Physical and Mechanical Properties of Bulk Cargo
An ideal bulk cargo of the grab bucket should possess the characteristics of fine granules, dispersion, and isotropy. Its physical and mechanical properties are mainly expressed by bulk density, force, and angle of internal friction. Bulk density is the mass per unit volume of the bulk cargo, measured in t/m³. Bulk cargo particle size refers to the calculated particle size, measured in mm. The calculation method for bulk cargo particle size is as follows: extract a certain quantity of bulk cargo, apply statistical methods, that is, classify the statistical values of the natural particle size of the bulk cargo into different sizes, multiply the mass of each grade by the average particle size of the corresponding grade, add them together, and then divide by the total mass of the bulk cargo.
The internal friction angle (or internal friction coefficient) of bulk cargo can be approximated by its natural slope angle (or natural angle of repose). A smaller internal friction coefficient indicates better flowability of the bulk cargo.
Basic bulk cargo parameters directly affect the grabbing resistance encountered by the grab bucket during the grabbing process. Therefore, when designing a grab bucket, the bucket's weight, geometric dimensions, and pulley block ratio must be correctly selected for different bulk cargoes.
| Bulk density (bulk weight t/m3) | 0.4~0.63 | 0.8~1.0 | 1.25~2.0 | 2.5~3.2 | 4.0~4.5 |
| Bulk cargo example | Dry grain |
Anthracite Powdered alumina Coke Melted and dried sodium carbonate Dried slag Small and medium-sized crushed slag Coal of various grades
|
Small pieces of gypsum Snow-like gypsum Apatite concentrate Iron alum Gravel Dry small pieces of clay Pebble Dry soil Molding sand Medium-fast limestone Lime Rock Powdered fragments Dry sand Blocked cement Large bricks |
Sintered ore Granite Small and medium-speed iron ore Manganese ore |
Extra-large rapid iron ore Tungsten ore Heavy metal ore |
