Frazier Air Permeability Instrument - Instructions for Set-Up for High & Low Pressure Models


The Frazier Differential Pressure Instruments are built into a table and are shipped completely assembled and calibrated.

The procedures for preparing them for use is as follows:

            1.  Uncrate the instrument by carefully removing the wood crate and inner paper cover.  Keep in mind that the instrument contains delicate exposed glass tubes.

            2.  Lift the table containing the instrument off of the crate base and place it where it will be used.

            3.  Verify that the variable transformer indicates "o" and switch is in the off position and plug the instrument into an appropriate electrical outlet.

            4.  Level the instrument by means of the leveler screws under each table leg.  The table should be roughly leveled in this way and then precisely leveled by means of the built in bubble level. In the Low Pressure Instrument this is accomplished by means of the two thumbscrews under the inclined manometer.  In the High Pressure Instrument continue the adjustment by means of the leg leveler screws.  The Bubble Level itself should never be moved or adjusted or the instrument will be caused to become out of calibration.  The built in bubble level is used solely to indicate the correct slant of the inclined manometer.  This level should never be adjusted as it indicates the correct inclination of the inclined glass tube.  Adjustment of the level itself will destroy the calibration of the instrument. It must be returned to the factory for recalibration if the level is disturbed.

            5.  Add the proper Red Oil - Specific Gravity 0.827  (included in the shipment) to the two manometers until they read zero.   Be sure not to overfill above the zero mark.

            If your instrument is a Low Pressure instrument one manometer reservoir can  is on the right side of the table and the inclined manometer is attached to the back board.  The filler hole for the inclined manometer is next to the large adjusting knob on the right side. This filler hole has to be closed tightly to avoid air leakage.

            If you instrument is a High Pressure instrument both manometers reservoir cans  are located on the table. A slight up or down movement of the scale to bring the zero line of the scale to the level of the oil in the glass tube is permissible only for the right hand manometer.  The left hand manometer scales should never be adjusted.  However adjust the oil level so that the top level of the oil is at least 1/4 inch below the top of the reservoir can.

            6.  Clamp the 4 mm standard test plate into the 2 3/4 inch diameter test opening on the top of the table (where the samples are normally tested) and screw the 4 mm nozzle into the chamber below the table.  The door should then be latched closed firmly, but it need not be air tight.

            The transformer switch should then be placed in the "on" position and its knob should slowly be rotated to increase the speed of the blower until the inclined manometer reads 0.5" of water (The instrument reads in inches of water even though oil is in the manometer.)

            The reading of the right hand vertical manometer should then be noted.  Be sure not to run the oil over the top of the manometer. The corresponding air flow "Frazier Number" should be taken from the 4 mm column of the proper calibration chart.  Most likely the reading will not be a whole inch such as given in the calibration chart.  Air flow at the 1/10 of an inch can be computed from the calibration chart by doing a straight interpolation between the whole inches given.  For example the air flow for 10.5 should be assumed to be halfway between the reading for the 10" and the  11" on the calibration chart.

[Air Flow (in cubic feet, per square foot of sample material per minute at 30" of Mercury, 70 deg F., and  65% relative humidity)]

            If you obtain substantially the same reading as the actual calibration shown on the card that was included with the Test Plate, you can be confident that the instrument is working correctly.  This reading should be repeatable for years.  If you obtain a significant variation, either the calibration of the test plate or nozzle (or both) has changed or the instrument itself is not in good operating order.  The most common reason why the instrument would not be operating properly is that oil has been drawn into the system through operator error.  Other special test plates are available to check the calibration of each of the other nozzles.  See the "Test Plates and Calibration" FAQ.

            7.  Samples are tested by the same procedure as per 6 above.  (A test plate represents an unchanging sample).  However the operator should be alert, especially when testing unknown samples, not to increase the speed of the blower to the extent that one or the other of the manometers has oil pulled into the system. Please note that oil in the two manometers does not move at the same speed.  This movement varies with the sample tested.  Extreme caution should be taken.  If oil is pulled into the system (e.g.. the oil disappearing over the top of the glass tubes or beyond the highest available reading) the instrument will not read correctly until the oil is completely cleaned out.  Please see the "Maintenance Instructions" - since oil in the system is always due to operator error and it is the most common problem please note that it is not covered by the warranty.