Zhejiang Dongri Valve Co., Ltd.
An air separation unit (ASU) does not run on one fluid — it produces liquid oxygen (LOX), liquid nitrogen (LIN) and liquid argon (LAr) from a single train, and each product line imposes a different Valve duty. Specifying a cryogenic Ball Valve for air separation unit LOX and LIN service means matching oxygen-cleaning rules, temperature floors and purity needs to the right product stream, because a valve that is perfect for LIN can be a genuine hazard on LOX.
This guide breaks the air separation unit cryogenic valve specification for oxygen nitrogen argon into per-line requirements so a buyer can write a defensible list.
In an LNG plant the cryogen is one flammable-avoidance problem. In an ASU the three product lines are three different problems from one cold box: oxygen is a fire and explosion hazard if contaminated, nitrogen is a clean cryogen, and argon is an inert but high-purity cryogen. The LOX LIN LAr product line valve requirements ASU therefore cannot share one spec — the cleaning and trim rules diverge at the product header.
LOX line (−183°C). Oxygen service is the strict one. Every ball valve on the LOX side must be degreased and oxygen-cleaned to ASTM G93 / CGA G-4.1, assembled hydrocarbon-free, with a cleaning certificate and full material traceability. Copper-bearing trim is banned in LOX service, and the seat and stem must use non-combustible, compatible surfaces. A Metal Hard Sealed Ball Valve is favored here because a metal seat removes the soft trapped-volume concern and resists ignition, while the body stays austenitic stainless. Fire-safe behavior is referenced to API 607 for the API Ball Valve isolation points.
LIN line (−196°C). Liquid nitrogen is a pure, non-reactive cryogen, so the duty is standard deep-cryogenic: PCTFE or RPTFE seats, an ISO 28921-1 extended bonnet, and a qualified −196°C test. Small-bore utility runs use a Floating Ball Valve; larger headers use a Trunnion Mounted Ball Valve. No oxygen-cleaning rule applies, but cleanliness still matters for product purity.
LAr line (−186°C). Liquid argon is inert but demands high purity, so the valve must avoid contamination and hold a tight shutoff. A full-stainless trunnion mounted ball valve with cleaned PCTFE seats covers the main run, and a Forged Steel Ball Valve is preferred on higher-pressure column drains where wall integrity protects purity. Like LIN, argon needs cryogenic qualification, not oxygen cleaning.
A stainless body with the wrong seat leaks while still "correct" on paper. For LIN and LAr the PCTFE/RPTFE seat holds preload through shrinkage and passes LN2 seat-leak tests; for LOX a cleaned PCTFE or metal seat is mandatory, and copper trim is out. The forged steel ball valve route earns its place on high-pressure column and drain lines where porosity would threaten purity, not because forging survives colder than casting at the same chemistry.
Standards split by hazard: an API ball valve to API 607 proves fire-safe behavior for LOX isolation at ambient, while ISO 28921-1 and BS 6364 prove the cryogenic cycle and seat-leak performance at −196°C for all three lines. A complete air separation unit cryogenic valve specification for oxygen nitrogen argon dual-references both, because LOX fire-safety and cryogenic proof are separate certificates.
The LOX line lives or dies on documentation. Insist on a degreasing and oxygen-cleaning certificate (ASTM G93 / CGA G-4.1), material mill certificates, and a witnessed cold seat-leak test. The LOX LIN LAr product line valve requirements ASU should list cleaning class per line — LOX at the strictest, LIN and LAr at a lower clean-but-pure level — so the cryogenic ball valve for air separation unit LOX and LIN you receive is provably fit for the header it serves.
Q1: Can one valve serve all three product lines? Downward compatibility mostly holds for temperature, but the cleaning class does not. A LIN- or LAr-qualified valve is not automatically LOX-clean, and a copper-trim valve is disqualified on oxygen regardless of cold rating. The LOX LIN LAr product line valve requirements ASU must be read per line, and the LOX valves bought to the strictest spec.
Q2: Why is LOX cleaning non-negotiable? Oxygen plus a hydrocarbon trace and an ignition source is a classic fire path. Degreasing and ASTM G93 cleaning remove the fuel; banning copper-bearing trim and using non-combustible seats removes the easy-ignition surfaces. Skip either on a metal hard sealed ball valve or a soft-seated ball valve and the LOX line becomes a liability, not an asset.
Do LOX valves need special materials? They need oxygen-compatible, non-combustible trim and a full degreasing certificate more than exotic alloys. Austenitic stainless bodies with cleaned PCTFE or metal seats and banned copper trim are the norm; the certificate matters as much as the metal.
Is LIN service the same as LNG service? Cryogenically yes — both sit near −196°C and need ISO 28921 bonnets and PCTFE seats — but LIN has no oxygen hazard and no fire-safe cleaning rule. An LNG valve and a LIN valve share the cold qualification; an LOX valve adds cleaning that neither needs.
What certificates prove an ASU valve is compliant? A material mill cert, an ASTM G93 / CGA G-4.1 oxygen-cleaning cert for LOX lines, ISO 28921-1 or BS 6364 cryogenic test reports, and API 607 fire-safe proof where LOX isolation is specified.
Zhejiang Dongri Valve Co., Ltd. has built valves in its own China factory since 1996. Dongri supplies ASU projects across all three product lines — CF8M, 9% nickel and F316 bodies, floating ball valve, trunnion mounted ball valve and forged steel ball valve configurations, PCTFE or metal seats, ISO 28921 bonnets and witnessed cold tests. Dongri documents every line with dual-certified reports. As a direct manufacturer and supplier, Zhejiang Dongri Valve Co., Ltd. handles OEM/ODM customization and wholesale program pricing for air-separation repeat orders, and runs OEM/ODM batches from its China factory with full API and cryogenic dual documentation.
Send Dongri your ASU product-line map and get a per-line air separation unit cryogenic valve specification for oxygen nitrogen argon — so every cryogenic ball valve for air separation unit LOX and LIN you install is cleaned, qualified and documented for the header it actually serves.
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