Hypothetical design case
Guard door open. Assess stopping and restart.
A proposed access sequence with two safety questions and explicit evidence gaps.
Reviewed 2026-11-04 · Engineering interpretation · authoring reviewed
Scenario and hazard
Hypothetical automatic handling cell with a single gate and a retained load. Opening the gate allows entry into robot reach. Assess collision, trapping and dropped-load hazards. Servicing requires a separate hazardous-energy assessment.
SF-G1. Stop on opening
Proposed chain: monitored gate sensor → safety logic → supported robot stop interface and hazardous tooling. Specify the safe state for motion, gravity and stored energy. If a person can reach danger before the verified stop completes, evaluate further risk reduction such as guard locking.
SF-G2. Control restart
In this proposed sequence, gate closure restores one condition. An intentional reset from a suitable viewing position precedes a separate start command. Test whole-body access, hidden people, sensor faults and power restoration. Check this design assumption against the actual risk assessment and robot configuration.
Evidence and open inputs
Keep both functions in the risk assessment with their PLr rationale, circuit and software versions, reliability inputs and stopping measurements for credible loads and speeds. Test opening, faults, closing, reset and power return. PLr, achieved PL and stop time remain undetermined.
Sources & editions
OSHA Technical Manual, Section IV Chapter 4 ↗
Web edition checked 2026-11-04
VII and VIII.1, application assessment and non-collaborative safeguarding
OSHA 29 CFR 1910.147, control of hazardous energy ↗
Web text checked 2026-11-04
1910.147(a)(1)(i) and (a)(2), servicing scope
Universal Robots UR3e, Safety I/O ↗
PolyScope SW5.22 manual
Safety I/O table, configuration-dependent stop and reset behavior
Robot Safety Forum original engineering notes
Initial publication edition 2026-11-04
Proposed SF-G1 and SF-G2 scenario and tests