Schenck Weigh Feeder Calibration Procedure Pdf Free: A Step-by-Step Guide

This tutorial is all about weigh feeder.What is weigh feeder?Instruments used with weigh feeder.How do they work with each other? What is Weigh feeder?Movement of bulk material with precise weighing and at a fast speed is the key role in process industries.

Schenck Weigh Feeder Calibration Procedure Pdf Free

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Weigh feeder is a closed-loop control system, which controls the flow of material very accurately using controller and different instruments. This system accepts an external command from process computers like SCADA, HMI, DCS etc.This type of weigh feeder used in industries like Steel Plant, Cement Plant, Fertilizer and Chemical industries.

The instrument used in this system to control the flow rate is Closed-loop control with panels, Load cell to measure the weight of a predefined area on the belt and Encoder to measure the speed of the belt, AC Drive to control the speed of the motor which is connected on the gear box to drive the conveyor belt.Instruments used in weigh feeder systemClosed-loop controllerLoad cellTachoAC DriveClosed-loop Controller :The closed-loop controller is a micro controller-based instrument which can be programmed according to user requirement. Basically, it gets signals from load cell and encoder, these two signals are converted according to field instrument rating and then multiplied together to get the current rate of flow.This rate of flow is used to control the set flow which is given in the controller by using external controller or process computer. Also, there is a facility to generate the alarm or error if field environment is outside the given parameter.if(typeof ez_ad_units!='undefined')ez_ad_units.push([[300,250],'instrumentationtools_com-box-4','ezslot_17',165,'0','0']);__ez_fad_position('div-gpt-ad-instrumentationtools_com-box-4-0');The controller accepts a set flow rate via electrical signal which is 4-20 mA and also give an output flow rate is the same electrical signal. Controller also gives an electrical signal to control the speed of the motor through the AC drive according to set flow rate.

A gravimetric feeder, also know as a loss-in-weight feeder, is a self-calibrating dosing system that doses based on weight in speed. A volumetric feeder, on the other hand, does this based on volume in speed. In gravimetric dosing, the weight of the dosed additive is measured using a load cell that is the foundation of the entire system. Weight is calculated using loss-in-weight technology, which measures the reduced weight while dosing.

Nonlinearity is the load cell calibration curve's maximum deviation from a straight line, starting at zero load and ending at the cell's maximum rated capacity. Nonlinearity measures the cell's weighing error over its entire operating range. The worst-case nonlinearity specification of 0.018 percent is seen over the load cell's full range. The smaller the change in weight on your load cell, the smaller the error resulting from nonlinearity.

Hysteresis is the difference between two load cell output readings for the same applied load -- one reading obtained by increasing the load from zero, the other by decreasing the load from the load cell's maximum rated capacity. As with nonlinearity, the worst-case 0.025 percent hysteresis specification is seen over the load cell's full range, and the error caused by hysteresis diminishes with small weight changes. In an application such as batching, where you typically need accurate weight measurements only during filling, you can ignore the error caused by hysteresis. Hysteresis error normally falls into a different region on a load cell's calibration curve than nonlinearity error, as shown in Figure 1. As a result, the specifications for these two errors are combined on some load cells into an algebraic sum, called a combined error specification, of 0.03 percent.

Temperature changes affect load cell output by changing the load cell's sensitivity, and you must consider this effect unless you perform a new calibration for each large temperature change. The temperature effect on the load cell at zero load causes the cell's entire output range to shift. But if the load cell rezeroes (that is, tares in the net-weight mode) before it starts the weighing cycle -- such as in a batching application -- you don't need to be concerned about this temperature effect on zero load.

Shock loading. Shock loading occurs when heavy material is dumped onto a weighing system, causing forces greater than the system's rated capacity and damaging the system. You can use higher-capacity load cells that can handle this shock loading, but this will degrade the system's resolution (the smallest increment that the system can weigh). Controlling the material flow onto the weighing system with a feeder, specially designed loading chute, or other device can prevent shock-loading damage.

This system weighs 400 pounds of material in a 100-pound weigh hopper, requiring the load cells to support a total of at least 500 pounds. The hopper is suspended from three load cells, each with a rated capacity of 200 pounds, yielding a total capacity of 600 pounds. A 20F temperature change also occurs between seasonal system calibrations. 2ff7e9595c