Product category:
Machinery/plant guarding and protection
News Release from: Rockwell Automation (Allen-Bradley Guardmaster ) | Subject: Machine guarding
Edited by the Manufacturingtalk Editorial
Team on 12 January 2005
New materials address RSI in guarding
systems
Following the recognition of occupational overuse syndrome (OOS), or RSI as it is more widely known, the role of machine guarding to protect operators has been expanded.
Following the recognition of occupational overuse syndrome (OOS), or RSI as it is more widely known, the role of machine guarding to protect operators has been expanded Following the recognition of occupational overuse syndrome (OOS), or RSI as it is more widely known, the role of machine guarding in providing operator protection has been expanded and now deals with ways in which the guarding system itself can be redesigned to reduce its negative effects on the long-term health and well-being of operators
This article was originally published on Manufacturingtalk on 28 May 2002 at 8.00am (UK)
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Today, thanks to the introduction of new standards and greater awareness in the workplace, companies are more aware of the consequences of asking machine operators to open and close guards frequently during shifts.
They now realise that occupational overuse injuries can be serious and debilitating, and that people suffering from these injuries often need time off work.
Moreover, as absence is, by its very nature, unplanned, this causes much disruption to a business' productivity.
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There is, of course, another major reason why companies, generally, are having to move the problem of occupational overuse injuries up their agendas: the UK's burgeoning compensation culture.
Injuries resulting from OOS can be severe and incapacitating, leading to compensation claims that can be extremely costly.
Despite the new levels of awareness, many manufacturers still do not appreciate that efficient and safe machine guarding brings both economic as well as social benefits.
True, many of these manufacturers are under extreme cost pressures as a result of competition from far Eastern manufacturers.
However, they fail to realise that just 'slapping' a cover over the dangerous moving parts of a machine, without due regard to the needs of operators and production and maintenance functions, usually results in a guard that does not justify its expenditure; operators often bypassing its function - sometimes with catastrophic results.
Actual empirical evidence backs this assertion, revealing that a safety system, which is difficult to use is more liable to be removed or by-passed.
Also, the removal of awkward safety guards has been shown to be one of the most common pre-conditions for an industrial accident.
Traditionally, the material used for guarding systems has been robust, but heavy, sheet steel and wire mesh.
In the light of new market requirements, these materials are increasingly being replaced with lighter guarding arrangements employing either polished Perspex and gas spring support devices, or toughened glass with rotating wiper portholes.
Both of these discrete arrangements give the operator a weightless balanced lift when opening doors.
In addition, by allowing the working process to be seen clearly, they provide maintenance crews with valuable observation and thinking time when troubleshooting problems within the machine.
The availability of new lightweight and transparent solutions for guarding is also motivating manufacturers with difficult-to-guard machines - such as millers - to revisit them, with a view to providing improved guarding solutions.
A recent case is an international manufacturing organization, which is using four millers to machine aero-engine fan blades.
Unfortunately, the physical size of the blades means that some types overhang the machine envelope horizontally, whilst others extend vertically skyward.
The combination of these factors means that the machines are extremely difficult to guard, and certainly beyond the scope of standard guarding systems.
Following an appraisal of the machines by a team of safety consultants, EJA Engineering Solutions, an expert in providing special guards and integrated machinery safety systems, was called in to provide a turnkey solution to the guarding problem.
The first action undertaken by the engineers from EJA was to visit the site to view the machines, talk to the operators about how the machines were operated, and solicit from them their views concerning the guarding operation.
Past experience has convinced EJA that this inclusive, 'buy-in' type of approach to guarding is extremely important, as it is the best possible way to ensure that when a guard is fitted, it stays fitted.
Interestingly, the outline specification that emerged from the shop floor consultations was very much in keeping with the initial thoughts of the EJA engineers charged to provide a solution.
The specification was essentially that of a hinged and sliding guard that in operation resembled the mechanism of a welder's helmet.
The advantage of this design was that it could elongate to accommodate all sizes of fixtures, would not interfere with the manufacturing process and could be interlocked for maximum safety.
Based upon this initial premise, EJA engineers produced a series of prototypes, which they brought to the manufacturing site for appraisal.
The prototypes were tried in situ on the machines and the specification was gradually honed to provide the optimum operating characteristics, both in terms of safety and efficiency of machine operation.
The final design comprises two, 200mm wide x 250mm deep polycarbonate screens on spring loaded hinges, which allow the guards to be 'flipped' up (i.e elongated) to accommodate blade changes, and then slotted down and interlocked (via a Guardmaster IMP safety interlock switch) before the machine can be started.
The design is both simple and effective and offers excellent flexibility with its extensive capabilities for easy adjustment.
In total, four of the guards have been supplied.
These were manufactured by EJA at its Wigan, UK, plant, and then installed on the machines and commissioned.
Since installation they have all performed exactly to their design specification, providing greater levels of safeguarding, while maintaining and enhancing machine productivity.
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