Ball Valves for Air Separation Units (ASU)
ASTM G93 oxygen-cleaned cryogenic extended-bonnet SS316L ball and gate valves for ASU liquid oxygen (LOX), liquid nitrogen (LIN), and liquid argon (LAR) production columns.
Which ball valves are used for air separation units (asu)?
Air separation units (ASUs) produce liquid oxygen (LOX, −183°C), liquid nitrogen (LIN, −196°C), and liquid argon (LAR, −186°C) by cryogenic distillation. Oxygen service imposes the most stringent safety requirements of any industrial valve application - even trace hydrocarbons or particles in oxygen-rich streams can ignite and cause catastrophic burns and fires. All valves in oxygen service must be ASTM G93-cleaned (oxygen-cleaned), use only oxygen-compatible materials (no brass, no PTFE with high-pressure O₂), and carry EIGA Doc 13 documentation. Vajra supplies fully oxygen-cleaned extended-bonnet cryogenic valves with complete cleaning certification for ASU main column, LOX pump, and product tanker loading service.
Cryogenic Ball Valve (LOX Service)
LOX pump suction, LOX column draw, LOX product loading - extended bonnet for −183°C; ASTM G93 oxygen-cleaned
Critical Requirements
- ASTM G93 / CGA G-4.1 oxygen cleaning - all valves for LOX/GOX service must be degreased with approved solvents, then passivated; verified by UV light and/or white glove test; sealed in nitrogen-purged bags until installation
- EIGA Doc 13 (European Industrial Gases Association) - comprehensive oxygen safety standard; defines material compatibility, ignition mechanisms, and design requirements for oxygen valves
- No PTFE in high-pressure oxygen service (> 30 bar GOX) - PTFE can ignite in high-velocity O₂; use PCTFE or metal-to-metal seats instead; PTFE acceptable for low-pressure (<30 bar) LOX
- No brass, bronze, or copper alloys - acceptable for low-pressure oxygen, but ASU practice avoids them entirely due to particle contamination risk
- Extended bonnet per BS 6364 - minimum 350 mm bonnet extension for valves below −29°C to keep packing above cryogenic zone
- Impact testing - all cryogenic valve components must pass Charpy V-notch impact test at −196°C per ASTM A370
Service Challenges
- Liquid oxygen (LOX, −183°C) - powerful oxidiser; organic contamination causes ignition; all wetted materials must be oxygen-clean and compatible with ASTM G93
- Liquid nitrogen (LIN, −196°C) - inert but extremely cold; thermal shock on warm valves; vacuum-jacketed piping preferred
- Liquid argon (LAR, −186°C) - similar to LIN; noble gas, non-reactive, but same cryogenic and thermal shock concerns
- Gaseous oxygen (GOX, high pressure > 30 bar) - adiabatic compression ignition risk; fire hazard; metal burning in O₂; velocity limits apply
- Nitrogen in subcooled process - moisture condensation from air on cold surfaces; vacuum insulation or foam insulation prevents external condensation
Vajra Ball Valves
High-performance ball valves for reliable shut-off and control in various industrial applications.
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