Explain the methodology for calibrating a fuel feeding system to achieve precise fuel delivery rates.

Calibrating a fuel feeding system is crucial to ensure precise fuel delivery rates and maintain stable and efficient boiler operation. The methodology involves establishing a relationship between the feeder's control signal (e.g., motor speed, valve position) and the actual fuel delivery rate. First, ensure the fuel feeding system is operating under normal conditions, with representative fuel being used. Check the fuel level in the hopper or feeder and verify that there are no obstructions or issues affecting the flow. Second, select several setpoints for the feeder's control signal across its operating range. For example, if the feeder is controlled by a variable frequency drive (VFD) that adjusts the motor speed, select several speeds (e.g., 20%, 40%, 60%, 80%, and 100% of the maximum speed). Third, for each setpoint, measure the actual fuel delivered over a specific time interval. This can be done by diverting the fuel stream into a container placed on a calibrated scale. Collect the fuel for a known duration (e.g., 5 minutes, 10 minutes) and weigh the collected fuel. Repeat this measurement several times at each setpoint to obtain an average fuel delivery rate. Fourth, calculate the fuel delivery rate for each setpoint by dividing the weight of the collected fuel by the collection time. This gives the fuel delivery rate in units such as kilograms per minute or tons per hour. Fifth, plot the measured fuel delivery rates against the corresponding control signal setpoints. This creates a calibration curve that shows the relationship between the control signal and the fuel delivery rate. Sixth, use the calibration curve to adjust the feeder's control system. This may involve creating a lookup table or a mathematical equation that maps the desired fuel delivery rate to the appropriate control signal setpoint. Regularly verify the calibration of the fuel feeding system to account for wear and tear or changes in fuel characteristics. This ensures continued accuracy and reliability of the fuel delivery process.