Operate drain valves on different HPSH harps simultaneously, not in sequence, prior to and during hot, pressurized startups.
Most operators know it’s important to drain the high-pressure superheater during startup before steam flow is initiated to prevent accumulated water at the bottom of the harps from migrating up some tubes—quenching them and the upper headers/piping. But opening drain valves individually causes a pressure drop in the harp being drained that will pull water over the top from other harps, thereby causing the water migration you were trying to avoid.
Submitted by Bob Anderson, chairman, HRSG Forum
