What ultra-high purity requirements govern gas pipes?
SEMI F72 standards for surface finish. Outgassing <5×10⁻¹⁰ torr·L/sec/cm². Particle counts <0.1 particles/cm³ (>0.1μm). Moisture content <10 ppb. Metallic impurities <1 ppb.
How are gas distribution welds prepared?
Orbital welding with ultra-high purity argon. Double-pass welding for critical lines. Electropolishing to 0.25μm Ra. Passivation with nitric acid. Final rinsing with 18.2 MΩ·cm water.
What testing validates gas pipe integrity?
Helium leak testing to 1×10⁻⁹ atm-cc/sec. Residual gas analysis for contamination. Particle counting of purge gas. Moisture analysis by laser spectroscopy. Final certification with actual process gas.
How are gas cabinets connected to distribution systems?
VCR face-seal fittings for leak-tight joints. Purge-purged secondary containment. Double-walled tubing for hazardous gases. Grounding for static control. Restricted flow orifices for safety.
What maintenance prevents gas system contamination?
Annual leak testing of all connections. Particle monitoring during gas changes. Regular purge gas quality verification. Valve packing maintenance. Strict change control procedures.
