Rational selection and matching of efficiency levels of filtration equipment

Priority pre-filtration: efficiency generally G3, possibly with a bag filter.

Second pre-filtration stage: efficiency is generally F6, again with a bag filter.

Final stage: efficiency F7, with a partitionless filter.

Such multi-stage filtration systems are common in gas turbines and large air compressors and can be cheap or expensive, depending on the environment in which they are used.
In general, the priority filter element can take many different forms, of which the most economical and practical is the bag filter with a large effective filtration surface, which can be cleaned and is inexpensive; likewise, the choice of the final filter is also crucial, and the choice must not be sloppy but must ensure the efficiency and reliability of the filter.

In the design of the entire filtration system, we must first determine the last level of filtration equipment according to the requirements of cleanliness, followed by the selection of filters that can play a protective role, to protect the role of equipment can be collectively referred to as pre-filters.
The performance and efficiency of each filter need to be matched appropriately.
If the difference in efficiency between two adjacent filters is too great, the first level of equipment will not be able to play a protective role, while if the difference between the two levels is too small, the second level of equipment will be overburdened.

When used in clean rooms, it should be noted that the end of the high-efficiency filter must be protected by a filter with an efficiency specification of not less than F8, while the sub-high efficiency filter can be protected by a filter of F9 - H11 and the central air conditioning itself should be protected by a filter with an efficiency specification of not less than F5.
In short, the choice of the efficiency level of the pre-filter to protect the latter equipment is necessary to designers and site engineers for the use of the environment, spare parts costs, operating energy consumption, maintenance costs, and other factors for comprehensive consideration and analysis after the decision.