The UD+ compressed air filters from Atlas Copco save energy and space. © Atlas Copco

The pressure loss for our ^UD+, for example, is initially 0 bar. However, this value rises relatively quickly to a stable pressure loss of between 0.185 and 0.245 bar. This value usually stagnates over a long period of time. If you factor in the fact that every bar of pressure that is used more results in a six to seven percent increase in energy consumption, it becomes clear that energy efficiency also plays a role for filters: One to two percent of the total energy costs of a compressed air station are therefore lost through the filter.

There is a differential pressure indicator at the top of our filters. If this rises above a certain level and the pressure loss is therefore too high, the filter must be replaced. As a rule of thumb, this is the case after around 4000 operating hours. We design the filters and their maintenance according to the reference conditions. And we also pay attention to the environment, for example. If the environment is very damp and dusty, filters become clogged more quickly and need to be changed more often.

How high can the costs of a clogged filter be?

If we take a typical oil-injected compressor such as our GA series with 90 kilowatts of power and 10 bar pressure, the energy costs per year amount to 128,160 euros if the compressor runs for 8,000 operating hours and a kilowatt hour of electricity costs 0.15 euros. With a pressure loss of 0.25 bar due to a fairly good filter, the costs are 129,948 euros. With a filter that has a higher pressure loss of around 0.35 bar, the annual energy costs are already 130,728 euros. In other words, this seemingly small difference of just 0.1 bar in pressure loss already means 780 euros more in energy costs per year.

If I need oil-free compressed air - is it better to use an oil-free compressor or should I place appropriate filters upstream of the application?

Absolutely oil-free compressed air is only necessary in some industries. For example, for applications in the food or paper industry, the pharmaceutical industry or in paint shops. In such cases, the customer requires so-called "technically oil-free" air. The required air purity can only be achieved with oil-free compressors. We offer such machines in our Z series, all of which have been certified accordingly by TÜV.

For most applications, however, it is sufficient to clean the compressed air generated by the compressors with filters. Even if these had to be changed more frequently in the case of contaminated ambient air, the purchase of a Z-compressor (Z = Zero = "zero oil") would in no way pay for itself compared to an oil-injected GA compressor with the same performance data - or at least not just because no filters are required.

However, you should be careful with this comparison anyway. Depending on the performance class, our new oil-free ^ZR-VSD+ compressors, for example, are significantly more efficient than the oil-injected GA compressors or vice versa. And since energy consumption is generally very high, you would have to look at each case individually and then compare the investment costs and all operating costs over the service life.

Are there differences in the quality of filters that need to be taken into account?

When selecting a filter, efficiency, differential pressure, service life until the next service and ease of maintenance are important parameters - in other words, it must be easy to change. There are wound and pleated filters. Atlas Copco uses wound filters. The advantage of this design is the larger filter surface and the higher filter efficiency. However, it is also particularly important to be on your guard against product piracy. Because if a filter does not achieve the promised ISO class, the quality of the compressed air can suffer - with all the negative consequences, including product liability. Tests that we have carried out in Belgium with branded filters and cheap products have shown that, despite external similarities, the energy efficiency of the filters can also be very different.

Overall, we advise users to also look at the filters in terms of energy efficiency and not just the performance data of the compressor. This is because an ill-conceived filter concept, cheap goods or clogged filters can certainly increase the pressure loss - or even endanger the product if the required air quality is not achieved. Quite apart from the fact that the costs may well exceed those of a new filter due to the higher energy consumption.