Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
D. Vermeulen Continu doseren van stortgoed.
Literature survey, Report 91.3.2907.TT, Transport Engineering and Logistics.
Continuous feeding of bulk solids plays a role where continuous mass-flows of bulk solids are required. It is required that the mass-flows can be adjusted accurately.
This accuracy depends on the feeding-mechanism generating the required mass-flow. The accuracy of a feeding mechanism depends on the technical design and the control-system.
In this report two important feeding-methods are dealt with, the volumetric feeding and the feeding with mass-measuring.
The design of the volumetric feeder is very simple, but the accuracy is limited. This accuracy, depending on the used pre-feeder, varies from 2-5%. A characteristic of the control system is the absence of a comparison between measured and set value.
For feeders with mass-measuring several principles of mass-measuring are used. The highest accuracy is achieved by the gravimetric feeding methods. The two main gravimetric methods are belt-weighing and the loss-in-weight system. Belt weighing makes use of a weighbelt, which introduces a dead-time. This dead-time has a negative effect on the control characteristics. The accuracy varies from 1-1,5%.
The loss-in-weight system is very accurate: in the range 0,5-1%. The system has good control-characteristics by the absence of a dead-time. A disadventage is the high investment compared with other feeding systems.
In practice it proven to be necessary that user and manufacturer of feeding systems make clear agreements about the definition and calculation of the required accuracy. The accuracy in terms of errors can be calculated out of measurement-results obtained from a check-measurement.
Reports on Transport Engineering and Logistics (in Dutch)
