What should be noted when using stainless steel pipes for medical oxygen pipelines

What should be noted when using stainless steel pipes for medical oxygen pipelines? 

When using stainless steel pipes for medical oxygen pipelines, strict control is required in multiple aspects such as material selection, processing and installation, safety protection, and daily maintenance to prevent oxygen leakage, contamination, or safety accidents. The following are key precautions and operational guidelines:

1. Material and selection considerations

1. Strictly select stainless steel grades

Choose 304L/316L: Low carbon content (≤0.03%) to avoid intergranular corrosion. 316L is more suitable for humid environments (such as areas with frequent disinfection) due to its molybdenum content (Mo).

Reject non-medical-grade stainless steel: Do not use ordinary industrial-grade stainless steel (with high carbon content and insufficient corrosion resistance), as oxygen flow can cause internal wall rusting and contamination. 

2. Focus on metallurgical quality and surface treatment

Require high purity: Select steel produced by electroslag remelting (ESR) process, with low inclusion content; the inner wall needs to be electrolytically polished (Ra ≤ 0.4 μm) to reduce microbial adhesion and oxygen flow resistance.

Eliminate inferior pipes: Avoid using pipes with cracks, folds or oxide scale on the surface. When receiving the goods, check the material certificate (including composition analysis, mechanical property report). 

II. Key Points for Processing and Installation

1. Strictly prohibit oil contamination throughout the process

Tool oil-freeization: Use dedicated oil-free tools (such as pneumatic cutting machines) during cutting and bending operations. Operators must wear oil-free gloves to prevent sweat and oil from contacting the inner walls of the pipes.

Decontamination mandatory requirement: Before installation, immerse / rinse the pipes in carbon tetrachloride or ethanol to ensure that the oil residue is ≤ 5mg/m² (detectable by ultraviolet light fluorescence reaction).

Use argon gas protection (TIG welding) during welding, and prohibit applying oil-based flux near the weld seams. 

2. Control of Welding and Interface Sealing

Welding process standards: Automatic TIG welding (TIG welding) is preferred. The weld seams must undergo 100% radiographic testing (RT) or eddy current testing (ET) to eliminate defects such as pores and slag inclusions.

When using flange connections, metal gaskets (such as stainless steel spiral wound gaskets) are used. Non-combustible gaskets like rubber or asbestos are prohibited to prevent oxygen leakage or combustion.

Prohibited pipe connections: Threaded connections (where thread gaps are prone to accumulate oil and air leakage) are strictly prohibited. Welding or socket-type connections (requiring matching oil-free joints) should be used instead. 

3. Pipeline Layout and Support Specifications

Stay away from hazardous sources: Maintain a distance of ≥1.5m from gas pipelines and electrical lines. Avoid cross-connections; if unavoidable, use metal sleeves for isolation.

Avoid high-temperature areas (such as next to boilers or heating pipes), with the ambient temperature not exceeding 60℃. Prevent leakage at the interface due to the thermal expansion and contraction of stainless steel. 

Support and fixation requirements: The supports should be made of stainless steel. The spacing should be ≤ 3m (for pipes with DN25 and below). To prevent metal particles from being generated due to vibration and friction of the pipes.

When passing through walls or floors, stainless steel sleeves should be added. The gap between the sleeve and the pipe should be filled with non-combustible materials (such as asbestos rope) to prevent gas leakage and fire. 

III. Safety Protection and Static Electricity Control

1. Construction of Static Electricity Grounding System

Full system grounding: Grounding devices should be installed every 100 meters for stainless steel pipelines, with a grounding resistance of ≤ 4Ω; copper wires with a cross-sectional area of ≥ 6mm² should be used to connect at the flange connection points to ensure static electricity conduction.

Prohibition of Contact with Insulating Materials: Pipeline supports should not use insulating materials such as plastic or rubber to prevent the accumulation of static electricity. 

2. Fireproof and explosion-proof measures

Oil prohibition signs and warnings: The outer surface of the pipeline is sprayed with a blue "oxygen" mark, and the words "prohibit oil" and "strictly prohibit open flames" are marked to alert the construction personnel to avoid open flame operations.

Oxygen leakage detection: After installation, conduct a pressure test (with a working pressure of 1.15 times) and apply soapy water to the interface to detect bubbles. It is strictly prohibited to use flammable gases (such as hydrogen) for pressure testing. 

IV. Cleaning and Acceptance Standards

1. Post-installation Deep Cleaning

Segmented flushing procedure:

01. Use clean compressed air (treated with oil-free drying) to blow the pipes, with a flow rate of ≥ 20 m/s, to remove welding slag and metal debris.

02. Use purified water (conductivity ≤ 10 μS/cm) for cyclic flushing until the particle count in the outlet water (≥ 5 μm particles ≤ 100 per L) is detected.

03. Finally, use high-purity nitrogen gas (purity ≥ 99.99%) to dry, to avoid residual moisture that may breed microorganisms. 

2. Acceptance Test Items

Pressure Test: Hydraulic test (working pressure 1.5 times, hold pressure for 30 minutes without leakage) or pneumatic test (applicable to water-avoidance systems).

Cleanliness Verification: Wipe the inner wall with white filter paper, no visible impurities; Oil detection uses ultraviolet light irradiation, no fluorescence reaction. 

V. Daily Maintenance and Usage Prohibitions

1. Regular Inspection Contents - Leak Detection: Use an oxygen detector (range 0-100%) to test the interface monthly. If the concentration exceeds 0.5%, immediate investigation is required.

Visual Inspection: Check if the pipeline is deformed, corroded or has mechanical damage, and if the supports are loose, and if the blue markings are clear.

2. Prohibited Behaviors and Risk Mitigation

Prohibit Unauthorized Modifications: Do not drill holes or weld non-pressure-bearing components on the pipeline. If modifications are necessary, they must be carried out by a professional team in accordance with GB 50751 standards.

Avoid Illegal Operations: When opening the oxygen valve, operate slowly to avoid high-speed airflow impacting the inner wall and generating static sparks. 

It is prohibited to use oxygen to purge pipelines or equipment (as this may cause dust explosions). Cleaning should be done using nitrogen or oil-free compressed air. 

VI. Relevant Standards and Emergency Handling

1. Reference Specifications

GB 50751-2012 "Technical Specifications for Medical Gas Engineering": Covers requirements for material selection, installation, and inspection throughout the entire process. 

YY/T 0801-2010 "Seamless Metal Piping for Medical Gases and Vacuum Applications": Specifies the cleanliness and performance indicators of stainless steel pipes. 

2. Emergency Handling of Emergencies

Oxygen Leak Emergency Response: Immediately close the upstream valve upon detecting a leak, evacuate personnel, and prohibit the operation of electrical equipment (to prevent static sparks). After purging and replacing with nitrogen, carry out maintenance.

Fire Response: If a fire is caused by oil contamination, use a carbon dioxide fire extinguisher to extinguish the fire. Do not use water (as it may cause sudden cooling and cracking of the pipes). 

Summary

The core characteristics of the stainless steel pipes used in medical oxygen pipelines are "oil-free, clean, and anti-static". Every aspect from material selection to operation and maintenance must be based on safety, and strictly follow national standards. Special attention should be paid to the risk of combustion and explosion that may be caused by oil contamination, as well as potential hazards such as static electricity accumulation and welding defects. Through standardized operations and regular inspections, the reliability of the oxygen transportation system can be ensured.