Combustion Control System–linkageless control with POSITION FEEDBACK or fUEL/AIR metering with cross limits

  1. The system shall be a parallel position control system with position feedback of fuel valve(s) and air damper.
  2. The system shall have the option to select full metered control with cross-limits, without requiring additional control hardware, I/O cards or re-engineering.
  3. Regardless of control type selected the following options shall be included as standard, with the ability to enable them in the field without requiring additional control hardware, I/O cards or system re-engineering:
  4. Excess O2 indication
  5. Oxygen trim control with output to FD fan VFD
  6. Stack temperature indication
  7. Online, instantaneous boiler efficiency calculation and indication
  8. Bias ramp option for plant master input
  9. The following options shall be available with the addition of a single input or output module. Options shall be enabled from the controller panel without requiring system re-engineering.
  10. Flue gas recirculation (FGR) control with separate curves for oil and gas
  11. Opacity monitoring and indication
  12. Retransmission of a selected variable via 4-20mA signal, including:
  13. Gas or oil flow
  14. Drum pressure
  15. Boiler load
  16. Real-time efficiency calculation and indication, using the Heat Loss method
  17. Stack temperature indication and high temperature trip
  18. Opacity indication and high opacity trip
  19. The system’s setup menus and operating displays shall adapt to user selections and hide unused functions from the setup and operating screens.
  20. The Boiler Master shall be capable of functioning either as a Bias Station, receiving an external Plant Master signal or a Drum Pressure controller comparing measured steam to setpoint and modulating the fuel valves accordingly.
  21. Failure of the plant master shall not affect continued operation of the individual boiler. Provision shall be made for independent operation of the Boiler Master loop if the signal from the Plan Master is no longer available, without reconfiguration of the control strategy. It shall be possible to wire both the Plant Master and Drum Pressure signals to the controller, and for the operator to switch between control strategies from the front panel of the controller provided the Boiler Master loop is in manual, without reconfiguration or rewiring. Automatic bumpless transfer from Manual to Automatic mode shall be provided.
  22. The demand signals for fuel and air shall have separate characterization curves for oil and gas for the fuel valves, FD damper actuator, VFD output option, and FGR damper option.
  23. The Oxygen control loop shall provide a limited adjustment to the Air Flow control loop remote setpoint for the amount of air for the current amount of fuel. Separate characterization tables for load programmed setpoints for oil and gas shall be provided.
  24. When parallel position control is selected, feedback signals from the fuel valve(s) and air actuator are required for operational safety. If any feedback signal is not present, or the deviation between the output and the feedback signal is greater than a predetermined percentage for 3 seconds, the system shall send a signal to the BMS to cause the boiler to trip.
  25. Full metering control shall use actual fuel flow and air flow measurements for cross-limiting. Positioning systems that depend on actuator feedback pots for cross limiting are not acceptable.
  26. Measured fuel flow as well as shift and continuous totals for each fuel shall be indicated, with the provision to clear shift totals from the front panel.
  27. When full-metering is selected, cross limits on fuel and air shall automatically ensure that air increases before fuel on a demand increase, and that fuel decreases before air when demand decreases, guaranteeing sufficient combustion air at all times and preventing a fuel-rich atmosphere. Additionally, the control system shall ensure that fuel demand cannot be increased beyond a certain amount above the measured air flow, and air demand cannot be decreased beyond a certain amount below the measured fuel flow.
  28. To provide for additional safety and ease of operation the controllers shall have automatic mode switching based on the status of the Air Controller and the BMS. For example, when the Air Controller is placed in Manual (MAN) mode the fuel controller shall be automatically switched to Manual, the Boiler Master shall track total fuel percentage and the Oxygen Trim controller shall track a constant value. All loops shall reject to Manual mode on bad signal quality.
  29. When the fan is equipped with both a damper and a Variable Frequency Drive and the Oxygen Trim option is enabled, the demand for air shall provide a signal to the pre-programmed positionslocated in separate characterization tables for oil or gas, for the fan VFD and damper.
  30. Separate light-off and low-fire settings shall be available for gas and oil for the fuel valves, air damper, VFD and FGR damper.
  31. A logic interface to the BMS shall be provided where a contact closure will position the fuel valves to a pre-programmed light off position. The controllers shall also contain logic to prevent fuel automation until the airflow is automated.
  32. All loops shall be capable of complete local operation and visualization via dedicated displays. If the controllers are connected to a computer console or operator interface panel for normal operation, failure of the console or panel shall not deprive operations personnel of the ability to visualize and run the boiler in manual or automatic with full control of all functions.
  33. Access to all setup parameters shall be password protected.
  34. Controllers shall have easily-readable, integral displays that provide operating and alarm information in clear English language format. The system shall not require a separate operator panel in order to perform setup and operation activities.
  35. All inputs and outputs shall be galvanically and optically isolated such that a failure of one I/O point shall not cause failure of any other.
  36. Communication via RS-485 Modbus RTU shall be included as standard.
  37. The system memory shall be nonvolatile with 10-year data retention.
  38. The system shall provide the option for backup memory that can retain the configuration and user-entered data for up to 10 years. The backup memory shall be portable and may be used to copy configurations between controllers in the event of a hardware failure without requiring connection to a computer or configuration software.
  39. Controllers shall carry a 2-year warranty after date of shipment.
  40. The system shall be factory manufactured and tested according to FM/CSA Class 1, Division 2, Groups A,B,C,D. The control system shall be a MicroMod Automation, RochesterNY, MeterPAK combustion control system.
  41. A software package for setup and tuning shall be available as an option, without requiring a license or license fee. Software shall allow access to all setup, tuning and operating parameters, including enabling/disabling of options, and provide real-time trend window to facilitate loop tuning. The software shall provide the option to store setup parameters as a file on a local computer or remote server.