# Replacing liquid oxygen tanks with VSA on-site oxygen

The ULTRAOX VSA datasheet states that this Ultra Controlo industrial oxygen plant can replace existing cryogenic systems with liquid oxygen tanks, delivering 75% to 95% oxygen at 50 kPa; by comparison, a 2008 Global Aquaculture Advocate article describes delivered liquid oxygen as up to 99.9% pure and needing no electricity.

## How the two supplies work

Liquid oxygen is made off site: WHO’s Foundations of medical oxygen systems (2023) describes air separation plants for production and bulk liquid storage situated offsite and typically managed by private companies. A 2008 Global Aquaculture Advocate article by engineer Philip Nickerson describes liquid oxygen as normally trucked in, stored in a bulk tank and evaporated as required by the user; it does not require electricity and is delivered by its own pressure. WHO adds that heat leak and surface evaporation make the liquid vaporise continuously, a loss that depends on the size and insulation of the tank and on ambient conditions and can be as much as about 5% per day.

A VSA plant makes oxygen on site from air. WHO describes VSA plants as using a vacuum system to draw the gas into the production equipment, with an oil-free blower that lowers filtration requirements and removes the risk of oil carry-over. The WHO document was written for medical oxygen systems.

## What changes when you switch

|  | Delivered liquid oxygen | On-site VSA |
|---|---|---|
| Purity | Up to 99.9% (Nickerson, 2008) | ULTRAOX VSA: 75% to 95% at 50 kPa (datasheet) |
| Electricity | Not required; delivered by its own pressure (Nickerson, 2008) | Needed for on-site generation; the reliability of the electrical service is a selection factor (Losordo, 2014) |
| Delivery pressure | Delivered by its own pressure (Nickerson, 2008) | ULTRAOX VSA: 50 kPa; higher pressures with an additional oxygen booster supplied on demand (datasheet) |
| Cost factors cited | The price of liquid oxygen, which usually depends on the distance from the production plant (Losordo, 2014) | Electricity cost (DOE, 2001) and the reliability of the electrical service (Losordo, 2014) |

## Sizing, peaks and backup

Writing about fish farms, Nickerson notes that oxygen generation is not necessarily cheaper than buying liquid oxygen: a generator sized for a facility’s maximum oxygen consumption rate could cost much more than liquid oxygen. Liquid oxygen can automatically back up a generator if power is lost or the unit loses capacity, and he considers a combination of the two probably the most economical option. In glass making, a 2001 paper by the US Department of Energy and Energetics records that the first commercial VPSA plant was installed to supply oxygen on site, replacing the liquid oxygen delivered to an early oxy-fuel furnace, and names consumption volume, electricity costs and proximity to existing oxygen production plants as the factors that decide the supply method.

## ULTRAOX VSA

The ULTRAOX VSA datasheet states that this Ultra Controlo industrial oxygen plant can replace existing cryogenic systems with liquid oxygen tanks or work as the main source of supply. It delivers 75% to 95% oxygen at 50 kPa, reaches higher pressures with an additional oxygen booster supplied on demand, has a totally oil-free production system and an oxygen dew point below −50 °C at atmospheric pressure, is supplied on a skid or in a container, and has a life cycle calculated for 150,000 hours. Its seven models deliver 22 to 288 m³/h at 90% oxygen and 18 to 240 m³/h at 93%.

ULTRAOX VSA is an industrial line, not a medical oxygen plant. Its datasheet lists aquaculture, wastewater treatment, hydrogen sulphide (H2S) reduction, gold leaching in mines, pulp bleaching and industrial furnaces among its applications.

### Can the liquid oxygen tank stay as a backup?

Nickerson (2008) notes that liquid oxygen can automatically back up a generator if power is lost or the unit loses capacity, and that combining the two is probably the most economical option.

### Does ULTRAOX VSA need a booster for higher pressures?

ULTRAOX VSA delivers oxygen at 50 kPa; for higher pressures, its datasheet offers an additional oxygen booster supplied on demand.

## Sources

- [WHO, Foundations of medical oxygen systems (17 February 2023), sections 1.6 and 2.1](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [P. Nickerson, Oxygen sources for aquaculture farms, Global Aquaculture Advocate (July/August 2008), Global Seafood Alliance](https://www.globalseafood.org/advocate/oxygen-sources-aquaculture-farms/)
- [T. M. Losordo, A look at aeration, oxygenation, Global Aquaculture Advocate (March/April 2014), Global Seafood Alliance](https://www.globalseafood.org/advocate/look-at-unit-processes-in-ras-systems/)
- [E. Levine (US Department of Energy) and K. Jamison (Energetics), Oxy-Fuel Firing for the Glass Industry: An Update, ACEEE proceedings (2001)](https://www.aceee.org/files/proceedings/2001/data/papers/SS01_Panel1_Paper33.pdf)
- [ULTRAOX VSA datasheet, p. 2 and p. 3](https://www.ultracontrolo.com/products/ultraox-vsa)
- [Ultra Controlo, Medical gas answers: Does Ultra Controlo make oxygen plants for industry?](https://www.ultracontrolo.com/medical-gas-answers#industrial-oxygen-plant-vsa)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/industry/vsa-oxygen-to-replace-liquid-oxygen/