AS ISO 19880.8:2021 – Gaseous hydrogen — Fuelling stations Part 8: Fuel quality control.
— identification of potential impurities;
— methods to control and remove these impurities;
— sampling impurities and frequency;
— monitoring of impurities or process controls;
— description olsolid and liquid particulate filters;
— cleanliness and maintenance procedures.
It is important to understand that quality should be maintained throughout the complete supply chain of the product (from production source to fuelling station nozzle), such that the impurities that are given In the specification remain below the threshold values.
Each component of the supply chain shall be investigated taking into account the already existing barriers for a given contaminant.
NOTE An effective quality control approach can further ensure the quality of the hydrogen by providing a proactive means to Identify and control potential quality Issues which can Include sampling and monitoring, Additionally, use of quality assurance can improve the decision making if a quality problem arises.
8.2 Prescriptive methodology
The prescriptive approach to hydrogen quality assurance considers potential sources of contaminants and establishes a fixed protocol for analysing and addressing potential contaminants. The prescriptive approach can be applied for the clearly identified supply chain.
The prescriptive quality assurance plan shall be determined taking Into account all hydrogen production methods, hydrogen transportation methods and non-routine procedures which exists in the area where the assurance plan Is applicable.
NOTE Annex C presents lapanese hydrogen quality guidelines which is an example of a prescriptive quality assurance plan.
8.3 Risk assessment methodology
The risk assessment approach determines the probability to have each impurity above the threshold values o[speclIicatlons given in Clause 5 and evaluates severity of each impurity for the fuel cell vehicle (see Annex A). As an aid to clearly defining the risk(s) for risk assessment purposes, three fundamental questions are often helpful:
— What can go wrong: which event can cause the impurities to be above the threshold value?
— What is the likelihood (probability of occurrence expressed relative to the number of fuelling events) that impurities can be above the threshold value?
— What are the consequences (severity) for the fuel cell vehicle?
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. To determine the probability of the occurrence that impurities in hydrogen exceed the threshold value. Table 1 defines the occurrence classes.
For each impurity of the specification and for a given fuelling station (including the supply chain of hydrogen), a risk assessment shall be applied to define the global risk.
NOTE 2 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 benefit-cost analysis, for understanding the optimal level of risk control. Risk control can 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, a decision shall be taken in order to either refuse the risk and 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 risk when it exceeds an acceptable level (o or “ zone in Thb1e3). Risk reduction typically includes actions taken to mitigate the severity and/or probability of occurrence. However, this document only deals with the mitigation of probability of occurrence,
8.4 Impact of impurities on fuel cell powertrain
It Is necessary to evaluate the possible consequences on a fuel cell car If each Impurity exceeds the ISO 14687-2 threshold value. The impact for the car will depend on the concentration of the contaminant.
Table 4 shows a summary of the concentration-based impact of the impurities on the fuel cell. The contaminants and their chemical formulas are given In the first two columns of Table 4.
An estimation of the exceeded concentration above the ISO 14687-2 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.