Filter Element Test Procedures

When testing filters, it is imperative to select the proper test fixture or adapter that is compatible to the filter shape and size. It may be necessary to fabricate or source the fixture for new element configurations. Additional steps may be necessary to insure that the element is fully sealed to the test fixture and no air leaks exist around the base or any openings (e.g. holes for mounting or fittings).

It is important to flow the filter in the correct orientation as to the direction of designed air flow. This is the direction of air moving from the dirty side to the clean side of the element.

To determine the appropriate flow range for the filter under test, a preliminary flow test must be performed. Select intake flow range #10 (1000 cfm ). Start the flow bench motor and allow the test pressure to stabilize at 1.5” H2O. Observe the cfm reading on the digital readout. Shut off the flow bench motor and select the intake flow range that is one step higher than the preliminary test reading.

Round Filter Test Procedure

When testing round air filters, entry base plates manufactured with a .250” entry radius will be installed on the air intake duct of the SF-1020. A base plate will be selected with an entry diameter closest to the inside diameter of the filter. The filter to be tested is centered over the hole in the entry plate. A corresponding diameter, 0.250” thick, aluminum top plate is used to seal the top of the round air filter.

These top plates have a ~.125” hole in the center to incorporate a Dwyer Instruments pitot/static pressure tube to read the static pressure inside the filter element. It is important to note that the static pressure is measured through the holes in the tube that are around the circumference about an inch from the tip and the static pressure tap from the SF1020 is connected to the static pressure tap on the side of the Pitot tube. The Pitot tube tap on the end of Dwyer Pitot tube is to be capped. Care must be taken to avoid clogging any of the holes in the Pitot tube as this will adversely affect the accuracy of the device.

The Pitot tube is inserted into the hole of the top plate to a depth of approximately 1” below the top of the filter element and the area around it sealed with a bit of clay. To measure the flow, set the SF1020 Bench to a fixed 1.5” H2O differential pressure and select the appropriate intake flow range that was derived from the preliminary test above. Turn on the bench blower fan, allow the readings to stabilize. The operator can then freeze the digital display reading at exactly 1.50” H2O and record the cfm reading.

Flat Panel Test Procedure

To test flat panel air filters, a panel filter test fixture has been fabricated. The plenum of the fixture measures 17” long x 10.5” wide x 5.75” deep. The bottom of the box has a 9” diameter hole with a 0.500” entry radius. The panel filter air box will be installed on the air intake duct of the SF-1020. A Dwyer pitot/static tube is positioned in the lower corner of the plenum. The top of the box features 4 adjustable slides to accommodate various size panel filters.

The panel air filter to be tested is to be placed on in the air box and the slides adjusted to provide a positive seal on all 4 sides. For panel filters that are not rectangular or are multi sided, care must be taken to seal the entire filter perimeter to the test fixture so there are no leaks. Connect the static pressure tap of the SF-1020 to the static pressure tap on the side of the Dwyer Pitot tube. The Pitot tube tap on the end of Dwyer Pitot tube is to be capped.

To measure the flow, set the SF1020 Bench to a fixed 1.5” H2O differential pressure and select the appropriate intake flow range that was derived from the preliminary test above. Turn on the bench blower fan, allow the readings to stabilize. The operator can then freeze the digital display reading at exactly 1.50” H2O and record the cfm reading.

Conical and Universal Clamp-on Test Procedure

When testing a conical or universal clamp-on filter, various small base plate adapters manufactured with 2” to 5” diameter holes will be installed on the air intake duct of the SF-1020. A base plate adapter will be selected with an entry diameter large enough for the filter base of the filter to mate with the surface of the adapter. The filter neck or clamping surface, if one exists, will be inserted through the adapter hole and the base of the filter will be sealed to the adapter plate to ensure no leakage.

In preparation for testing, a ~.125” diameter hole will need to be drilled into the top of the filter to allow insertion of a Dwyer Pitot tube for static pressure measurement. It is important to place the hole in or as near to center of the filter as possible.

It is important to note that the static pressure is measured through the holes in the tube that are around the circumference about an inch from the tip and the static pressure tap from the SF1020 is connected to the static pressure tap on the side of the Pitot tube. The Pitot tube tap on the end of Dwyer Pitot tube is to be capped. Care must be taken to avoid clogging any of the holes in the Pitot tube as this will adversely affect the accuracy of the device.

The Pitot tube is inserted into the hole on the top of the filter to a depth of approximately 2” below the top of the filter element and the area around it sealed with a bit of clay. To measure the flow, set the SF1020 Bench to a fixed 1.5”H2O differential pressure and select the appropriate intake flow range that was derived from the preliminary test above. Turn on the bench blower fan, allow the readings to stabilize. The operator can then freeze the digital display reading at exactly 1.50” H2O and record the cfm reading.
 

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