Do You Really Know Your Gas Consumption and Cost? – Part II (Liquid Nitrogen)

In continuation of our previous blog titled, Do We Really Know Our Gas Consumption and Cost? (1), this article explores the technical and financial aspects of using liquid nitrogen in industries.

In the last article, we highlighted how confusion in nitrogen gas measurement units can lead to heavy losses. This time, we’ll focus on:

• Impact of the Unit of measurement on the overall actual consumption and procurement costs
• How liquid nitrogen is actually consumed
• The hidden costs and wastage involved
• How PSA nitrogen plants can dramatically reduce costs

Case Study: Semiconductor Industry Using Liquid Nitrogen

A client from the semiconductor manufacturing industry (SMT line) shared their requirement for setting up a PSA nitrogen plant. Their initial request was:

• Nitrogen Flow: 100 Nm³/hr
• Pressure at usage point: 6 Barg
• Purity required: 99.999%

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 Nitrogen flow, purity and required pressure at the point of use. 

Since the customer was already using a liquid nitrogen 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:

1. Nitrogen Purity Analysis

• OEM’s recommended Nitrogen purity for SMT line: 99.99%
• Default Liquid Nitrogen Purity: 99.9997% – higher than what was required.
• Nitrogen Production Cost Difference in terms of purity
  
  1. 99.999% nitrogen: ₹8.48/Nm³
  2. 99.99% nitrogen: ₹4.80/Nm³
• Key Insights
  
  1. Nitrogen purity of 99.99% is widely acceptable in SMT line applications.
  2. PSA Nitrogen plants can generate Nitrogen as per the required purity level, thereby providing significant monetary savings on the production costs. The evidence above demonstrates that production costs are reduced by nearly 50%.
  3. There are also additional cost benefits that arise from lower maintenance and operational costs. Selecting the right Nitrogen purity reduces the overall life cycle cost of a PSA plant. 
• To read more about the cost implications of nitrogen purity, please read our blog titled, Understanding Nitrogen Purity in PSA Nitrogen Generators (2).

2. Nitrogen Flow Calculation Error

To determine the nitrogen gas flow required for the application, we asked the customer to explain how they calculated the value mentioned in their RFQ (100 NM³/hr). They told us that they had reviewed their liquid nitrogen supplier’s invoice and divided the total nitrogen 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 nitrogen 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 35% between the customer’s calculated nitrogen flow requirement and the actual flow required. 

Unit Conversion Table

In most cases, the liquid nitrogen supplier invoices the nitrogen gas in Sm³, Kg or Litres of nitrogen instead of Nm³. Please verify the units used to measure nitrogen gas accurately to determine the exact nitrogen requirement for your application. The table below helps you with this conversion:

3. Wastage and Losses with Liquid Nitrogen

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

• Evaporation Loss/Boil-off: Liquid nitrogen 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 nitrogen converts into gas when exposed to direct sunlight and atmospheric heat, leading to an increase in the pressure of nitrogen 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 nitrogen 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 nitrogen in liquid tanks, a lot of liquid nitrogen is wasted in the form of spillage, which is usually ignored.
• Unknown leftover during refilling:  Industries using liquid nitrogen usually face this issue, where they have a fixed frequency of refilling liquid nitrogen without taking into consideration the quantity of remaining liquid nitrogen inside the tank at the time of refilling.

 Loss Calculation

Actual Nitrogen Requirement (After Absstem Audit)

  Corrected Nitrogen Requirement (After Absstem Visit)

As we can see, the difference was observable in terms of all parameters, i.e., flow, purity & wastage. The right choice of PSA nitrogen plant for this particular industry can save more than double the capital expense and almost 3 times the operational cost, every year, in the case explained above. 

If you will calculate the lifecycle cost taking into consideration the life of a PSA nitrogen plant is a minimum of 10 years, then we can easily say that the decision to buy the Nitrogen plant as per the initial client data would have turned into an economic disaster. 

To compare the ROI of your PSA nitrogen plant with that of a liquid nitrogen 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 ≠ better (unless it is needed).
    3. Account for wastage – evaporation and filling losses in liquid nitrogen add hidden costs.

A PSA Nitrogen Plant with 6-18 months ROI is a smarter, sustainable alternative to liquid nitrogen supply for different industries.

Consult Us

Looking to optimise your nitrogen 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. (2024). Understanding Nitrogen Purity in PSA Nitrogen Generators
  3. Absstem Technologies. (2024). How to calculate the ROI (Return on Investment) of PSA Nitrogen Generator compared to Liquid Nitrogen or Nitrogen Cylinders