Nitrogen generator purity levels typically range from 95% to 99.999%+, and the correct level depends entirely on the application. Its inert properties make it virtually undetectable to the senses. That also means it can safely come into contact with virtually any product or surface and prevent contamination or combustion of flammable and explosive materials by eliminating reaction with oxygen in ambient air. Used for blanketing, flushing, and purging industrial equipment, nitrogen gas also retains the freshness of packaged food products and guarantees a much longer and more sustainable shelf life.
Purity is not a “more is better” decision. Different grades and purity levels of nitrogen gas are required to achieve these objectives, and higher purity requirements increase both equipment size and operating cost. Onsite nitrogen generators ensure a consistent supply of nitrogen gas at just the right purity for the specific application. Onsite nitrogen generator purity levels must be maintained according to the specific requirements of the industrial application for which it’s being used. Keep reading to learn about the different industrial applications nitrogen is used for and the purity levels each one requires.
What Is Nitrogen Gas Purity?
Nitrogen gas purity is the percentage of pure nitrogen present in a gas stream relative to residual contaminants such as oxygen, water vapour, carbon dioxide, and argon. Each of these elements can lower the purity level of the nitrogen gas and may render it unsuitable for certain industrial applications. For nitrogen to be considered completely pure, it needs to have a concentration of 99.999%+.
Purity is expressed two ways: as a percentage (99.5%) or as parts per million of residual oxygen (ppm O2). The two describe the same measurement. Industries with tighter tolerances typically state purity in ppm because the percentage figure gets harder to read past four nines.
How is Nitrogen Purity Measured and Classified?
Nitrogen gas that’s produced using onsite nitrogen generators is immediately analyzed to determine the purity levels before it’s allowed to enter the facility’s pipe network. This process ensures that the nitrogen purity levels are sufficiently graded to perform the tasks or processes for which the gas is intended.
An internal instrument known as an oxygen sensor or analyzer is utilized to determine the nitrogen purity levels and display the nitrogen purity number in real time to give an accurate reading. The oxygen sensor or gas analyzer presents a specific value that represents nitrogen purity as a percentage of nitrogen or parts per million of oxygen in the nitrogen gas stream.
Types of Nitrogen Purity Levels
Nitrogen purity ratings may vary according to each manufacturer’s discretion. High purity nitrogen gas is usually classified as zero grade or N5.0. This means that the nitrogen contains an extremely low concentration of impurities such as water vapour, oxygen, carbon dioxide or hydrocarbons.
There are different N ratings for different nitrogen purities. For example, a grade of N3.0 translates to a 99.9% purity rating. The first digit, which is the 3, indicates that there are three nines in the reading and the second digit, the 0, indicates that there are no other digits that follow the last 9.
Ultra-High Purity (UHP) Nitrogen Gas
Ultra-high purity (UHP) nitrogen gas has an extremely high concentration of 99.999% with only 10 ppm of oxygen present or less. The impurity levels are so minimal that they’re completely negligible and have no bearing on the quality or efficacy of the nitrogen gas. Since UHP nitrogen gas has such a high concentration with an inconsequential quantity of impurities such as oxygen, water vapour/moisture, and hydrocarbons, it’s most commonly reserved for scientific processes and applications.
Low Purity Nitrogen Gas
When nitrogen gas has a purity rating of 99.9% or lower, then it’s typically considered to be low-purity or low-grade nitrogen. Purity grades and criteria typically vary by industry application, but low purity nitrogen can also be branded as industrial quality nitrogen.
PSA vs. Membrane Nitrogen Generators: What Purity Can Each Produce?
Not all onsite nitrogen generators reach the same purity ceiling. Pressure Swing Adsorption (PSA) nitrogen generators use two adsorption beds packed with carbon molecular sieve (CMS) to strip oxygen and trace gases out of compressed air. PSA systems can typically achieve nitrogen purities from 95% up to 99.9995%, making them the standard choice when an application requires anything above 99%.
Membrane nitrogen generators separate nitrogen from compressed air using semi-permeable hollow-fiber membranes rather than adsorption. Membrane systems typically produce nitrogen in the 95% to 99.5% range. They’re not built to reach UHP levels, but for applications in that band they run with fewer moving parts and lower maintenance requirements than a PSA system.
If the application needs 99% purity or higher, PSA is almost always the right technology. If the requirement sits at or below 99%, a membrane system can often deliver it at a lower installed cost.
The Purity-to-Cost Relationship
Purity and cost don’t scale in a straight line; they scale exponentially. Getting nitrogen from 95% to 99% purity is a relatively small jump in equipment size and energy draw. Getting from 99% to 99.999% is a much larger jump, because the generator has to work harder to capture the last few parts per million of oxygen. Each additional “nine” of purity means more adsorption media, longer cycle times, or a larger membrane bank.
For nitrogen purities in the 95% to 97% range, onsite generation typically runs under $0.02 per cubic meter. Above 99.5% purity, that cost roughly doubles to triples. Specifying more purity than an application actually requires is one of the most common and most avoidable sources of wasted capital on an onsite nitrogen system.
Required Nitrogen Generator Purity Levels by Industry
Nitrogen purity level requirements vary from one industry application to another. Here are the general purity level requirements for some of the top industries in the world.
| Industry | Typical Purity Range |
|---|---|
| Heat Treating | 99.9% – 99.999% |
| Laser Cutting | 97% – 99.995%+ (depends on metal) |
| Food and Beverage | 99% – 99.9% |
| Pharmaceutical | 97% – 99.999% |
| Oil and Gas | 95% – 99% |
| Power Generation | 95% – 99.9% |
| Electronics Manufacturing | 99.9% – 99.999% (95% – 99.5% for blanketing/cleaning) |
| Tire Inflation and Fire Sprinklers | 95% – 98% |
Why Choose Advanced Gas Technologies
Considering the ubiquity of nitrogen gas across various industrial sectors, it makes practical, environmental, and financial sense to install onsite nitrogen generators that are capable of providing a steady stream of nitrogen gas with varying purity levels for different applications. Advanced Gas Technologies provides state-of-the-art PSA and membrane nitrogen gas generators that feature adjustable nitrogen purity settings to suit your application requirements. Contact us today to learn more.