Compressed Gas Piping Systems

Recommendations for compressed gas piping systems include the following:

• Piping systems should conform to a recognized code such as ASME B31.1 Power Piping, ASME B31.3 Process Piping, or ASME B31.12 Hydrogen Piping and Pipelines.
• To prevent leaks when exposed to an external fire, the piping system should be fire resistant.
• The piping material should be selected for robustness, low permeability, and fire resistance. The material chosen should be specifically rated or approved for use with hydrogen at the planned pressure.
• Optimum material selection depends on:
  • The temperature range
  • The pressure
  • Purity and cleaning requirements
  • Installation factors (structure, environment)
• In most instances, austenitic stainless steels such as Type 304 or 316 are satisfactory for end use applications.
• See Material Compatibility for more information regarding material selection.

            Piping system for hydrogen transport (Source: Department of Energy Fuel Cell Technology Program)

• Design of the piping system should consider ways to facilitate internally cleaning the piping when needed.
• Considerations for underground piping include:
  • External corrosion
  • Protection from inadvertent excavation
  • Preventing hydrogen from entering an enclosed space if a leak occurs
  • Using only welded joints
• Alternates to direct burial of piping include:
  • Route the pipe in open trenches with removable grating so that it can be inspected and maintained.
  • When pipe can be routed without any mechanical joints, place the pipe in a corrosion resistant sleeve that is open at both ends.
• Piping should not be left open to the atmosphere. Openings should be plugged, capped, or flanged or routed to a vent stack.
• To assure dispersion of small leaks, piping should be routed outdoors whenever possible.
• Piping should be routed so that it is:
  • Not covered by wall, floor, or ceiling finishes
  • Readily available for visual inspection and leak detection, and
  • Protected from physical damage
• The hydrogen system should have the necessary connections for isolating, venting, purging and leak testing, along with those needed to prepare the equipment for maintenance.
• When part of the system will remain operational while another part needs work, consider a double block and bleed arrangement to isolate active parts of the system from equipment being maintained and to facilitate purging.

Regardless of system design, a procedure for purging any piping to remove all air, moisture, or oxidizing gas or substance must be developed and documented.