IEC 62046 Explained — Placing Protective Equipment: Reach-Over, -Through, -Around and -Under

Most engineers know ISO 13855. It is the equation everyone quotes, S = K × T + C, and it answers a single question: how far back from the hazard does the protective field have to sit so the machine stops before a hand reaches the danger? That is a necessary calculation. It is not a complete installation. A curtain mounted at a textbook-perfect distance is still useless if the operator can step over the top beam, duck under the bottom one, walk around the end, or push an arm through a gap. IEC 62046 is the standard that closes those holes.

The full title is IEC 62046:2018, “Safety of machinery — Application of protective equipment to detect the presence of persons.” It is Edition 1.0, published March 2018, prepared by IEC Technical Committee 44. It cancelled and replaced the older IEC/TS 62046:2008 Technical Specification — meaning it was promoted from a TS into a full International Standard. As of 2026 it remains the current edition. The site already covers the distance maths in depth; this is the companion piece on placement.

What does IEC 62046 actually cover?

IEC 62046 specifies requirements for the selection, positioning, configuration and commissioning of protective equipment that detects the momentary or continued presence of persons near dangerous machine parts in industrial applications. The devices in scope are the electro-sensitive protective equipment (ESPE) defined in the IEC 61496 series — AOPDs (light curtains), AOPDDRs (laser scanners), and vision-based protective devices — plus pressure-sensitive mats and floors defined in ISO 13856-1. It is written for protecting persons aged 14 and older.

The clause structure is worth knowing because it maps to the actual job: Clause 4 covers selection of protective measures; Clause 5 covers general application requirements, including positioning and configuration of the detection zone (5.1), stopping-performance monitoring (5.4), start interlock (5.5), restart interlock (5.6), muting (5.7) and reinitiation (5.8); and Clause 6 covers the particular requirements per device type — AOPDs, AOPDDRs, VBPDs and pressure-sensitive mats. If you build machines, Clause 5 is where you live.

How does IEC 62046 relate to ISO 13855 and ISO 13849-1?

IEC 62046 sits on top of two other standards and pulls them together. The minimum safety distance is calculated under ISO 13855 from the approach speed of the body. The safety performance — the Performance Level (PL) under ISO 13849-1 or the Safety Integrity Level (SIL / SILCL) under IEC 62061 — is rated separately. IEC 62046 uses both: its Clause 4.5 formalises the human characteristics, approach speed K and the intrusion factor C — the same K and C that drive S = K × T + C. Then it tells you how to apply the device so those numbers mean something in the real layout.

One detail from the 2018 edition deserves a flag. It includes a Table 1, “ESPE Types and achievable PL or SIL,” that caps the achievable SIL per IEC 62061 and the achievable PL per ISO 13849-1 by device type. And it states plainly that a SILCL, PL or SIL number on its own is not sufficient to indicate a device's suitability as a safeguard. That sentence should be printed on every purchasing desk. A Type 4 / PL e curtain bolted where a person can reach over it is a high-performance device in an unsafe installation. The rating tells you how reliably it does its job, not whether you gave it the right job.

What are reach-over, reach-through, reach-around and reach-under?

These are the four ways a body gets to the hazard despite the field, and IEC 62046 requires the detection zone — supplemented by mechanical guarding where necessary — to defeat all four. They are simple once you picture them:

• Reach-over — stepping or reaching above a horizontal or angled field. Defeated by the height of the top beam or by an adequate distance for the increased reach.
• Reach-under — crawling or reaching beneath the lowest beam. Defeated by keeping the bottom beam low enough.
• Reach-through — passing a body part through an opening larger than the device's detection capability. This is governed by resolution: a 14 mm finger-detection curtain closes gaps a 40 mm hand-detection one leaves open.
• Reach-around — going past the side of the protected field. Defeated by sizing the field wide enough or by hard guarding the flanks.

The point IEC 62046 hammers is that the detection zone has to be positioned and dimensioned against all four at once. The distance calculation only addresses approach straight through the field. Everything else is geometry, and geometry is where most field failures actually happen.

What heights should multiple-beam light barriers use?

For multiple-beam light-beam access guards — AOPDs used as trip devices across a walk-through opening rather than a full vertical plane — IEC 62046 gives standard beam heights above the reference plane. They are worth memorising:

• 2 beams: 400 mm and 900 mm.
• 3 beams: 300, 700 and 1100 mm.
• 4 beams: 300, 600, 900 and 1200 mm.

The logic is the reach geometry again: the lowest beam prevents reach-under, the highest beam prevents reach-over. The general rule for vertical and horizontal access guards is that the bottom beam sits no higher than 300 mm above the reference plane to stop crawling under, and the top beam no lower than 900 mm to stop stepping over. Get those two numbers wrong and the intermediate beams will not save you.

One update changes the 2-beam picture. ISO 13855 was revised to ISO 13855:2024, which effectively rules out 2-beam light grids by limiting the spacing between two beams to a maximum of 400 mm — a person can otherwise climb through or reach between the 400 mm and 900 mm beams. If you are specifying a new multiple-beam guard, treat 3-beam as the practical floor and check the 2024 text before reusing an old 2-beam layout.

What are trip and presence-sensing functions?

IEC 62046 (Clause 4.4) treats three uses of protective equipment, and the difference governs how you place and configure the device. A trip function initiates a stop the moment detection occurs — the operator breaks the field, the machine stops. A presence-sensing function keeps the machine stopped for as long as a person remains inside the detection zone, which is what you need when someone can stand behind the field, inside the hazard area, out of sight of the start button. The third is a combination of the two.

This is why a horizontal area device on a robot cell so often needs presence sensing plus a restart interlock: a trip-only field lets the machine restart while a person is still standing in the danger zone. A DAIDISIKE DQSA area light curtain covering a walk-in footprint is a presence-sensing application; a DQC hand-guard curtain across the mouth of a press is a trip application. Same family of device, different clause of IEC 62046, different configuration.

How does IEC 62046 govern muting?

Muting is the temporary, automatic and safe suspension of the protective function so material can pass through the detection zone without stopping the machine — the pallet moving out of a palletiser is the classic case. IEC 62046 specifies it in Clause 5.7, split into muting for access by persons (5.7.2), muting for access by materials (5.7.3), and mute-dependent override (5.7.4). The governing requirement is blunt: muting must not be capable of being activated by a person, and it must not be defeatable.

Annex D is where the geometry lives. It gives photoelectric muting-sensor configurations — two-sensor crossed-beam and four-beam arrangements with timing or sequence control, and a maximum permitted time between sensor signals. The crossed-beam pattern is the trick: the two muting sensors cross at a point such that only an object of the expected length, travelling in the expected direction, trips both within the allowed window. A person cannot reproduce that signal pattern by walking through. The sensor signals are monitored independently, so a stuck or bridged sensor is detected rather than silently enabling a permanent mute.

A muting indicator — the muting lamp — is required to signal that the protective function is suspended, and IEC 62046 addresses its monitoring. Annex D also includes explicit methods to avoid manipulation of the muting function and figures on muting-timeout behaviour, where the mute is terminated either by the ESPE itself or by a timer. The distinction between muting and blanking trips people up constantly; we keep them straight in muting vs blanking.

So how do you use IEC 62046 on a real job?

Calculate the distance under ISO 13855. Then place the device under IEC 62046: confirm the detection zone defeats reach-over, reach-through, reach-around and reach-under; set multiple-beam heights to the standard values; decide whether you need a trip function, a presence-sensing function, or both, and add start and restart interlocks accordingly; design any muting with crossed-beam or four-beam sensor geometry, a bounded time window, independent monitoring and a monitored muting lamp. Finally, check that the device Type supports the PL or SIL your risk assessment demands — remembering that the rating alone does not make the installation safe. The distance is the part everyone calculates. The placement is the part that actually protects the operator.