VERIFYING THE ACCURACY OF WIRE CLOTH SIEVES

Transcription

1 Test Procedure for VERIFYING THE ACCURACY OF WIRE CLOTH SIEVES Texas Department of Transportation TxDOT Designation: Tex-907-K Effective Dates: August 1999 August SCOPE 1.1 This test procedure describes methods for both the visual examination of wire cloth sieves for defects and proper construction and for the verification of the wire cloth for dimensional accuracy. 1.2 The values given in parentheses (if provided) are not standard and may not be exact mathematical conversions. Use each system of units separately. Combining values from the two systems may result in nonconformance with the standard. 2. REFERENCE DOCUMENTS 2.1 ASTM E AASHTO M 92. PART I VISUAL EXAMINATION 3. APPARATUS 3.1 Evenly lighted background. 4. PROCEDURE 4.1 Perform at six-month intervals. 4.2 Visually examine the sieve, viewing through the wire cloth toward an evenly lighted background, to aid inspection of the openings. 4.3 The wire cloth should be of brass, bronze, or stainless steel, but not coated or plated. Reject if the cloth has punctures, obvious defects, creases, wrinkles, is loose, or if any opening appears distorted, damaged or off size compared to others. CONSTRUCTION DIVISION /99 08/11

2 4.4 The wire should be uniformly fastened to the frame. s of 710 µm (No. 25) and smaller should be smoothly soldered around the periphery of the screen with no crevices to catch fine material. 4.5 The frame shall be of seamless construction, made of brass or stainless steel Reject if the sieve is new and the frame is cracked If the sieve is used and the frame cracked, repair by brazing or soldering with a smooth finish. 4.6 Frames shall fit into each other with an easy sliding fit. Dimensions should be according to Table The sieve should have a label containing: a reference to ASTM E 11 or ASTM specifications the metric size (i.e., in millimeters or microns) the sieve designation as given in Table 2, Column 2 and the name of the manufacturer or distributor. Table 1 Standard Frame Dimensions, mm Nominal in inches (see Note 1) Average, in millimeters Typical Frame Height from top to Wire Cloth, in millimeters (see Note 2) Frame inside diameter (@5 mm from top) Frame Outside to to to to to to Note 1 Other diameters or shapes may be specified by the user. Note 2 Other heights may be used. Table 2 Nominal Dimensions and Variations for Wire Cloth s in Each Maximum Maximum ½ ½ CONSTRUCTION DIVISION /99 08/11

3 Table 2 Nominal Dimensions and Variations for Wire Cloth s in Each Maximum Maximum ¾ ½ ¼ / / / / / / / / No. 3½ No No No No No No No No No No No No No No No No No No No No No No No No No No No No CONSTRUCTION DIVISION /99 08/11

4 Table 2 Nominal Dimensions and Variations for Wire Cloth s in Each Maximum Maximum No No No No PART II PHYSICAL EXAMINATION 5. APPARATUS 5.1 Dial or digital calipers. 5.2 Optical comparator, either projection-type or hand held, with internal scales. 6. PROCEDURE 6.1 Perform at time of purchase and as needed. 6.2 The design, readability, and precision of the measuring device should permit accurate measurement of the width of the openings and the diameter of the wires. Use a projection-type optical comparator equipped with ruled screens matched to lenses or a digital readout, or a hand-held magnifier with an internal scale. Dial or digital calipers are suitable for larger openings For sieves 16 mm (5/8 in.) and larger, the readability of the measuring device should be at least 0.01 mm For sieves smaller than 16 mm (5/8 in.), the readability device should be at least mm. 6.3 Measure the width of the openings and the diameter of the wires for both directions of the cloth's weave. Keep separate lists of measurements for each direction. Note 3 One direction of the weave the warp and the other is the shoot. For the square openings in these sieves, it is only important to keep the measured values for each direction separate. 6.4 Measure the width and wire size of openings in two or more areas of the sieve. Measure at least ten openings in each direction in each area. For sieves with 20 or fewer openings, measure all openings. 6.5 Take measurements at or near the midpoint of the openings. CONSTRUCTION DIVISION /99 08/11

5 6.6 Average the openings in each direction separately. Reject if either or both average values do not fall within the range of Table 2, Column Count all openings in each direction, separately, whose width falls within the range in Table 2, Column 4. Reject the sieve if this number is greater than five percent of the total number of width measurements in that direction. If the sieve has less than fifty openings, reject if there are more than three openings outside this range in either direction. 6.8 Reject the sieve if any opening is larger than the value in Table 2, Column Average the diameter of the wires in each direction separately. Reject the sieve if either average falls outside the Table 2, Column 6 range Verify that the frame dimensions meet the requirements of Table 1. CONSTRUCTION DIVISION /99 08/11