F Flow conditions An important parameter for calculating the minimum discharge opening width of a arch or knot is the critical open yield strength Æ’ cc . The solution to Æ’ cc is to represent the flow factor Æ’ æµåŠ¨ on the flow function FF, the intersection CC is Æ’. e.g. Johnson (JRJohanson) measurement and calculation of 10% aqueous iron ore is 11 is shown in FIG. (2) Unloading port of mine silo (1) Size of unloading port to avoid arching: Where B a ———unloading port width (unloading port length L a >2.5Ba), m; Where D p ——— discharge port diameter (or diagonal length), m; [next] (3) Funnel discharge (production volume): Johnson pointed out that only under the condition of blocking the silo, when the material size is larger than 250 microns, the discharge of the funnel is: Where Q v ———discharge amount, m 3 /h;
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Colour
Product standard
Usage and property
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GB/T5574-2008
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GB/T5574-2008
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GB/T5574-2008
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GB/T5574-2008
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GB/T5574-2008
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D a ———Drawing port diameter, m;
D p ———average particle size, m;
ƒ cc ———critical open yield strength, Pa;
γ———the bulk density of the material, kg/m 3 ;
g———gravitational acceleration, g=9.81m/s 2 .[next]
(2) Avoid the size of the discharge port of the knot:
K—the knot factor, as shown in Figure 12;
Other symbols are the same as before.
B———Discharge port width, m;
L———the length of the discharge port, m;
D———Dropping port diameter, m;
θ ch ———Half angle of the flow channel, (°);
g———gravitational acceleration, g=9.81m/s 2 ;
Æ’ Æ’ --- critical flow factors (for arching);
ƒ ƒ•a ——— Actual flow factor (for a defined discharge port):
ƒ a •a =σ 1 /ƒ cc =σ 1 /σ y (11)
σ 1 =γBgƒ ƒ (12)
{Example 1} 10% water-containing coarse iron ore, the fluidity is shown in Fig. 11. Find the size of the discharge port of the tapered steel bucket. Solution steps:
(1) For the smallest overall silo height to obtain the maximum overall flow capacity, the new steel hopper bucket half angle does not exceed 20 ° (Figure 8).
(2) Determine the half angle of the bucket θ 1 = 10 °; by testing the internal friction angle of the material δ ' = 46 °, the friction angle with the wall ф ' = 25 °.
(3) The effective internal friction angle δ of the material that must be assumed at the beginning of the design of the bucket. It can be seen from Fig. 11a that δ is between 55° and 70°, assuming δ=60°.
(4) It can be found from Fig. 10a that when ф'=25° and δ=60°, ƒ ƒ =1.08.
(5) Draw ƒ ƒ =1.08 line on Figure 11c. The intersection of this line and the flow function FF curve is the critical point, so that the critical open yield strength (stress) can be obtained, ƒ cc =9kPa, compaction stress σ 1 = 10 kPa; corresponding σ 1 = 10 kPa, δ = 60 ° (assuming δ = 60 °).
(6) According to δ=60°, then ƒ ƒ =1.06, then draw ƒ ƒ =1.06 line on Fig. 11c, get σ 1 =9kPa, ƒ cc =8.5kPa, and get δ=67°. Then we can determine δ = 60°, ƒ cc = 8.5 kPa, γ = 2120 kg/m 3 .
(7) Avoid the minimum discharge opening width of the (conical bucket) arching according to the formula:
Parameters: specific gravity: 1.4-1.7g/cm; breaking tenacity: 3-5Mpa; elongation: 200-300%; hardness: 70 ±5°