Dazo Water Fuel Technology

3.1.2 Operation and Maintenance

Anyone who will operate or maintain hydrogen-fueled vehicles should receive hydrogen safety training. At a minimum, this training should cover the characteristics of hydrogen, operation of onboard safety systems, hydrogen fueling operations, and actions to take in an emergency.

During maintenance, never substitute fuel system replacement parts that have not been specifically tested and certified for use with hydrogen (for example, lines, valves, and regulators designed for use with natural gas).

While they may look and function the same, they may be subject to hydrogen embrittlement. In addition, compressed natural gas fuel systems typically operate at lower pressures (maximum 3,600 psi) than hydrogen fuel systems.

Periodically check all connections in the hydrogen fuel system for leaks using procedures outlined in the manufacturer’s service manual. Tighten or repair all leaking joints, no matter how small the leak. Leak checks should also be conducted after repair or replacement of any fuel system lines or valves.

Never loosen any joint in the fuel system while the connected components are under pressure. Shut down the system and isolate and vent components as directed in the manufacturer’s service manual. Torque all joints to the levels specified in the service manual. Do not over tighten. Overtorquing can cause leaks.

Air must never be allowed to enter the hydrogen fuel system. If exposed to the atmosphere, some components, particularly hydrogen fuel cylinders, must be purged with nitrogen before being refilled with hydrogen. See the manufacturer’s service manual for specific purging procedures.

Periodically check the exterior surface of hydrogen fuel cylinders for nicks, dents, and cuts that could weaken the structure. See the manufacturer’s service manual for information on the allowable level of wear and damage before cylinders need to be replaced. The Federal Motor Vehicle Safety Standards applicable to natural gas fuel cylinders (FMVSS 304, 49 CFR 571.304) specify that a visual inspection by a “qualified container inspector”11 must be conducted “at least every 36 months or 36,000 miles or at the time of re-installation.” The inspection procedures for damage assessment are outlined in pamphlet C-612 from the

Compressed Gas Association. While standards specifically applicable to hydrogen cylinders have not yet been developed, at a minimum, the requirements applicable to natural gas fuel cylinders should be followed.

Local laws and regulations may require more frequent cylinder inspections, for example, in conjunction with annual registration safety inspections. The fuel system, including the high-pressure storage tanks, should also be visually inspected after any accident, and be retested or replaced as required.

Periodically check and calibrate hydrogen sensors in accordance with the schedule and procedures in the manufacturer’s service manual.

Periodically check operation of the fan in the hydrogen diffuser and any ventilation fans in accordance with
the schedule and procedures in the manufacturer’s service manual.

The fuel system will likely include a coalescing filter to remove any oil that might carry over into the hydrogen fuel from the fuel station compressor. Check and empty or replace this filter periodically in accordance with the schedule and procedures in the manufacturer’s service manual.

Do not ignore warning lights or alarms. Do not attempt to override automatic system shutdown unless absolutely necessary (e.g., to move vehicle off of railroad tracks).

Always make sure that the main switch is off before servicing the vehicle. Before working on the fuel cell system or gaseous hydrogen storage system, also disconnect the vehicle’s 12/24-VDC battery and close the manual fuel valves to isolate hydrogen in the storage cylinders.

Do not try to repair damaged fuel lines—replace them.

Do not walk on hydrogen fuel cylinders or expose them to damage from impact or abrasion. Do not allow strong chemicals, such as battery acid or metal cleaning solvents, to contact the hydrogen fuel cylinders.
Always electrically ground and bond the vehicle when fueling and defueling. Connect the ground strap or cable at the fuel station if one is provided.

Before fueling, check that the onboard fuel port is free of dirt and debris. Always replace the fuel port dust cover after fueling.

Do not smoke or use a cell phone when servicing or fueling the vehicle.

If the vehicle must be defueled for servicing of the hydrogen fuel system, the rate of fuel release must be carefully controlled. Follow the instructions in the manufacturer’s service manual. Unless the hydrogen storage tanks will be removed, always leave a small amount of pressure in the tanks so that the internal pressure is a few psi above atmospheric pressure. Any time tank pressure falls below atmospheric, it is possible for air to enter, and the tank must be purged with nitrogen before refilling with hydrogen.