Nitrogen Gas Purity Grades for Different Industry Uses
Due to its inert nature, gaseous nitrogen can be used across various purging, blanketing, and flushing operations. Depending on the type of process involved, different grades of nitrogen purity are needed to fulfill unique manufacturing needs.
This article discusses the categories of nitrogen gas for industrial use, and their appropriateness for different manufacturing processes.
What Is Nitrogen Gas Purity?
Nitrogen gas purity refers to the proportion of a nitrogen gas that is present in a sample taken from its stream when compared to impurities present. Nitrogen gas can be categorized as high purity or low purity depending on the ratio of pure gas to the contaminants like oxygen, water vapor, carbon monoxide, and carbon dioxide.
This categorization based on nitrogen concentration plays a key role in determining the suitability of nitrogen to any industrial process.
High-Purity vs. Low-Purity Nitrogen
The purity of a sample of nitrogen gas is determined by the percentage/concentration of pure nitrogen in it. For gas to be classified as high purity, it must possess at least 99.998 percent nitrogen while lower purity nitrogen gas usually contains a higher proportion of impurities.
High-Purity Nitrogen Gas
Gaseous nitrogen with concentrations above 99.998% is considered to be a high-purity fraction. High purity nitrogen gas can be graded in different ways by different manufacturers however they are mostly considered to be “zero grade” fractions. Zero grade high purity nitrogen gas is categorized as such because they contain less than 0.5 parts per million of hydrocarbon impurities.
Other key characteristics of high-purity nitrogen gas are:
- Oxygen concentration ≤ 0.5 parts per million
- Carbon monoxide/carbon dioxide no more than 1.0 parts per million
- Water not greater than 3 parts per million
Low-Purity Nitrogen Gas
Nitrogen gas ranging between 90 to just under 99.9% is considered to be low-purity. Common low purity nitrogen gas brands include:
- Extra dry
How to Check Purity of Nitrogen Gas
Nitrogen gas manufacturers name their products differently with no standardized naming conventions. As a result, a low-purity gas from one producer might be mistaken for a high-purity gas by another based on its name alone. The only definitive way to determine gas rating is to check the manufacturer’s guide on their unique gas concentrations.
Nitrogen Gas Purity Classification
Classifying pure nitrogen gas is done with the grading system using digits within each minimum purity rating. The first digit of each grade refers to the number of “nines” present in it while the second digit represents the number following the last nine. For example grade, N3.0 is equal to 99.9% purity and is a pure grade gas purity classification (no second digit attachment).
Pure grade nitrogen classifications include N2.0, N3.0, N4.0, N5.0, N6.0, and N7.0.
What Is Ultra High Purity (UHP) Nitrogen Gas?
Ultra-high purity nitrogen gas refers to a nitrogen gas concentration of 99.999% with negligible impurities. UHP nitrogen specifications are strict with variations rendering the classification invalid.
The oxygen content of UHP gas can be no greater than 2 parts per million by volume (ppmv), total hydrocarbons cannot exceed 0.5 parts per million by volume, and moisture no greater than 1 part per million by volume). UHP nitrogen gas is typically used in scientific applications.
What Is Oxygen-free Nitrogen (OFN)?
Oxygen-free nitrogen is defined as gaseous nitrogen-containing no more than 0.5 parts per million of oxygen. OFN gas is typically maintained at 99.998% purity. This grade of nitrogen gas is useful in scientific research and calibration processes where oxygen impurities might alter outcomes or cause incorrect results.
Nitrogen Gas Purity Grades by Industry/Application
As mentioned above, the concentration of nitrogen required in different industrial processes varies greatly. The key consideration in choosing a grade of nitrogen is the effect of impurities on the selected application. Sensitivity to moisture, oxygen, and other contaminants are critical factors to consider.
Food-Grade Nitrogen/ Beverage Grade Nitrogen
Nitrogen is commonly used in different steps of food/beverage production, packaging, and storage. Nitrogen in food packaging and processing is used to preserve the shelf life of processed food/drinks by eliminating food oxidants, preserving flavor, and preventing rancidity. Food-grade nitrogen gas requirements typically fall between 98-99.5% purity.
Pharmaceutical manufacturing processes require high levels of purity to prevent contamination and alteration of their final products. Many drugs require high-grade nitrogen with a purity between 97-99.99%. This high to ultra-high purity nitrogen is used for nitrogen blanketing storage tanks, receptacles, and other equipment used in drug manufacturing.
High purity nitrogen is also used in drug packaging to help retain freshness and keep active ingredients from deteriorating.
Gaseous nitrogen with purity levels ranging from 95-99% is useful in the oil and gas industry to reduce the risk of fires and explosions in associated processes. Chemical storage tank inerting and pipeline purging with gaseous nitrogen helps minimize the risk of sudden combustion of their contents.
Industrial Nitrogen Grade Purity
Some industrial applications and their nitrogen grade requirements are outlined below.
Electronic & Semiconductor Manufacturing Grade Nitrogen
The typical nitrogen grade requirements in electronics and semiconductor production are usually at least 99.99-99.999%. Some processes like parts cleaning and adhesive blanketing utilize lower concentrations of nitrogen (95-99.5%).
Plastics Manufacturing Grade Nitrogen
Nitrogen grade requirements for plastics synthesis is 95-98% for injection molding processes, 99.5% for gas-assist injection molding, and 98-99.5% for blown film extrusion.
Metalworking Grade Nitrogen
Metalworking grade nitrogen varies widely from 95-99% for heat treatment to 99-99.999% for laser cutting processes.
Power Generation Grade Nitrogen
Power generation processes like gas seal purging, boiler layup, natural gas line purging, and demineralized water blanketing require nitrogen gas with purities between 95-99.6%.
NiGen’s Onsite Nitrogen Generators Cover Most Applications
At NiGen, we supply and maintain efficient onsite nitrogen generators suited to various industrial manufacturing processes. Our wide range of products and services ensure all your nitrogen requirements are fulfilled at each stage of your production cycle.