The difference between industrial gas purity and quality – and why it matters
Countless professional and industrial applications require industrial gases, nitrogen (N2) and oxygen (O2) being the most prevalent. Whether companies purchase this gas or generate their own, the issues of purity and quality inevitably come up. A common misconception is that these two terms refer to the same thing. They do not. In addition, going for the highest in either category doesn’t necessarily pay off. On the contrary. Let’s dive into the how and why…
Industrial gas purity
Let’s be very clear: industrial gas of the highest purity isn’t the “best” gas. For example, nitrogen with a purity of 99.999% isn’t necessarily “better” than N2 with a purity of 95%. It simply has a higher concentration of nitrogen compared to trace gases (mostly oxygen). The application for which the gas is used will determine the purity it requires. For example: processes that involve the heating of metals (such as laser cutting and annealing) need a high nitrogen purity to prevent oxidation at rising temperatures. On the other hand, most blanketing applications only need 95-98% nitrogen purity to achieve their goal of avoiding fire and explosion. Using N2 of a higher purity for blanketing will generate no additional benefits.
Why does this overspecification of gas purity matter? Because on-site gas generators give companies the freedom to produce their own oxygen or nitrogen with the right purity for their application. This in turn allows them to significantly lower their industrial gas costs, as producing lower purity gas requires less energy.
Read more about how nitrogen or oxygen purity affect their cost.
Purchased gas in cylinders, dewars or bulk deliveries, on the other hand, is always of the same high purity as a consequence of its cryogenic production process. That means that a large section of its users gets (and over-spends for) a high purity for which their application has no need.
Industrial gas quality
Industrial gas quality refers to the presence of contaminants. These contaminants fall into three main categories: dust, water, and oil – as specified in the international ISO 8573-1 standard. Many industrial applications have specific ISO 8573-1 class requirements, which are more stringent for industries such as pharmaceuticals and food and beverage. Of course, subpar gas quality is a problem for every application, as contamination and corrosion can affect production systems and final products.
This means that gas can be of high purity, but not necessarily of high quality. It is one of the reasons why purchased gas comes in different industrial, foodgrade, and other qualities. Its high purity is fixed because of its production process, but its quality can be controlled more – which also comes at a cost.
On-site gas generators offer a higher quality as standard. Because they require clean inlet air to operate reliably and to protect their components, the nitrogen or oxygen they produce is also of high quality. For example, Atlas Copco nitrogen and oxygen generators comply by default with the very stringent ISO 8573-1 Class [1:2:1]. Additional filtration is available to allow very specialized applications to reach Class [1:1:0]. Here too, the highest quality will not benefit applications that don’t need it, while it does come with the extra cost of additional filtration.
The importance of understanding industrial gas requirements
In the end, the goal is not to have gas with the highest purity and quality. It is about getting both right. Which means the application is key, as is the users’ gas and production system. Because the weakest link in the system will determine the purity and quality level that can be guaranteed. There's no point generating gas of supreme quality if the network that distributes it is polluted. There's no point in putting 99.999% purity nitrogen in a food container if the packaging material cannot retain that purity level.
While purchased gas offers limited flexibility in quality and hardly any in purity, on-site generation does allow users to set and achieve the gas purity and quality they need. This is an important reason why on-site generators generally offer the benefit of a lower price per unit of gas. Users can get the optimal mix of gas purity and quality to meet their production requirements with maximum cost efficiency.
