On Your Guard – A Designer’s Guide to Machinery Guarding Standards (13th Edition – October 2018)
There is no hiding from the fact that guarding is a crucial element of a machine or production line, yet the guarding design is often left until last and not given as much thought as the aspects that are seen to relate directly to productivity. Nevertheless, guards usually control the interaction between operator and machine, so it should be remembered that their design can be a significant factor in optimising a machine’s performance.
A perceived difficulty with designing guards is that there are numerous regulations and standards that must be complied with. In fact, as the designer becomes more familiar with the ‘rules’, the ‘game’ becomes easier. Alternatively, specialists such as Procter Machine Safety can be employed to undertake the complete design, manufacture and installation, including electrical aspects.
This guide seeks to direct the reader towards the main standards for machine guarding and machinery safety in general, as well as providing some advice on how the standards can be applied. At the end, there are lists of useful resources and sources of additional information.
Machine Guarding is a matter of life and death …
- In 2017/18 there were 15 fatal injuries in the manufacturing industries.
- In 2017/18, across all industries, contact with machinery caused 13 fatal injuries
- Between 2013/14 and 2015/16, in the manufacturing industries there were an average of 66,000 self-reported non-fatal workplace injuries, of which 12% (approximately 8000) were due to contact with machinery (Source: HSE)
The importance of guarding
Most employers today have at least a basic understanding of safety issues and accept that their employees are one of the company’s biggest assets. But many still see machine guarding expenditure as a necessary evil rather than a key investment that can really help deliver improved productivity.
If guards are well designed they will not interfere with an efficient operation; ill-considered guards invariably do. Worse than that, poorly designed guards encourage operators, maintenance staff and management to bypass them, which can compromise quality and significantly increase risks.
Machinery safety regulations
Machinery safety in the UK is driven by two main sets of regulations: The Supply of Machinery (Safety) Regulations 2008 as amended (the UK implementation of the European Machinery Directive 2006/42/EC, requiring all machines placed on the market in the European Economic Area (EEA), Switzerland and Turkey to carry a CE mark) and The Provision and Use of Work Equipment Regulations 1998 (PUWER 98). In addition, there are The Health and Safety at Work etc Act 1974 and The Management of Health and Safety at Work Regulations 1999.
To comply with the requirements of The Supply of Machinery (Safety) Regulations 2008, a machine needs to pass these tests:
- The machine must comply with the EHSRs (Essential Health and Safety Requirements) of the Supply of Machinery Safety Regulations.
- The machine must have been assessed as complying with the EHSRs.
- There must be a Declaration of Conformity.
- The supplier must assemble a Technical File.
- The supplier must provide the information necessary to operate the machinery safely, such as instructions.
- The supplier must have followed one of the prescribed conformity assessment procedures.
- The machine must carry a CE mark.
- The machine must ‘in fact’ be safe.
For partly completed machinery the requirements are simpler:
- The supplier must prepare the technical documentation.
- The supplier must prepare the assembly instructions.
- There must be a Declaration of Incorporation.
Unlike The Supply of Machinery Safety Regulations 1992, and the 1994 and 2005 amendments, the new Regulations (which came into force on 29 December 2009 to implement the Machinery Directive 2006/42/EC) stipulate that safety components must also be CE marked. In certain circumstances, therefore, machine guards need to be CE marked. See ‘Useful Resources’ below for a Guide to the New Machinery Directive, a White Paper CE Marking of Guards, and the European Commission has published both a Guide to application of the Machinery Directive 2006/42/EC and a report Safety fences as safety component under the Machinery Directive 2006/42/EC. Alternatively, contact Procter Machine Safety if in doubt whether or not there is a need to CE mark guards or, indeed, other components for which guarding is a secondary function such as covers, lids and acoustic enclosures.
In practice, the way suppliers and users of machines can most easily meet their legal obligations is to ensure that their machines, guards and other safety devices conform to harmonised European standards (Euronorms). These standards have been developed to ensure an equally high standard of machine safety across the EU. The good news for users of machines in the UK is that these standards incorporate most of the principles of BS 5304:1975 and 1988 (the Code of practice for the safety of machinery), which served British industry well for a long period and, although no longer current, is now available from BSI as a Published Document, PD 5304:2014.
The main standards and published documents applying to machine safety and machine guarding are shown in the tables below. Machinery Directive Harmonised Standards are classed as A-type, B-type and C-type standards, so the list below has been divided the same way, with non-harmonised standards and other documents shown at the end. The list below focuses on the main standards; readers should use the ‘Useful resources’ section of this present guide to check whether any other standards need to be applied to the machinery or equipment in question.
Other types of machinery, from cranes to sewing machines, also have their own requirements. A full list of standards harmonised to the Machinery Directive is available on the European Commission’s website (see ‘Useful Resources’ below).
Additional information is also available from the HSE’s website: from the I am interested in… menu select More topics then select Work equipment and machinery, and from the I work in… menu select More industries then select Engineering and Manufacturing.
Risk assessment and reduction
Today the accepted approach to the design of any machine guarding system is based on risk assessment. BS EN ISO 12100:2010 (which replaced BS EN ISO 14121-1, which itself replaced BS EN 1050) sets out different methods; these must take account of the probability and degree of possible harm relating to any foreseeable injury. More guidance on Risk Assessment can be found in the HSE’s leaflet A brief guide to controlling risks in the workplace INDG163 (rev4), which has replaced the previous publication Five steps to risk assessment INDG163.Most HSE publications can be downloaded for free, or hard copies can be purchased.
A free Risk Assessment Calculator is also available from Procter Machine Safety. This is based on the requirements of the A-Type harmonised standard BS EN ISO 12100:2010 and is designed to be simple to use, making extensive use of checklists (see ‘Useful Resources’ below).
Once a machine has been assessed, if the resultant risk is considered unacceptable, measures should be applied to reduce the risk rating — which often includes guarding. This iterative process is repeated until the measures applied to reduce the risk to an acceptable level.
Risk reduction measures should be implemented in a hierarchical, three-step process:
- Inherently safe design (ie design-out the hazards)
- Safeguarding and complementary protective measures
- Information for safe use
Additional measures may also be required such as training, safe working procedures, permit-to-work systems and personal protective equipment.
Working with the standards
BS EN ISO 14120, which is the main guarding standard (replacing BS EN 953), covers all machinery from simple drive couplings to very complex installations involving robots, conveyors and processing machinery. The standard lists those aspects of machinery, people and the design and construction of guards that need to be considered.
Machine aspects to be considered are, of course, the functions of the machine and the hazards arising from these. Obvious ones include entanglement or impact from moving parts, and less obvious ones are, for example, the potential for ejection of broken tools, hazardous materials and invisible emissions including noise and radiation. Guards should minimise exposure to these hazards by the selection of appropriate materials, construction methods and correct safety distances — as specified in BS EN ISO 13857.
Before starting the design
The successful design of machine guards needs a clear understanding of all the ways in which people interact with the machine at all phases of its life including commissioning, production and maintenance. Before designing any guarding, the designer should talk to the operators and maintenance staff that will use the machine; if the machine operates for more than one shift per day, the designer needs to talk to the operators and maintenance staff from all shifts because the working practices may not be the same.
Well-designed guards should permit machines to be loaded, unloaded, cleaned and maintained efficiently without exposing people to hazards (remember that around 25-30 per cent of fatal injuries in the manufacturing industries occur while maintenance is being carried out).
Machine guarding can be constructed from a variety of materials and the skill of the designer lies in creating a system that will be fully compliant with the regulations and standards, yet will also be user-friendly, cost-effective and aesthetically pleasing. The main choice of infill materials is between sheet steel, welded wire mesh and clear polycarbonate — though sheet steel guards can also be provided with mesh or polycarbonate windows.
On machines where process viewing is necessary, adequate lighting must be provided to ensure compliance with BS EN 1837, Safety of machinery. Integral lighting of machines, and to discourage operatives from attempting to bypass the guarding.
If ejected parts are an issue, sheet steel or polycarbonate are typically chosen, while welded wire mesh (weldmesh) is cost-effective for many other applications. In corrosive environments or where frequent washdowns are required, stainless steel is preferred. If a heavy use or abuse is anticipated, heavy-duty materials and construction should be employed.
Noise reduction is increasingly important today, so acoustic foam or other sound-deadening material can be added to sheet metal panelling. Sealing around guards can also help to reduce noise levels, and sealing is highly beneficial if fluids or dust are present. In some cases, the best option is to construct an acoustic enclosure around the machine.
BS EN ISO 14120:2015 requires fixings for fixed guards to remain attached to the guard or the machinery when the guard is removed. While this appears to make the situation clear, in fact designers need to be decide whether or not a guard (or another component with a secondary safety function) is a ‘fixed guard’ and whether or not it is foreseeable that the guard will be removed for maintenance, cleaning or other reasons (if not, then there is no need to use retained/captive fasteners). More information about fixings for fixed guards is available in a free White Paper from Procter Machine Safety, How to specify fixings for machine guards (see ‘Useful Resources’ below).
When designing either fixed or moving guarding, the designer should refer to the standard that covers safety distances to prevent hazard zones being reached, namely BS EN ISO 13857. A free Safety Distance Calculator is available from Procter Machine Safety for establishing the required safety distances and heights of machine guards in accordance with BS EN ISO 13857 (see ‘Useful Resources’ below)
The new Machinery Directive 2006/42/EC is more explicit in its requirements relating to ergonomics — and there are currently 20 relevant Harmonised standards. Not all of these standards are required when designing machine guards, but it is clear that ergonomics cannot be ignored. Helpful information is available in a European Commission publication Guidance on the application of the essential health and safety requirements on ergonomics.
The section of BS EN ISO 14120 covering human aspects addresses the human/machine interaction, including reducing the need for frequent access and ensuring that, where the need for access cannot be eliminated, access is controlled so that the machine can only be approached when it is in a safe condition. This is usually achieved by interlocking the access guards/gates. The need for non-essential access can be reduced by, for example, designing guards with good process viewing and locating lubrication points outside the guarding.
If interlocks are required, it is vital to select components that are suitable for the machine’s risks and safety-related control system, depending on whether the designer is working to functional safety standard BS EN ISO 13849-1 or BS EN 62061. Typically the interlocks will be of the mechanical type using roller plungers or metal tongues, switches incorporated within hinges, or non-contact types utilising coded magnetic or electronic technologies.
Whichever type is selected, the switches must be installed correctly if they are to perform properly and not start to fail (either to a safe or unsafe condition) when the guard hinges or runners begin to wear. BS EN ISO 14119 gives more information about interlock selection.
For perimeter guards and machinery where whole-body access is possible, key exchange systems are often the most appropriate, as the person entering the guarded area can take a key with them to prevent the machine from being restarted (assuming the safe system of work is followed). If frequent access is required and the machine has a short stopping time, photo-electric guards can be very effective, though care must be taken to observe the correct distance between the guard and hazard (see BS EN ISO 13855). Other options are laser area scanners and pressure-sensitive mats.
Conventional opening guards can be manually operated or powered. In the case of powered guards, it may be necessary to install ‘safe edges’ on the leading edges of the guards to prevent them from becoming hazards themselves.
Two of the changes introduced when BS EN ISO 14120 replaced BS EN 953 relate to the choice of fixed or movable guards where access is required only for machine setting, process correction or maintenance.
- first, EN 953 states that movable guards should be used if the frequency of access is ‘high (e.g. more than once per shift)‘ but now ISO 14120 defines ‘high’ as ‘e.g. more than once per week‘.
- second, in EN 953 fixed guards should only be used ‘if the foreseeable frequency of access is low, its replacement is easy, and its removal and replacement are carried out under a safe system of work’, with no definition provided for ‘low’, so users were left to assume that ‘low’ is any frequency that falls outside the scope of ‘high’. In contrast, ISO 14120 defines ‘low’ as ‘e.g. less than once per week‘.
There is an ambiguity here regarding whether fixed or movable guards should be used if access is required once per week (not more, not less), as this is a foreseeable situation (maintenance, calibration and checks/adjustments might be scheduled to take place weekly). It could be argued that the machine designer should err on the side of safety and specify (interlocked) movable guards rather than fixed guards that are removed and replaced under a safe system of work. On the other hand, the designer may be tempted to save costs by installing fixed guards that do not require hinges or linear bearings, or the interlock, wiring and additional inputs on the safety-related control system.
The other issue here is that under EN 953 the frequency of access was considered to be high if access was required more than once per shift; in contrast, ISO 14120 redefines ‘high’ as once per week, which could result in many more machines meeting this criterion and therefore having to be equipped with movable guards rather than fixed guards. The implications for design and manufacturing costs could be considerable.
If in doubt, ask
This guide is intended to point machine designers in the right direction for designing safe, cost-effective guards that comply with the relevant UK and European regulations and help to optimise the machine’s performance.
If further assistance is required, Procter Machine Safety can advise on current regulatory requirements as well as undertake risk assessments and site surveys, and then design, fabricate and install bespoke guarding, including electrical integration, to suit virtually any machine or process.
For perimeter guarding, Procter Machine Safety offers a choice of modular systems in both steel and aluminium. Standard elements include sliding, hinged and lifting guards, as well as fixed panels with infills of welded wire mesh, sheet steel and polycarbonate. Furthermore, the company can also design and manufacture bespoke components to complement the standard elements where these would not be ideal. Customers pay only for what they need because they can select from a choice of modular systems of different strengths and specifications — or use a combination of different specifications for various areas around a machine. All perimeter guards are offered on a supply-on basis or Procter can provide an installation service if required.
All can be downloaded from www.machinesafety.co.uk/free-downloads/free-machine-safety-guides or email [email protected]
Free Risk Assessment Calculator
Based on the requirements of BS EN ISO 12100 and designed to be simple to use.
Free Safety Distance Calculator
Establishes machine guard safety distances and heights in accordance with BS EN ISO 13857.
Free Guide to the New Machinery Directive 2006/42/EC
To help companies comply with the Directive that came into force on 29 December 2009.
Free White Paper: Machinery Directive and Fixings for Fixed Guards
Explaining the amended requirements for Guard Fixings under the new Machinery Directive.
Free White Paper: CE Marking of Machine Guards
Explaining the requirements relating to CE marking of guards under the Machinery Directive.
Free White Paper: EN 349, Minimum Gaps to Avoid Crushing
Explaining the requirements of the standard for minimum gaps to prevent crushing.
Free White Paper: Differences Between BS EN 953 and BS EN ISO 14120
Explaining what changes have been introduced in BS EN ISO 14120, which replaces and supersedes BS EN 953.
Free White Paper: Conveyor Guarding
Explaining the hazards associated with conveyors, regulations and standards, and how to safeguard conveyors without adversely affecting productivity.
Free White Paper: The 2014 Edition of PD 5304
Explaining the changes in the new edition of BSI’s Guidance on the safe use of machinery.
Free Guide to Work Shop Safety
A guide to guarding small machine tools typically used in workshops.
Free Machine Accident Investigation Kit
To help companies meet their statutory obligations and prevent future accidents.
Free Ergonomics Guidance
European Commission publication Guidance on the application of the essential health and safety requirements on ergonomics.