Application of Nitrogen Gas in Pressure and Leak Testing

Nitrogen gas plays a vital role in various industrial applications, one of them  being pressure testing and leak detection. This article  addresses some of the most  common questions about the use of nitrogen for pressure testing, explaining its benefits, required purity levels, consumption, and cost-effectiveness compared to other gases.

What is Pressure testing?

Pressure testing is a method used to detect leaks to verify the strength and safety of a component or system. It involves applying pressure, typically equal to or higher than the component’s design working pressure, to check its ability to hold pressure without leaks or deformation.

Why is Nitrogen used for Pressure Testing?

Nitrogen is widely used for pressure testing due to its inert nature, low oxygen content, and dryness. These properties make it ideal for testing sensitive components, especially where the presence of oxygen or moisture could cause oxidation or damage.

Key Benefits of Nitrogen in Pressure Testing:

• Non-reactive: Its low oxygen content ensures no chemical reaction with the item being tested.
• Moisture-free: As a dry gas, nitrogen prevents moisture-induced corrosion.
• Cost-effective and abundant: With nitrogen having the highest composition (78%) in the atmospheric air , it is more affordable than other inert gases.

Can Other Gases Be Used for Pressure Testing?

The right answer is yes. Theoretically, inert gases like argon and helium can also be used. The differences lie in the cost of production of these gases.

Cost of production of Nitrogen ~ 100 times < Cost of production of Argon

Cost of production of Nitrogen ~ 1000 times < Cost of production of Helium 

Therefore, Nitrogen becomes the best solution. The reason for the low cost of production of nitrogen is the availability of abundant nitrogen (78%) in the atmosphere.

What Nitrogen Purity is Required for Pressure Testing?

The standard purity level for nitrogen used in pressure testing ranges from 99.5% to 99.9%, depending on the sensitivity of the application. These purity levels ensure the gas is sufficiently inert for accurate and safe testing. To get more clarity about the purity of nitrogen gas, please read our blog titled Understanding Nitrogen Purity in PSA Nitrogen Generators (1)

How much Nitrogen is required for Pressure Testing?

The nitrogen volume required depends on the internal volume of the item and the pressure at which testing is done. The below formula can be used to calculate the same.

Nitrogen Gas Required (Nm³) = Internal Volume × Test Pressure (Barg)

Example: If a pipeline has an internal volume of 5 m³ and is tested at 20 barg, you will require:
5 × 20 = 100 Nm³ of nitrogen gas

What is the Nitrogen pressure required for Pressure testing or leak testing?

Nitrogen pressure used in testing depends on the working pressure of the equipment:

• High-pressure cylinders: Tested at 250–300 barg
• Pipelines and exchangers: Often tested between 6–20 barg

Always test at or above the rated working pressure of the system.

Sources of Nitrogen for Pressure Testing

Traditionally, liquid nitrogen tanks or nitrogen cylinders were used as a source of nitrogen gas for Pressure Testing applications, but with advancements in technology, Nitrogen is produced by on-site nitrogen generators, which separate nitrogen from atmospheric air. 

The cost of nitrogen reduces drastically when produced via a PSA nitrogen generator. The table below  illustrates the cost of Nitrogen from different sources:

Please note that Nitrogen produced from PSA nitrogen generators is at an output pressure of around 8 Barg.  This low-pressure Nitrogen is then further pressurised via gas boosters to the high pressure needed for the specific application. The cost of boosting is comparatively low compared to the generation cost, hence, we have ignored the cost in the above table.

To read more about the cost of different sources of nitrogen, please read our blog, How to calculate the ROI (Return on Investment) of PSA Nitrogen Generator compared to Liquid Nitrogen or Nitrogen Cylinders (2) 

Can high-purity nitrogen of 99.99 or 99.999% be used for Pressure Testing?

In most cases, 99.5 to 99.9 %% nitrogen gas is used for Pressure Testing. This will cost you around ₹2.6/- per cubic meter when produced by aPSA Nitrogen Generator.

The cost of nitrogen production via PSA technology increases significantly as we move from lower to higher purity. This is mainly because producing higher-purity Nitrogen requires more energy (a high amount of compressed air). 

For example, generating nitrogen at 95% purity requires significantly less power than producing nitrogen at 99.9990% purity, since removing the final traces of oxygen from the gas mixture is an energy-intensive process.

The table below shows how electricity consumption affects the cost of production of nitrogen at different purity levels, assuming the cost of electricity as ₹8/- per unit, as per our blog titled Understanding Nitrogen Purity in PSA Nitrogen Generators (1).

Table 2: Cost of Nitrogen used for Pressure Testing

As the table shows, the power consumption, and consequently, the cost, increases as nitrogen purity rises. 

For instance, producing nitrogen at 95% purity costs ₹1.76 per Nm³, whereas producing 99.9995% purity nitrogen costs ₹10.56 per Nm³. This significant difference highlights the need to carefully match the nitrogen purity level to the application requirements to optimise costs.

 Why are PSA Nitrogen Generators the preferred choice for Pressure Testing applications?

Compared to the traditional sources of nitrogen gas, like cylinders or liquid tanks, PSA nitrogen generators are far more beneficial for an application like Pressure Testing. Below are the benefits of the PSA Nitrogen generator over traditional sources like cylinders or liquid nitrogen:

1. Compact Size – Compact Nitrogen systems are help in saving a lot of space compared to liquid tanks
2. Fully automatic systems – As advanced PSA nitrogen generators are fully automatic with auto stop and IDLE features, these systems prove to be a boon for pressure testing application as nitrogen usage is not constant and varies with time. PSA nitrogen generators go into IDLE mode during low usage of nitrogen to save energy.
3. In-house Nitrogen generation – As Nitrogen is produced on-site in PSA nitrogen generators from compressed air, there is no dependency on 3rd party vendors and logistics for refilling of gas, like in the case of cylinders or liquid tanks.
4. Reduction in carbon emission – As nitrogen is produced onsite in PSA nitrogen generators, there is no logistics involved, hence carbon emission is negligible.
5. Low cost of Nitrogen – Nitrogen produced by PSA nitrogen generator is at least 5 times cheaper than other sources. Please refer to our blog titled Comparison of the Cost of Nitrogen Gas from Different Sources (3) for more details.

Conclusion

Pressure testing is essential in industries like oil & gas, manufacturing, HVAC, and more. Nitrogen is the preferred gas for this application due to its inert properties, affordability, and availability. While traditional sources like cylinders and tanks are still in use, on-site PSA nitrogen generators offer unmatched efficiency, cost savings, and operational flexibility.

Consult Us

Need help choosing the right nitrogen solution for your facility? Our experts are here to assist.

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

References

1. 1. Absstem Technologies. (2024). Understanding Nitrogen Purity in PSA Nitrogen Generators
   2. Absstem Technologies. (2024). How to calculate the ROI (Return on Investment) of PSA Nitrogen Generator compared to Liquid Nitrogen or Nitrogen Cylinders
   3. Absstem Technologies. (2024). Comparison of the Cost of Nitrogen Gas from Different Sources