ISA-TR77.42.02:2014

ISA–TR77.42.02–2014, Fossil Fuel Power Plant – Compensated Differential Pressure Based Drum Level Measurement, focuses on improving the accuracy of water level measurement in fossil fuel power plant boiler steam drums using differential pressure transmitters. This technical report explains why compensating for changes in steam drum pressure and fluid density is important, especially for boilers operating above 200 PSIG, to prevent errors that can cause equipment damage. It describes how these measurements work, common installation setups and practical tips like proper piping orientation to avoid air pockets. This report offers detailed equations and methods for applying compensation using modern digital control systems, helping operators better interpret drum level signals under different conditions. It explains the limitations of traditional sight glass readings versus compensated measurements. Additionally, it provides a clear understanding of how to address drum level measurement challenges with differential pressure technology in power plants.