TM 10-6640-238-13 2-25 i. Gum Bath System Controls and Indicators.  Figure 2-10 and Table 2-10 list the controls and indicators for the gum bath system. Table 2-10.  Gum Bath System Controls and Indicators Index Number Control or Indicator Function 1 Exhaust Fan Switches and Indicator Lights Indicator lights are on to indicate exhaust fan operation. 2 Air Flow Indicator Provides indication of air flow to gum bath.  Calibrated in pounds and ounces, corresponding to flow of air in liters per second. 3 Steam Flowmeter Indicates steam flow rate. 4 Pyrometer Indicating and controlling device for gum bath preset temperatures. 5 Gum Bath Hood Light Switch Controls hood light operation. 6 Air Flow Regulator Regulates air to gum bath.  Rate of flow required is 1 liter per second ( 15%). 7 Temperature Control (Steam) Temperature control of high pressure boiler steam output up to 550F (228C). 8 Boiler Sightglass Indicates water level in low pressure boiler. 9 Operating Control Maintains low pressure boiler steam output to gum bath. 10 Pressure Gauge Indicates boiler pressure. 11 HI Limit Control and Pressure Relief Valve Protects boiler from damage if boiler pressure is too high. 12 Boiler On/Off Switch Controls operation of low pressure boiler. 13 Low Pressure Boiler Automatic Water Feeder System Maintains low pressure boiler water level. 14 INT Switch Turns gum bath circuit On or OFF. 15 AUX Switch Turns high pressure boiler heater circuit ON or OFF. 16 Fume Hood Light Switch Controls exhaust fans operation.