Gravimetric screw feeders
Regardless of whether you are interested in feeding a fixed amount of material or if your process requires constant flow, we have a solution for you. Differential feeders operating in loss-in-weight mode are an interesting solution in the flow range 0,5 ÷ 30 000 [l/h]. These are the most economical solutions, among gravimetric feeders, and their design ensures easy cleaning and long-lasting work.
The first step is to define material parameters, such as: grain size, bulk density, moisture, bulk angle and the required portion in the desired time interval or the required mass flow. Thanks to the information received from you, depending on the kind of material, we select the type of feeder.
The weighing system consists of a rigid platform based on smaller units on 1 or 2 single point load cells or on 3 beam load cells. In case of larger models, the scale is built on a special frame and consists of two single point sensors. This design eliminates the risk of swaying and high torque. All sensors are made of stainless steel and have a degree of protection IP68 / IP69K. Each scale is secured against overload and has transport security.
The DSL G screw feeder is able to dosing bulk materials with different parameters, even hard-flowing, rat-holing and cohesive. It consists of a main trough, a horizontal agitator, a precise scale and a extension hopper. The DSL generates material flow thanks to a rotating screw, aided by a horizontal agitator, which ensures full filling of the feeding tool and protects against material bridging or rat-holing. Typical hoppers with walls of a special geometry allow a certain flow of various bulk materials. Feeders can be equipped with feeding tools in the form of a screw or a spiral (helix). Thanks to this solution the feeder is ideally suited for applications where materials extremely differ – from powders with grains of individual micrometers up to large granulates and pellets, for feed rates from 0,5 to 30 000 [l/h]. For customers in the food and pharmaceutical industry, welds and internal surfaces are additionally grinded. The feeder has been designed so that the access to the interior was not problematic, thanks to which keeping the cleanliness is extremely easy.
- loose materials of various types – both well- and hard-flowing, easily aerated, with a tendency to uncontrolled flow or clumping.
- maximum dosing error after calibration +/- 0,5% of the set value,
- screw feeder equipped with a precise scale and extension hooper,
- 3 basic versions of DSL35, DSL75 and DSL150 depending on the feed rate and diameter of the feeding tool,
- feed rate from 0,5 to 30 000 [l/h],
- feeding tools with diameters from 18 to 150 [mm],
- total extension hooper capacities from 30 to 2400 [l],
- agitator prevents bridging and rat-holing of the material,
- for materials particularly difficult to feed, the possibility of installing an additional vertical agitator
- easy disassembly of the screw and agitator,
- elements in contact with the material made of stainless steel 1.4301 (AISI304) or 1.4404 (AISI316L), other powder painted or stainless steel,
- internal surfaces: polished stainless steel, welds continuous,
- external surfaces: blast-cleaning with glass granules or electropolished, welds spot or continuous,
- optional hygienic version: continuous internal and external welds, surfaces in contact with ground material (Ra<0,8), ground welds,
- for automatic and manual refilling,
- ability to work as a separate device or in mixing lines, also as part of packaging systems.
How does it work?
Loss in weight feeders (LIW = „loss-in-weight”) operate on a continuous measurement of the weight of the entire dosing unit with the material, placed on the strain gauges. The weighted assembly is flexibly connected to the hopper equipment and the discharge pipeline to eliminate external forces. During feeding, either continuously or in batch, the loss of mass from the device is measured and the mass flow of the material determined on this basis. The PID controller used in the system controls the dosing speed depending on the required flow. When the amount of material decreases in the hopper, it is topped up without interrupting dosing. During this time, the feeder goes into the volumetric mode, i.e. supplies material with the speed just before filling the tank. After filling back, the gravimetric mode is restored. The advantages of static balance are used here in continuous dosing with a screw or vibratory feeder.