1、 ANSI/ASAE S424.1 MAR1992 (R2017) Method of Determining and Expressing Particle Size of Chopped Forage Materials by Screening American Society of Agricultural and Biological Engineers ASABE is a professional and technical organization, of members worldwide, who are dedicated to advancement of engine
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10、N D A R D ANSI/ASAE S424.1 MAR1992 (R2017) Copyright American Society of Agricultural and Biological Engineers 1 ANSI/ASAE S424.1 MAR1992 (R2017) Revision approved September 1992; reaffirmed January 2017 as an American National Standard Method of Determining and Expressing Particle Size of Chopped F
11、orage Materials by Screening Developed by the ASAE Forage Harvesting and Utilization Committee; approved by the ASAE Power and Machinery Division Standards Committee; adopted by ASAE April 1986; revised editorially March 1988; approved as an American National Standard June 1988; revised March 1992;
12、revision approved by ANSI September 1992; reaffirmed by ASAE December 1996; reaffirmed by ANSI March 1998; reaffirmed January 2007, February 2012, January 2017. Keywords: Forage, Particle size, Sieving, Test procedure 1 Purpose and Scope 1.1 The purpose of this Standard is to define a test procedure
13、 to determine the particle size distribution of chopped forage materials and to define a method of expressing the particle length of the material. The determined particle size distribution can be used to evaluate forage harvesting machine and handling equipment variables and to define forage physica
14、l length in animal feeding trials. 1.2 This Standard shall be used to determine the particle size of chopped forage materials where the reduction process yields particles such as that material produced by shear-bar type forage harvesters. It is not intended for use on material produced by flail-type
15、 harvesters where substantial fractions of the material may be extremely long. 1.3 This Standard is intended for use in the field as well as in the laboratory. It is intended to separate chopped forage samples without drying them first. 2 Test Equipment 2.1 For particle measuring purposes, a set of
16、square-hole screens having widths of 406 mm (16.0 in.) lengths of 565 mm (22.25 in.) and specifications shown in Table 1 shall be used. The screens shall be supported in frames with depths of 63.5 mm (2.50 in.) and arranged horizontally in a stack such that the screen with the largest opening size i
17、s at the top. Those with smaller openings shall be arranged with progressively smaller hole sizes below each other. If screens with different size openings from those listed in Table 1 are used, the actual dimensions for the openings shall be used in the data analysis and shall be reported. Pertinen
18、t screening dimensions should be in geometric progression with the smallest selected to be appropriate to the particle size spectrum of the sample. Table 1 Dimensions of square hole screens for testing purposes Screen No. Nominal Size Opening Square Hole Diagonal Screen Thickness Open Area % mm in.
19、mm in. mm in. 1 19.0 0.75 26.9 1.06 12.7 0.50 45 2 12.7 0.50 18.0 0.71 9.6 0.38 333 6.3 0.25 8.98 0.35 4.8 0.19 33 4 3.96 0.156 5.61 0.22 3.1 0.12 395* 1.17 0.046 1.65 0.065 0.64 0.025 41.5 Pan - - - - - - - * 14 mesh woven wire cloth with 0.64 mm (0.025 in.) diameter wires. All others are aluminum
20、sheets or plates. ANSI/ASAE S424.1 MAR1992 (R2017) Copyright American Society of Agricultural and Biological Engineers 2 2.2 A suitable screen shaker is required. The shaker shall oscillate the screen stack in a horizontal plane. The center of one end of the screen stack shall oscillate in a straigh
21、t horizontal line on a slider block. The opposite end of the screen stack shall be supported on horizontal crank arms, the crank end centers of which are located 765.2 mm (30.12 in.) from the center of the slider block pivot located on the other end of the screen stack. The centers of the arms shall
22、 travel in a horizontal circle with a diameter of 117 mm (4.62 in.) (see Figs. 1 and 2). NOTE: Information on plans for constructing such a screen shaker may be obtained from the American Society of Agricultural Engineers. Figure 1 Top view of forage particle separator showing screen motion land and
23、 feeder position Figure 2 Schematic diagram of forage particle separator ANSI/ASAE S424.1 MAR1992 (R2017) Copyright American Society of Agricultural and Biological Engineers 3 2.3 The screen shaker shall drive the screen stack at a frequency of 2.4 0.08 Hz (144 5/cycles/min). 2.4 The shaker should b
24、e operated with the screens level. 2.5 A weighing balance having an accuracy of at least 0.5 g shall be used for weighing the fractions. 3 Method of Screening 3.1 Uncompressed samples of 9 to 10 L of forage should be used. Samples of 2 to 3 L of material may be used if extra care is taken to recover
25、 the material from each screen. For field work, the larger samples are usually preferred. The sample volume size should be reported with the data. 3.2 Place the sample on the top of the sample feeder (near the closed end) above the top screen of the screen set and operate the shaker for 120 s. 3.3 T
26、he tapered louvers on the feeder should be preset to feed the sample to the top screen in 20 to 30 s. The louvers may be inclined to change the feeding time. This adjustment is made using successive trials with practice samples similar to the crop material to be evaluated for particle size distribut
27、ion. 3.4 Material on each screen and bottom pan shall be weighed and recorded. 3.5 If the amount retained on the top screen exceeds 1% of the total sample mass, representative subsamples should be obtained from this screen and measured manually. The average length may then be used in the data analys
28、is as geometric mean length, 1X. 3.6 The screening process should be repeated to produce 3 sets of data. These data sets may be averaged or analyzed separately with the procedure specified in the report. 3.7 A representative sample of the unscreened material shall be used for moisture content determ
29、ination. Moisture content (wet basis) shall be reported along with particle size data. 3.8 Screen openings must be kept free of forage particles so that effective screening can be accomplished. A stiff bristle cleaning brush, or compressed air, is useful for cleaning screens which have become clogge
30、d with forage particles. Screens may need to be cleaned periodically to remove plant residue materials. Plant residues may be removed by washing with water containing a detergent. Screens and the particle separator must be air dried before use. 3.9 If static electricity becomes a problem when separa
31、ting dry forage materials, liquid laundry static control may lightly be sprayed onto the sample before separating. 3.10 If separation problems occur due to high crop moisture levels, samples can be dried in a low temperature oven (65C) to a target moisture of approximately 50% moisture wet basis bef
32、ore separating. 4 Data Analysis 4.1 Analysis of mass distribution of all chopped forage materials is based on the assumption that these distributions are logarithmic normally distributed. 4.2 Calculation of particle size 4.2.1 The size of particles shall be reported in terms of geometric mean length
33、, Xgm, and standard deviation, Sgm, by mass. 4.2.2 Calculated values are obtained as follows: ANSI/ASAE S424.1 MAR1992 (R2017) Copyright American Society of Agricultural and Biological Engineers 4 =iiigmMxMX)log(log1(1) ()2121logloglog=igmiigmMXXMS(2) where: Xi = diagonal of screen openings of the i
34、thscreen X(i-1) = diagonal of screen openings in next larger than the ithscreen (just above in a set) Xgm = geometric mean length iX = geometric mean length of particles on ithscreen = (Xi Xi-1)1/2 (3) Mi = mass on ithscreen (actual mass at the conditions of screening or percent of total; decimal or
35、 percent form) Sgm = standard deviation NOTE: iX is measured manually as described in paragraph 3.5. If it is less than 1% of the total, it is treated as zero. 4.2.3 Material passing through screen No. 5 and collected in the pan shall be considered to have a geometric mean length of 0.82 mm (0.0325
36、in.). This becomes 6X in equations (1) and (2). 4.2.4 An example of how the equations may be used to find geometric mean particle length and standard deviation for a sample data set follows: Percent mass distribution of a chopped alfalfa sample Screen No. Screen Diagonal, mm Percent Total Mass on Sc
37、reens, % Cumulative Undersize, % 1 26.9 3.8 96.2 2 18.0 8.1 88.13 8.98 25.1 63.04 5.61 26.9 36.1 5 1.65 34.2 1.9 Pan 1.9 - 100.0 - The average measured length of the particles on the top screen (No. 1) was 48 mm. This becomes 1X in equations (1) and (2). Equation (3) and the above information are us
38、ed to obtain the following mean lengths for particles in each fraction: 1X = 48 2X = (18.0 26.9)1/2 = 22.0 3X = (8.98 18.0)1/2 = 12.7 4X = (5.61 8.98)1/2 = 7.10 5X = (1.65 5.61)1/2 = 3.04 6X = 0.82 ANSI/ASAE S424.1 MAR1992 (R2017) Copyright American Society of Agricultural and Biological Engineers 5
39、 Equations (1) and (2) are used to obtain () () ( ) ( ) ( )mm6.950.0190.3420.2690.2510.0810.0380.82log0.0193.04log0.342(7.1)log0.26912.7log0.25122log0.08148log0.038log1=+=gmXmm262019034202690251008100380956820log0190956043log342095617log2690956712log251095622log081095648log0380log2222221.=+=gmSwhere
40、: Xgm = X50 = particle length at 50% probability Sgm = X84 / X50 = standard deviation X84 = particle length at 84% cumulative probability 4.2.5 Graphical solutions for geometric mean length and standard deviation may be obtained by plotting the results on logarithmic normal probability graph paper.
41、Figure 3 shows an example of a plot of the data from paragraph 4.2.4. Figure 3 Cumulative percent undersized particles versus screen diagonal opening size for alfalfa for graphic determination of mean length and standard deviation References 1. Finner, M. F., J. E. Hardzinski ,and L. L. Pagel, 1978. Evaluating particle length of chopped forages. ASAE Paper No. 78-1047. St. Joseph, MI: ASAE. 2. Stockham, J. D., and E. G. Fochtman. 1977. Particle size analysis. Ann Arbor Science Pub., Inc.
