Plant selection of control valve is introduced
In thermal power industry, the use of the control valve working condition of a special, simplified, electricity only water, steam cycle processes, but in this process to choose control valve is both simple and complex. Simple is simple process medium, only two kinds of water and steam, water is complex and steam temperature and pressure range is big, bring a series of problems such as: flashing, cavitation, erosion, corrosion, noise. But the first thing to consider is safety and reliability of the control valve. 1, the feed valve ( Lord, attached to the boiler feed water valve, compound feed water regulator) Control requirements: control boiler into the water to ensure steam evaporation, maintain boiler water level ( Lord, enclosed type boiler feed water valve system contains two control valves, one for the boiler starts to use, a water supply for normal use. Condition: the boiler startup pressure valve 100 - general 300 kilograms, flow is small, when normal operation of the pressure difference is small, large flow, flow adjustable ratio of 75:1 ~ 100:1. Valve requirements: WCB/WC9, for double valve cavitation resistance starting valve in the system requirements, to V closed ranks, the complex characteristics of the utilization of feed valve need to trim at the same time meet the needs of the boiler startup and normal operation. General valve selection for the failure. 2, boiler feed pump minimum flow circulation valve control requirements: the start and stop the operation of the boiler feed pump, eliminate because flow is too small, temperature increase, water pump cavitation damage. Old power stations have to use the minimum flow control valve switch type, as well as the use of mechanical pump valve automatic cycle. Condition: the pressure drop of - 160 350 kilograms, is the largest power station in the system under differential pressure valve, flow rate of 30% of normal flow. Valve requirements: resistance to cavitation, block structure, grade V seal level, the pump start and stop running when the valve work continuously, pump normal boot after the valve closed, valve is usually a failure. 3, high-low heater drain valve ( Feed water heater hydrophobic, condensed water heater drain) Control requirements: control the location of condensed water heater, timely will condensate discharge, high water discharge, the normal water level of hydrophobic. Condition: saturated water, heater control valve differential pressure is commonly between 6 - 30 kg, the last level of trap connected directly to the condenser or deaerator. Valve requirements: resistance to flash scour, V or VI levels of seal, valve is usually a failure. 4, deaerator water level control valve control requirements: provide traffic maintain the normal water level, deaerator eliminated by adding steam temperature gas dissolved in the water. Condition: startup phase flow is small, the differential temperature, normal flow, small pressure difference, working condition of similar feed valve. Valve requirements: effective during low flow resistance to cavitation. 5, desuperheating valve ( Attemperator) Control requirements: the high pressure water injection into the steam to steam temperature control requirements. Working conditions: water, differential pressure larger valve requirements: a variety of types: type nozzle, auxiliary atomization type, self-contained type and type to the clamp. 6, (the temperature and pressure-releasing valve High and low pressure bypass valve) Control requirements: the high temperature and high pressure steam to adjust to a certain temperature and pressure of steam, to provide a turbine bypass channel, boiler turbine and work independently. Condition: high temperature and high pressure steam, valve requirements: thermal shock, noise reduction, response quickly.