Design Considerations

To minimizes the potential for a large gas release inside the facility, hydrogen is generally supplied to the indoor facility from an outdoor area that may include production, compression, and storage equipment. The best practices described in Facility Design and Construction and Hydrogen System Components are applicable to the outdoor storage area.

Best practices applicable to the indoor portion of the hydrogen fueling system include:

• Dispensers should be installed in unconfined areas of large rooms having ceiling heights greater than 7.5 m (~25 feet). Where this is not possible, a mechanical ventilation system should be installed in accordance with the applicable codes and standards.
• Indoor refueling activities should only take place in buildings with fire sprinklers and fire alarms.
• Noncombustible construction should be within 5 m (~16 feet) of the dispenser.
• The dispensing area should be equipped with a manually operated emergency stop button (ESB) located remotely from the dispenser, but within sight.
• The ESB should end the fueling process and isolate the hydrogen outside of the facility. A manual shutoff valve, as well as automatic shutoff valves with sufficient redundancy, should be provided.
• Consistent with the facility fire prevention plan, a portable fire extinguisher may be provided for the purpose of extinguishing a combustible material fire in the area of the dispenser. Please see Fire Protection and Suppression. Only personnel trained in hydrogen properties and firefighting should attempt to control a hydrogen-related fire.
• The dispenser and hydrogen piping should be protected from vehicle impact, by the installation of bollards around the dispenser for example.
• To detect leaks, hydrogen supply pressure should be monitored continuously.
• A means of excess flow prevention should be provided. Means to limit flow include excess flow valves, flow-limiting orifices, and control systems to limit the total flow.
• Some installations utilize area gas and flame detectors to ensure safe operation. Other installations rely on leak detection by loss of pressure in a closed segment.
• When used, hydrogen gas and flame detectors should be connected to audible and visible alarms and to any building-wide alarm systems. Detectors may also be used to shut off the hydrogen supply to the facility.

• Hydrogen dispensers should be listed or approved for indoor operation.
• The dispenser and hydrogen supply piping should be electrically bonded.
• The dispenser should utilize a nozzle designed in accordance with SAE J2600 for the specific pressure rating of the hydrogen storage tank on the industrial truck. SAE J2600-designed nozzles are mechanically coded to connect only to vehicles that can be safely filled with the dispensing pressure. These nozzles have been extensively tested and approved, contain double-block-and-bleed features, and cannot be opened unless connected to an industrial truck.
• The dispenser should have self-sealing break-away joints to minimize gas leakage in the event of an industrial truck pull-away incident. Break-away connections should be mechanically supported to ensure that a "drive-off" event will cause the break-away connection to release.
• Where multiple types of vehicles and/or fuel tanks reside within a single facility, a means should be provided within the dispenser to ensure that they can all be safely filled. This may require a vehicle identification system to provide different fueling protocols as needed.
• Dispenser controls should be provided to prevent the vehicle fuel tank from exceeding 125% of its service pressure. Special care must be taken where multiple pressures are dispensed at the same facility.

• See Compressed Gas Piping Systems and Compressed Gas Piping System Components for more information.
• Supply piping should have the number of joints to limit potential sources of leaks.
• Overpressure protection should be provided in the form of regulators, pressure switches and relief devices. See Compressed Gas Relief Devices.
• All vents from the dispenser should be piped outdoors to a safe location. See Venting.