a safe workplace, so far as reasonably practicable.
In other words, the ‘rules’ relating to safety are much the same — regardless of the age of the building.
The building designer or manager must therefore conduct a risk assessment on any work that may be required to be undertaken and give consideration to a number of issues including:
• the life/remaining life of the building;
• the likely frequency of the work to be carried out;
• the risks to which the worker may be exposed; and
• the severity of any resulting injury.
The issue of ‘reasonable practicability’ on the control of risk is usually managed by the application of The Hierarchy of Risk Control where the risks are identified and are then ranked against what would be the highest level of protection and reliability to the lowest.
As far as working at height issues are concerned, the OHS/WHS Regulations list the following preferred order of control (from highest to lowest) for consideration:
• Work on the ground or on a solid platform;
• Use a temporary work platform eg, scaffolding or EWP;
• Use a work positioning system eg, industrial rope access systems;
• Use a fall arrest system; and
• Use a fixed ladder or administrative controls.
The question of cost is often raised, and Safe Work Australia has addressed this in its interpretative guidelines by stating:
“Cheaper, available and suitable options may be used instead of a costlier option that may further minimise the risk or severity of harm, where the cost of the costlier option is grossly disproportionate to the risk.”
Further categorisation of risk control can be defined as ‘active’ and ‘passive’ systems.
In general terms, active systems are operated and controlled by the worker while undertaking the work task — harness-based working at height and rope access applications would be in this category. The passive systems are set up once by the original installer and require no adjustment during the work operation — walkways, guardrails etc would be an example of this category.
Formal definitions cite passive fall prevention as follows:
“[P]assive fall protection device means material or equipment, or a combination of material and equipment, that is designed for the purpose of preventing a fall, and that, after installation, does not require any adjustment, alteration or operation by any person to ensure the integrity of the device to perform its function.”
Confusion then arises when an example of passive fall protection is given as a “temporary work platform” and is further expanded to include “building maintenance equipment, including a building maintenance unit”.
Clearly a BMU is powered equipment — where the operator has control over the movement of the device and can change the position of the workplace.
It is therefore the consideration of the Working at Height Association (WAHA) that both rope access and the use of a BMU place both those operations in the work positioning category and removes the BMU from the passive category. It is therefore considered that their respective levels of safety fall into the same category.
A FURTHER RECOMMENDATION IS THAT ALL BMU OPERATORS AND THOSE WITHIN TEMPORARY SWINGING STAGES SHOULD WEAR A CHIN STRAP HELMET AT ALL TIMES TO PROVIDE A CONTROL MEASURE AGAINST WORKER INJURY FROM FALLS AND FALLING OBJECTS, THIS IS OFTEN OVERLOOKED AND IS ANOTHER STRONG RECOMMENDATION FROM WAHA.
Now let us look at the basic operations of the two systems.
A BMU is a mechanical/electrically controlled platform that is suspended from structural ‘arms’ down the face of the building. The platform is supported by steel wire ropes connecting — through winches — the structural arm to the platform. The operation of the winches controls the height of the platform — and their simultaneous operation maintains the platform in a horizontal position.
Operators are located in the platform and they control both the horizontal movement along the building and the vertical movement up and down the building facade. Workers may carry their work tools and equipment in the platform with relative safety.
Working from a BMU is a serious working at height issue and the use of full body harnesses and shock absorbing lanyards are mandatory for those in the platform — but what should those workers anchor to?
If the worker anchors to the platform and, if a cable were to fail causing the platform to tilt greatly to one side — or fall to ground — the operator would be left suspended from the crippled platform — or fall to ground within it.
A potential control measure is that the workers remain attached via a fall arrest device to an independent rope, anchored to an engineered or fixed anchoring point directly above the platform. This will ensure that, in the event of a BMU failure, the worker is held at the work position on a separate suspension device, enabling controlled descent to a safe level for rescue. A further recommendation is that all BMU operators and those within temporary swinging stages should wear a chin strap helmet at all times to provide a control measure against worker injury from falls and falling objects; this is often overlooked and is another strong recommendation from WAHA.
The BMU structural anchorages, suspension ropes and winch systems require regular inspection and servicing and certification.
BMU operations do not require that the worker is trained in safe work at heights, however WAHA — and the industry in general — recommends that all those required to work at height have formal training and certification in that category.
Rope access systems
The rope access system works on the basis that two independent rope lines are attached to independent anchor points directly above the work area on the roof of the building. The worker attaches to both rope systems, with one rope designated as the ‘primary rope’ and the other as the ‘secondary rope’.
The primary rope takes the suspended weight of the technician, who can adjust his vertical and horizontal position by using standard rope access manoeuvres and rigging configurations to suit the work being undertaken. Significant horizontal adjustment may require the relocation of the ropes onto new anchors vertically above the new work area.
In rope access operations, tools and equipment have to be carried in attached ‘pod bags’ — with pull closure systems so that the contents don’t fall out if the bag becomes inverted. Individual lightweight tools are normally tethered to the operator or the pod bag to prevent them falling to ground. Heavier tools must be attached to a further independent rigged line.
In the event of some sort of failure on the primary rope, the operator remains securely attached to the secondary rope and can descend safely to an exit level.
Rope access systems require regular inspection, testing and recertification, and only competent inspection companies should conduct this critical task. Records must be maintained and kept on-site at all times for inspection and review.
With rope access operations, the operator is highly skilled and qualified in rope access techniques and adapts to the work task at hand.
In summary, both systems are at the same level within the hierarchy of control — work positioning, both have the requirement for regular inspection and certification and both have a high dependency on operator competence.
However, the practical difference between the two systems relates to installation and maintenance costs. A rope access system will:
• significantly reduce installation costs;
• reduce building structural requirements;
• provide the potential for multiple simultaneous operators and reduced clean time;
• eliminate BMU maintenance costs; and
• allow for quick set-up and pack-up times.
One practical limitation of rope access is the height of the building. There appears to be some consensus that where the building height is greater than 50 storeys, the practicalities begin to favour the use of a BMU.
The two technologies will therefore continue to work in harmony in this market, offering similar levels of safety.
Both methods involve work at height methods that are considered to be well down the Hierarchy of Control. Accordingly, they should attract and be able to demonstrate the most stringent control measures — both equipment and operators.
While BMUs may appear to offer increased safety, the reality is that rope access has a far lower incident rate and operates under a much higher level of safety management systems.
Regardless of the system in use, work continues on a daily basis to ensure the safety of workers required to operate at height.
Working at Height Association (WAHA)
Footnote: Rope access work requires a very thorough hazard and risk evaluation, increased worker competency and re-training, and dedicated supervision levels. The rope access industry is regulated by WH&S and two major industry groups — IRATA and ARAA — Australia wide. These industry groups support the regulator by advocating best practice standards that far exceed the requirements of local legislation.