How to efficiently and effectively meet your compressed air quality requirements
31 March 2017
All compressors will require some type of compressed air treatment in order to deliver the desired level of air quality. Whether it be process air, instrument air or breathing air – understanding the air quality required is essential in selecting the right compressed air treatment to effectively and efficiently meet these needs. In this blog we look at the 3 key steps you can take to ensure that you are producing the right air quality for your application.
Every compressor – regardless of type – draws in contaminated air, concentrates the contamination by compression and, if no measures are taken to remove it, passes it on to the compressed air network. Failing to successfully remove these airborne contaminants (solid particles as well as oil and water vapours) will lead to poor air quality which can create a number of problems for you such as;
- health and safety compliance issues,
- reduced lifetime of compressed air and associated equipment,
- heightened maintenance costs,
- elevated energy costs,
- end product contamination or spoilage.
To ensure that high quality compressed air is produced, all compressors will require some type of compressed air treatment. To determine what level of compressed air treatment is required it is worth reviewing the following steps;
1. Define the compressed air application
The first step to establishing the correct compressed air treatment required is to understand what the air will be used for. There are a number of uses for compressed air which each create different air quality requirements. Some examples may include;
Plant air; compressed air used to power pneumatic tools
Instrument air; compressed air used for paint spraying, powder coating and in laboratories
Process air; compressed air used to power processes such as those found in pharmaceutical and food industries
Breathing air; compressed air used for hospital air systems, grit blasting and spray painting
2. Classify the level of air purity required
Now we know the compressed air application we can use the compressed air purity classes ISO 8573-1(2010) tables to define what level of air quality is required.
ISO 8573 was created in order to establish an international definition of air quality levels. Air quality is defined into class ratings that cover the contaminants; oil content, water content and solid particles, where a lower class number denotes a higher air purity level.
These tables will help you to determine what compressed air treatment you require in order to meet the air quality class required for the application.
Generally speaking, the higher the air quality required – the higher the costs are to produce that compressed air due to increased capital equipment costs, as well as operating and maintenance costs. Understanding the level of air quality required is therefore essential to ensure that only the required compressed air treatment is chosen.
3. Select the appropriate compressed air treatment
Once you understand the application and purity level required you can select the appropriate compressed air treatment required. Here’s a rundown of some of the main types of air treatment available;
Compressed Air Dryers
Quality, efficient compressed air treatment begins with drying. There are a number of dryer options available which each work on varying operation principles. The choice of dryer will depend on the compressed air application and air quality required. Types of compressed air dryers include;
- refrigeration dryers; generally used to treat ‘normal’ works- and control air- for pressure dew points 2oC to 15oC
- membrane dryers; are the perfect choice for fixed or mobile applications (e.g. in containers or trucks) where space is at a premium or where the compressed air requires additional drying after the refrigeration drying process, e.g. areas subject to sub-zero conditions on a seasonal basis. They are also ideal as point-of-use dryers for smaller compressed air volumes and can be installed directly upstream from the air-consuming equipment e.g. on CNC machines.
- desiccant dryers; heatless or heat regenerating desiccant dryers provide pressure dew points down to -70oC and are used to treat air for applications requiring exceptionally dry air, such as those in the electronics, food and beverage industries. They are also commonly used for systems that are subject to sub-zero conditions and provide quality process air e.g. for the pharmaceutical industry.
Compressed Air Filtration
A compressed air system will need filters in order to create the air quality level required. Compressed air filters are therefore a key component in delivering compressed air of all air purity classes in accordance with ISO 8573-1.
There are a number of compressed air filtration options to consider. Generally these breakdown into those that operate prior to the compression and/or drying process (pre-filters) or after this process (after-filters).
The efficiency of a compressed air filter will largely depend on pressure loss. Opting for high efficiency filters will not only reduce the burden on upstream compressors but also provide significant cost savings potential.
Condensation is an unavoidable result of air compression. If not reliably drained off at all collection points, it can cause costly downtime and damage to the compressed air system through corrosion as well as impact on the overall air quality. Condensate drains ensure the safe and reliable drainage of condensate without air loss.
High quality, reliable condensate drains are an essential component of any compressed air system. There are a number of condensate drain versions available which will suit different operating conditions – from highly aggressive condensate to freezing temperatures to high pressure or vacuum applications.
The condensate that is removed from a compressed air system is a chemically aggressive fluid. It mainly consists of water but also contains oil and dirt particles. This combination of substances can consequently cause serious environmental harm if released in its raw state.
Water resource legislation will stipulate that contaminated water must be treated to achieve prescribed safety levels regarding purity. Whilst condensate treatment is not a necessary component of an air treatment package in terms of allowing you to achieve a desired level of air quality, it is nevertheless an imperative component that must be considered for the safe and legal disposal of condensation.
There’s a lot to think about when it comes to selecting the correct and most cost effective compressed air treatment to meet your air quality requirements. As selecting the right compressed air treatment is essential if you want to ensure that you are effectively and efficiently producing the right air quality for your application, it may well be worth seeking the advice of a compressed air specialist when making your final selection.
Compressed Air Association of Australasia (March 2017): Fact Sheet 1: Compressed Air System Selection and Efficient Production
Compressed Air Association of Australasia (March 2017): Fact Sheet 3: Efficient Compressed Air Treatment
KAESER Compressors (October 2015): Compressed Air Engineering – Basic principles, tips and suggestions
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