BS ISO 5636-3:2013 pdf free

BS ISO 5636-3:2013 pdf free.Paper and board一Determination of air permeance (medium range)
To calibrate a variable-area flow-measuring device, disconnect the test assembly from the downstream end of the rubber or plastic tubing and connect in its place the soap-bubble meter. Set the valves to deliver air through the flowmeter to be calibrated and then through the soap-bubble meter at the connection point (3). Start the airflow, place the manostat weight corresponding to a pressure of 1,47 kPa on the shaft and start it spinning. Set the valves to deliver through the variable-area flowmeter to be calibrated to the soap-bubble meter. Adjust the needle valve to give a conveniently measurable air flow and ensure that the flow rate remains constant. Rapidly squeeze the rubber bulb at the bottom of the volumeter so that a soap bubble enters the volumeter tube. Note the time in seconds for it to move between marks representing a known volume. The volumeter range should be chosen so that the time taken for the bubble to pass from the first to the second graduation is longer than 30 s.
Repeat the procedure at about six different air flow rates distributed over the flowmeter measurement range such that all readings are greater than 20 % of the scale range.
If a float becomes wedged in the spring at the bottom or top of a variable-area flowmeter tube, tap the instrument lightly while passing air through the tube. If this fails to free the float, loosen the bottom and top bushings around the tubes with a special spanner, take off the metal block at the top of the variable-area flowmeter and remove the tube. A recurrence of sticking can be prevented by adjusting the shape of the springs. The bottom spring should terminate in a horizontal loop centred in the variable-area flowmeter. The top spring should terminate in a vertical loop centred in the variable-area flowmeter.If a variable-area flowmeter tube or float is dirty, giving high readings, remove the float from the tube,clean both with liquid detergent or a suitable solvent, then dry in the air stream. If liquid detergent is used, add to the tube, flush with water, reversing the flow several times, and use diluted aqueous solution [a volume fraction of about 10 %] to clean the float. Finally, rinse both with distilled water, and dry in an air stream.BS ISO 5636-3 pdf free download.