At a glance
Key points
- Use the glossary to align engineering and purchasing language.
- Define safety functions explicitly in project specifications.
- Check current standards for formal definitions.
- Avoid using ‘interlock’ and ‘guard locking’ as interchangeable terms.
- Record assumptions such as safe state, access frequency and stopping time.
1. A–G
- Actuator
- The coded or mechanical element that operates an interlock switch when a guard reaches its intended position.
- Danger zone
- A space in or around machinery where a person can be exposed to a hazard.
- Emergency stop
- A complementary protective measure intended to avert or reduce an existing or impending hazard; it is not a substitute for primary safeguarding.
- Fixed guard
- A guard affixed so that it can only be opened or removed using the intended method, normally a tool.
- Guard
- A physical barrier designed as part of the machine to provide protection, such as a casing, screen, door or enclosing fence.
- Guard locking
- A function that keeps a movable guard closed until defined release conditions are met.
2. H–P
- Interlock
- A device or arrangement that monitors guard position or another condition and influences machine operation.
- Light curtain
- An electro-sensitive protective device using an array of light beams to detect interruption of a protected plane.
- Muting
- A temporary automatic suspension of a protective function during an allowed condition, commonly controlled material transfer.
- Performance Level (PL)
- A discrete level used in ISO 13849-1 to describe the ability of safety-related parts of control systems to perform a safety function under foreseeable conditions.
- PLr
- The required Performance Level determined for a safety function through risk assessment.
- PUWER
- The Provision and Use of Work Equipment Regulations 1998, governing suitability, maintenance and safe use of work equipment in Great Britain.
3. R–Z
- Reset
- A deliberate action acknowledging that conditions are ready for operation; reset should not itself initiate hazardous movement unless specifically justified.
- Risk assessment
- A structured process of identifying hazards, estimating and evaluating risk, and selecting risk-reduction measures.
- Safe state
- The condition defined for a safety function in which the relevant risk is reduced, such as stopped movement or isolated energy.
- Safety distance
- The minimum separation intended to prevent a person reaching a hazard before it has become safe.
- Safety function
- A function whose failure can result in an immediate increase of risk, defined by its input, logic, output and required response.
- Validation
- Confirmation, by examination and evidence, that the implemented safety-related measures meet their specified requirements.
4. Use precise terms in project specifications
Instead of writing “fit safety switches”, define which guards are monitored, what movement must stop, whether locking is required, how release is authorised, where reset occurs and what happens after a fault. Precise language reduces gaps between mechanical design, control programming and commissioning.
Where a term has a formal definition in legislation or a standard, use the current source for the final project document. This glossary is explanatory rather than normative.
Sources and review basis
Authoritative references
This guide summarises general engineering considerations. Current legislation, guidance and standard editions should be confirmed for the specific project.
How Oxford Machine Guarding can help
We can survey the equipment, define the mechanical guarding and safety-system scope, develop the design, supply and install the solution, and provide testing and handover records appropriate to the agreed project boundary.
Important: this guide provides general technical information. It is not a substitute for a machine-specific risk assessment, legal advice, or verification by the responsible dutyholder.
