Sheet 4343-14
North American TwinBed ® II Maintenance Check List
BURNER and LNI INJECTORS
Visually check observation ports on back of Injectors to make sure passage is clear and gas flow is not obstructed. Direct charged aluminum melters have metal splash that can deposit metal and dross on the furnace wall. For safe, efficient, low NOx operation the burner injectors must be able to inject fuel gas without obstruction. Contaminants must be removed that build up on the furnace wall around the injectors. Clean material from around the injectors by reaming through the injector nozzle (if passage is straight through) to clear the opening and carefully scraping the wall around the injector to remove buildup. NOTE: The wall must be scraped in addition to reaming or the fuel gas may be diverted behind the material or change the gas stream which could hinder burner operation. Refer to Sheet 4343-12 for injector installation instructions. Weekly visually check bed material through sight port on regenerator hatch. Periodically check burner bed pressure drop to determine extent of bed plugging. Refer to Sheet 4343- 4 for bed cleaning instructions and a form for recording bed pressure drops. ELECTRICAL CONTROLS Check Overtemperature Control and instrumentation regularly for proper electrical operation and for accuracy against a good standard. Check thermocouples used on control and safety instruments once a month by comparing against a standard. Replace if error is found to be more than an acceptable variation for the process and temperature.
Check: UV scanner signal to flame supervision control. UV scanner adapter lens for dirt (if scanner signal drops).
Turn each burner/pilot off. This will cycle the flame supervision system through the ignition sequence which includes flame relay component check and check for flame signal before ignition trial. Daily testing of UV scanners is strongly recommended by FM Global. This is not required if the scanners are self checking type. VALVES and ACTUATORS Check weekly: Linkages on control valves; Flue gas damper and actuator; Operation of cycling solenoids and air cycling valves Safety standards and insurance underwriters require periodic checking of safety devices such as solenoid valves, pressure switches and main shut off valves for proper operation. Maintain and perform routine cycling checks as detailed in manufacturer's literature. Cycling checks include opening and closing the automatic shutoff gas valves. Installation 1177D gives lubrication instructions for 1177D Cycle Valves for air and exhaust. The valves should be greased once every three months with a lubricant rated for 450 o F.
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