CEN/TC 268

Date: 2025-03

prEN 17124:2025

Secretariat: AFNOR

Hydrogen fuel — Product specification and quality assurance for hydrogen refuelling points dispensing liquid or gaseous hydrogen — Proton exchange membrane (PEM) fuel cell applications for vehicles

Wasserstoff als Kraftstoff — Produktfestlegung und Qualitätssicherung — Protonenaustauschmembran (PEM) - Brennstoffzellenanwendungen für Straßenfahrzeuge

Carburant hydrogène - Spécification de produit et assurance qualité pour les points de ravitaillement en hydrogène distribuant de l'hydrogène liquide ou gazeux - Applications des piles à combustible à membrane à échange de protons (MEP) pour les véhicules

ICS:

Contents Page

European foreword 3

1 Scope 4

2 Normative references 4

3 Terms and definitions 4

4 Requirements 5

5 Hydrogen Quality Assurance Methodology 6

5.1 General Requirements – Potential sources of impurities 6

5.2 Prescriptive Approach for Hydrogen Quality Assurance 6

5.3 Risk Assessment for Hydrogen and Quality Assurance 6

5.4 Impact of impurities on fuel cell power train 9

6 Hydrogen Quality Control Approaches 11

6.1 General requirements 11

6.2 Spot sampling 11

6.3 Monitoring 11

7 Routine Quality Control 11

8 Non-routine Quality Control 11

9 Non compliances 12

Annex A (informative) Impact of impurities 13

Annex B (informative) Example of Supply chain evaluation with regards to potential sources of impurities 17

Annex C (informative) Example of Risk Assessment template 21

Bibliography 23

European foreword

This document (prEN 17124:2025) has been prepared by Technical Committee CEN/TC 268 “Cryogenic vessels and specific hydrogen technologies applications”, the secretariat of which is held by AFNOR.

This document supersedes EN 17124:2022.

This document has been prepared under a standardization request addressed to CEN by the European Commission. The Standing Committee of the EFTA States subsequently approves these requests for its Member States.

This document specifies the quality characteristics of liquid or gaseous hydrogen fuel dispensed at hydrogen refuelling stations for use in proton exchange membrane (PEM) fuel cell vehicle systems, and the corresponding quality assurance considerations for ensuring uniformity of the hydrogen fuel.

There are no normative references in this document.

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

constituent

component (or compound) found within a hydrogen fuel mixture

3.2

contaminant

impurity that adversely affects the components within the fuel cell system or the hydrogen storage system

Note 1 to entry: An adverse effect can be reversible or irreversible.

3.3

detection limit

lowest quantity of a substance that can be distinguished from the absence of that substance with a stated confidence limit

3.4

fuel cell system

power system used for the generation of electricity on a fuel cell vehicle, typically containing the following subsystems: fuel cell stack, air processing, fuel processing, thermal management and water management

3.5

hydrogen fuel index

fraction or percentage of a fuel mixture that is hydrogen

3.6

irreversible effect

effect which results in a permanent degradation of the fuel cell power system performance that cannot be restored by practical changes of operational conditions and/or gas composition

3.7

on-site fuel supply

hydrogen fuel supplying system with a hydrogen production system in the same site

3.8

off-site fuel supply

hydrogen fuel supplying system without a hydrogen production system in the same site, receiving hydrogen fuel which is produced out of the site

3.9

particulate

solid or liquid particle (aerosol) that can be entrained somewhere in the delivery, storage, or transfer of the hydrogen fuel

3.10

reversible effect

effect which results in a non-permanent degradation of the fuel cell power system performance that can be restored by practical changes of operational conditions and/or gas composition

The fuel quality requirements at the dispenser nozzle shall meet the requirements of Table 1.

NOTE The fuel specification is not process or feedstock specific. Non-listed contaminants have no guarantee of being benign.

Table 1 — Fuel quality specifications for PEM fuel cell road vehicle applications

A quality assurance plan for the entire supply chain shall be created to ensure that the hydrogen quality will meet the requirements listed in Clause 4. The methodology used to develop the quality assurance plan can vary but shall include one of the two approaches described in this document. The general description of these two approaches are described in 5.2 and 5.3.

For a given Hydrogen Refuelling Station (HRS), the contaminants listed in the hydrogen specification referred to Table 1 could be present. There are several parts of the supply chain where impurities can be introduced. Annex B describes potential impurities at each step of the supply chain.

When a contaminant is classified as potentially present, it shall be taken into account in the Quality Assurance methodology (risk assessment or prescriptive approach) described below.

A prescriptive approach can be applied for clearly identified supply chains. The prescriptive approach is not defined in this document.

Risk assessment consists of identifying the probability of having each impurity above the threshold values of specifications given in Table 1 and evaluating the severity of each impurity for the fuel cell car. As an aid to clearly defining the risk(s) for risk assessment purposes, three fundamental questions are often helpful:

— What might go wrong: which event could cause the impurities to be above the threshold value?

— What is the likelihood (probability of occurrence) that impurities could be above the threshold value?

— What are the consequences (severity) for the fuel cell car?

In doing an effective risk assessment, the robustness of the data set is important because it determines the quality of the output. Revealing assumptions and reasonable sources of uncertainty will enhance confidence in this output and/or help identify its limitations. The output of the risk assessment is a qualitative description of a range of risk. The probability of an occurrence, in which each hydrogen impurity exceeds the threshold value, is defined by the following table of occurrence classes:

Table 2 — Occurrence classes for an impurity

The range of severity class (level of damage for vehicle) is defined in Table 3.

Table 3 — Severity classes for an impurity

The final risk is defined by Table 4, titled “Acceptability table”, and which combines results from Tables 2 and 3.

Table 4 — Acceptability table

For each impurity of the specification and for a given HRS (including the supply chain of hydrogen), a risk assessment shall be applied to define the global risk. Risk control includes decision making to reduce and/or accept risks. The purpose of risk control is to reduce the risk to an acceptable level. The amount of effort used for risk control should be proportional to the significance of the risk. Decision makers might use different processes, including a benefit-cost analysis, for understanding the optimal level of risk control. Risk control might focus on the following questions:

— Is the risk above an acceptable level?

— What can be done to reduce or eliminate risks?

— What is the appropriate balance among benefits, risks and resources?

For each level of risk, decision shall be taken in order to either refuse the risk and then find mitigation or barriers to reduce it, or accept the risk level as it is. Risk reduction focuses on processes for mitigation or avoidance of quality risks when it exceeds an acceptable level (yellow or red zone in Table 5). Risk reduction might include actions taken to mitigate the severity and/or probability of occurrence.

In the yellow zone, the risk could be acceptable but redesign or other changes should be considered if reasonably practicable. Further investigation should be performed to give better estimate of the risk. When assessing the need of remedial actions, the number of events of this risk level should be taken into consideration in order to be As Low As Reasonably Practicable (ALARP).

The risk assessment shall be done at each step of the supply chain (production, logistics and refuelling stations) for each impurity mentioned in Table 1. It shall consider normal operations and maintenance. An example of such approach is given in Annex C.

The severity level of each impurity shall be determined. Indeed, the impact on the car if each impurity exceeds the threshold values given in Table 1 will depend on the concentration of the contaminant. The following Table 5 shows the summary of the concentration based impact of the impurities on the fuel cell.

For more information on the impact of the impurities on fuel-cell, see Annex A.

In the first two columns the contaminants with their chemical formulas are given. An estimate of the exceeded concentration above the threshold value for each impurity is named “Level 1” and is given in column 5. According to this concentration, a severity class is given in column 4 for each impurity. This severity class covers the impact of this impurity above the threshold value up to this limit.

If higher concentrations that exceed Level 1 can be reached, the Severity Class is given in column 6.

Table 5 — Severity Classes (SC) — Impact of impurities on fuel cell powertrain

Quality control for the purpose of quality assurance may be performed at the dispenser nozzle or at other location in accordance with the quality assurance risk assessment.

There are two kinds of quality control at an HRS: on line monitoring or off line analysis after spot sampling.

These methods shall be used individually or together to ensure hydrogen quality levels.

Spot sampling at an HRS involves capturing a measured amount for chemical analysis. Sampling is used to perform an accurate and comprehensive analysis of impurities, which is done externally, typically at a laboratory. Since the sampling process involves drawing a gas sample, it is typically done on a periodic basis and requires specialized sampling equipment and personnel to operate it.

The sampling procedure shall ensure and maintain the integrity of the sample.

NOTE ISO 19880‑9 and ISO 21087 include recommendations for sampling procedure.

An HRS can have real time monitoring of the hydrogen gas stream for one or more impurities on a continuous or semi-continuous basis. A critical impurity can be monitored to ensure it does not exceed a critical level, or monitoring of canary species are used to alert of potential issues with the hydrogen production or purification process.

When used, monitoring equipment should be installed in-line with the hydrogen gas stream and shall meet the process requirements of the HRS, as well as be calibrated on a periodic basis.

Routine analysis shall be performed on a periodic basis once every specified time period or once for each specific number of deliveries if a quality certificate is not available. The methodology selected in hydrogen quality assurance plan determines the type and frequency of the routine analysis. A prescriptive methodology may be used as described in 5.2 or a risk assessment methodology may be used as described in 5.3. Information on the routine analysis for each step of the supply chain is provided in Annex B.

The hydrogen quality plan shall:

a) include sampling and analysis when a new fuelling station is commissioned;

b) identify any other reasonably foreseeable non-routine conditions requiring subsequent sampling

and analysis actions.

Some common non-routine conditions include but are not limited to the following:

— a new production system is constructed at a production site or a new HRS is first commissioned;

— the production system at a production site or HRS is modified;

— a routine or non-routine open inspection, repair, catalyst exchange, or the like is performed on a production system at the production site or HRS;

— a question concerning quality is raised when, for example, there is a problem with a vehicle because of hydrogen supplied at the production site or HRS, and a claim is received from a user directly or indirectly;

— an issue concerning quality emerges when, for example, a voluntary audit raises the possibility that quality control is not administered properly;

— analysis necessary for testing, research or any other purposes;

— after any severe malfunctions of transportation system of compressed hydrogen, liquid hydrogen and hydrogen pipeline.

In case of quality control showing results not compliant with Table 1, appropriate action shall be taken by the operator to prevent further out of specification H2 refuelling of the vehicles.

1. 
   (informative)
   
   Impact of impurities
   1. General

The following chapter gives a brief description of the impact of impurities on the stack, fuel cell components and the complete fuel cell powertrain. Detailed information can be found in the relevant literature and journal publications. It shall be noted that Annex A refers to known impurities and their effects on the fuel cell powertrain at the time of publication. It cannot be excluded that further impurities exist. Furthermore, in most cases, only the impact of a single impurity has been investigated and there is still the need for fundamental research regarding the impact of a combination of the different impurities on the fuel cell power train.

• 1. Inert Gases: Argon, Nitrogen

The main effect due to the presence of inert gases such as argon (Ar) and nitrogen (N2) is to lower the cell potential due to the dilution effect of the inert species (dilution of the hydrogen gas) and inertial (diffusion) effects. Nevertheless, under consideration of the threshold value current stack designs, fuel cell components and fuel cell powertrains are not adversely affected by inert constituents. High inert gas concentrations will lead to power losses, increased fuel consumption and loss of efficiency. Furthermore, hydrogen starvation caused by high inert gas concentrations could lead to permanent damage of the fuel cell stack or car stop. Inert gases will accumulate in the anode loop and could affect venting and recycle blower control. Further sources report that the presence of N2 hinders desorption of adsorbed carbon monoxide (CO) from the surface of the anode catalyst. It should also be noted that inert gases can affect the accuracy of mass metering instruments for hydrogen dispensing.

• 1. Oxygen

Oxygen (O2) concentrations lower than the threshold value do not adversely affect the function of the fuel cell. Reactive gas mixtures shall be prevented. However, it could be a concern for some on-board vehicle storage systems, for example, by reaction with metal hydride storage materials.

• 1. Carbon Dioxide

The contamination effects of carbon dioxide (CO2) depend on the concentration, fuel cell operation conditions and anode catalyst composition. First of all, CO2 dilutes the hydrogen gas and could affect venting and recycle blower control of the fuel cell powertrain. Furthermore, CO2 can be catalytically converted via a reverse water gas shift reaction into CO that in consequence poisons the catalyst. In addition, co-occurrence of CO and CO2 in hydrogen has an accumulated influence on cell performance. CO2 could adversely affect on-board hydrogen storage systems using metal hydride alloys.

• 1. Carbon Monoxide

Carbon Monoxide (CO) causes severe catalyst poisoning that adversely affects the performance of the fuel cell power train. CO binds strongly to Pt sites, resulting in the reduction of the effective electrochemical surface area (ECSA) available for H2 adsorption and oxidation. The catalyst poisoning effect is strongly related to the concentration of CO, the exposure time, the cell operation temperature and anode catalyst types. Although the effects of CO on the fuel cell can be reversed through mitigating strategies, such as material selection of membrane electrode assembly (MEA), system design and operation, the lifetime effects of CO on performance is a strong concern. Especially lower catalyst loadings needed for cost optimization and longer hydrogen protection times lead to more severe poisoning effect. Therefore, CO needs to be kept at very low levels in hydrogen fuel.

• 1. Methane

Methane is one of the very few hydrocarbons that does not contaminate PEMFCs. It does not react with the catalyst so dilution is the major effect that shall be considered with methane gas.

• 1. Water

Water (H2O) is an issue for hydrogen dispensing systems due to the potential formation of ice in the on-board vehicle tank system or fuel cell components. Excess water can exist in liquid state and can cause corrosion of metallic components. Already low quantities could lead to severe impacts on the components. Furthermore, water does affect the function of the stack. Water provides a transport mechanism for water-soluble impurities, especially as solvent for cations like Na+, K+, Ca2+, Cs+ and NH4+ when present as an aerosol. The cations absorb to and block the functional groups of the ionomer and thereby reduce the proton conductivity of the membrane. Water is only a concern for the stack in very large quantities. It can lead to water management issues that could limit the current and increase the overpotential. Water should remain gaseous throughout the operating conditions of system. It is believed that water affects MeH cycle life due to exothermic reactions.

• 1. Sulfur compounds

Sulfur containing compounds are severe catalyst poisons that at even very low levels can cause irreversible degradation of fuel cell performance. The specific sulfur compounds that are addressed are in particular: hydrogen sulfide (H2S), sulfur dioxide (SO2), carbonyl sulfide (COS), carbon disulfide (CS2), methyl mercaptan (CH3SH). Beside these specific compounds further sulfur compounds can exist. The adsorption of the S-containing species to the active sites of the catalyst prevents the hydrogen from adsorbing at the catalyst surface resulting in significant performance drop. Following reactions of the adsorbed sulfur compounds result in the formation of the very stable platinum sulfide which makes it impossible to recover the fuel cell catalyst from contamination. Lower catalyst loadings are particularly susceptible to catalyst poisoning contaminants.

• 1. Ammonia

Ammonia (NH3) contamination causes some irreversible fuel cell performance degradation by reducing the proton conductivity of the ionomer. NH3 migrates into the membrane and reacts with protons to form NH4+ that then absorb to and block the functional groups of the ionomer. The level of deterioration depends on both NH3 concentration and exposure time. Performance decay is also attributed to the adsorption of ammonia on the catalyst surface blocking the active sites.

• 1. Total Hydrocarbons

Different hydrocarbons have different effects on fuel cell performance. The main effect is the adsorption on catalyst layer, reducing the catalyst surface area and thereby decreasing the cell performance. Another effect is the decomposition into carbon monoxide, which then adsorbs on the catalyst layer. The severity of the effect depends on the type of hydrocarbon. Generally, aromatic hydrocarbons adsorb more strongly on the catalyst surface than other hydrocarbons inhibiting access to hydrogen. Acids, aldehydes, etc. degrade performance. Phthalates, squalene and erucamide, which could be found in seals and hoses, will cause problems on the stack side. Methane (CH4) is considered an inert constituent since its effect on fuel cell performance is to dilute the hydrogen fuel stream (see A.6).

• 1. Formaldehyde

Formaldehyde (CH2O) has a similar effect on fuel cell performance as carbon monoxide. The adsorption process of formaldehyde on the catalyst is the same as for CO followed by an immediate conversion of CH2O to CO and H2. The adsorption of the produced CO on the catalyst layer leads to a reduction of the catalytic surface area, which decreases the cell performance. Contamination due to formaldehyde can be recovered by changing the cell voltage and by purging with pure hydrogen. Therefore, formaldehyde can be considered a reversible contaminant with the same impact on the fuel cell as for CO. Lower catalyst loadings are particularly susceptible to catalyst poisoning contaminants.

• 1. Halogenated Compounds

Halogenated compounds adsorb on the catalyst layer, reduce the catalytic surface area and decrease the cell performance. The performance degradation caused by halogenated compounds is an irreversible effect. The biggest concern is about chlorine (Cl2) in hydrogen from electrolysis of water. Chloride, for example, promotes the dissolution of Pt by the formation of soluble chloride complexes and subsequent deposition in the fuel cell membrane. Potential sources include chloralkali production processes, refrigerants used in processing, and cleaning agents.

• 1. Helium

The main effect resulting from the presence of helium (He) is to lower the cell potential due to the dilution effect of the inert species (dilution of the hydrogen gas) and inertial (diffusion) effects. It should be considered that hydrogen sensors show interference with helium. Higher inert gas concentrations could also affect the venting and recycle blower control. Current stack designs are not adversely affected by higher inert gas concentrations. Nevertheless, higher inert gas concentrations will lead to power losses, increased fuel consumption and loss of fuel cell efficiency.

• 1. Solid and liquid particulates (Aerosols)

Aerosols are dispersed solid and/or liquid particles in a gas. These particulates could be introduced in the production, storage or delivery of hydrogen fuel. A maximum solid and liquid particle concentration is specified to ensure that filters are not clogged and/or solid and liquid particles do not enter the fuel system and affect operation of valves and fuel cell stacks. A maximum particulate size diameter is not specified yet but should be addressed in fuelling station standard and/or future revision of ISO 14687. Particulate sizes should be kept as small as possible.

There are various effects of station operating fluids and solid particulates on the stack, fuel cell components and the complete fuel cell powertrain. These particulates originate from the operation of HRS and show severe impacts. This group of substances comprises cleaning agents, oils, lubricant oils, siloxanes, ionic liquids, decomposition products of ionic liquids, additives, metals, metal oxides and metal ions. One effect of these substances is the adsorption to the active site of the fuel cell catalyst which prevents the hydrogen from adsorbing at the catalyst surface resulting in a significant performance drop. Other effects are the reduction of the proton conductivity of the membrane, impact on storage systems and interference of H2 sensors. Generally, the use of operating fluids shall be minimized as far as possible. If the use of operating fluids is mandatory, means shall be provided by the hydrogen refuelling station (HRS) to hinder these operating fluids from contaminating the vehicle fuel cell powertrain.

The contamination due to aerosols is of extreme importance as illustrated by the following example of using SnO2, the oxide of the tetravalent tin as a model substance. This heavy metal oxide is present in the solid state of matter with a molar mass of MSnO2 = 150,69 g ⋅ mol−1 and a density of ρSnO2 = 6,95 g ⋅ cm−3 at 20 °C. Under the assumption of a spherical particle shape with a diameter of dparticle = 0,1 µm and under consideration of the Avogadro Constant NA = 6,022 ⋅ 1023 mol−1, the number of SnO2-molecules nSnO2 in the particle can be calculated as follows:

(1)

(2)

These 14,5 million SnO2-molecules can lead to irreversible impacts in microelectronic structures. Therefore, it is necessary to filter out any solid and liquid particles close to the fuelling nozzle to prevent any impact on the fuel cell power train.

1. 
   (informative)
   
   Example of Supply chain evaluation with regards to potential sources of impurities
   1. Potential Sources of Impurities

For a given HRS, the contaminants listed in the hydrogen specification referred to in Clause 4 might be present. There are several parts of the supply chain where impurities can be introduced. This section describes the potential impurities in each step of the supply chain. An example of typical supply chains is given in Figure B.1.

Figure B.1 — Example of typical HRS supply chain

When a contaminant is classified as potentially present, it shall be taken into account in the Quality Assurance methodology (risk assessment or prescriptive approach) described at Clause 6.

• 1. Production
     1. General

The contaminants that could be introduced at production depend on the production technology and on the barriers as well as control implemented.

• • 1. Reforming

Reforming is the most common H2 production method today. It uses various type of feedstocks, such as, natural gas, biogas, naphtha, methanol, and NH3. The feedstock is usually converted into a synthetic gas (Syngas), and shift reacted to produce more H2 and CO2, then purified. The most common purification way is by pressure swing adsorption (PSA).

The contaminant potentially present in the hydrogen depend on the process technology and on the purification. It should be investigated on a case by case basis for each production source.

The result is given in Table B.1.

Table B.1 — Impurities potentially present in H2 produced by SMR

• • 1. Alkaline Electrolysis

Alkaline electrolysis has been used for more than a century to produce H2 from H2O using electricity. The hydrogen produced at the anode is usually purified from the remaining O2 through a catalytic reactor and then dried through a Temperature Swing Adsorption (TSA). Table B.2 investigates the potential sources of contaminations. Such contaminations mainly come from H2O and the air.

Table B.2 — Impurities potentially present in H2 produced by Alkaline Electrolysis

• • 1. Proton exchange membrane (PEM) electrolysis

PEM electrolysis is the electrolysis of H2O in a cell equipped with a solid polymer electrolyte that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes. Table B.3 investigates the potential sources of contaminations. Such contaminations mainly come from H2O and the air.

Table B.3 — Impurities potentially present in H2 produced by PEM Electrolysis

• • 1. Byproducts

Hydrogen may be obtained through purification of H2-rich effluent by-products of the chemical/ petrochemical industry. Given the large variety of potential feeds to be purified and processes involved, a specific dedicated analysis is required for each source to identify the potential contaminants and associated probabilities.

• • 1. New production methods

There are a number of new production methods under investigation such as photocatalytic, algal, bacterial, etc. Each of them shall be the object of a dedicated evaluation if the produced H2 is used for the supply of an HRS.

• 1. Transportation
     1. General

This clause relates to additional contaminants that could be introduced in the H2 during transportation.

• • 1. Dedicated H2 Pipeline

This subclause does not cover the supply of hydrogen through natural gas converted pipelines.

When transported in pipelines, H2 is usually under relatively high pressure (>40 bar). Contamination of any kind during normal operation is “very unlikely”.

During maintenance, the potential sources of contamination are:

— N2 if insufficiently purged after maintenance;

— H2O if insufficiently dried after maintenance.

Normal criteria for N2 purging after maintenance is O2 below 2 %. This is what is required for safety reasons before allowing to fill the system with H2. If the H2 purging is done to reach 100 µmol/mol N2 before the operation is commenced, the O2 levels will be less than 2 µmol/mol. If improper purging occurs, and the O2 levels exceed 5 µmol/mol at 2 % concentration, then the N2 levels will be greater than 250 µmol/mol. This implies that the probabilities to exceed threshold due to wrong purging are in the same order of magnitude for both O2 and N2.

Table B.4 — Impurities potentially introduced during dedicated H2 pipeline transportation

• • 1. Filling centre and tube trailer

A filling centre may be attached to a production site or to a pipeline network. They are used to fill gaseous pressurized tube trailers. Contamination during normal operation is “very unlikely”.

During maintenance, the potential sources of contamination are:

— O2 or N2 if insufficiently purged after maintenance;

— H20 if insufficiently dried after maintenance.

Normal criteria for N2 purging after maintenance is O2 below 2 %. This is what is required for safety reasons before allowing to fill the system with H2.

Starting with a system containing N2 with less than 2 % O2, if H2 purging is done to reach 100 µmol/mol N2 before putting into operation, the O2 levels will be less than 2µmol/mol. If improper purging occurs, and the O2 levels exceed 5 µmol/mol at 2 % concentration, then the N2 levels will be greater than 250 µmol/mol. This implies that the probabilities to exceed threshold due to wrong purging are in the same order of magnitude for both O2 and N2.

Tube trailers may be filled at different sources. It is necessary to take into account the risk of contamination due to the residual H2 contained in a tube trailer coming from a different location if this is relevant at the considered HRS. This shall be taken into account if necessary in the risk analysis.

Table B.5 — Impurities potentially introduced during centralized distribution and tube trailer transportation

• 1. Hydrogen Refuelling Station

Contamination during normal operation shall be assessed with consideration of the technology used on a case-by-case basis. During maintenance, the potential sources of contamination are:

— N2 if insufficiently purged after maintenance;

— H2O if insufficiently dried after maintenance.

Table B.6 — Impurities potentially introduced at HRS

• 1. Special operations: Commissioning, Maintenance

For any equipment in the supply chain, special operation such as commissioning or maintenance periodic testing could involve purging/inerting with nitrogen, open to the atmosphere or allowing air into the hydrogen path, cleaning with specific agents including halogenated components or Volatile Organic Compounds. For all components on the supply chain, following a maintenance operation, or at commissioning.

Table B.7 — Impurities potentially introduced during special operations

• 1. Particles

Particles may be originated due to various phenomenon at each level of the supply chain. By default, they shall be considered as potentially present for each of them, except if specific design measures (filtering) permit the demonstration of the opposite.

1. 
   (informative)
   
   Example of Risk Assessment template

This annex gives an example of template which can be used for a risk assessment. It may need to be updated in case of any changes. Other templates may be chosen.

Following the procedure described in Clause 5, the risk assessment is achieved by identifying the probability of having each impurity above the threshold values of specifications and evaluating the severity for the fuel cell car, assuming some values of impurities above the specification. This risk assessment is done for each part of the supply chain, for example: SMR, pipeline distribution and the HRS itself. It should be carried out with the relevant knowledgeable people.

The following steps should be followed for each impurity:

a) Select one contaminant (nitrogen for instance, see Table 1);

b) Identify its possible sources of contamination to exceed the threshold value;

c) Assess the initial risk for each possible source (if necessary, create a line by source);

1) Determine the level of contamination above or under level 1 (defined in Table 5),

i. If under level 1, enter “No” in the contamination risk column of the initial risk (column H in Table C.1) and report the severity of column D in column J in Table C.1,

ii. If above level 1, enter “Yes” in the contamination risk column of the initial (column H in Table C.1) and report the severity of column F in column J in Table C.1,

2) Evaluate the probability of occurrence according to Table 2,

3) Report the acceptability according to Table 4,

d) If outside the acceptable risk area, identify the existing barriers which can reduce the risk,

e) Evaluate the residual risk following the same protocol as for the initial risk taking into account the barriers,

f) The residual risk, after the evaluation, should be outside the unacceptable risk area. Otherwise, additional barriers should be applied to reduce the risk.

NOTE A barrier can be technical and/or organisational including procedures, trainings, analysis, purification systems or any other solutions to reduce the risk of contamination.

Table C.1 — Risk assessment template

Bibliography

[1] ISO 14687, Hydrogen fuel quality — Product specification

[2] ISO 19880‑1, Gaseous hydrogen — Fuelling stations — Part 1: General requirements

[3] ISO 21087, Gas analysis — Analytical methods for hydrogen fuel — Proton exchange membrane (PEM) fuel cell applications for road vehicles

[4] ISO 19880‑9, Gaseous hydrogen — Fuelling stations - Part 9: Sampling for fuel quality analysis