Oxygen & UHP Cleaning of Instrumentation Fittings, Valves & Tubing (ASTM G93 / CGA G-4.1)
Crestflo cleans, verifies and documents instrumentation fittings, valves, regulators and tubing so they're safe for oxygen service and ultra-high-purity (UHP) service. That means degreasing to strip out hydrocarbons, oils and particulate, checking for non-volatile residue (NVR), and packaging clean to the methods and cleanliness levels set out in ASTM G93 / G93M and CGA G-4.1, at whatever cleanliness level you specify. Every part carries its heat number plus an EN 10204 material test certificate. Delivery follows our standard framing: ready stock for standard items, made-to-order for specials, 6–8 week delivery.
Oxygen and ultra-high-purity cleaning covers instrumentation-grade stainless and high-nickel / CRA fittings, valves, regulators and tubing. It doesn't cover medical-gas copper tube, cleaned-and-bagged copper, or sanitary food-grade fittings.
Request a quote with your cleanliness spec, or send a print to our engineering team.
What Is Oxygen Cleaning? Definition, NVR & Hydrocarbon-Free Surfaces
Oxygen cleaning is the controlled removal of hydrocarbons, oils, greases, particulate and non-volatile residue (NVR) from a component so that its wetted surfaces won't ignite in an oxygen-enriched atmosphere. A part processed this way is described as oxygen-clean or oxygen-cleaned. Its surfaces are hydrocarbon-free to a defined and verified cleanliness level, typically per ASTM G93 or CGA G-4.1.
The distinction that matters on a specification: oxygen-clean describes the cleaning state of a finished part, while oxygen-compatible describes a material's suitability for oxygen service. This page is about the cleaning state, the process, verification, packaging and documentation by which a fitting, valve or tube is prepared for oxygen or high-purity gas and fluid service. O₂ clean and O2 clean are shorthand for the same cleaning state.
Why It Matters: Ignition Risk in Oxygen Service
Oxygen sharply cuts the ignition energy needed to set off hydrocarbons. A film of machining oil, a fingerprint, even loose particulate that would be harmless in air can ignite in gaseous oxygen (GOX) or liquid oxygen (LOX) service under adiabatic compression, particle impact, or promoted ignition. That releases enough energy to ignite the component itself. So certified cleanliness isn't a cosmetic finish; it's a safety requirement. The cleaning process removes the fuel. Verification proves it's gone before the part ever enters service.
Oxygen & UHP Cleanliness Levels: NVR, Particulate & Surface Finish
ASTM G93 sets cleanliness by the maximum allowable NVR and particulate. CGA G-4.1 defines equivalent cleanliness for oxygen equipment as a maximum hydrocarbon limit in ppm. UHP service, meanwhile, brings its own demands: surface finish and moisture control. Which level applies depends on the service in question, GOX and LOX oxygen systems differ from semiconductor and analytical UHP work, and that choice gets specified on the order. Values follow the applicable standard, but they can be adjusted to fit the requirement.
| Cleanliness parameter | What it controls | Basis | How it is specified |
|---|---|---|---|
| Non-volatile residue (NVR) | Residual oils, greases and hydrocarbons after solvent extraction | ASTM G93 / CGA G-4.1 | Level / NVR limit per ASTM G93, specify on RFQ |
| Particulate | Loose particles that can act as ignition or contamination sites | ASTM G93 | Particle size / count limit, specify on RFQ |
| Hydrocarbon film (UV) | Fluorescing hydrocarbon residue | ASTM G93 UV method | Pass / fail to the specified level |
| Surface finish (UHP) | Internal roughness for high-purity flow | SEMI / ASME BPE | Standard UHP EP target ≤ 10 µin Ra, specify your target on RFQ |
Our Oxygen & UHP Cleaning Process: Degrease, Passivate, Verify, Package
The procedure below follows ASTM G93 and CGA G-4.1 practice. Finishing steps such as passivation and electropolish get applied wherever the specification calls for them. Cleanliness level, surface finish, and any passivation chemistry are set by your order.
| Step | Purpose | Method | Standard reference |
|---|---|---|---|
| Inspect & disassemble | Expose all wetted surfaces | Visual / borescope | ASTM G93 |
| Degrease | Remove hydrocarbons, oils, greases | Aqueous / solvent / ultrasonic degrease | ASTM G93 / CGA G-4.1 |
| Rinse | Remove cleaning agents and residues | High-purity / DI-water rinse | ASTM G93 |
| Passivate (as specified) | Restore the passive chromium-oxide layer | Citric or nitric per ASTM A967 / A380 | ASTM A967 / A380 |
| Electropolish (UHP, as specified) | Smooth, low-Ra internal surface | EP to specified Ra target | SEMI / ASME BPE |
| Dry | Remove moisture | Filtered / inert-gas or clean-oven dry | ASTM G93 |
| Verify | Confirm NVR, particulate and hydrocarbon limits | See verification methods below | ASTM G93 |
| Package clean | Preserve cleanliness through transit | Capped, double-bagged, purged | CGA G-4.1 |
| Document | Traceable cleanliness and material record | Heat number + MTC + cleanliness certificate on request | EN 10204 |
How We Verify Oxygen & UHP Cleanliness
Cleanliness gets confirmed through the verification methods laid out in ASTM G93, with acceptance held to whatever level the order specifies. Positive Material Identification happens in-house. Where destructive or accredited testing is called for, though, the work goes to ISO/IEC 17025-accredited laboratories. Third-party inspection is available on request.
| Method | What it detects | Acceptance basis | Type |
|---|---|---|---|
| NVR gravimetric (solvent extraction) | Residual hydrocarbons, oils and greases | NVR limit for the specified ASTM G93 level | Quantitative |
| UV / black-light fluorescence | Fluorescing hydrocarbon films | No fluorescence at the specified level | Qualitative |
| Water-break / wettability | Residual films that break a continuous water film | Continuous, unbroken water film | Qualitative |
| Particle count / cleanliness | Loose particulate | Particle limit for the specified level | Quantitative |
| PMI (Positive Material Identification) | Confirms the supplied alloy | Matches the specified grade | In-house |
Clean Packaging & Oxygen-Clean Certification: Double-Bagged, Traceable Parts
Oxygen-cleaned parts get capped, double-bagged and purged per CGA G-4.1 clean-packaging practice. That way, the cleanliness we verify at our works holds up until the part actually goes in. Documentation ties every part back to its heat number. And because Crestflo runs a single-chain process, machining, finishing and cleaning the same part, cleanliness traces straight to the same lot as the material certificate.
| Deliverable | Detail |
|---|---|
| Material Test Certificate | EN 10204 3.1 standard; 3.2 on request |
| Heat / lot number | Marked on every part for full traceability |
| Cleanliness certificate of conformance (certificate of cleanliness / CoC) | Documents method and verification results, available on request |
| Clean packaging | Capped, double-bagged and purged per CGA G-4.1 |
See our material traceability page for how heat numbers and MTCs are controlled.
Oxygen Clean vs UHP Clean: What's the Difference?
Both processes strip out hydrocarbons, but they're solving different problems. Oxygen-clean focuses on NVR and hydrocarbon removal so nothing ignites in GOX/LOX service. UHP-clean is different, high-purity precision cleaning, sometimes called semiconductor-grade cleaning. It layers on tight particulate control, moisture control and surface-finish requirements (electropolished, low-Ra internal surfaces) for semiconductor and analytical systems, where the real risk isn't ignition but trace contamination wrecking process purity.
| Oxygen-clean | UHP-clean | |
|---|---|---|
| Primary risk controlled | Ignition in oxygen service | Trace contamination / particle shedding |
| Key metric | NVR, hydrocarbon film | Particulate, moisture, surface finish (Ra) |
| Typical finish | Passivated | Electropolished, passivated |
| Governing references | ASTM G93 / CGA G-4.1 | ASTM G93 + SEMI / ASME BPE |
| Typical service | GOX / LOX oxygen systems | Semiconductor, analytical, high-purity gas |
Standards We Clean & Verify To
Crestflo cleans and verifies items to the methods and cleanliness levels set out in the standards below, then documents the result. You can customize this to your specified level. The standard entities themselves are covered in depth on the linked pages.
| Standard | What it governs | Deep-dive |
|---|---|---|
| ASTM G93 / G93M | Cleaning methods and cleanliness levels for materials and equipment used in oxygen-enriched environments | ASTM G93 oxygen cleaning |
| CGA G-4.1 | Cleaning equipment for oxygen service (hydrocarbon / NVR limits) | CGA G-4.1 oxygen cleaning |
| ASME BPE | Surface finish for hygienic and ultra-high-purity service | ASME BPE |
| ASTM A967 / A380 | Passivation and cleaning practice for stainless steel | Applied as a finishing step |
| EN 10204 | Material test certificate types (3.1 / 3.2) | EN 10204 MTC |
Crestflo holds ISO 9001 / 14001 / 45001 & PED certification, and it runs NDT and PMI in-house, sending destructive testing out to labs accredited under ISO/IEC 17025.
Which Products We Oxygen- & UHP-Clean
Compression tube fittings, face-seal fittings, orbital-weld and high-purity fittings, instrumentation valves, high-purity regulators and electropolished tubing are all available oxygen-clean or UHP-clean, supplied as oxygen service fittings, oxygen service valves and high-purity tubing. Just specify the cleanliness level and any surface-finish target on your RFQ.
| Product | Clean type | Product page |
|---|---|---|
| VCR face-seal fittings | O₂ / UHP | VCR face-seal fittings |
| VCO O-ring face-seal fittings | O₂ / UHP | VCO face-seal fittings |
| Orbital-weld / high-purity fittings | UHP | Orbital-weld fittings |
| Instrumentation valves | O₂ / UHP | Instrumentation valves |
| High-purity regulator | O₂ / UHP | High-purity regulator |
| Electropolished tubing | UHP | Electropolished tubing |
Passivation and electropolish are performed in-house, see our finishing capability.
Materials Suited to Oxygen & UHP Service
Oxygen and UHP cleaning applies to stainless and high-nickel/CRA instrumentation components. 316 / 316L stainless is the default choice. For jobs that demand more corrosion resistance, we step up to 904L. And for high-energy oxygen service, Monel 400 is the pick, since it offers excellent oxygen compatibility. Inconel, Hastelloy and titanium Gr2 round out the available options. Brass isn't part of the US instrumentation range.
- 316 / 316L stainless steel, Crestflo's default choice for oxygen and UHP instrumentation
- 904L, higher chloride and corrosion resistance
- Monel 400, excellent oxygen compatibility
Industries: Semiconductor, Hydrogen, Analytical & Oxygen Systems
Oxygen-clean and UHP-clean components serve semiconductor fabs, hydrogen systems, analytical and sampling systems, and GOX/LOX oxygen gas systems. For fab-level selection guidance see the high-purity semiconductor selection guide.
Why Crestflo for Oxygen-Clean & UHP Parts
Because Crestflo machines, finishes and cleans the part in one traceable chain, cleanliness ties back to the same heat number and material certificate, not outsourced after the fact to a supplier who cleans bought-in parts. Compression tube fittings are qualified for drop-in interchange under ASTM F1387; instrumentation valves are built to ASME B16.34 and the applicable API standards. We offer small MOQs and private-label programs, EN 10204 3.1 MTCs (3.2 on request) with a heat number on every part, and a 6–8 week made-to-order lead time versus 20-plus weeks typical of the majors.
Crestflo is the instrumentation division of a four-decade-old, Government-of-India-recognized export house with a Middle-East delivery track record. Standard product is of Indian origin; US / European melt is available on request, with full material traceability, see US-origin & TAA compliance. Reach the US engineering team at sales@crestflousa.com or +1 346 594 9005 (Houston, TX).
Request a quote with your cleanliness level and finish spec, or request a sample. We Engineer Confidence.
Oxygen & UHP Cleaning FAQ
How do you clean fittings for oxygen service?
Parts get inspected and disassembled first, then degreased to strip away every trace of hydrocarbons and oils, whether that's done aqueously, with solvent, or ultrasonically. From there they're rinsed, passivated where called for, and dried. Non-volatile residue and particulate levels are checked before anything ships, and packaging happens clean. The whole process follows ASTM G93 and CGA G-4.1, tuned to whatever cleanliness level you specify.
What does "oxygen clean" mean?
It means the wetted surfaces of a component have been cleaned of hydrocarbons, oils, greases and particulate matter that could ignite in oxygen-enriched service. Cleanliness is defined and verified against a recognized standard, such as ASTM G93.
What is the proper cleaning procedure for oxygen equipment?
Inspect and disassemble the unit, then degrease, rinse, and dry it. Verify NVR and particulate levels, and package the piece clean, following ASTM G93 / CGA G-4.1. Where the specification calls for passivation and electropolish, we add those steps too.
What standards do you clean and verify to?
ASTM G93 / G93M and CGA G-4.1 govern the oxygen cleaning, while ASME BPE sets the surface-finish targets for UHP service. Where specified, passivation follows ASTM A967 / A380.
What cleanliness level do you certify to?
Cleanliness level, NVR limit and any particulate or surface-finish target all come from ASTM G93 / CGA G-4.1, and your order will spell out which ones apply. Just tell us the service, GOX, LOX or UHP. We'll clean, verify and document to that level. Values follow the applicable standard, and we can customize to whatever you need.
Do I get a cleanliness certificate?
Yes, the parts ship with an EN 10204 3.1 material test certificate (3.2 on request), with the heat number marked on every part. A certificate of conformance covering the cleanliness verification results is available on request too.
What lubricant can be used with oxygen?
Only oxygen-compatible, fully fluorinated (PFPE) lubricants rated for oxygen service are allowed. Standard hydrocarbon oils and greases must never go anywhere near oxygen-service parts. If a job calls for lubrication, note it on your RFQ so the right oxygen-compatible product gets used.
Which alloys do you oxygen- and UHP-clean?
316 / 316L (default), 904L, Monel 400, Inconel, Hastelloy and titanium Gr2 make up the stainless and high-nickel / CRA alloy lineup. Brass isn't part of the US instrumentation range.
What's the difference between oxygen clean and UHP clean?
Oxygen-clean handles hydrocarbon and NVR removal, mainly for ignition safety. UHP-clean goes further, adding tight control over particulates, moisture and surface finish (electropolish / Ra) for semiconductor and analytical work.
Which products can be oxygen-cleaned?
Tube and compression fittings, VCR / VCO face-seal fittings, orbital-weld and high-purity fittings, instrumentation valves, high-purity regulators, and electropolished tubing round out the offering.
What's the lead time for oxygen-clean parts?
Ready stock covers standard items; specials get made to order. Delivery runs 6–8 weeks, against 20-plus weeks typical of the major brands.
Are the parts made in the USA?
Standard product comes from India. US or European melt is available on request, and we provide full material traceability. For TAA/DFARS options, check our US-origin and compliance page.