Machine guarding the 'unguardable'

The safeguarding of machines is invariably a complex process, especially so when the operation is milling aero-engine fan blades which protrude outside or above the machine parameters.

The safeguarding of machines is invariably a complex process, especially so when the operation is milling aero-engine fan blades which protrude outside or above the machine parameters.

Under such operating conditions standard guards are totally ineffective, so Sermatech Repair Services turned to the Engineering Solutions Team at EJA to provide a full turnkey solution, with a specialist design of guard which accommodates the many differing sizes of blades and fixtures used on the milling machines.

Based at Ripley in Derbyshire, Sermatech Repair Services is part of Airfoil Technologies International (ATI), a global organization providing leading-edge repairs for commercial flight gas turbine components.

Sermatech has always taken a proactive approach to safety.

However, the nature of the work the company undertakes means that providing adequate safety provision on some types of machines is often a demanding task.

A recent case in point is four milling machines, which are used to machine fan turbine blades.

The variations in the size of blades are numerous, resulting in the use of a large variety of different size fixtures.

In addition, the physical size of the blades means that some types overhang the machine envelope horizontally, whilst others extend vertically skyward.

Overall, 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 safety consultants, Sermatech's Health and Safety Manager, Ian Williams, called in EJA's Engineering Solutions team, experts in providing special guards and integrated machinery safety systems, to provide a turnkey solution to the guarding problem.

The first task undertaken by engineers from EJA was to visit the Sermatech 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.

Reinforcing this argument is the statistic showing that the removal of awkward safety guards is one of the most common preconditions for an industrial accident.

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 Sermatech Repair Services 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 were required.

These were manufactured by EJA at its Wigan plant and then installed on the machines and commissioned by the company as part of its full turnkey responsibility.

Since installation they have all performed exactly to their design specification, providing greater levels of safeguarding, while maintaining and enhancing machine productivity.

Back to top