What Should Be Noted When Using Stainless Steel Pipes for Medical Oxygen Pipelines?

Prioritize 304L/316L: Their low carbon content (≤0.03%) prevents intergranular corrosion. 316L, with molybdenum (Mo) added, is more suitable for humid environments (e.g., frequently disinfected areas) due to better corrosion resistance.

Reject non-medical stainless steel: Avoid industrial-grade types like 201 or 304, which have higher carbon content and insufficient corrosion resistance, risking inner wall rust and oxygen contamination under oxygen flow.

High purity requirements: Choose steel produced via electroslag remelting (ESR) to minimize inclusions. The inner wall must undergo electrolytic polishing (Ra≤0.4μm) to reduce microbial adhesion and oxygen flow resistance.

Reject defective pipes: Inspect for cracks, folds, or oxide scales on the surface. Verify material certificates (including composition analysis and mechanical property reports) upon delivery.

Before installation, soak or rinse pipes with carbon tetrachloride or ethanol to ensure oil residue ≤5mg/m² (test via UV light for fluorescence).

Use argon-shielded TIG welding; avoid oily fluxes near welds.

Oil-free tools for processing: Use dedicated oil-free tools (e.g., pneumatic cutters) for cutting and bending. Operators must wear oil-free gloves to prevent sweat or grease from contacting the inner wall.

Mandatory degreasing:

Prefer automatic TIG welding. Welds must undergo 100% radiographic testing (RT) or eddy current testing (ET) to eliminate defects like pores or slag inclusions.

For flange connections, use metal gaskets (e.g., stainless steel spiral-wound gaskets); avoid flammable materials like rubber or asbestos to prevent leaks or combustion.

Welding standards:

Prohibited connections: Threaded joints are forbidden (thread gaps trap oil and leak easily). Use welded or ferrule connections with oil-free fittings.

Use stainless steel brackets with spacing ≤3m (for pipes ≤DN25) to avoid metal particle generation from vibration-induced friction.

Add stainless steel sleeves when passing through walls/floors; fill gaps with non-combustible materials (e.g., asbestos rope) to prevent fire from leaks.

Maintain ≥1.5m distance from gas pipelines and electrical lines; avoid cross-laying. If unavoidable, use metal sleeves for isolation.

Keep away from high-temperature areas (e.g., boilers, heating pipes). Ambient temperature ≤60℃ to prevent leakage from thermal expansion/contraction.

Support requirements:

Full-system grounding: Install grounding devices every 100m with resistance ≤4Ω. Bridge flange connections with copper wires (cross-sectional area ≥6mm²) to ensure static conduction.

Avoid insulating materials: Brackets must not use plastic or rubber to prevent static buildup.

Labels and warnings: Mark pipes blue with "Oxygen" and "No Oil" / "No Open Flames" to alert workers against ignition sources.

Leak testing: After installation, conduct a pressure test (1.15× working pressure). Check joints with soapy water for bubbles; never use flammable gases (e.g., hydrogen) for testing.

Staged flushing:

Pressure test: Hydraulic test (1.5× working pressure, 30-minute hold with no leaks) or pneumatic test (for water-sensitive systems).

Cleanliness verification: Wipe the inner wall with white filter paper—no visible impurities. Check for oil via UV light (no fluorescence).

Leak detection: Monthly check joints with an oxygen analyzer (0-100% range). Investigate immediately if concentration exceeds 0.5%.

Visual inspection: Check for deformation, corrosion, or mechanical damage. Ensure brackets are secure and blue labels remain legible.

Open valves slowly to avoid static sparks from high-velocity oxygen.

Never purge with oxygen (risk of dust explosions); use nitrogen or oil-free compressed air.

No unauthorized modifications: Drilling or welding non-pressure components is forbidden. Alterations must follow GB 50751 by professionals.

Safe operation rules:

GB 50751-2012 Technical Code for Medical Gas Engineering

YY/T 0801-2010 Seamless Metal Pipes for Medical Gases and Vacuum

Oxygen leaks: Close upstream valves, evacuate personnel, avoid electrical operation (to prevent sparks). Repair after purging with nitrogen.

Fires: Use CO₂ extinguishers for oil-contamination-induced fires. Never use water (risk of pipe cracking from rapid cooling).