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C0204_18e1_4

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The Blaine air permeability apparatus consists essentially of a means of drawing a definite quantity of air through a prepared bed of cement of definite porosity. The number and size of pores in a prepared bed of definite porosity is a function of the size of the particles, and determines the rate of airflow through the bed. The apparatus shown here shall consist specifically of the parts described in section 4.2 through 4.8. The permeability cell shall consist of a rigid cylinder 12.70 plus or minus 0.10 millimeters in inside diameter, constructed of an austinetic stainless steel. The interior of the cell shall have a finish of 0.81 micrometers, or 32 micro inches. The top of the cell shall be at right angles to the principal axis of the cell. The lower portion of the cell must be able to form an airtight fit with the upper end of the manometer, so there is no air leakage between the contacting surfaces. A ledge 1/2 to 1 millimeter in width shall be an integral part of the cell, or be firmly fixed in the cell 55 plus or minus 10 millimeters from the top of the cell for support of the perforated metal disk. The top of the permeability cell shall be fitted with a protruding collar to facilitate the removal of the cell from the manometer. The disk shall be constructed of non-corroding metal, and shall be 0.9 plus or minus 0.1 millimeters in thickness, perforated with 30 to 40 holes, 1 millimeter in diameter, equally distributed over its area. The disk shall fit inside of the cell snugly. The center portion of one side of the disk shall be marked or inscribed in a legible manner, so as to permit the operator always to place that side downwards when inserting it into the cell. The marking or inscriptions shall not extend into any of the holes, nor touch their peripheries, nor extend into the area of the disk that rests on the cell ledge. The plunger shall be constructed in austinetic stainless steel, and shall fit into the cell with a clearance of not more than 0.1 millimeters. The bottom of the plunger shall sharply meet the lateral surfaces, and shall be at right angles to the principal axis. An air vent shall be provided by means of a flap 3 plus or minus 0.3 millimeters wide on one side of the plunger. The top of the plunger shall be provided with a collar such that when the plunger is placed in the cell and the collar brought in contact with the top of the cell the distance between the bottom of the plunger and the top of the perforated disk shall be 15 plus or minus 1 millimeter. The filter paper shall be medium retentive, corresponding to type 1 grade B in accordance with specification E-832. The filter paper disks shall be circular with smooth edges, and shall have the same diameter as the inside of the cell. Filter paper disks that are too small may leave part of the sample adhering to the inner wall of the cell above the top disk. When too large in diameter the disk shall have a tendency to buckle and cause erratic results. The U tube manometer shall be constructed according to the design shown here, using nominal 9 millimeter outside diameter standard wall glass tubing. The top of one arm the manometer shall form an airtight connection with the permeability cell. The manometer arm connecting to the permeability cell shall have a midpoint line etched around the tube at 125 to 145 millimeters below the topside outlet, and also at other distances of 15 plus or minus 1 millimeters, 70 plus or minus 1 millimeters, and 110 plus or minus 1 millimeters above that line. A side outlet shall be provided at 250 to 305 millimeters above the bottom of the manometer for use in the evacuation of the manometer arm connected to the permeability cell. A positive airtight valve or clamp shall be provided on the side outlet not more than 50 millimeters from the manometer arm. The manometer shall be mounted firmly and in such a manner that the arms are vertical. The manometer shall be filled to the midpoint line with a non-volatile, non-hygroscopic liquid of low viscosity and density, such as dibutyl phthalate, also known as dibutyl 1-2 benzene dicarboxylate, or a light grade of mineral oil. The fluid shall be free of debris. The timer shall have a positive starting and stopping mechanism, and shall be capable of being read to the nearest 5/10 of a second or less. The timer shall be accurate up to 5/10 of a second or less for time intervals up to 60 seconds, and to 1% or less for time intervals of 60 seconds to 300 seconds.

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Duration: 4 minutes and 34 seconds
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Language: English
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Posted by: abuckmaster on Aug 7, 2019

C0204_18e1_4

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