Do You Really Know Your Gas Consumption and Cost? – Part IV (Liquid Oxygen)

This article continues our blog series:

1. Do We Really Know Our Gas Consumption and Cost? Part I (1)
2. Do You Really Know Your Gas Consumption and Cost? – Part II (Liquid Nitrogen) (2)
3. Do You Really Know Your Gas Consumption and Cost? – Part III (Nitrogen Cylinders) (3)

In this series, we explained how confusion in gas measurement units can lead to costly errors. This time, we shift focus to Liquid Oxygen (LOX) – exploring its technical, financial, and operational aspects, including:

• The impact of the unit of measurement (UOM) on actual consumption and costs
• How liquid oxygen is stored, consumed, and billed
• The hidden costs and wastage losses involved(evaporation, filling, and leftover gas)
• How PSA Oxygen Plants can cut costs by more than half

Case Study: Auto Parts Manufacturing Industry (Brazing Application)

A client from the auto parts manufacturing sector approached us with a request to set up a PSA Oxygen Plant for brazing. Their initial specifications:

• Oxygen Flow: 50 Nm³/hr
• Pressure at usage point: 6 Barg
• Purity required: 99.5%

To ensure that our proposal is technically in line with the customer’s specifications, we requested the customer to visit their facility to validate these requirements.

Our team visited the client site and conducted a detailed audit of the customer’s process, application, and associated gas requirements in terms of Oxygen flow, purity and required pressure at the point of use. 

Since the customer was already using a liquid Oxygen setup in their plant, we studied their current usage patterns, refilling and billing cycles, to gain a detailed understanding from a techno-commercial perspective. Below is a gist of the observations made by our team:

Oxygen Purity Analysis

• Oxygen Purity required for Brazing: ≥ 90%
• Default Liquid Oxygen Purity: 99.9% – (higher than required)
• Oxygen Production Cost by Purity

Note: Electricity cost assumed at ₹8/unit.

• • Key Insights
    • The Oxygen purity of 90-96% is widely acceptable in brazing applications.
    • PSA Oxygen plants can generate Oxygen as per the required purity level, thereby providing significant monetary savings on the production costs. The evidence (explained above) demonstrates that production costs are reduced by more than 50%. 
    • There are also additional cost benefits that arise from lower maintenance and operational costs. Selecting the right Oxygen purity reduces the overall life cycle cost of a PSA plant. 
    • To read more about the cost implications of Oxygen purity, please read our blog titled, Comparison of the Cost of Oxygen Gas from Different Sources (4).

Oxygen Flow Calculation Error

To determine the Oxygen gas flow required for the application, we asked the customer to explain how they calculated the value mentioned in their RFQ (50 NM³/hr). They told us that they had reviewed their liquid Oxygen supplier’s invoice and divided the total Oxygen gas volume by the total working hours. While this method was theoretically acceptable, it overlooked one critical factor – the Unit of Measurement (UOM).
The requirement was calculated based on the following data:

What’s wrong with this data? As visible from the above, the client divided the liquid Oxygen volume directly by hours, ignoring the unit conversion.

After factoring in the UOM conversions, we found the actual usage was much lower.

Please look at the table below:

The above analysis clearly highlights a discrepancy of nearly 16% between the customer’s calculated Oxygen flow requirement and the actual flow required. 

                                                                                      16% lower actual consumption vs. client estimate

Quick Conversion Reference

Wastage and Losses with Liquid Oxygen

Another key factor to consider is the process losses that occur during the use of liquid Oxygen 

• Evaporation Loss/Boil-off: Liquid Oxygen is stored in large vacuum-insulated tanks installed outside at designated areas (as per the PESO guidelines).  Since achieving 100% insulation is practically impossible, liquid Oxygen converts into gas when exposed to direct sunlight and atmospheric heat, leading to an increase in the pressure of Oxygen inside the liquid tank, which is then released into the atmosphere to maintain the pressure inside the tank within safety limits. This leads to loss of Oxygen gas (called evaporation loss or boil off). On average, daily evaporation losses can reach up to 3% of the total stored volume, and may be even higher depending on site-specific conditions.
• Filling losses: During the refilling of liquid Oxygen in liquid tanks, a lot of liquid Oxygen is wasted in the form of spillage, which is usually ignored.
• Unknown leftovers during refilling:  Industries using liquid oxygen usually face this issue, where they have a fixed frequency of refilling liquid oxygen without taking into consideration the quantity of remaining liquid oxygen inside the tank at the time of refilling.
•  

 Loss Calculation

Actual Oxygen Requirement (After Absstem Audit)

Corrected Requirement: PSA vs VPSA Plants

As we can see, the difference was observable in terms of all parameters, i.e., flow, purity & wastage. The right choice of Oxygen plant for this particular industry can save more than 30% capital expense (in case of PSA Technology) and almost 3 to 5 times the operational cost, every year, in the case explained above. To understand more about PSA and VPSA oxygen plants, please read our blog titled, What is a VPSA or VSA Oxygen Generator ? (5).

Lifecycle Cost Impact

If you calculate the lifecycle cost, taking into consideration the life of a PSA or VPSA Oxygen plant is a minimum of 10 years, then we can easily say that the decision to buy the Oxygen plant as per the initial client data would have turned into an economic disaster. By contrast, PSA/VPSA plants deliver ROI in 12–30 months.

To compare the ROI of your PSA Oxygen plant with that of a liquid Oxygen setup, please use our proprietary Absstem ROI calculator using the link here.

Conclusion

This case highlights three key lessons:

1. Check unit conversions (litres vs Nm³ vs kg) to avoid oversizing.
2. Match purity with application requirements – higher purity ≠ always better (unless it is needed).
3. Account for wastage – evaporation and filling losses in liquid Oxygen add hidden costs.
4. A PSA Oxygen Plant with 12-30 months ROI is a smarter, sustainable alternative to liquid Oxygen supply for different industries.

Consult Us

Looking to optimise your Oxygen cost? Contact our experts:

• Email: [email protected]
• Phone: 1800 3010 3394
• Website: www.absstem.com

References

1. Absstem Technologies. (2025). Do We Really Know Our Gas Consumption and Cost?
2. Absstem Technologies. (2025). Do You Really Know Your Gas Consumption and Cost? – Part II (Liquid Nitrogen)
3. Absstem Technologies. (2025). Do You Really Know Your Gas Consumption and Cost? – Part III (Nitrogen Cylinders)
4. Absstem Technologies. (2025). Comparison of the Cost of Oxygen Gas from Different Sources
5. Absstem Technologies. (2025). What is a VPSA or VSA Oxygen Generator?