(Click here to view article in digital edition)
Although significant strides have been made in making manufacturing environments safer places to work, the number of injuries and fatalities that occur is still shockingly high. The Health and Safety Executive’s (HSE) figures for 2017-18 showed that there were 15 fatalities in the manufacturing sector during this period and over 60,000 non-fatal injuries including everything from minor abrasions, burns or cuts to fractures, lacerations, crushing injuries or even amputation. Contact with machinery is the cause of a significant proportion of these incidents and it is therefore no surprise that the need for better guarding is closely scrutinised.
The European Machinery Directive 2006/42/EC specifies range requirements relating to the design and manufacture of machinery in order to help improve safety. It stipulates the required characteristics of guards and protective devices, and Section 1.4 defines different types of guards. Meanwhile, when it comes to moving transmission parts, it states that guards must either be fixed or interlocking movable devices and the latter should be used where frequent access is envisaged.
EN ISO 14120 defines a fixed guard as a ‘physical barrier, designed as part of a machine, to provide protection’ and it must be removable only with the aid of tools, while interlocking movable guards can be doors, panels, gates or other physical barriers that can be opened without using tools. When machinery is in operation each guard needs to be interlocked with a machine control system so that the hazards covered by the guards are controlled and managed when a guard is opened.
Preventing users from reaching around, under, through or over guarding is vital, particularly when interlocking movable guards are in place. Section 5.7 of BS EN 1088 states, rather verbosely, that ‘If the specification of the safety interlocking device is such that it is possible to defeat the safety function solely by a reasonably foreseeable action at the interlocking device itself, and if the device itself is to be relied upon to prevent defeat, it should provide measures to minimise the possibility of defeat.’
This suggests that it should protect against the possibility that an operative could choose to circumvent the correct procedure, by installing EN ISO 14120 compliant barriers that must be secure and strong, so that workers are not able to bypass, remove, or tamper with them. Whatever the reason, a machine needs to be adequately guarded and, as well as carrying out a thorough risk assessment, workers should be aware of the disciplinary actions that they could face as a result of tampering with machine guards. As well as normal operation, a risk assessment should factor in the dangers relating to activities such as cleaning, setting and maintenance.
In order to make machines safer, in recent years there has been a sharp increase in the use of safety light guards, which provide a suitable alternative to mechanical guarding and can provide enhanced flexibility to improve machine throughput.
Safety light guards detect a presence in a defined protected field and don't require any action from a machine operator. These optoelectronic devices are classed as Electro-Sensitive Protective Equipment (ESPE) in BS EN 61496-1 2013 and BS IEC 61496-2 2013, and can reliably detect any individuals that are present in the vicinity of moving machinery – acting as an alternative to mechanical barriers and other forms of traditional machine guarding. Just as importantly, they provide a high level of accessibility to machinery and can monitor large areas.
There are different types of safety light guarding systems to choose from, depending on the required function, level of safety and type of risk. However, most comprise of a transmitter head and receiver head, which contain electronics and optics that generate an infrared light between the two heads and defines a detection zone. Any interruption to the infrared from a detected movement initiates a machine stopping procedure and automatically disconnects all hazardous machinery via two safety channels, referred to as the output signal switching device or OSSD1 and OSSD2.
In order to restart a machine, an operator must press a reset button that must be positioned outside of the danger area. So that the production process isn’t delayed any longer than necessary, some safety light guards are equipped with an auto-reset option that can automatically start machinery once the detection zone is clear. Furthermore, muting can allow increased productivity by ensuring continuation of the machine operation by controlling when the light guards are active. However, this should only be carried out following a risk assessment of the machine to ascertain if there are any hazards involved in doing so.
One injury through machine operation is one too many and safety light guards are an excellent method of making a machine safe by electrical means. The HSE has produced an excellent guide titled ‘Application of Electro-Sensitive Protective Equipment Using Light Curtains and Light Beam Devices to Machinery’, which offers advice on issues such as proximity of optoelectronic protection devices to machinery, installation, inspections, labelling and safety testing.
Print this page | E-mail this page
Discover the future of engineering today
Download a copy of our digital magazine