Ambient-air vaporisers: construction, ratings and commissioning
The YQK low-pressure and high-pressure ratings, plus the full sequence for installation, purging and stepped pressure testing.
An ambient-air vaporiser boils cryogenic liquid at atmospheric temperature. It is used mainly to vaporise liquid oxygen, nitrogen, argon and carbon dioxide for cylinder filling, and is built in high-pressure and low-pressure versions.
Principle: ambient air is the heat source, and heat exchange takes place through LF21 star-section tubes, turning the cryogenic liquid into gas at a controlled temperature. The unit consists of star-shaped finned heat-conducting tubes, liquid and gas guide tubes, a frame and base, and inlet and outlet connections. The star fin tube has eight symmetric fins and is made of LF21 antirust aluminium alloy, resistant to corrosion and weathering; the guide tubes are T2M copper, resistant to pressure and impact; the base and frame are LF21 aluminium angle sections.
Low-pressure series (YQK50/16 to YQK400/16): capacity 50–400 Nm³/h, working pressure 1.6 MPa, design pressure 1.76 MPa, test pressure 2.40 MPa, limit pressure 8.0 MPa, heated by ambient air.
High-pressure series (YQK50/150 to YQK400/150): capacity 50–400 Nm³/h, working pressure 15 MPa, design pressure 16.5 MPa, test pressure 22.5 MPa, limit pressure 75 MPa, heated by ambient air.
Foundation: build to the foundation drawing. It must be solid, fire-resistant and heat-resistant, with grease and other combustibles removed; asphalt surfacing is not permitted. Ambient-air vaporisers are normally installed outdoors with good ventilation.
Installation and commissioning: lift into place and level; tighten the anchor bolts; connect inlet and outlet and check the whole system; flush the system with carbon tetrachloride to remove grease; purge with nitrogen to remove moisture and particles; vent with 6–12 m³ of oxygen at zero pressure; then raise pressure in steps — 5 MPa held for 10 minutes, 10 MPa held for 10 minutes, 15 MPa held for 10 minutes — and put the unit into service once no leak is found.
Precautions: the site must be well ventilated, away from high-pressure sources, grease and ignition, with a clean floor; provide a safety exit and safety signage; keep fire-fighting equipment on hand; outdoor installations need static earthing and lightning protection; ambient range −20 to +50 °C, with 200 Nm³/h units common in the south and 400 Nm³/h in the north; operators follow the procedures of JB 6898.
Written by the Tairan engineering team from project records and standard documents. Please cite the source when quoting.