Engineering selection guide
A mesh description alone cannot establish a safe distance from a machine hazard. A label such as 50 × 30 mm may describe the clear opening or the wire spacing, and those are different dimensions. Guard height, floor gap, nearby structures and the direction of access also matter.
First establish what the mesh dimensions mean
Pitch is the centre-to-centre spacing of adjacent wires. Clear opening is the unobstructed space between them. For an ideal rectangular grid using equal-diameter round wire, and ignoring coating and tolerances, nominal clear opening is pitch minus wire diameter in each direction. Thus 50 × 30 mm pitch with 3 mm wire gives an illustrative 47 × 27 mm opening. This arithmetic is not a safety-distance assessment; tolerances, coating, welds and the actual maximum opening still need checking.
The current MG20 trial baseline is nominal 20 × 100 mm pitch with Ø3 mm wire, not 50 × 30 mm. Its aperture definition remains subject to confirmation. Do not treat a catalogue label or the browser mesh rendering as a verified measurement.
Assess every possible access route
| Access route | Information to record |
|---|---|
| Through mesh or joints | Actual opening geometry, orientation and distance to the nearest reachable hazard. |
| Over the guard | Hazard height, protective structure height and horizontal separation. |
| Under the guard | Maximum gap over the real floor, the hazard location and foreseeable limb access. |
| Around ends or openings | End returns, posts, conveyors, service penetrations and other possible reach paths. |
ISO 13857:2019 addresses separation distances for upper and lower limb access. Its published scope makes clear that distance alone does not resolve every hazard, and climbing requires additional consideration. Use the applicable cases and conditions in the standard for the actual installation. ISO 13857:2019 overview.
The MG20 standalone-bay trial's nominal 100 mm floor clearance is a geometric starting point, not an approved safe gap. Floor slope, channels and local depressions can increase the opening. Distinguish panel height from the installed protective-structure height measured from the relevant standing surface. A 1900 mm panel height alone does not demonstrate that reaching over is prevented.
Check guard performance as well as reach
A reach-distance check does not establish resistance to impact, ejected parts, heat or other process hazards. Select the guard construction for the application and review its supports, fixings and foreseeable loading. ISO 14120 addresses guard selection and construction; it does not cover interlocking devices. ISO 14120:2015 overview.
Include normal operation, setting, cleaning and maintenance in the assessment. Identify platforms, steps or stored items that change where a person can stand, and locations where someone may try to bypass the guard. A conveyor opening or required access point needs its own protective arrangement rather than an unexplained gap in the perimeter.
Prepare a reviewable guard layout
Put the mesh definition, measured openings, guard and hazard heights, minimum separation, floor profile and access points on the drawing. Record the risk assessment and the standards used, including the relevant machine-specific requirements. Have the final arrangement checked by the responsible machinery-safety engineer before installation.
Explore MG20 trial configurations and request CAD to plan the physical arrangement. The current models are for concept evaluation; they are not a certificate of guarding performance or installation approval.