ASME CSD-1–2009 pdf download.Controls and Safety Devices for Automatically Fired Boilers.
CW-140 Requirements for Water Level Controls for High-Pressure Steam Boilers (a) Each automatically fired, high-pressure steam boiler, except miniature boilers, shall have at least two automatic low-waterfuelcut-offdevices. Wheninstalled external to the boiler, each device shall be installed in individual chambers (water columns), which shall be attached to the boiler by separate pipe connections below the waterline. A common steam connection is permissible. Each cut-off device shall be installed to pre- vent startup and cut off the boiler fuel or energy supply automatically when the surface of the water falls to a level not lower than the lowest visible part of the gage glass. One control shall be set to function ahead of the other. Each miniature boiler shall have at least one low- water fuel cut-off device (see also CW-210). (b) Functioning of the lower of the two controls shall cause safety shutdown and lockout. The manual reset may be incorporated in the lower cut-off control. Where a reset device is separate from the low-water fuel cutoff, a means shall be provided to indicate actuation of the low-water fuel cutoff. The manual reset device may be of the instantaneous type or may include a time delay of not more than 3 min after the fuel has been cut off. (c) The fuel cut-off device may be inserted internally or attached externally to the boiler. An external cut-off device may be attached on piping connecting a water column to the boiler or combined with a water column. Water column piping and connections shall be at least NPS 1. If the low-water fuel cutoff is connected to the boiler by pipe or fittings, no shutoff valves of any type shall be placed in such piping.
CW-150 Requirements for Operating and Safety Controls for Electrically Heated Boilers Electric resistance and electrode boilers shall have a boiler feed control system that shall maintain the operating level in steam boilers and operating water pressure on hot-water boilers. Where uncovering of the electrical element can lead to an unsafe condition, the boiler shall be provided with low-water fuel cutoff(s) in accordance with Part CW. Boiler feed control and low- water fuel cutoff may be common to one control. In the case of electrode-type boilers, where the reduction in water level provides a self-limiting control on input, low-water fuel cut-off controls are not required. CW-200 AUTOMATIC FUEL CUTOFF FOR FORCED CIRCULATION BOILERS CW-210 Requirements for Flow or Temperature- Sensing Devices for Forced Circulation Boilers (a) In lieu of the requirements for low-water fuel cut- offs in CW-100, a water tube or coil-type boiler, requiring forced circulation to prevent overheating and failure of the tubes or coils, shall have an accepted safety control to prevent burner operation at a flow rate inadequate to protect the boiler unit against overheating, at all allowable firing rates. This safety control shall shut down the burner and prevent restarting until an ade- quate flow is restored. Positive means shall be provided to determine during testing that the accepted safety control has functioned upon an inadequate flow condi- tion. The positive means shall enable the accepted safety control to remain in the running safety lock circuitry during testing. The safety control must be automatically restored to service after completion of system testing. (b) When there is a definitive waterline, a low-water fuel cutoff complying with the applicable portions of CW-100 shall be provided in addition to the sensing device required in (a) above. Functioning of the low- water fuel cutoff shall cause a safety shutdown and lockout.