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Swing Vane Anemometer

Air Filter Gauge

Air Filter Gauge

  Dwyer Instruments part # Cat. # Price
Swing Vane Anemometer MATKII 0-3 Model 25 1500-09 $ 58
  • Manometer-type gauge measures pressure differentials across a cleanroom’s air filter to ensure correct filter operation
  • Incorporates a curved, inclined-vertical tube for wide pressure range and more increments at low readings
  • Provides measurements above and below atmospheric as well as of differential pressure
  • Accurate to within ±3% of full scale
  • Easy to install

This Swing Vane Anemometer helps you ensure the correct operation of air filters and thus helps maintain the standards you require for your cleanroom.

It provides an accurate reading (in inches of water column) of pressure differentials across a filter. By comparing the resistance pressure with manufacturer’s recommended values, you can determine when a filter needs servicing or replacement before air leakage or contamination occurs. This gauge also helps you ensure that filters are properly installed; it should indicate an initial reading in conformance with the manufacturer’s data.

Its construction is simple yet rugged. The one-piece, noncontaminating, virtually indestructible molded white styrene-acrylonitrile housing holds the indicating tube and fluid wells, shock mounted glass level vial, zero adjust plunger, and leak-proof “O” ring seals. The front panel features molded ABS knobs. The aluminum scale is epoxy coated. Moderate overpressures are accommodated by an overflow tank.

For normal stationary installation, simply mount the gauge on any vertical surface with the two mounting screws provided. A built-in spirit level simplifies leveling before mounting screws are tightened. Fill the reservoir, adjust the fluid level to zero, connect the tubing, and the gauge is ready for operation.

Range: 0-3 inches water column
Fluid Requirements: Uses 0.826 sp. gr. (red oil)
Weight: 10.5oz. (298 g.)

Selecting the Proper Air Filter and Swing Vane Anemometer*
Air Filters are incorporated into the ventilation system of a cleanroom to remove an extremely wide variety of contaminants from the air, including particles smaller than a micron, 0.000039" (0.001 mm). Because variables involved in such ventilation systems vary radically—depending on the exact cleanliness standard, size of facility, rate of ventilation and many other factors—filter selection must be made by a qualified engineer in cooperation with the filter manufacturer.   Once a filtering system has been selected, one problem remains: how to judge when the filter has reached its effective lifespan. Because of the wide variation in the types and concentrations of contaminants in the air being filtered, length of service and visual inspections are an unreliable guideline. The most widely used method of determining when a filter needs to be serviced or replaced is to measure the pressure drop across the filter by means of an air filter gauge.

The Function of an Swing Vane Anemometer
An Swing Vane Anemometer measures pressure drops across the filter in order to determine whether or not the filter is operating within its design range of effective use. This is not the same as measuring filtering efficiency. Filter efficiency has to do with the ability of the filter to remove particulate matter from the air stream, and is generally measured in precisely controlled tests that vary according to the type of filter.   One method is to compare the weight of a carefully compounded dust mixture trapped in the filter with the weight of the dust released. Another method, originated by the NBS/NIST, compares the opacity of the dust collected on filter paper from two air samples of equal flow rate, one of which is filtered air. The efficiency of the filter is thus evaluated on the basis of the dust spots. A third method measures a resistance of DOP (Dioctyl-phthalate) smoke, a homogeneous aerosol of 0.3 micron size, to test a special class of high efficiency filter.

Recommended Resistances for Air Filters
All filter manufacturers supply technical data which indicate the initial resistance in inches of water column for the filter at its rated air flow, and a recommended resistance at which point the filter should be replaced or serviced. These values vary according to the type of filter. For most filters used in a cleanroom environment, however, the range between initial and replacement resistance is typically between 0.01 and 0.1" WC.   During air filter installation, air filter gauges hence provide the additional function of ensuring proper installation and proper air-flow design. The gauge should indicate a pressure resistance in conformance with the manufacturer's recommendations. If pressure is too low, the filter may be handling less than the rated air volume due to open bypasses or improper air balancing, incorrect installation or air leaks. If pressure is too high after initial assembly, the filter may be incorrectly installed or the system may be handling more than the rated air volume.

*Source: Dwyer Control & Gauges

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