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AS 4974-2008 pdf free download
AS 4974-2008 pdf free download.Copper, lead and zinc sulfide concentrates Determination of transportable moisture limits Flow-table method.
This annex describes the design of equipment suitable for determining the transportable moisture limit (TML) by the flow-table method.
A.2 Design requirements for the flow table and frame
The flow-table apparatus shall be constructed in accordance with Figure A.1. The apparatus shall consist of an integrally cast iron frame and a circular rigid table top 254 mm ± 2,5 mm In diameter, with a shaft attached perpendicular to the table top by means of a screw thread. The table top, to which the shaft with its integral contact shoulder is attached, shall be mounted on a frame in such a manner that it can be raised and dropped vertically through the specified height with a tolerance in height of ± 0,13 mm for new tables and ± 0,39 mm for tables in use, by means of a rotating cam. The table top shall have a fine machined plane surface, free of blowholes and surface defects, and this shall be described as shown in Figure A.1. The table top shall be of cast brass or bronze, having a Rockwell hardness number not less that HRB 25 with an edge thickness of 8 mm, and shall have six integral radial stiffening ribs. The table top and attached shaft shall weigh
4 kg ± 0.05 kg and the mass shall be symmetrical around the centre of the shaft.
The cam and vertical shaft shall be of medium-carbon tool steel, hardened as indicated In Figure A.1. The shaft shall be straight and the difference between the diameter of the shaft and the diameter of the bore of the frame shall be not less than 0,05 mm and not more than 0,08 mm for new tables, and shall be maintained at between 0,05 mm and 0,26 mm for tables in use. The end of the shaft shall not fall upon the cam at the end of the drop, but shall make contact with the cam not less than 120° from the point of drop. The face of the cam shall be a smooth spiralled curve of uniformly increasing radius from 13 mm to 32 mm in 360°, and there shall be no appreciable jar as the shaft comes into contact with the cam. The cam shall be so located and the contact faces of the cam and shaft shall be such that the table does not rotate more than one revolution in 25 drops. The surfaces of the frame and of the table which come into contact and the end of the drop shall be maintained smooth, plane, horizontal and parallel with the upper surface of the table, and shall make continuous contact over a full 360°.
The supporting frame of the flow table shall be integrally cast of fine-grain, high-grade cast iron. The frame casting shall have three integral stiffening ribs extending the full height of the frame and located 120° apart. The top of the frame shall be chilled to a depth of approximately 6,4 mm and the face shall be ground and lapped square with the bore to give 360° contact with the shaft shoulder, The underside of the base of the frame shall be ground to secure a complete contact with the steel plate beneath.
The flow table may be driven by a motor, connected to the cam shaft through an enclosed worm gear-speed reducer and flexible coupling. The speed of the cam shaft shall be approximately 1,666 s1 (100 rev/miri). The motor drive mechanism shall not be fastened or mounted on the table base plate or frame.
The performance of a flow table shall be considered satisfactory if, in calibration tests, the table gives a flow value that does not differ by more than five percentage points from flow values obtained with a suitable calibration material.AS 4974-2008 pdf free download.
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