Effect of steam cut-off on direct contact heaters in series in FBTR steam cycle

During normal operation of the plant, sudden loss of steam supply resulting from tripping of turbine and non-opening of the valve on the line supplying live steam can result in pressure decay in contact type feed water heaters. The resulting pressure differential across the trays increases many-fold over that existing at normal load and may buckle the trays and its supports. The pressure decay in the heater reduces the available NPSH to pump. As a result, the pump can be severely damaged due to cavitation. This report describes a mathematical model to obtain the pressure differential factor and available NPSH by analysing the three direct contact heaters in series and offers some solutions to the problem. The computational model and the computer listings are also given. (auth.)