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PD CEN/TR 17924:2025 - TC Tracked Changes. Safety and control devices for burners and appliances burning gaseous and/or liquid fuels. Guidance on hydrogen specific aspects, 2025
- A-30478059.pdf [Go to Page]
- undefined
- European foreword
- Introduction
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Classification [Go to Page]
- 4.1 Classes of control
- 4.2 Classification of hydrogen
- Table 1 — Hydrogen test gas characteristics — gas dry at 15 C and 1 013,25 mbar
- Table 2 — Hydrogen and hydrogen-based fuel classification by application
- Table 3 — Fuel quality specification for applications other than PEM fuel cell road vehicle and stationary applications
- 5 Common properties
- Table 4 — Gas properties
- 6 General considerations regarding design and construction [Go to Page]
- 6.1 Mechanical parts of the control [Go to Page]
- 6.1.1 Theoretical background
- Figure 1 — Leakage models by theory
- Figure 2 — Pinhole calculations derived from leakage rate measurements at Δp = 15 kPa
- Table 5 — Summary of internal and external leakage rate requirements in current standard editions [Go to Page]
- 6.1.2 Holes
- 6.1.3 Breather holes [Go to Page]
- 6.1.3.1 Alternative requirements for breather holes
- Table 6 — Breather hole and housings leakage rates referring to air as test gas [Go to Page]
- 6.1.3.2 Turbulent flow model and calculations
- Table 7 — Calculation of leakage rates and their relation to different combustible gases in case of diaphragm fracture or fracture of non-metallic housing parts (turbulent flow) [Go to Page]
- 6.1.3.3 Leakage rate measurements and calculations
- Table 8 — Test leaks and their design pressures
- Table 9 — Measurements and calculations of leakage rate ratios for different combustible gases, related to methane, in case of diaphragm fracture (70 dm³/h air leakage rate) [Go to Page]
- 6.1.3.4 Conclusions on leakage rate measurements and calculations in case of diaphragm fracture
- 6.1.3.5 Considerations based on a risk assessment [Go to Page]
- 6.1.3.5.1 Design – failure mode conditions
- Figure 3 — Example of risk scenarios in case of diaphragm fracture
- Table 10 — Worst-case calculations of minimum required breather hole air exchange flow rates BACmin for different combustible gases to stay below 25 % of their LEL at certain leakage rate limits
- Table 11 — Measurements and calculations of minimum required room volumes BVmin at a typical air exchange rate of 0,3 1/h for different combustible gases to stay below 25 % of their LEL at certain leakage rate limits [Go to Page]
- 6.1.3.5.2 Application specific requirements in case of diaphragm fracture
- Table 12 — Calculation of minimum required dilution in case of diaphragm fracture at a maximum air leakage rate of 70 dm3/h for different combustible gases to stay below 25 % of their LEL at applications [Go to Page]
- 6.2 Materials [Go to Page]
- 6.2.1 General material requirements
- Table 13 — Suitability of metallic materials with respect to hydrogen
- Table 14 — Suitability of non-metallic materials with respect to hydrogen [Go to Page]
- 6.2.2 Housing [Go to Page]
- 6.2.2.1 General
- 6.2.2.2 Alternative requirements for housings
- 6.2.2.3 Measurements and calculations
- Table 15 — Measurements and calculations of leakage rate ratios for different combustible gases, related to methane, in case of fracture of non-metallic housing parts (30 dm³/h air leakage rate) [Go to Page]
- 6.2.2.4 Conclusions on leakage rate measurements and calculations in case of fracture of non-metallic housing parts
- 6.2.3 Zinc alloys
- 6.2.4 Springs
- 6.2.5 Resistance to corrosion and surface protection
- 6.3 Electrical parts of the control [Go to Page]
- 6.3.1 Electrical components [Go to Page]
- 6.3.1.1 Test by ignition trial
- 6.3.1.2 Test of ignition source
- 7 Performance [Go to Page]
- 7.1 Leak-tightness [Go to Page]
- 7.1.1 Laminar flow model and calculations
- Table 16 — Calculation of leakage rates and their relation to different combustible gases (laminar flow) [Go to Page]
- 7.1.2 Leakage rate measurements and calculations
- Table 17 — Test leaks and their design pressures
- Table 18 — Measurements and calculations of leakage rate ratios for different combustible gases (e. g. for 120 cm³/h) [Go to Page]
- 7.1.3 Conclusions on leakage rate measurements and calculations
- 7.1.4 Considerations based on risk assessment
- Table 19 — Measurements and calculations of minimum required air exchange flow rates ACmin for different combustible gases to stay below 25 % of their LEL at certain leakage rate limits
- Table 20 — Measurements and calculations of minimum required room volumes Vmin and minimum safety margins SMmin at a typical air exchange rate of 0,3 1/h for different combustible gases to stay below 25 % of their LEL at certain leakage rate limits
- Table 21 — Calculation of minimum required dilution at a maximum air leakage rate of 120 cm3/h for different combustible gases to stay below 25 % of their LEL at applications [Go to Page]
- 7.2 Durability [Go to Page]
- 7.2.1 Elastomers in contact with gas
- 7.2.2 Lubricants in contact with gas
- 8 Marking, instructions [Go to Page]
- 8.1 Instructions
- Annex A (informative) Modifications and/or additions to subclauses of CEN/TC 58/WG 11 standards due to introduction of hydrogen admixtures as combustible gas
- Table A.1 — Specific considerations to CEN/TC 58/WG 11 standards
- Annex B (informative) Modifications and/or additions to subclauses of CEN/TC 58/WG 12 standards due to introduction of hydrogen admixtures as combustible gas
- Table B.1 — Specific considerations to CEN/TC 58/WG 12 standards
- Annex C (informative) Modifications and/or additions to subclauses of CEN/TC 58/WG 13 standards due to introduction of hydrogen admixtures as combustible gas
- Table C.1 — Specific considerations to CEN/TC 58/WG 13 standards
- Annex D (informative) Modifications and/or additions to subclauses of CEN/TC 58/WG 14 standards due to introduction of hydrogen admixtures as combustible gas
- Table D.1 — Specific considerations to CEN/TC 58/WG 14 standards
- Annex E (informative) Risk assessment, standardization, certification, and operation of gas appliances with admixtures fluctuating up to 20 vol.-% hydrogen to natural gas
- Table E.1 — Overview on risk assessment, standardization, certification, and operation of gas appliances with admixtures fluctuating up to 20 vol.-% hydrogen in natural gas
- Annex F (informative) Risk assessment, standardization, certification, and operation of gas appliances using hydrogen referring to ISO 14687:2019, Type I, Grade A
- F.1 General
- Table F.1 — Overview on risk assessment, standardization, certification, and operation of gas appliances using hydrogen referring to ISO 14687:2019, Type I, Grade A
- F.2 Hydrogen Grade A and impurities: Risk analysis concerning CO thermal overload
- Table F.2 — Effects of various permissible hydrogen Grade A gas impurity specifications
- Table F.3 — Some variations due to various permissible hydrogen Grade A gas impurities
- F.3 Reaction equations which explain carbon monoxide formation [Go to Page]
- F.3.1 Hydrogen
- F.3.2 Methane, ethane, and propane
- Table F.4 —Maximum theoretical CO level calculations for impurities with air as oxidizer
- F.4 Conclusions for carbon monoxide and thermal loads
- Annex G (informative) Proposal for leakage rate requirements and tests for gas pipe work including controls (e. g., valves, regulators, pressure switches) used in gas appliances (e. g., forced draught gas-burners or industrial thermo-processing equi...
- Figure G.1 — Test time for pressure decay test depending on test volume
- Figure G.2 — Example of equipment for a forced draught gas burner: Gas supply pressure not exceeding inlet pressure of line components used
- Figure G.3 — Example of equipment for a forced draught gas burner — gas supply pressure exceeding inlet pressure of gas line components used
- Figure G.4 — Example of equipment for a forced draught gas burner — gas supply pressure not exceeding inlet pressure of gas line components used downstream M1 with high gas pressure overload protection device
- Annex H (informative) Diaphragm fracture or fracture of non-metallic parts leakage rate mitigation measures
- Figure H.1 — Minutes to fill a completely sealed room of 0,1 m3 with different gases up to 25 % of their LEL (up to 10 dm³/h: laminar flow; from 30 dm³/h: turbulent flow)
- Figure H.2 — Minutes to fill a completely sealed room of different size with different gases up to 25 % of their LEL at 70 dm3/h air leakage rate (all turbulent flow)
- Figure H.3 — Air exchange rates required for rooms of different size with different gases to stay below 25 % of their LEL at 70 dm3/h air leakage rate (all turbulent flow)
- Annex I (informative) Leakage rate mitigation measures
- Figure I.1 — Days to fill a completely sealed room of 0,1 m3 with different gases up to 25 % of their LEL (all laminar flow)
- Figure I.2 — Days to fill a completely sealed room of different size with different gases up to 25 % of their LEL at 120 cm3/h air leakage rate (all laminar flow)
- Figure I.3 — Air exchange rates required for rooms of different size with different gases to stay below 25 % of their LEL at 120 cm3/h air leakage rate (all laminar flow)
- Bibliography [Go to Page]
