Many filter manufacturers make “dry filters” often made of paper, cardboard or other types of material (media).
The air intake flows through the filters and dirt particles are trapped in the structure and on the surface.
As an example, a car driven at 100 km’s / hr would collect 60 grams of dirt in 10.000 km’s.
Without a filter, the dirt would cause heavy wear of the pistons, piston rings, engine bearings and other mechanical components.
Machinery and Vehicles exposed to harsher environmental conditions place higher demands on the filtration system. This often results in shorter change intervals of the filters.
Earthworks machinery are exposed to extremely high levels of dust. Theoretically an air filter would need to be changed every four days! A new filter that weighs 3.3 Kg’s, can weigh 4.245 Kg’s after 4 days. An extra 0.85 Kg’s of dirt is trapped in the filter.
To save money, air filters are frequently “knocked” or “blown out” with compressed air.
In a local test, “Knocking” removed 412 grams of dirt and “Blowing” increased dirt release to 668 grams.
Despite both cleaning methods the used filter was still 182 grams heavier than a new filter.
Risks to consider;
- Knocking the filter can deform the retaining caps / rings / seals so that it cannot seal properly. This can also create a bypass where unfiltered passes around the filter media.
- Blowing out filters seems to be a safer cleaning method. But when we observe the damaging affect on the structure of the filter paper this method is not recommended either.
- Operators are often unaware of the maximum Air Pressure that can be applied. You risk creating small tears or holes in the filter medium and the structure of the filter media will be damaged.
- Comparing new and blown out filter paper shows that the compressed fibres can no longer trap dirt particles. If the compressed air is wet, there will be more efficiency issues and risks of media damage.
- Air flow is also reduced, reducing performance and increasing the differential pressure drop across a filter. This can lead to increased motor strain and higher energy consumption.
- Differential pressures can be so high that filter media tears and the filter function fails entirely.
- Wet cleaning can also reduce filter efficiency dramatically and cause shrinkage, allowing dirt to bypass via gaps in the filter frame or media.
- Filter failure can lead to a product recall and cross contamination of other products.
All cleaning methods come with considerable risks and it’s up to you to decide whether to take on these risks or simply to use a new filter.
If too much dirt is trapped the filter should be replaced instead of cleaned so in my opinion cleaned filters are not comparable to new filters.