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FILTER SELECTION

Figure 18.GENERAL PURPOSE FILTER FLOWS

Figure 21.RECOMMENDED FILTRATION LEVELS. Once all of the contaminants have beenconsidered the degree of cleanliness of air for each part of an industrial plant or process can be determined. By only employing the correct filters in the right location energy andmaintenance costs can be kept to aminimum. The volume of air involved in each stage must always be considered as under- sized, inappropriate filters are a prime cause of high energy costs. A very general guide to the typicallevels of cleanliness required for commonprocesses is given in figure 21. Each appli-cation should however be considered on its own merits.Recommendations on air drying areparticularly difficult since this is dependant upon the temperature of the compressed air main adjacent to the application/machine the level of pressure reduction and air flow rate. For well laid out generation anddistribution systems drying is seldomrequired in countries of typically low to moderate relative humidities and ambient temperatures.When choosing a filter to cleancompressed air ensure:-

PipeUnitFlow (dm
3 /s)* Size ApplicationTypical Quality Classes OilDirt

The correct type of filter and elementrating is selected for particle removal.

1/8 " F0715 Air agitation13

The liquid removal efficiency is highand that re-entrainment is not possible.

1/4 " F72G30 Air bearings22

Ease of maintenance and liquidcondensate collection is possible.

1/2 " F64G70 Air gauging22
F74G83

Easy visibility of condensate and/orelement ensures that function is achieved or shows if maintenance is required. This may be a pressure drop device,liquid level indicator or transparent bowl. In order to aid determining the typeof water and particle removal, figure 20 shows ISO8573 Air Quality Classification.

Air motors44
1 " F15175 Brick and glass machines54 *Flow at 6,3 bar and 0,5 bar pressure drop. Cleaning of machine parts34 Construction45 Conveying, granular products24 Conveying, powder products13

Figure 19.HIGH EFFICIENCY FILTERFLOWS

Fluidics, power circuits25 Fluidics, sensors23 PipeUnitFlow (dm
3 /s)*OilSizeRemoval Foundry machines45 Class** Food and beverages11 1/8 " F392,82 Hand operated air tools55 1/4 " F72C4,52 Machine tools54 3/8 " F64C162 Mining55 F64B71 Micro-electronics manufacture11 F74C162 Packaging and textile machines53 1/2 " F64H282 Photographic film processing12 F64L111 Pneumatic cylinders35 F74H282 Pneumatic tools54 1 " F53602 Pneumatic tools (high speed)43 F52601 Process control instruments23 1 1/2 " F47852 Paint spraying11 F471203 Sand Blasting45 2 " F472002 Welding macines55 F472863 General Workshop air54
llll 0101001 000 *Flow with 6,3 bar inlet to achieve ‘class’requirements.**See figure 20. Figure 20.

AIR QUALITY CLASSIFICATIONS ISO 8573

Quality ClassDirtWater Pressure Dew-pointOilParticle Size in Microns°C (ppm vol.) at 7 bar g(including vapour) mg/m
3 10,1-70 (0,3)0,01 21–40 (16)0,1 35–20 (128)1 415+3 (940)5 540+7 (1 240)25 6—+10 (1 500)— 10