OTSG Water Side Dynamics: Part 4 скачать в хорошем качестве

OTSG Water Side Dynamics: Part 4

The series explains how the measured steam quality behaves to changes in key operating conditions. Part 1 lays out the benefit of improved reliability, and why it is important to understand the water side behaviour.  The familiar concept of “Shrink and Swell” in a drum boiler is reviewed, as it is important for the understanding of OTSG water side behaviour. Part 2 describes how the pass Venturi (or flow nozzle) infers the steam quality, and why this reads false when there are changes in operating conditions.  The general theory that defines the change in water holdup in the OTSG is described.  This behaviour is analogous to the Shrink and Swell phenomena in a drum boiler. Part 3 describes why OTSG light off may result in a sudden increase in steam pressure or lead to hammering in the startup line, and explains how to avoid this problem.  The consequence of a sudden loss of water flow rate is presented, and the prolonged response is used to justify softening several alarms and trips. Part 4 describes why the pump swap procedure can cause a sudden increase or decrease in feed water temperature.  A sudden drop in water temperature causes a sudden blip in operation: there is a short term decrease the measured steam quality, but a shot term increase the actual steam quality that may result in dry-out.