System Design Features

• Piping systems for the delivery of hydrogen should be designed and installed by a person qualified by specific training and experience with hydrogen piping systems.
• Manual shutoff valves should be provided near each point of use.
• The point-of-use valve should be located away from the potential hazards and within immediate reach.
• Where the cylinder valve is located within immediate reach, a separate point-of-use shutoff valve is not required.
• Line regulators that have their source away from the point of use should have a manual shutoff valve near the point of use.
• An emergency gas shutoff device in an accessible location outside the use area should be provided in addition to the manual point-of-use valve in each educational and instructional laboratory space that has a piped gas supply system.
• Piping should be designed for a pressure greater than the maximum system pressure that can be developed under abnormal conditions.
• Piping systems, including regulators, should not be used for gases other than those for which they are designed and identified unless a thorough review of the design specifications, materials of construction, and service compatibility is made and other appropriate modifications have been made.
• Shut-down controls should be provided and linked to a thermocouple/alarm system so that the temperature rise from an exothermic reaction can be managed.
• Where plastic (Tygon-type) tubing is used for hydrogen gas delivery, the tubing should be tested for hydrogen permeability to minimize leakage. Tubing connections should be clamped to barbed or press-fit type connections.

Pressure Relief

• Each and every portion of a piping system should have uninterruptible pressure relief.
• Any part of the system that can be isolated from the rest of the system should have adequate pressure relief.
• A pressure relief system should be designed to provide a discharge rate sufficient to avoid further pressure increase and should vent to a safe location.
• Pressure relief should be plumbed to a safe discharge location outside or to the fume hood exhaust.

Labeling

• All shutoff valves should be clearly marked.
• Permanent hydrogen piping should be labeled as such at the supply point, at each discharge point, and at regular intervals along its length. Where hydrogen gas piping penetrates a wall, the piping should be labeled on both sides of the wall. Color-coding may be another way to mark hydrogen piping.

Note: Good general guidance will be available in the ASME B31.12 Code for Hydrogen Piping and Pipelines.