Storage and Piping

System Design Features

• Piping systems should be designed, fabricated, installed, examined and tested in accordance with the applicable code. Examples of such codes are ASME B31.1, ASME B31.3 and ASME B31.12.
• Piping systems 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. Where possible, such valves should be easy to activate quickly and positively and give a visual indication of position. For example, a quarter-turn valve is preferred over a needle valve or gate valve.
• Point-of-use shutoff valves should be located away from the potential hazards and within immediate reach.
• 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 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 and should be protected by appropriately vented Pressure Relief Devices (PRDs) – see below.
• Piping systems, including regulators, should not be used for gases other than those for which they are designed unless a thorough review of the design specifications, materials of construction, and service compatibility is conducted. See Material Compatibility.
• Shut-down controls should be provided and linked to a heat detection alarm system so that the temperature rise from an exothermic reaction can be managed.
• Plastic tubing should
  • not be used near heat sources
  • not be used for vent lines
  • be tested for hydrogen permeability to minimize leakage
  • have secure connections
• Because of their leak and joint separation potentials, quick connect joints should be avoided
• Excess flow valves or flow restrictors should be considered for controlling maximum hydrogen flow
• For more information, see Compressed Gas Piping Systems. 

Pressure Relief

• Each system should have pressure relief in accordance with the applicable code.
• Piping designed to withstand the maximum excursion pressures may not need to be equipped with a relief device.
• 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. See Venting.

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 is available in ASME A13.1 Scheme for the Identification of Piping Systems

System Checkout

• In addition to the leak test required by the codes to prove a system is suitable for service, systems should be leak checked immediately prior allowing any hydrogen to enter the system.
• A common method to do the leak check is to pressurize the system with an inert gas such as nitrogen and use a soap bubble solution to locate leaks during system/vessel checkout. Use of helium gas along with helium leak detectors to find the smaller leaks is recommended if available.