ISA 77.43-1994

Formerly S77.43-1994. Addresses the unit/plant demand development subsystem for boilers with steaming capacities of 200,000 lbs/hr (25 kg/s) or greater. This subsystem includes firing rate demand development, throttle/header pressure control, and unit megawatt/steam flow control as applicable. Addresses: (1) a single boiler supplying a single turbine, typical of an electric utility power plant and (2) a single or multiple boiler supplying a common distribution header, typical of an industrial power plant. Specifically excluded are: dispatch control; turbine/generator control (other than turbine demand); combustion controls (covered by ISA-S77.41); steam distribution control systems; economic loading of boilers; and fluidized bed boilers.