Lesson 8 - Gases
In this lesson we take a closer look at gases, including compressed air. We will look at the quality requirements and specifications for use in the brewery. Different compressed air generation methods will be considered. For nitrogen and oxygen, we will look at the common uses, quality requirements, and options available for supply, storage, usage, and generation.
Compressed Air Quality
Air quality requirements are determined by the application the air is used for.
If we look at all the compressed air applications in the above list, we see that many of these are in direct contact with the product. Thus, there will be more stringent requirements for these applications. Some applications, such as instrument air, have other standards in order to safeguard the equipment.
Where compressed air is in contact with the product, it must be:
-
Free of particulate matter
-
Free of microbiological contaminants
-
Free of oil and grease
-
Dry to prevent microbial growth and corrosion in valve and equipment operations
-
Free of other gaseous contaminants, e.g. carbon monoxide, carbon dioxide, sulphur dioxide, or nitrogen oxide
-
Free of components that cause flavour taints
ISO 8573.1:1000 is the most commonly used standard to classify compressed air. Compressed air is classified according to the degree of contamination with solid particulates, water, and oil, with each of these having parameter ranges for classes from Class 0 to Class 9. The table below gives the contaminant parameters for these classes.
Table: Contaminant levels for different classes
|
ISO 8573.1:2010 Class |
Solid Particulate |
Water |
Oil |
||||
|
Maximum number of particles per m3 |
Mass concentration mg/m3 |
Vapour pressure dew point °C |
Liquid g/m3 |
Total oil (aerosol liquid and vapour) |
|||
|
0.1-0.5 micron |
0.5-1 micron |
1-5 micron |
|
|
mg/m3 |
||
|
0 |
As specified by the equipment user or supplier, and more stringent than Class 1 |
||||||
|
1 |
≤ 20,000 |
≤ 400 |
≤ 10 |
- |
≤ -70 |
- |
0.01 |
|
2 |
≤ 400,000 |
≤ 6,000 |
≤ 100 |
- |
≤ -40 |
- |
0.1 |
|
3 |
- |
≤ 90,000 |
≤1,000 |
- |
≤ -20 |
- |
1 |
|
4 |
- |
- |
≤10,000 |
- |
≤ 3 |
- |
5 |
|
5 |
- |
- |
≤100,000 |
- |
≤ 7 |
- |
- |
|
6 |
- |
- |
- |
≤ 5 |
≤ 10 |
- |
- |
|
7 |
- |
- |
- |
5-10 |
- |
≤ 0.5 |
- |
|
8 |
- |
- |
- |
- |
- |
0.5-5 |
- |
|
9 |
- |
- |
- |
- |
- |
5-10 |
- |
|
x |
- |
- |
- |
>10 |
- |
>10 |
>10 |
Thus, depending on the requirements, air quality could be specified differently for different contaminations. For example, class 1.2.1 would mean class 1 for particulates, class 2 for water, and class 1 for oil.
In the brewing industry, class 0 in relation to oil often refers to oil free whilst class 1 is seen as ‘technically oil free’.
Different applications may have different requirements. For very stringent requirements, it may be necessary to treat the compressed air just before use.
The compressed air quality can be affected by:
-
The source of the air
-
The compressor equipment
-
Conditioning or treatment equipment
-
Downstream distribution systems
Let’s now look at some of the typical equipment used to deliver compressed air.