Automatic recirculation valve

Application

Automatic recirculation valve, ARV for short, is a multi-functional valve. Primary purpose of ARV is to ensure that pre-defined minimum flow passes through centrifugal pump in low load operation. In low flow operation, feedwater pump is running at low efficiency, most of the energy consumed is converted into heat. There is no sufficient of water for lubrication due to partial evaporation of water trapped in pump. Automatic recirculation valve protects pump from damage by overheating and cavitation.

Another function of ARV is to protect pump from reverse flow by serving as check valve. In thermal power plant, boiler feed pumps are in parallel design with one set in stand-by status. During startup stage, pump is put into operation one by one. ARV isolates standby unit from backflow. It enables pump swap to happen without water hammer damage.

Working principle

Core part of automatic recirculation valve is a flow sensitive, spring loaded valve disc, which is lifted and held in certain position according to flow rate. In normal operation, disc rises to top and bypass is closed. When process flow is lower than preset flow rate, main disc movement will be transferred to bypass disc through a lever, bypass is opened. Part of water is directly to deaerator feedwater tank through bypass path. When process flow continues to decrease until main flow is closed, bypass is in full open position to enable minimum flow to pass through centrifugal pump.

Advantages

• Self-contained mechanical device, no need for external power source.
• Recirculation path will only be opened in low flow situation to minimize energy consumption.
• Modulating valve disc, which is interconnected with bypass.
• Hard sealing surface cladded with alloy to provide excellent resistance to heat, wearing, and corrosion.
• Multiple function: flow perception, recirculation flow control, non-return service, bypass pressure reduction.

Specification

Standard: ASME B16.34
Pressure: PN160～PN320
Size: DN50～DN300
Material: WCB, 25#, ASTM A216 WCB, ASTM A105
Temperature: WCB:-29℃～425℃
Connection: flange