Machine guarding

Machine guarding is a physical safety measure designed to prevent people from coming into contact with hazardous parts of a machine. Its purpose is to restrict or eliminate access to hazard zones where risks exist, such as moving parts, cutting and shearing points, crushing zones, hot surfaces, or sources of released energy.

According to ISO 12100:2010, machine guarding is part of risk reduction through technical protective measures. Guards are applied when hazards cannot be sufficiently eliminated through inherently safe design. They may be fixed, interlocked, or combined with safety components, depending on the risk assessment and machine function.

Machine guarding is legally required when a risk assessment shows that people may be exposed to hazardous machine functions and these hazards cannot be adequately eliminated through inherently safe design or organisational measures alone.

Within the European Union, this obligation arises from the Machinery Directive 2006/42/EC. The directive requires machines to be designed and constructed so that exposure to hazards is prevented, preferably by means of guards or protective devices. When hazardous moving parts are accessible during normal operation, set-up, or maintenance, machine guarding is generally required.

Machine guarding must comply with applicable harmonised standards governing the design, construction, and positioning of guards.

The primary standard for the design and mechanical properties of guards is ISO 14120:2015. For guards equipped with safety interlocks, ISO 14119:2013 applies. Safety distances and permissible openings are specified in ISO 13857:2019, which defines how access to hazard zones is prevented. The positioning of guards and other protective devices in relation to approach speeds is addressed in ISO 13855:2010.

The exact standards that apply depend on the type of machine and the risks identified in the risk assessment.

Machine guarding is a fundamental element of CE marking for machinery. To affix the CE mark, the manufacturer must demonstrate compliance with the essential health and safety requirements of the Machinery Directive, including the performance of a documented risk assessment.

Guards form part of the required risk reduction measures and must be included in the technical construction file. They must also be correctly described in the instructions for use. Missing, insufficient, or incorrectly designed machine guarding indicates non-compliance with the Machinery Directive and may invalidate the CE marking.

There is no single prescribed height for machine guarding. The required height depends on the position of the hazard, the distance between the guard and the hazard zone, and the possibility of reaching over or around the guard.

ISO 13857 provides tables that define minimum guard heights in combination with horizontal or vertical distances to the hazard. When a guard is positioned directly adjacent to a hazard zone, a height of approximately 1,400 millimetres or more is typically required. At greater distances, a lower guard may be acceptable. The correct height must always be determined based on the standard and the specific application.

ISO 13857 geeft richtlijnen voor minimale hoogtes in combinatie met horizontale of verticale afstanden tot het gevaar. Wanneer een afscherming direct aan een gevaarzone grenst, is doorgaans een hoogte van circa 1400 millimeter of meer vereist. Bij grotere afstanden kan een lagere afscherming toelaatbaar zijn. De juiste hoogte moet altijd worden vastgesteld op basis van de normtabellen en de specifieke situatie.

The safety distance is the minimum distance between the guard and the hazard zone that prevents a person from reaching the hazard. This distance depends on factors such as the size of openings in the guard, the direction of approach, and the body parts that could potentially access the hazard.

ISO 13857 specifies safety distances for different opening sizes, including mesh apertures and perforations. Larger openings require greater distances to the hazard zone. These requirements apply to fixed guards, mesh guards, and other physical barriers.

ISO 13857 bevat tabellen waarin veiligheidsafstanden zijn vastgelegd voor verschillende openingen, zoals maaswijdtes van gaaspanelen of perforaties. Grotere openingen vereisen grotere afstanden tot de gevaarzone. Deze afstanden zijn van toepassing op vaste afschermingen, gaasafschermingen en andere fysieke barrières.

Mesh panels can be used for machine guarding when visual inspection of the process is required or when ventilation and heat dissipation are necessary, provided that all safety requirements are met.

The mesh size must be selected in relation to the distance to the hazard zone, in accordance with ISO 13857. In addition, mesh panels must be mechanically strong enough and comply with the construction requirements of ISO 14120. Mesh guarding is not suitable where parts, chips, or materials may be ejected at high speed, as it does not provide adequate containment in such cases.

In most industrial robot cells, machine guarding is required. Industrial robots can generate high speeds and forces and therefore pose significant risks to people in the surrounding area. ISO 10218-2 requires robot installations to be safeguarded using physical guards, interlocked access points, or equivalent protective measures.

Only in collaborative applications, as described in ISO/TS 15066, may physical guarding be partially replaced by other protective concepts. This is permitted only when a risk assessment demonstrates that speeds, forces, and potential contact are within safe limits. For conventional industrial robot applications, physical machine guarding remains almost always required.