Focusing on the operating costs associated with the use of dust extraction and filtration technology, it is necessary to include not only the electricity costs. Another operating costs are induced by compressed air for filter medium regeneration and refurbishment costs. It is also important to focus on the lifetime of the bag media and other important parts of the dust extraction system and the cost of replacing them.
For baghouse extraction system, one of the most costly, periodically variable parts is the bag medium itself. The bag media has different, manufacturer-defined lifetimes for different types of filtering devices.
In the first purchase of the extraction unit and its accesories, the price of spare parts and their declared lifetime are not perceived by clients as important, which can subsequently cost them unpleasant sums.
The lifetime of the bag media affects a lot of operating factors. The factors are: the type of dust extracted, the baghouse air-to-cloth ratio, the type and shape of the bag elements, the bag material itself and many other factors. The reasons why filter media needs to be changed are:
High pressure drop
It is caused by the pores of the filtration material being clogged at a level that can no longer be regenerated. The impossibility of regeneration is caused by penetration of dust into the bag fabric substance. Dust particles stick between fibers and they can no longer be removed from the filtering substance. This problem often occurs with lower-grade, low-porosity filter materials of small area mass. The biggest problem with the compound filter medium is the zig-zag fold shape where the dust particles fill the infolded spaces and can not be regenerated.
Leaking dust through the bags
Dust leaks are caused by damage to the bag media. Damage may be caused either by the fatigue of the filter material after exceeding its lifetime in a better case or by rupturing or a scrape-through caused by abrasive dust in a worse case. It is always reasonable to deal with the situation with a supplier or manufacturer of filtering equipment. Have the filtering device repaired and modified to prevent damage before the expiration of the declared service life.
It should always be a responsibility of the supplier of the baghouse or designers to assess these factors. The filtering device must fulfill the required function, must be operationally economical and must declare a certain lifetime of the bags and the cost of replacing them.
Experience of the Operators
- Filter media with a life of approximately 2000 – 6000 operating hours (cartridge filters)
- Filter media with a lifetime of approximately 20,000 operating hours (fabric filters)
- Filtration media with a working life of more than 20,000 hours (plastic filters)
For Option 1 (cartridge filters), it is especially important to assess the costs of cartridge replacements, since it is more than likely to be a regular annual cost that can negatively affect the operators maintenance budget.
Between Option 2 and 3, it is necessary to assess not only the cost and durability of the filter media but also the efficiency of the baghouse in relation to the pressure drop of the filter media and the consumption of electrical energy, which is directly dependent on these factors. The high lifetime of the filter media can be balanced by disproportionately higher power consumption due to overcoming the higher pressure drops of the bags. We have devoted a separate chapter to this very situation for you in “Effect of the baghouse pressure drop on the annual maintenance costs of a dust extraction system“