Brochure

In the normal range of plant operation, the boiler feedwater regulator experiences high ow rates with low differential pressure. However,
during startup, this valve experiences low ow rates with very high differential pressure, which can cause severe cavitation damage. Some
feedwater systems are designed using one valve to handle startup and normal operating conditions. Others are designed using a separate
small startup valve to handle low ow, cavitating conditions and a second larger valve to handle high ow rates required for normal operation.
Boiler Feedpump Recirculation
The boiler feedpump recirculation valve faces some of the toughest conditions of any control valve in a power plant. The boiler feedpump
takes its suction from the deaerator at relatively low pressure, and increases the pressure to approximately 10% above the main steam
pressure. During startup or low load conditions, ow to the boiler may not be adequate to meet the minimum ow requirements of the boiler
feedpump.
Boiler feedpump recirculation valves protect the feedpump by ensuring adequate ow is passing through the pump at all times. These valves
will experience extreme cavitation caused by high temperatures and pressure drops.
Boiler Feedwater Startup and Regulating
Product Solutions
26 | Fisher
®
Pulp and Paper Solutions
Power and Steam Cycle
n MAXIMUM FLOW CONTROL Pneumatic actuation provides highly accurate step positioning and stable valve response.
n FLOW RESPONSE Optional accessories ensure quick step valve positioning for precise throughput and control.
n FLOW THROUGHPUT Valve design ensures high turndown even in extreme owrates.
n TIGHT SHUTOFF Advanced sealing technology provides tight shutoff and extends valve’s service life.
n CAVITATION MITIGATION Provides low-ow cavitation protection during startup and standard operation, and reduces
vibration and noise.
n POSITIONER FEEDBACK Linkage-less and non-contact feedback improves reliability in high vibration applications.
Fisher EH control valve, 585C actuator, FIELDVUE DVC6200
Power and Steam Cycle