30/40 mm hand protection · 3–6 m range
Content updated:
Typical ranges and response time, with sizing tips. This guide explains how to select and deploy 30 mm / 40 mm safety light curtains for hand protection across 3–6 m working distances. It provides a selection matrix, ISO 13855 quick calculator with the correct C term for hand resolutions, mounting/alignment notes, and acceptance records.
Quick answer: For a 3–6 m opening, check detection capability and operating range independently. A 30 mm or 40 mm label may describe beam pitch rather than the smallest reliably detected object. Use the exact configuration’s maximum response time and verify all access routes. A coarser detection capability does not by itself establish longer range or better contamination tolerance.
1) Where 30/40 mm are the right choice
Use the safety light curtain range and selection criteria to shortlist a series, then verify its declared 30 mm or 40 mm detection capability and required span together. This page focuses on that resolution-and-range decision.
Use cases
- General machine guarding where hand access is credible but finger access is unlikely.
- Conveyors, robot loading zones, press lines with wider openings, packaging cells.
- Installations needing longer range (3–6 m) with documented optical performance at the installed span.
Engineering characteristics
- Detection capability and beam pitch differ; wider spacing does not prove resistance to dirt or oil mist.
- Use the maximum ON-to-OFF response time for the exact model, height and operating mode.
- The legacy through-field example uses C = 8×(d−14): 30 mm → 128 mm, 40 mm → 208 mm. This is not a complete ISO 13855:2024 assessment.
2) Selection matrix (3–6 m working distances)
| Model class | Resolution | Protective height (typ.) | Working range | Response time | Notes |
|---|---|---|---|---|---|
| Compact opening | Declared 30 mm candidate | Match active field to opening | Documented span must cover installation | Maximum ON-to-OFF, exact model | Confirm reach-through and reach-over requirements |
| General opening | Compare declared 30 and 40 mm | Check active endpoints, not housing length | Verify operation at required 3–6 m | Include mode and cascade effects | Do not infer optical margin from detection capability |
| Extended range | Selected by risk assessment | Verify coverage and access around ends | Require documented long-range configuration | Use its documented worst case | A 6 m requirement is not met by every model |
| Window-protected | Verify approved assembly | Keep full field unobstructed | Apply accessory derating from manual | No generic accessory time increment | Check reflective clearance and cleaning plan |
These rows identify evidence needed for selection; they are not generic product specifications. Use the exact manual and the complete machine stopping time in the applicable positioning calculation.
3) ISO 13855 quick calculator (hand resolutions)
When finger access remains credible, review the 10 mm detection-capability and protective-height checks. For final positioning, apply ISO 13855:2024; the helper below only illustrates a legacy through-field term.
Stop + ESPE + logic + others
C term (auto): 128 mm
Limited legacy through-field example: S = K×T + C + margin, with K fixed at 2000 mm/s, C = 8×(d−14) for the declared 30/40 mm detection capability, and a 100 mm floor. It does not assess reach-over, reach-under, bypass access or every ISO 13855:2024 requirement. Use the maximum complete stopping time; this is not installation approval.
4) Mounting & alignment (best practice)
Mechanical
- Use rigid brackets; avoid long cantilevering. Verify frame squareness.
- Maintain the manufacturer’s minimum reflective clearance on every side of the field. Tilting the columns by a generic angle does not establish safe detection.
- Cable routing and shielding must follow the sensor, safety controller and drive manuals.
Alignment routine
- Coarse align (spirit level), then power on and read indicators.
- Maximize horizontally → vertically; torque fasteners while watching stability.
- With hazardous motion prevented, use the exact test piece prescribed for the device and configured detection capability. Follow the complete field and boundary path in the manual; do not substitute a larger 40 mm piece for a required 30 mm piece.
5) Acceptance & periodic verification
| Item | Test | Expected | Result | Notes |
|---|---|---|---|---|
| Resolution check | Use the exact device-prescribed test piece over the complete manual-specified path and accessible boundaries, with hazardous motion prevented | Specified safe state throughout; a larger test piece is not an acceptable substitute | ||
| OSSD coherence | Block/unblock beams | Both safety outputs reach the safe state within documented limits | ||
| EDM | Simulate feedback fault using the approved safe test procedure | Reset inhibited | ||
| Reset logic | Verify documented monitored reset behavior | No hold-to-reset | ||
| Safety distance | Compute S | Installed S ≥ calculated |
CSV template (copy)
Machine/Line,Location,Resolution,Height,Range,Ttotal(ms),K(mm/s),C(mm),Margin(mm),S(mm),Date,By,Notes
,,Exact declared value,Exact active height,Actual span,,,,,,,,Confirm actual model and positioning method6) Troubleshooting
| Symptom | Probable cause | Fix |
|---|---|---|
| False trips at long range | Parallel power cables, strong light, reflections | Re-route cables and use approved shielding; meet reflective clearance and repeat the detection test |
| Intermittent misses | Vibration/misalignment | Stiffen mounts; re-align; verify torque and frame squareness |
| Cannot achieve S distance | Stop time underestimated | Measure actual stop-time; re-calc S; move curtain/upgrade stop path |
7) FAQ
30 mm or 40 mm — which should I choose?
Use the declared detection capability required by the risk assessment, not beam pitch. A 40 mm rating allows more intrusion than 30 mm in the same applicable through-field calculation. Neither value by itself guarantees a longer range, easier alignment or resistance to oil mist.
How do ranges relate to response time?
Check the selected model, height, synchronization and operating mode. Optical span alone does not establish the maximum response time. Use the documented ON-to-OFF time for the actual configuration when calculating the complete stopping time.
Do I still need test rods for hand protection?
Yes. Use the test piece specified for the exact device and its configured detection capability. Check the full protective field and accessible boundaries according to the manual, with hazardous motion prevented, and document the result.