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Weighfeeder Application Questionnaire
SITRANS weighfeeders from Siemens can improve the accuracy of processing, blend consistencies, accountability, and record keeping. All weighfeeders come standard with a belt weigh bridge and speed sensor. An integrator is required to complete the system.
The weighfeeder is used to deliver an accurate mass flow rate of material. In the majority of applications, material is profiled by an adjustable mechanical shear gate, which fixes the correct material bed depth for a given particle size.
The feed rate is then maintained and adjusted by varying the speed of the belt. However, in some cases the belt speed is constant with rate control (if any) done by a pre-feeding device.
The system consists of three components: weight and speed sensing, integration and control, and the mechanical conveying system. Using the belt load and the belt speed signals, small incremental totals of weight per time are measured by the integrator and then the flow rate is calculated. The measured flowrate is compared against the desired flowrate and the on-board PID controller makes necessary corrections to the belt speed.
Weighfeeder operation
SITRANS WW100
The platform weigh bridge mounts directly to a corrosion-resistant platform load cell. The direct load design eliminates all intermediate mechanical suspension and allows material weight to be directly applied to the load cell.
This design minimizes zero drift normally caused by intermediary suspension components and allows for the use of a very sensitive precision platform load cell. Load cell size and construction are chosen for each specific application.
SITRANS WW200
A stainless steel platform weighdeck with a Delrin slider bar assembly mounts directly to two corrosion-resistant, sealed platform load cells. The direct load design eliminates all intermediate mechanical suspension and allows material weight to be directly applied to the load cells. The frame of the WW200 is sturdy and rigid, ensuring stable and repeatable results, maximizing resolution and weighing accuracy.
SITRANS WW300
SITRANS WW300 suspends a single weigh idler on platform load cells. Its design eliminates all moving parts in the weighing
process and subsequent maintenance and replacement problems. There are no links or flexures. Two corrosion-resistant precision strain gauge load cells provide weight sensing signals to an integrator. This design feature minimizes zero drift and maximizes
resolution and weighing accuracy.
SITRANS WW310
A modular design with external access to all bearings, speed sensors and load cells the WW310 is easy to maintain. Two corrosion resistant single point platform load cells mounted directly to a rugged idler ensure consistent weighing accuracy.
Criteria | SITRANS | SITRANS | SITRANS | SITRANS WW310 |
|---|---|---|---|---|
Typical industries | Bulk chemicals, tobacco, food, water treatment | Bulk chemicals, tobacco, food, recycling | Cement, mineral processing, coal, mining, pulp and paper | Cement, mineral processing, coal, mining, pulp and paper |
Typical applications | High-accuracy, low-capacity for minor ingredient additives | Low- to medium-capacity for minor ingredient additives | Medium- to high-capacity for macro ingredient additives | Medium- to high-capacity for macro ingredient additives |
Design rate range | 45 kg/h ... 18 t/h | 0.45 ... 100 t/h | 4.5 ... 800 t/h | 4.5 ... 270t/h (5 ... 300 STPH) |
Belt speed | 0.005 ... 0.36 m/s | 0.005 ... 0.36 m/s | 0.005 ... 0.36 m/s | 0.005 ... 0.36 m/s (1 ... 70 fpm) |
Accuracy1) | ± 0.25 ... 0.5 % | ± 0.5 % or better | ± 0.5 % or better | ± 0.5 % or better |
Specified range | 10 ... 100 % based on speed | 10 ... 100 % based on speed | 10 ... 100 % based on speed | 10 ... 100 % based on speed |
Sensing element | Long length platform weigh bridge | Platform weigh bridge | Single idler scale | Single idler scale Dual load cells |
Approvals | CE, RCM | Stainless steel options meet USDA and FDA requirements for food processing |
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1) Accuracy subject to: On factory approved installations the weigh feeder system’s totalized weight will be within the specified accuracy when compared to a known weighed material test sample. The test rate must be within the specified range of the design capacity and held constant for the duration of the test. The minimum material test sample must be equivalent to a sample obtained at the test flow rate for three revolutions of the belt or at least ten minutes running time, whichever is greater.
