AS NZS 1301.441:2018 pdf free.Methods of test for pulp and paper Method 441: Determination of roughness/ smoothness (air leak methods)- Sheffield method (ISO 8791-3:2017, MOD).
5.1 Air supply, free of water, oil and other contaminants, at a pressure of 420 kPa to 950 kPa. A small compressor using laboratory air is preferred to external compressed air.
5.2 Pressure-regulating device, consisting of a primary regulator to reduce the pressure to between
205 kPa and 210 kPa, and another regulator to adjust the pressure at the measuring head to 10,3 kPa
(variable-area flowmeters) or 9,85 kPa (electronic flowmeters).
5.3 Pressure manometer, with a range from 0 kPa to 20 kPa to enable the air pressure at the measuring head to be set to the specified pressure within 2 % of the nominal value.
5.4 Flow-measuring device, of either a variable-area or an electronic type. The air flow shall be measurable to an accuracy of ±5 % of the measured value.
5.4.1 Variable-area flow-measuring device, consisting of three variable-area flowmeters, each having a tapered glass column containing a metering float suspended by the air flow in the column (see Reference [7]). The three columns shall be chosen such that they enable measurement to be made on a continuous scale of flow rate from 10 mi/mm to 3 000 ml/min, with some overlap of scales between columns. Each column shall be provided with a means of adjusting the flow rate (float-position knob) and a means of span calibration (calibrating knob). This type of instrument shall operate at a supply pressure of 10,3 kPa.
At air flow rates greater than 1 200 ml/min, the pressure drop in the Sheffield system is substantial and, to ensure the reproducibility of results, it is necessary that the tubing used to connect the flowmeter to the measuring head be carefully controlled with a length of 150 m ± 0,01 m and an internal diameter of 6,25 mm ± 0,25 mm. For the same reason, openings in valves and other fittings on the instrument shall not be changed from those provided by the instrument manufacturer.
5.4.2 Electronic flow-measuring device, for measuring the air flow to the test assembly (measuring head). The inlet pressure to the measurement device shall be controlled at 985 kPa.
NOTE The 9,85 kPa pressure is the typical pressure measured downstream of variable-area flow tubes that have been calibrated using the zero and span adjustment air bleeds to atmosphere.
5.5 Test assembly.
5.5.1 The measuring head, together with a dead weight, shall have a mass of 1 640 g ± 2 g, shall have two concentric annular lands made of, or coated with, a corrosion-resistant material and be designed to contact the test piece. The annular lands shall have a total area of 97 mm2 ± 3 mm2 each land shall have a width of 0,380 mm ± 0,010 mm. The outer diameters of the outer and inner lands shall be 47,70 mm ± 0,03 mm and 34,3 7 mm ± 0,03 mm, respectively.
The test assembly, an example of which is shown in Figure 2, shall include a detachable measuring head mounted so that it can be brought into contact with a test piece placed on an optically flat plate.AS NZS 1301.441 pdf download.