PD CEN/TR 17924:2025 - Page 2

Safety and control devices for burners and appliances burning gaseous and/or liquid fuels. Guidance on hydrogen specific aspects. | Status: Current

1 Scope This document is written in preparation of future revision of standards dealing with the general safety, design, construction, and performance requirements and testing of safety, control or regulating devices (hereafter referred to as controls) for burners and appliances burning hydrogen (see 3.2) or hydrogen admixtures (see 3.3). This document refers to controls with declared maximum inlet pressure up to and including 500 kPa and of nominal connection sizes up to and including DN 250. The purpose of this document is to provide guidance on hydrogen specific topics, which need to be considered in the future standardization of controls covered by CEN/TC 58 documents including:

• — automatic shut-off valves;
• — automatic burner control systems;
• — flame supervision devices;
• — gas/air ratio controls;
• — pressure regulators;
• — manual taps;
• — mechanical thermostats;
• — multifunctional controls;
• — pressure sensing devices;
• — valve proving systems;
• — automatic vent valves.

Hydrogen will play a significant role in the future in several energy segments and requirements and test methods need to be verified and adapted, if necessary. The main target of this document is to lay the ground for defining requirements and tests for controls used for safety related functions (e. g., safety valves, automatic burner control systems, gas/air ratio controls) or regulating devices. Summaries of subclauses to be addressed in the respective standards of each CEN/TC 58 WG are given in

• — Annex A: Specific considerations to CEN/TC 58/WG 11 standards,
• — Annex B: Specific considerations to CEN/TC 58/WG 12 standards,
• — Annex C: Specific considerations to CEN/TC 58/WG 13 standards, and
• — Annex D: Specific considerations to CEN/TC 58/WG 14 standards.

Aspects to be included for gas appliances (e. g., boilers, forced draught gas-burners, or industrial thermoprocessing equipment) covering e. g., risk assessment, standardization, certification, and operation are listed in

• — Annex E: Risk assessment, standardization, certification, and operation of gas appliances with admixtures fluctuating up to 20 vol.-% hydrogen to natural gas, and
• — Annex F: Risk assessment, standardization, certification, and operation of gas appliances using hydrogen referring to ISO 14687:2019, Type I, Grade A.

Proposals for leakage rate requirements and tests for gas pipework including controls (e. g., valves, regulators, pressure switches) used in gas appliances (e. g., forced draught gas-burners or industrial thermoprocessing equipment) and the impact on the installation room size are shown in Annex G. Considerations to be taken to stay below possible lower explosion limits in gas appliances (e. g., boilers, forced draught gas-burners, or industrial thermoprocessing equipment) and its installation rooms are shown in

• — Annex H: Examples of mitigation measures in case of diaphragm fracture or fracture of non-metallic parts for different combustible gases to stay below 25 % of their LEL, based on measurements and calculations, and
• — Annex I: Examples of mitigation measures in case of leakages for different combustible gases to stay below 25 % of their LEL, based on measurements and calculations.