The Compressive Wafering of Grass Hay (III)

Wafering of Italian-Ryegrass by Roller-Die Method (II)

Abstract

Wafers and cubes of Italian-ryegrass were made with roller-die type apparatus, and their characteristics such as change of density, tensile strength. falling shock durabity, ASAE tumbling durability, cone penetrating resistance and drying rate were investigated. From these characterestics together with those of resistance forces and waferability reported in the preceeding paper, the following results were obtained synthetically:
1. The density ρ of wafer was a reliable index for indicating the intensity or durability of wafer and its maximum value was obtained at abont 20% moisture content (wet basis) of hay. For dried hay (20% mc), the ρ value with tapered die was smaller than that with standard die (No. 1) and for wet hay (40% mc) the former was fairly larger than the latter. On the other hand, the ρ values with inclined die and cubed die were smaller than those with standard dies of No. 2 and No. 1 respectively. The ρ of dried wafer (12% mc) was smaller than that of undried wafer just after formed, while that of wafer of rehydrated hay by spraying was also considerably smaller than that of on-ground-dried hay at the same moisture content. The ρ value at 100°C of hay temerature was always larger than at 80°C. The ρ characteristics of wafers of italian-ryegrass and that of guinea-grass were almost the same.
2. The temsile strength T of wafer was also a reliable index for intensity, because the tendency of T value was almost the same as that of ρ value except that the T of the wafer dried to 12% mc was larger than that of just after formed. The T value of italian-ryegrass was smaller than that of guinea_grass.
3. The F value of falling shock durability (rate of residual weight) was scattered probably due to the data calculated by ASAE method without using the same mean weight of wafers. The A value from ASAE tumbling method changed little with varying me of hay from 12% to 30%. Hence, F and A values were not suitable for the valuation of durability in this investigation.
4. To evaluate the durability of wafer. the physical and the practical methods may be taken. For the practical method, the total weight or total volume of samples extruded must be held constant, and the available minimum weight (or volume) of samples must also be held constant in the processing after fallen or tumbled. The falling height and the falling times of falling method and the tumbling speed and the tumbling times of ASAE method must be properly determined respectively by the conditions.
5. The maximum resistance force of cone to wafer for die No. 1 was obtained at 20% mc. The resistance force P_c of dried wafer (12% mc) was smaller than that of undried just formed, and the P_c of wafers formed from the rehydrated hay was also smaller than that from on-ground-dried hay at the same moisture content.
6. The drying rate of wafer formed by hay of 40% mc decreased to zero after 2 to 3 hours when dried in the oven at 100°C. The mean drying rate of cube was smaller than that of wafer. The drying rate of wafer formed by inclined die was higher than that of straight die at the early drying stage, but the wafer of tapered die was harder to be dried than that of straight die.
7. As a whole, good results were obtained with the hay of about 20% mc and 100°C, but rehydrated hay was undesirable for wafer forming. It was considered that the valuation of waferability and wafer density indicate the intensity or durability of wafer satisfactorily.