Belt weigh feeder

 Weigh feeder 

The belt weigher is designed to continuously weigh the amount of material transported on a conveyor belt. 

The measuring principle 

The material is guided over a platform arranged below belt and limited by two carrying idlers. 

Via one or multiple weighed idlers, the material amount on the platform exerts a force on load cell L/C. 

Weighed idlers are connected to the frame structure, e.g. via leaf-spring parallel guidance.

The load cell output voltage is proportional to the platform load. It is amplified and transferred to the microprocessor with the use of an analog/digital converter. 

Only half of the material weight load is applied to the weighed idler. Weighing technology considers the weight pattern of platform load in the computation of the effective platform length. For the single-idler platform, the following holds true: 

Leff = Lg / 2

Leff = Effective platform length in m

Lg = Total platform length in m 

Belt load Q is computed as follows: 

Q = QB / Leff

Q = Belt load in kg/m

QB = Weight of load on platform in kg 

Another significant measurement value is the belt speed acquired by a speed transducer and converted into a corresponding pulse frequency.

DISOCONT controller of made of Schneck process uses belt load and speed to compute the feed rate by the 

following formula: I = Q * v = QB * v / Leff

I = Feed rate in kg/s

v = Belt speed in m/s

Q = Belt load in kg/m

QB = Weight of load on platform in kg

Leff = Effective platform length in m 

* Gravimetric Mode (Controlled) 

The actual feed rate is controlled for the preset feed rate. 

The maximum possible setpoint corresponds to the nominal feed rate. If the input value is too big, the system reports an error.

* Volumetric Mode 

(Uncontrolled)
The feed unit is set proportional to the set feed rate. Changes in hopper weight do not influence feed unit control. At rated conditions, the feed rate approximately corresponds to the defined set point. Setpoint is limited to three times the nominal feed rate. If the value is exceeded, the system reports an error. 

* Volumetric Synchronous Mode

 In contrast to volumetric mode, the current belt speed setpoint is not computed using nominal belt load but the belt load measured before change-over. This ensures that change-over takes place without jerks.

 

 new factor= (weigh bridge/weigh feeder)*old factor

how to check a load cell

https://creativeeeeblog.blogspot.com/2020/12/how-to-test-load-cell.html

Calibration

TARE

Prerequisites: 

* BELT EMPTY

* BELT RUNNING

* BELT IN CENTER NOT DRIFTED

* FEEDER RUNNING IN VOLUMETRIC MODE

* LOAD CELL ARE CLEANED






Common faults in weigh feeder

* No power

* Material stuck in load cell

* Speed sensor or wire faulty

* Load cell faulty

* Belt drifting

* Vfd problem

* Material overloaded

* Rollers are jam

* Cables problem


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