Spring Pull-Out Sink Faucet,Pull Out Spring Kitchen Tap,Pull Out Spring Neck Taps,Spring Pull Out Sink Faucet Heshan Janno Kitchen and Bath Technology Co.,Ltd , https://www.janno-ks.com
Feed water system thermal system and capacity
(1) Minimum flow system After the high-pressure feed pump is started (or in operation) and the outlet valve is not opened (or closed), most of the work done by the prime mover is converted into heat and the feed water temperature at the pump inlet will increase. The temperature exceeds the permissible temperature of the saturated vapor pressure of the water in the de-oxygening tank, vaporization will occur. To prevent this phenomenon from damaging the feedwater pump, a portion of the flow of feedwater is led out before the outlet valve of the feedwater pump, The heat generated so that the feed pump does not occur in the low-flow operation of the vaporization. Lead to the part of the flow that the so-called pump minimum flow (or recirculation flow). The recirculation system including the minimum flow valve is called the minimum flow system. The minimum flow range is determined by calculation and in combination with the test. Domestic and foreign information shows, and hydraulic, NPSHr, speed, water temperature, operating clearance and structure design. The general minimum flow rate is 20% ~ 30% of the pump design point flow. For supercritical units (above 600MW), the minimum flow rate of the feed water pump is continuously adjusted instead of the two-point switch, so as to avoid large fluctuations in the system when the minimum flow rate is running. Practice has proved that the minimum flow valve to determine the parameters and system layout, related to the safe and stable operation of the feed pump. (2) Warm pump system From theory and design point of view, the correct operating procedure is that the high pressure boiler feed pump should be warm pump before start-up, especially for the pneumatic feed pump group which should be used for low speed crank before starting, It is particularly important to avoid jamming and grinding as a result of thermal deformation in the pump body where hot water enters the cold state and thereby damaging parts of the pump. Of course, in an emergency, too late to start the pump that is not entirely impossible pump. From the experience of pneumatic pumps used by many power plants in our country, there are many cases of jamming and grinding in the segmented pump core without heating pump, and it is forced to execute the start-up procedure of directing the small steam engine. Internal pump is a volute type feed pump, to adapt to low-speed crankshaft and cold start much better. The supercritical unit uses the inner pump to axially split the warm pump system of the volute type high pressure feed water pump, the system is simple and easy to operate. The current domestic subcritical unit of the pump system is also changed to this method. (3) Feedwater pump group controllable high-capacity large-capacity unit, the feedwater pump group requires more and more controllable degree. In addition to the normal temperature, pressure and flow rate to be monitored, the vibration (including shaft vibration, axial force, speed, noise and failure) should be monitored and input into the computer for analysis. , Easy to fault analysis, to ensure safe and reliable pump operation, to meet the requirements of the unit full of hair growth, (4) the configuration of the water pump capacity of supercritical units, the current configuration at home and abroad in two ways: a general The unit-based thermal power unit configuration is 2 × 50% pneumatic pump unit + 1 × 30% starting backup electric pump group, there are 2 × 50% pneumatic pump group + 1 × 30% starting electric pump group. Pump, and then as a backup pump, so electric pump head can be greatly reduced, with the configuration of the motor, gearbox (gearbox or hydraulic coupling) capacity can also be reduced, thus reducing the project cost.Currently, Foreign large-scale supercritical units have adopted l × 100% pneumatic pump + 1 × 30% start-up pump, and stable operation in the million-kilowatt-class units, the premise is l00% capacity high-pressure feed water pump must be safe By.