WI 20012: Gaseous Hydrogen Fuelling Stations
Karen Hall, National Hydrogen Association
ISO/TC 197 Draft Technical Specification (DTS) 20012, Gaseous hydrogen-Fuelling stations is available for comments and a vote. Approval by two-thirds of the P-member countries voting is needed to publish the Technical Specification.
The NHA has a vote on the US Technical Advisory Group (TAG); therefore, staff is soliciting comments from members. If you interested in commenting please respond to David Mann (MannD@hydrogenassociation.org) for the draft document. Please note it can be provided only to NHA members for the purpose of reviewing the draft for the NHA vote and comment through the US TAG. Other interested parties will need to contact their national TAG for an opportunity to input.
There are a few things to note about this draft international document. Firstly, it is a Draft Technical Specification. A Technical Specification (TS) is an intermediate deliverable that provides an option when the subject in question is still under development and technical issues can not be resolved within the appropriate time limits. A TS is considered a “prospective standard for provisional application” because there is an “urgent need for guidance on how standards in this field should be used to meet an identified need” (source: ISO Directives).
In 2003 when this item was raised in ISO TC 197 as a New Work Item Proposal to develop an International Standard, the US voted against starting work at the time, because much of what is necessary to complete an International Standard on hydrogen refuelling stations was not yet known. This was the primary reason that a similar work item in ISO TC 197 had been discontinued previously.
WG11 ran into challenges and determined that it would be more appropriate to prepare a Technical Specification. There was much discussion in 2005 and 2006 about the need for data to complete the task. In particular, there were serious open questions regarding setback distances. There were also questions about whether to make the document applicable to retrofitted stations or only new stations. The Work Group had a difficult challenge to gather needed data and build consensus on open issues. Due to these challenges, work was extended on the TS, and it is now available for comment and vote. If 2/3 of the P-member countries vote in favour of the DTS, it will be published as a TS, with the aim of further developing the item to an International Standard.
The document clearly is not ready to be an International Standard. The question now is whether we feel it is ready to be published as a TS, as it stands. There are a number of technical issues remaining. Some US experts have raised concerns about a few of these issues as follows:
- The resistivity of the surface of the fuelling station pad to earth ground is addressed in the US model codes, where the European Standard EN 1081: 1998 Determination of Electrical Resistance – Resilient Floor Coverings is cited. ISO 20012 doesn’t specify the resistance between the surface of the fuelling pad and earth ground resistance. There is concern that this is a significant oversight and that it should be specified at 1MOhm for global consistency in the grounding of the fuelling station pad. This is can be achieved if concrete is used as the fuelling pad.
- A Pressure Ramp rate "Fuelling Corridor" needs to be specified as the fuelling protocol to ensure that vehicles will be fuelled in a safe and consistent manner. There is a testing program sponsored by 6 major vehicle manufacturers and energy companies that is underway to establish the fuelling protocol robustly. It will finish by December of this year. The DTS should be revised in early 2008 to include the protocol so that vehicles could use fuelling stations safely on a global basis. This would allow harmonization with SAE TIR J2601.
- The present text implies that the fire and explosion risk prevention must take into account ANY and ALL malfunctions and misuses. Common practice is to exclude “catastrophic failures”.
- There is a requirement to periodically inspect, leak check, and replace of hoses at end of cycle life. This is a procedural requirement, not a design requirement, and therefore is outside the scope of the DTS.
- The DTS requires an emergency shutoff device on every dispenser. This will give the general public access the ESD and make the fuelling system vulnerable to nuisance emergency shutoffs. Providing an ESD at the dispenser is not common practice for gasoline fuelling stations. If there is an incident at a dispenser, attempting to access an ESD there may actually put the operator in a greater hazard than if they simply evacuated the area.
- The safety distances in the DTS seem to have been determined by surveying other standards (NFPA 55, etc.) and selecting the SHORTEST distance for each situation. It is unclear that analysis was performed to validate the distances selected. Using these distances will cause this specification to be in conflict with many other standards. Additionally, a great deal of work is being performed to more scientifically determine these safety distances. NFPA 2 (and likely other standards) will be adopting these distances when the reports are published. This will lead to conflicting requirements between published codes and standards and the TS.
- Allowing equipment, storage, piping, etc. only on horizontal roofs of single story buildings is unnecessarily restrictive. In fact the natural buoyancy of hydrogen may make the highest possible location preferred in some installations. And, supports could easily accommodate equipment (especially storage) on a pitched roof. If some national codes limit installations to single story roofs as implied by the text, then that is fine for those nations. It is not necessarily a good reason for inclusion in an international TS or IS.
- The PRV Set point is specified in the DTS as 1.38 times Nominal working pressure (NWP). The issue is whether it should be 1.4 for harmonization with common practice to use two significant figures in PRV set points.
The document clearly is not ready to be an International Standard. The question now is whether we feel it should be published as a TS, as it stands. If 2/3 of the P-member countries vote in favour of the DTS, it would be published as a Technical Specification without changes and comments could be considered in the subsequent effort to develop the International Standard. If the DTS fails to receive 2/3 of the votes for approval, it would go back to the Work Group for resolution of comments, and a second DTS would be prepared. Although a TS is not an International Standard, many US experts are concerned that the nature of the omissions in the DTS warrant a second DTS. Otherwise there would be a published TS that is in conflict with US codes and standards, which could impact commercialization on a global level. Therefore NHA members are encouraged to contact Karen Hall to indicate how you would like the NHA to vote. In addition, comments of any nature (technical, general, or editorial) are welcome.
Comments to be considered in the NHA vote should be sent to Karen Hall (HallK@hydrogenassociation.org) no later than November 3.
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