Why should I change my compressed air filter element?
June 12th 2009

Today, many manufacturers offer filtration products for the purification of contaminated compressed air, with many being selected based only on their initial purchase cost, with little or no regard for the air quality they provide or their lifetime cost of operation.

Compressed air purification equipment is vital for the removal of system contamination, therefore when purchasing this type of equipment, Air Quality, Energy Efficiency and Lifetime Costs must always be considered.

Once installed, compressed air purification equipment (filters & dryers) must be regularly maintained to ensure that they deliver premier air quality and that operational costs are minimised. Therefore it is essential to follow manufacturers maintenance instructions and ensure that associated costs are factored into the annual maintenance budget for the production plant.

How do you maintain air quality?

At the heart of every compressed air filter is the filter element which should not only provide effective contaminant removal, but is also largely responsible for the energy consumption of the filter.

As the primary function of a compressed air filter is to provide contaminant removal to a specifed air quality, then the primary reason to change filter elements should always be to maintain air quality.

When fitted, a differential pressure gauge should only be used as an indicator of the operating costs throughout a filters working life, or indeed, of premature blockage. They are not gauges in the true sense as they are not calibrated and only offer limited accuracy.

Why should I change my filter element ?

To achieve the stringent air quality levels required by both modern manufacturing industry and ISO 8573-1:2001 the international standard for compressed air quality, highly specialised filtration materials are employed in the construction of filter elements, which have both a finite capacity and life to retain contamination. It is important to remember that when the filter life has expired, the required air quality can no longer be maintained.

Filters are installed to provide contaminant removal to a specific air quality requirement, therefore the primary reason to change filter elements should always be to maintain air quality and they should therefore be replaced every 12 months.

Once installed and in operation, the filter housing and element provide a restriction to the flow of compressed air, reducing the available system pressure after the filter. The reduction of system pressure is known as “pressure loss” and is often measured across filters and recorded as a “pressure drop” or as “differential pressure”.

Differential pressure gauges are not service indicators or air quality indicators; they simply measure differential pressure and indicate premature blockage. As filtration media breaks down, even a hole the size of a pin-point can result in the filter media rupturing, allowing all contamination to be carried past the filter into the system. If this should happen, a differential pressure gauge would not record this occurrence and the filter element would never be replaced until the user detected contamination downstream.

Cost of Ownership - Pressure drop considerations

A compressor requires electrical energy to produce a volume of compressed air at a given pressure, the higher the pressure the more energy required. Pressure can be directly converted into energy consumption, so the higher the pressure loss across the filter the greater the operational costs to the user.

Therefore, it may prove to be good economical sense to change a filter element prior to the manufacturers recommended change period if the differential pressure becomes excessive e.g. on systems prone to high particulate contamination.

A balance between risk and cost

Ultimately the filter element should be changed based upon maintaining air quality and in accordance with the manufacturers recommendations. Consideration should also be given to system pressure losses (and therefore operating costs) as the cost of a replacement element is often significantly lower than the energy cost associated with operating with higher differential pressures.

Often the users emphasis is on the cost of maintenance and replacement parts when in reality these costs are insignificant to those associated with product spoilage should a filter element fail. What seems like a cost saving in the short term can turn out to be a costly mistake.

Having already identified the cost to your business of contaminated compressed air and the need for high quality purification equipment, why compromise air quality for the cost of a filter element?

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