Tunnel boring machines - Safety requirements; German and English version prEN 16191:2023 / Note: Date of issue 2023-02-24*Intended as replacement for DIN EN 16191 (2014-09).

Standard Background and Technological Evolution

EN 16191:2023, "Safety Technical Requirements for Tunnel Boring Machines," is a comprehensive revision of the 2014 version. Developed by CEN/TC 151 Technical Committee, it aims to provide specific safety requirements for the EU Machinery Directive 2006/42/EG. This is a Type C standard, providing protective measures against significant hazards in the design, manufacture, use, and maintenance of tunnel boring machines (TBMs) and related equipment (such as shield tunneling machines, miniature tunnel boring machines, and auger drilling rigs).

Compared to the 2014 version, the main technical changes include: **revised definitions** (such as adding terms like "accessible cutterhead" and "pressure transfer chamber"), **comprehensively updated safety requirements** (emphasizing strengthened clauses on pressure chambers, cutterhead locking, ventilation and gas monitoring, and fire protection), **updated list of major hazard** (adding hazards such as laser radiation and high-pressure fluid jets), and **updated Appendix ZA** (corresponding to the EU Machinery Directive). The standard also introduces a "Performance Level PLr" requirement for the design of safety-related control systems. The standard imposes strict requirements on the **cutterhead** locking device:** when the cutterhead stops, a device must be provided to prevent accidental rotation, with a resistance capacity of at least 5% of the maximum cutterhead torque or 10 kN of eccentric load (whichever is greater). For tunnel boring machines with a diameter ≥ 7.5 m, the width of the access passage to the rear of the cutterhead must be ≥ 0.6 m, and the cross-section ≥ 0.45 m². For machines operating in closed mode, cutterheads with a diameter ≥ 5.5 m must be equipped with a remote visual inspection system and a structural wear detection system.

Dimensions	EN 16191:2014	EN 16191:2023
Cutterhead Locking Requirements	Only require prevention of rotation	Specify force values and monitoring requirements (hydraulic cylinder redundancy, load holding valve)
Channel Dimensions	Diameter not distinguished	Classified by D≤3.8 m, 3.8-7.5 m, >7.5 m
Hazard List	16 items	Added lasers, high-pressure fluids, etc., for a total of 9 categories
Control System PLr	No Specific Class	Specified PLr (Class B/C/D)
Rescue Chamber Requirements	Briefly Mentioned	Appendix E specifies dimensions, air supply, power supply, etc.

Pressure Chamber and Pressure Transfer

For machines that require access to the excavation chamber via a pneumatic lock, the standard references prEN 12110-1:2023 and prEN 12110-2:2023, and additionally requires: dual setup of breathing gas supply lines, warning signs must be installed at oxygen discharge points, the movement of the pressure transfer chamber (shuttle) must use mechanical devices to prevent gravity slippage, the vertical lifting speed must not exceed 3 m/min, and the lifting platform must comply with FprEN 1570-1. The intermediate chamber must provide a fixed floor area of at least 2.5 m² and a minimum clearance of 1.7 m. Ventilation and Gas Monitoring All machines (except miniature TBMs) must be equipped with explosion-proof atmospheric monitoring devices to monitor oxygen and methane concentrations. The default methane alarm threshold is 1% (volume fraction), and the automatic shutdown threshold is 1.5%. When the methane concentration reaches the shutdown threshold, all non-explosion-proof electrical machinery must immediately and automatically shut down, but the monitoring system, emergency lighting, and evacuation alarm system must continue to operate. The ventilation system must ensure that the gas, dust, and temperature in all areas comply with national exposure limits.

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Implementation Recommendations

The manufacturer and user should **agree on the intended use of the machine** early in the project, including geological conditions, groundwater, tunnel diameter, and environmental requirements (see 4.2.12).

Key implementation steps include: Risk Identification: Conduct a risk assessment based on the list of major hazards in Appendix A, paying particular attention to newly added hazards such as lasers, high-pressure fluids, and fire. Control System Design: Select the performance levels of safety-related components according to Table 3 (PLr requirements) and verify them according to EN ISO 13849-1. Escape and Rescue: Ensure the main passageway dimensions meet the requirements of Table 1, and equip it with a rescue cabin (if agreed) and comply with Appendix E. Noise and Vibration: Conduct noise measurements according to Appendix D, declaring the A-weighted sound pressure level and uncertainty (KpA=5 dB). Documentation and Labelling: Provide multilingual operating manuals, including emergency escape route maps, warning signs, and the CE mark. The draft standard is currently in the public consultation phase (ending April 24, 2023), and stakeholders can submit comments through the DIN or DKE websites. The final version is expected to replace EN 16191:2014 and provide an updated safety compliance framework for tunnel boring machines entering the EU market.