FIELD OF THE INVENTION
The invention relates to an apparatus and method to improve the accuracy of the bulk material weighing and metering conveyor of the endless belt type provided with a drive mechanism employing multiple load sensing devices and operating in gravimetric mode while any one of the multiple sensors fail or malfunction.
BACKGROUND OF THE INVENTION
The coal based power plants are equipped with coal feeder apparatus for measuring and controlling the feed rate of the coal into the furnace. The Coal feeders are equipped with belt to shear the material, modulates the speed of the belt to adjust flow rate of material being drawn from a source, such as a bunker, bin, silo, hopper, or other suitable storage. This fuel feeding rate is critical parameter, based on the amount of fuel fed the appropriate amount of air is to be supplied for ensuring efficient combustion. All the fuel and air input are measured in terms of tons per hour [TPH] metric unit. The coal feeding apparatus, consisting of a conveyor belt mounted on the set of pulleys, driven by a driving unit, for instance, a motor. The coal weighing apparatus have typically a set of load cell transducers or multiples of sensors to measure and generate signals based on the weight acting on the belt.
Both the feeding and measuring are controlled and processed respectively by a controlling unit located in the control room. The feeding rate is controlled by adjusting the speed of the drive whereas the load cell sensor readings are processed for deriving the actual weight based on calibration parameters.

Feeder apparatus gets the input, for arriving at the demanded feed rate (kg/s), from the master control system. In case of the coal based power plants, the overall demand for electrical power determines the amount of coal feeding rate. Typically, in a power plant, there would be 8-10 such coal feeding apparatus. The feeding rate demanded per feeder apparatus from the master control system depends on the actual plant generation requirement, calorific value of coal, combustion efficiency of the furnace, number of feeder apparatus in operation and many other parameters.
The difference between the actual flow rate and the demanded flow rate, is computed by the feeder apparatus section so as to increase or decrease the feed rate of the feeder, by controlling the speed of the drive connected with the belt. This demanded feed rate is continuously varying analog signal which is fed into the feeder control system as input demand feed rate. Generally, every measuring equipment needs accuracy to the class of its requirement. Here, in the case of power plant coal feeding, the weighing accuracy requirement of the feeder is more than 99.5%. The accuracy of the apparatus is ensured by the calibration of the feeder apparatus. During the calibration of the apparatus, two principal parameters are computed and are used for measuring and feeding the material.
The material may be conveyed over a weight measuring device such as the belt scale fitted with a set of load sensors. Between the weigh feeder input and output, the weight kilogram value per unit of length (kg/m), of the material may be measured at every scan. At any convenient location on the feeder apparatus the velocity of the belt may be measured or derived which provides meter per second (m/s) value. The instantaneous product of the above two measurements, kg/m x m/s = kg/s, is the actual flow rate which is compared to a demanded flow rate.

The mode of feeding operation of the apparatus where the weight measurement signal is based on the load cell sensor output is known as gravimetric mode of operation. For the apparatus to feed material in gravimetric mode, the following two conditions are to be satisfied:
> Both the load sensing device output signal should be within expected range.
> The difference between the individual sensor output shall be within acceptable range.
In case either of the two conditions are not valid for specific time period, the system switches over to volumetric feeding operation where the system computed historic density of the material is used for computing the material weight signal. Hence its clearly understood that, Volumetric feeders do not weigh the flow; they operate by delivering a certain volume of material per unit time. In the event a feed rate error occurs or a component malfunctions, an alarm signal is provided along with an error message. This allows correction of a problem before serious damage occurs and often prevents unscheduled outages. A weighing system malfunction will automatically convert the feeder to a volumetric mode of operation in which an average density is used to continue feeding while separate totals are maintained.
Typically, volumetric feeders are open-loop devices and cannot detect or adjust to variations in the material’s density. Due to the open-loop concept, headload variations and material buildup on the feed device change the volume per-revolution relationship, throwing off calibration without any outward sign. Gravimetric feeders automatically detect and adjust to these conditions. In cases of screw feeding of cohesive materials, it is possible in volumetric mode to have relatively no material discharging while the screws are running. Similarly, flood-through can also remain undetected

since the feeder has no way of knowing the out-of-control condition. Since the feed rate in a volumetric feeder is purely a function of speed, the feeder and the process below have no way of detecting this upset condition. Sometimes, even the use of level sensors in the feed hopper may not alert the process of this upset in a timely fashion. Most gravimetric feeders can automatically detect and alarm to these conditions.
The bulk density of coal will range from 750-1050 kg per cubic meter. This density change is primarily the result of changes in moisture and sizing of the coal. Density variations are directly related to the calorific value of the fuel by weight input to the firing process. Gravimetric Feeders monitor the weight of the coal and raise or lower the belt speed to instantaneously compensate for these changes in density. This improvement in the feed rate consistency, and thus the actual weight of fuel delivery, allows a closer matching of fuel to air to minimize unburned carbon losses and stack losses.
Gravimetric feeders have become the industry standard in coal fired power plants, providing the following features:
> • Fuel Savings through Boiler Efficiency
> • Combustion Efficiency/Loss of Ignition
> • Less Slagging and Fouling, leading to Less Corrosion
> • Less Nitrogen Oxides through Better Control of Excel Air
> • Stability and Response of Combustion Controls
> • Pulverizer/Cyclone/Combustor Performance
For accuracy requirements in the 1% to 5% range, volumetric feeders will usually suffice, while gravimetric feeders are used for performances in the 0.25% to 1.00 % range. Hence, the material weight signal needs to be generated precisely for operating in more accurate mode. The mode of

operation is switched from gravimetric, more accurate mode to volumetric, lesser accurate mode while one of the load cell sensor is faulty.
This is because, while both the load cells are functional and outputs signal within the expected range, we are in position to track the load cell healthiness. While one of the load cell sensor malfunctions or behaves erroneously, there is no existing method to track and find the single failed sensor among the multiple sensor system. If the healthy load cell is identified among the other sensors, we shall extrapolate the signal derived from the working, healthy load cell to arrive at the most appropriate material weight signal for the controller to operate.
To address this issue, the Indian patent publication IN167034A1 titled “Gravimetric Feeder Apparatus For Feeding Particuate Materials At A Feed Rate In Terms Of Weight Per Unit Time” propose an apparatus and method for feeding particulate material such as coal and other bulk materials a batch scale weighs the particulate material and delivers it periodically to a volumetric feeder through a hooper. A computer controller responsive to a feeding rate demand signal, the length of the period during which each batch is delivered from the scale, and the speed of the volumetric feeder, provides outputs indicating the feed rate produced by the volumetric feeder and can control the speed of the feeder to obtain the demanded feed rate. The result is that the material is fed at a feed rate in terms of units of weight per units of time, and the volumetric feeder is converted, by the addition of the batch scale and the computer controller, into a gravimetric feeder. The load cells are continually read so long as the batch weight remains low (below a predetermined weight).

In the solution proposed in DE4447051A1 titled “Dispensing feeder with gravimetric or volumetric measurement for delivery of portions of dry, bulk goods” the feeding system for the accurately apportioned delivery of dry goods, for use in bulk packing machines for example, consists of a storage hopper, which has an entry funnel and a screw-feed for the dry goods, leading to an Archimedes screw in a tubular casing for delivery of the apportioned goods into bags or similar. Weighing scales, linking the hopper and the screw feeder, can be set to deliver the required quantities by weight and are suitable for portions of more than one kilo. A switching unit permits volumetric use by switching over the drive motor from the scales to the Archimedes screw and counting its revolutions on a meter.
In the prior art as described and claimed, the invention discusses about only two modes of operation of the scale feeding system namely, gravimetric and volumetric and there is no description of a possible partial gravimetric mode of operation and there is no method to detect failure of any one of the sensor during the operation of the feeding system.
Accordingly, there exists a need in the art to improve the existing technologies to facilitate more efficient and reliable method to appropriate material weight signal by identification of the faulty load cell sensor among the multiple sensor to operate the apparatus in better accuracy compared to the volumetric mode, by using the signal output of the healthy load cell with simplified configuration.

OBJECTS OF THE INVENTION
It is therefore the object of the present invention is to improve the accuracy of the bulk material weighing and metering conveyor of an endless belt type provided with a drive mechanism by operating a feeder in a partial gravimetric mode while one of a multiple load sensing sensor is faulty.
Another object of this invention is to identify a faulty and healthy load cells among a plurality of sensors by analyzing a presently computed density and historic density of a material.
A further object of the invention is to obtain a most appropriate material weight signal, using a signal output of a healthy load cell.
A still further object of the invention is to continuously monitor the healthy load cell until the apparatus is operated in the partial gravimetric mode and update the historic density using the healthy load cell signal.
Yet another object of the invention is to detect any abnormality in the used load cell signal and switch over to a volumetric mode of feeding using a latest updated historic density.
SUMMARY OF THE INVENTION
The present invention discloses about apparatus and methods for feeding particulate materials, such as coal and other bulk materials, and particularly to improved methods and apparatus for feeding material gravimetrically (on a unit weight per unit time basis).

In one embodiment a bulk material weighing and feeding apparatus comprises a bunker to receive a input coal is disclosed. A gravimetric feeder inlet configured to have a coal chute to receive the input coal from the bunker. The coal chute comprising a pair of coal gates positioned on each end of the chute wherein a coal inlet gate located in an upper side of the chute and a coal outlet gate located in a bottom side of the chute. The gravimetric feeder having the driving module which is mounted on a feeder floor. A downstream equipment through a pulverizer inlet chute receives a measured and conveyed coal and an outlet feed the measured coal into an another pulverizer unit for further processing and conveyed to a furnace burners for combustion.
In a preferred embodiment a method for calculating material weight signal in a bulk material weighing and feeding apparatus comprising the steps of loading the gravimetric feeder with a plurality of load sensors which are uniformly loaded for deriving an actual weight based on a calibration parameters, controlling a feeding rate by adjusting the speed of the drive module and determining a relationship between a load cell output to the weight, a conveyor linear speed and the driving module rotations per minute using the calibration parameters.
In one embodiment the gravimetric feeder with the plurality of load sensors which are uniformly loaded weigh and generate a signal proportional to the weight of the material acting on it. An output signal of all load cell sensors are evaluated during gravimetric mode of operation. During this mode, an average historic density of the material is computed and updated to a controller. In gravimetric mode of operation an accurate feeding mode is determined. After determining the feed mode after detecting any anomaly the gravimetric mode is aborted and the gravimetric feeder switches to a volumetric mode of operation. The anomaly condition is listed below,

> Load sensing device output signals out of a specified valid range.
> Difference between an individual sensor output greater than acceptable range.
In one embodiment, during the volumetric mode of operation, the density is not updated and the previously computed density is utilized for calculation of the material weight signal and feeding accordingly. To determine a healthy load cell among the plurality of sensors uses the output signal of the working healthy load cell to arrive at the most appropriate weight signal for feeder. The weight signal hence computed, if found superior to that of the weight signal computed by volumetric mode and less accurate than that of the gravimetric mode shift to a partial gravimetric mode. Continuously monitor the healthy load cell until the weighing and feeding apparatus is operated in the partial gravimetric mode and update the historic density using the healthy load cell signal.
In a preferred embodiment the weighing and feeding apparatus operates in gravimetric mode of operation, both the healthy load cell signals are considered for determining at the material weight signal and to compute the material density. In partial gravimetric mode of operation, only one of the load cell signal is considered for computing the overall material weight signal by proportionally scaling the healthy load cell signal under the assumption that the material is uniformly distributed among the load cell sensors. By comparing the latest updated historic density and the previously computed historic density any anomaly in the healthy load cell signal is identified and after identification switch over to the volumetric mode of feeding.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 is a schematic arrangement of a location of a gravimetric feeder in a bulk material weighing and feeding apparatus for implementing embodiment of the present invention.
Fig.2 is a schematic arrangement of a preferred embodiment of the gravimetric feeder according to the present invention.
Fig. 3 shows a flowchart illustrating a method for detecting a healthy load cell among a plurality sensor mounted in the gravimetric feeder and operate in partial gravimetric mode during the load cell fault detection.
DETAILED DESCRIPTION OF THE INVENTION
Fig.1 is a schematic arrangement of a location of a gravimetric feeder [04] in a bulk material weighing and feeding apparatus (100) for implementing embodiment of the present invention. But as apparent to those skilled in the art, this is just an example for illustrating the principle of the present invention, and the present invention is not limited to this specific example.
With reference to FIG.1, the bulk material weighing and feeding apparatus (100) comprises a bunker (08) to receive an input coal. A gravimetric feeder (04) inlet configured to have a coal chute (02) to receive the input coal from the bunker (08). The coal chute (02) comprising a pair of coal gates positioned on each end of the chute wherein a coal inlet gate (01) located in an upper side of the chute and a coal outlet gate (03) located in a bottom side of the chute. The gravimetric feeder (04) having the driving module (09) which is mounted on a feeder floor (05). A downstream equipment through a pulverizer inlet chute (06) receives a measured and conveyed coal and an outlet (07) feed the measured coal into an another pulverizer unit for further processing and conveyed to a furnace burners for combustion.

In a preferred embodiment the bulk material weighing and feeding apparatus (100) is a coal feeder apparatus which is operated in different modes, namely, Local, calibration and remote. The remote mode is also known as material feeding mode. In the remote mode of operation feeds materials to the downstream equipment and an accuracy is determined in this mode. The accuracy of the feeder apparatus is determined by the calibration of the bulk material weighing and feeding apparatus (100) as well as the performance of a plurality of load sensing sensors (11) mounted on the gravimetric feeder (04).
Fig.2 is a schematic arrangement of a preferred embodiment of the gravimetric feeder (04) according to the present invention. Referring to the Fig.02, is the overall scheme of the gravimetric feeder [04] for feeding bulk solid materials using an endless conveyor belt [15] mounted on minimum of two pulleys rotated in the clock wise direction while the material feeding direction is from left to right side. The belt shears the material from the material inlet [10], the belt also rotates in clock wise direction conveys the coal through the gravimetric feeder (04). The plurality of load sensor [11] measures the weight acting across a known length [17]. The material weighed and conveyed is discharged into the feeder material outlet end [13]. The pulley to which the drive is attached is the head pulley [14] that is located closer to the material outlet end [13] of the v. The pulley which is located at the other end is denoted as tail pulley [16] which is closer to the material inlet.
In one embodiment operating the gravimetric feeder (04) in a partial gravimetric mode, during which the feeding accuracy is better than a volumetric mode of operation. In a preferred embodiment the method for calculating material weight signal in a bulk material weighing and feeding apparatus, comprising the steps of loading the gravimetric feeder(04)

with the plurality of load sensors (11) which are uniformly loaded for deriving an actual weight based on a calibration parameters. Controlling a feeding rate by adjusting the speed of the drive module (09) and determining a relationship between a load cell output to the weight, a conveyor (15) linear speed and the driving module (09) rotations per minute using the calibration parameters.
In a preferred embodiment, during a calibration process of the gravimetric feeder (04), a set of external sensors [18,19] are used for measure the time taken by the belt [15] to cross a predefined probe span length i.e. known length [17]. With the time measured and the known length, the linear speed of the belt [15] corresponding to the driving module [09] in the calibration motor rotations per minute is determined. When the marked belt is rotating at a constant velocity, set by the motor rotational speed, while each of the mark crosses the left side sensor [19] the electronics associated with the system starts the timer and stops, similarly the same marker crosses the right side sensor [18] while the belt is rotating in clock wise direction. The above defined process is repeated for predefined times and the average of the linear speed is computed. The linear speed and the motor set speed is compared to determine at the belt calibration parameter which is saved and used while feeding material along with other parameter for computing actual feed rate.
In one embodiment the coal based power plants are equipped with gravimetric feeder (04) for measuring and controlling the feed rate of the coal into the furnace. The gravimetric feeder (04) are equipped with belt (15) to shear the material, modulates the speed of the belt (15) to adjust flow rate of material (10) being drawn from a source, such as a bunker, bin, silo, hopper, or other suitable storage (08). The fuel feeding rate is critical parameter, based on the amount of fuel fed the appropriate amount of air

is to be supplied for ensuring efficient combustion. All the fuel and air input are measured in terms of tons per hour [TPH] metric unit. The gravimetric feeder (04), consisting of a conveyor belt (15) mounted on the set of pulleys (14, 16) driven by a driving module (09), for instance, a motor. The bulk material weighing and feeding apparatus (100) have a set of load cell transducer or plurality of load sensor (11) mounted on either side of the belt (15) to measure the weight acting on the belt (15). Both the feeding and measuring are controlled and processed respectively by a controlling unit (not shown) located at control room. The feeding rate is controlled by adjusting the speed of the drive whereas the plurality of load sensor (11) readings are processed for deriving the actual weight based on calibration parameters. For ex: both the material weighing load cells, namely A & B, provide instantaneous individual weight signals based on the sensor output. The load cell A, provides the weight of the material as An kg and load cell B, provides weight of the material as Bn kg at the time instance ‘n’. The sum of both weights are summed, An and Bn together to arrive at the instantaneous overall weight load in the weighing span. This weight is used to determine the demand motor speed for meeting the instantaneous feed rate demand from a master control system. In a preferred embodiment the gravimetric feeder (04) is a coal feeder apparatus.
In one embodiment the material could be conveyed over a weight measuring device such as the belt scale fitted with the plurality of load sensor (11). Between the weigh feeder input and output, the weight value per unit of length of the material may be measured instantaneously which gives belt load kg/m value from the load cell inputs at that instant, this weight signal is valid and used only while the feeder is operating in gravimetric mode. In case of the volumetric mode of operation, the estimate of the weight of the material on belt is deduced from the historic density of the material computed while the gravimetric feeder (04) was

operated in gravimetric mode or user entered value based on the requirement. The estimated weight computed in volumetric mode is prone for errors due to the change in material density and distribution over belt. Thus the kg/m, the belt load computed during volumetric mode is error prone. Hence to reduce the errors in gravimetric mode of operation is preferred.
Fig. 3 shows a flowchart illustrating a method (200) for detecting a healthy load cell among the plurality load sensor (11) mounted in the gravimetric feeder (04) and operate in partial gravimetric mode during the load cell fault detection illustrating the steps. In step 202 setting the feeder in gravimetric remote mode. In the step 202, the determined condition is “no” then no computation is required. In the step 206 the determined condition is “yes” then loadcell tracking error is calculated. In the step 208 if the computed tracking error is nil operate the machine in gravimetric mode. If the computed tracking error is positive, then in the step 210 compute density using LC1 and in the step 212 compute density using LC2. In the step 214 & 216 historic density is computed by addition & subtraction. In the step 218 absolute error of LC1 is computed. In the step 220 LC1ERR >LC2ERR is computed. In the step 222 Integrate for specific period LC1ERR and in the step 224 integrate for specific period LC2ERR is computed. In the step 226, LC2 deviates lesser than historic density and in the step 228 LCI deviates lesser than historic density.In the step 220 comparison is performed, if the computed result shows “yes” then in the step 230 trust LC2. If the computed result of the step 220 results in “NO” then in the step 232 trust LC1. In the step 234 partial gravimetric with LC2 is determined by the following steps: LC2 density is computed, after 15 mins historic density is updated. In the step 236 partial gravimetric with LC1 is determined by the following steps: LC1 density is computed, after 15 mins historic density is updated. In the step 238 if the computed LC2

density in range then follow the above partial gravimetric with LC2 mode and if the LC2 density is not in range then switch to volumetric mode in the step 240. Similarly, in the step 242 computed LC1 density in range then follow the above partial gravimetric with LC1 mode and if the LC1 density is not in range then switch to volumetric mode in the step 240.
In one embodiment, in a preferred location, the gravimetric feeder (04) velocity of the belt is measured which provides m/s value. For example: The product of the two measurements, kg/m x m/s = kg/s, is the actual flow rate which is compared to a demanded flow rate. The gravimetric feeder (04) gets the input, for arriving at the feed rate, from the master control system (not shown) in terms of a continuous analog current input. This analog current is generated by the master control system. Before switching from gravimetric to volumetric mode of operation, the plurality of load sensor (11) data are analyzed for determining the healthy load cell sensor among the mounted plurality of load sensor (11).
In one embodiment for example Consider an instance where, load cell A is faulty and load cell B is healthy. Let, the weight measured by the load cell B at the time instance n, be Bn. The total material weight at the instance n is now computed as 2 x Bn kg, while the load cell A is faulty. Similarly, while the load cell B is faulty, the total material weight at the time instance m is computed as 2 x Am kg, while the load cell B is faulty. During the analysis, the individual load cell based material density is compared with the historic density for a specific period of time to determine the health data of the load sensor, as explained in Fig. 03. Based on this analysis, the defect/ faulty and healthy load cell is identified.

In a preferred embodiment the gravimetric feeder (04) with a plurality of uniformly loaded load sensors (11) measures the instantaneous weight value per unit length (i.e. kilogram/meter value) during every scan between the weight feeder input (08) and the outlet (07) which determines the rotations per minute at which the driving module (09) rotates for attaining the appropriate linear speed of the conveyor or belt (15) at which the demanded feed rate from a master control system is fulfilled by the gravimetric feeder (04). The plurality of sensors is unequally loaded and the ratio of individual sensor loading is determined and the weightage /ratio of loading of load sensors to arrive at the required driving module (09) rotations per minute is calculated.
In one embodiment wherein the gravimetric feeder (04) obtains the material weight signal using a signal output of a healthy load cell and determining an instantaneous belt load for belt drive set point. A faulty load sensor is identified during the run time of the gravimetric feeder (04) by computing an individual load cell based material density and comparing it with a historic density for a specific period of time to determine the health data of the load sensors (11).
In one embodiment the plurality of uniformly loaded load sensors (11) monitor the selected healthy load cell among the plurality of the load cells and determine the gravimetric feeder (04) is operated in the partial gravimetric mode and update the historic density to a controller using a healthy load cell signal. Determine any abnormality in a flagged healthy load cell signal among the plurality of the load sensors. The plurality of uniformly loaded load sensors (11) continuously monitoring a measured material density using a signal output among the plurality of load cells and switch over to the volumetric mode of feeding which utilizes a latest

updated historic density and determines the set point for the driving module (09) for the appropriate linear speed of the belt or conveyor.
In one embodiment bulk material weighing and feeding apparatus uses the basic assumption that the weight is equally distributed across the plurality of load sensor (11). The signal representing material weight, computed by the apparatus, would be of great precision, omitting the deviations with respect to the volumetric measurement, which improves the accuracy of the gravimetric feeder (04) (I.e) coal feeding apparatus . Though through the invention, the bulk material weighing and feeding apparatus (100) could accurately compute the motor speed set point based on the actual weight sensed, which gives scope for the improved performance of the overall system. Implementing this apparatus improves the accuracy of feed rate computation of the bulk material weighing and feeding apparatus (100) along with aiding with improved combustion efficiency of the fuel in the furnace, in case of coal feeding apparatus.
The principle of the present invention has been illustrated by way of specific embodiments with reference to the drawings, though the skilled in the art should appreciate that the embodiments are just illustrative but can not be considered as limiting the scope of the invention that is defined by the accompanying claims.

WE CLAIM:
1. An apparatus for weighing and feeding a bulk material comprising:
- a bunker (08) to receive a input coal ; - a gravimetric feeder inlet (04) configured to have a coal chute (02) to receive the input coal from the bunker (08) and a plurality of load sensors (11);
- the coal chute (02) comprising a coal inlet gate (01) located in an upper
side of the chute and a coal outlet gate (03) located in a bottom side of the
chute wherein both the coal chute inlet and outlet positioned on each end
of the chute;
- the gravimetric feeder (04) having a driving module (09) which is
mounted on a feeder floor (05);
- a downstream equipment through a pulverizer inlet chute (06) receives a measured and conveyed coal; and
- an outlet (07) feed the measured coal into an another pulverizer unit for further processing and conveyed to a furnace burners for combustion.
2. A method for calculating material weight signal in a bulk material weighing
and feeding apparatus, comprising the steps of :
- loading the gravimetric feeder (04) with bulk material for deriving an actual weight;
- controlling a feeding rate by adjusting the speed of a drive module (09); and
- determining a relationship between a load cell output to the weight, a conveyor (15) linear speed and the driving module (09) rotations per minute using the calibration parameters.

3. The method as claimed in claim 2, wherein the gravimetric feeder (04) with the plurality of uniformly loaded load sensors (11) measures the instantaneous weight value per unit length (i.e. kilogram/meter value) during every scan between the weight feeder input (08) and the outlet (07) which determines the rotations per minute (rpm) of the driving module (09) which rotates for attaining the appropriate linear speed of the conveyor or belt (15) at which the demanded feed rate from a master control system is fulfilled by the gravimetric feeder (04).
4. The method as claimed in claim 2, wherein the plurality of sensors (11) is unequally loaded and the ratio of individual sensor loading is determined and the weightage/ratio of loading of load sensors to arrive at the required driving module (09) rotations per minute is calculated.
5. The method as claimed in claim 2 or 4, wherein the gravimetric feeder (04) obtains the material weight signal using a signal output of a healthy load cell and determining and instantaneous belt load for belt drive set point.
6. The method as claimed in claim 2, wherein a faulty load sensor is identified during the run time of the gravimetric feeder (04) by computing an individual load cell based material density and comparing it with a historic density for a specific period of time to determine the operating health of the load sensors (11).
7. The method as claimed in claim 2, wherein the plurality of uniformly loaded load sensors (11) monitor the selected healthy load cell among the plurality of the load cells and determine the gravimetric feeder (04) is operated in the partial gravimetric mode and update the historic density to a controller using a healthy load cell signal.

8. The method as claimed in claim 2, wherein the plurality of uniformly
loaded load sensors (11) continuously monitoring a measured material density using a signal output among the plurality of load cells and switch over to the volumetric mode of feeding which utlilizes a latest updated historic density and determines the set point for the driving module (09) for the appropriate linear speed of the belt or conveyor.