NFPA 8505-1998 Standard for Stoker Operation

NFPA 8505-1998 Standard for Stoker Operation. 5-4 Normal Operation. 5-4.1 The firing rate shall be regulated by increasing or decreasing the fuel and air supply simultaneously to the grate(s), maintaining normal air/fuel ratio at all firing rates. 5-4.2 Each stoker has adjustments for the distribution of the fuel. Manual adjustments for distribution of fuel are made from visual appearance of the fuel bed, furnace, and oxygen analyzer. Visual observations of the fuel bed conditions through open doors shall be made with extreme care. (See Sec- tions 7-9 and 7-10.) 5-4.3 Manual adjustments to the individual rows of overfire turbulence air nozzles for maximum furnace efficiency and minimum emission discharge shall be permitted. 5-4.4 Fuel shall be fed to maintain an even depth of ash. As the percent of ash in the fuel changes, it might be necessary to make adjustments. It is necessary to observe the depth of ash at the discharge end of the grates. 5-5 Normal Shutdown. Normal shutdown procedure shall be as follows: (a) The boiler load shall be reduced manually to minimum load. (b) Fuel shutoff gates, where furnished above the fuel feed- ers, shall be closed. (c) Remaining fuel downstream from the shutoff gate shall be burned out. (d) Normal furnace draft shall be maintained throughout this process. (e) The overfire air fan shall be left running. Exception: This rule may not apply to boilers where manufacturer’s recommendations state otherwise. (f) After fuel feed ceases and the fire is burned out, the overfire air and forced draft fan shall be operated in accordance with the manufacturer’s recommended cool- down rate. The overfire air fan shall be left running until the furnace and boiler are sufficiently cool to prevent damage to the overfire system from a back flow of hot gases. (g) Where the forced draft fan is shut off, a natural draft flow of air through the grates shall be provided. 5-6.2 When it is desired to restart the unit after it has been bottled up under pressure for a short time, and the grate fire continues, the hot-start procedure shall be as follows: (a) Establish the proper drum level. (b) Set the vent and drain valves in accordance with the boiler manufacturer’s instructions. (c) Verify an open flow path from the inlet of the FD fan to the stack. Where there is not sufficient natural draft for initial firing, the ID fan shall be...