Effect of temperature and pressure reducer

I. Use of temperature and pressure reducer (temperature and pressure reducer)

 Used  as turbine bypass. When boiler and turbine operate under non-matching condition, the difference between steam generated by boiler and steam required by turbine can pass through primary and secondary temperature and pressure reducing devices connected in parallel with steam engine instead of steam turbine and cylinder circulation part.(i.e. HP and LP bypass devices) will raise the higher steam pressure and temperature to the required steam parameters, and then introduce the steam into the condenser connection system. The bypass system has good functions for cold, warm and hot start-up of the unit, protection of the reheater, prevention of overpressure of the unit and recovery of working medium, and plays an important role in the stability, safety and economy of the unit; It is used to convert superheated steam of high temperature and high pressure into secondary steam of temperature and pressure required by users through decompression system and desuperheating system to meet various user needs.
 

II. Structural characteristics of temperature reducer (temperature reducer)

 Our company has more than 30 years of design and manufacture of temperature and pressure reduction devices, and has successively produced and put into operation nearly 200 sets of temperature and pressure reducers, desuperheaters and pressure reducers, with flow rates ranging from 0.5t/h to 410t/h and primary steam pressures ranging from 1.3MPa to 19MPa. Primary steam temperature from 1300C to 5650C of various initial parameters, down to the user requirements of the secondary parameters. The device adopts international and domestic advanced technology in design and process manufacture, with reasonable design, novel structure, good performance and reliable operation.

 Our company design, manufacture of temperature and pressure reduction device put into operation so far, fully meet the requirements of various operating conditions of users, especially the design and manufacture of high difficulty temperature and pressure reduction device, by the majority of users. Our company design, manufacture of temperature and pressure reduction device, with a unique style, horizontal layout, by the pressure reduction system, spray system, safety protection system and automatic control system, its structural characteristics are briefly described as follows:

Pressure relief system: pressure relief valves with three different structural forms

 Double-seat pressure reducing valve is mostly used for t 4500C,P 4.3MPa conventional temperature and pressure reducing device. Medium throttle channel for the double-seat form, large flow area, valve stem throttle hardfacing, valve stem material for stainless steel or nitride steel, after decades of testing, double-seat pressure relief valve as long as the use of the above parameters, no abnormal problems have occurred.

 Plunger type single-seat pressure relief valve, mostly used for pressure 9.8MPa, temperature 4500C or higher parameters. The valve is an improved product of imported company. The valve stem and valve clack are integrated. A plurality of flow passages are opened at the valve clack to decompose the steam flow into multiple plum blossom flow passages, which can prevent strong vibration and reduce noise in the valve. A curved porous bell jar is set in the valve to prevent steam from directly impacting the inner surface of the valve body. It has the characteristics of low noise, small vibration, good sealing performance, good pressure reduction effect and adjustment characteristics, and long service life. Hebei Thermal Power Plant, Tangshan Thermal Power Plant has been adopted, reflecting good.

 Desuperheating  and pressure reducing valve, mostly used for pressure> 9.8MPa, temperature> 4500C, this valve belongs to one of the imported technical products, the main feature is that the desuperheating and pressure reducing process is completed in the same valve, the valve stem and valve clack are integrated, a plurality of plum blossom channels can be opened at the valve clack, the valve is small in size, low in noise, small in vibration, good in steam atomization effect, simple in overall structure, desuperheating water is sprayed from bottom to top, and a curved porous bell jar is arranged at the valve core position, steam and water are mixed in the porous bell jar to form, And exchange in turbulent flow area, reduce the damage to valve body caused by thermal stress caused by rapid change of steam and water. Co-Cr-W hard alloy surfacing welding on valve sealing surface has high wear resistance and corrosion resistance. Changzhou Thermal Power Plant has been put into operation since 1996, and the effect is very good.

 Desuperheating water spray system: special structure nozzle, can be configured with two structural forms of valves

 Nozzle, the desuperheating and decompression device produced by our company, is characterized by the nozzle. The steam after decompression enters the desuperheating system. The flute-shaped pipe nozzle was used early. The desuperheating water sprayed by the flute-shaped

 Our company introduced technology, the use of special technology designed axial swirl mechanical atomization nozzle, this nozzle by the nozzle body, swirl sheet, water disc and other parts. Water in the nozzle through the water disc, swirl plate after high-speed rotation spray mist spray, and high temperature steam quickly mixed to reach the temperature required for secondary steam.

 The swirl vane nozzle is characterized by short mixing time of water and steam, sufficient mixing, avoiding water in outlet steam and ensuring the quality of secondary steam.

The feedwater distribution valve is equipped with two channels, one channel leads to the desuperheater through the nozzle to reduce the temperature of secondary steam, and the other channel leads to the deaerator. Conventional desuperheating and pressure-reducing devices are configured as such.

 Control valve is configured. The outlet of control valve is directly led to desuperheater through nozzle to reduce the temperature of secondary steam. When small flow water spray (1.5t/h) is applied, ordinary control valve is applicable; high pressure bypass, low pressure bypass and special temperature and pressure reduction device (such as Hebei Thermal Power Plant) shall select multi-stage throttle high pressure difference control valve.

Users can choose the valve structure form in the desuperheating system arbitrarily.

Safety protection system:

 Steam enters the secondary steam pipeline after passing through the desuperheater, where steam and desuperheated water are fully mixed. The device is equipped with safety protection device, thermometer and pressure gauge to monitor the pressure and temperature locally.

 Our   company does not supply the exhaust pipe of the safety valve outlet, which is taken care of by the user. The distance between the exhaust pipe and the center of the safety valve should be as short as possible to reduce the exhaust force generated during the action of the safety valve. The size is required in the system diagram of the temperature and pressure reduction device; Fixed support shall be installed under the steam pipeline safety valve, sliding support shall be installed in other places, drain point shall be installed at the secondary steam outlet, which shall be considered by the user according to the specific situation. For the specific description of the safety valve, see the safety valve product instruction manual; the safety protection device of this device is based on different technical parameters of secondary steam required by the user. Our company can adopt full-open spring safety valve or impulse safety device composed of pulse safety valve and main safety valve respectively. When the steam pressure after desuperheating and decompression exceeds the allowable high value, the safety valve will automatically trip and exhaust the steam to the atmosphere, so that the steam pressure in the pipeline is maintained within the allowable value, ensuring the safe operation of the desuperheating and decompression device.

automatic control system

 Steam   pressure regulation is assisted by pressure transmitter, which converts steam pressure fluctuation into electric signal, which is amplified by electronic regulator and transmitted to servo motor to drive pressure reducing valve to achieve the purpose of pressure reduction; steam temperature regulation is driven by servo motor to drive water supply distribution valve (or regulating valve) to adjust water spray amount to achieve the purpose of temperature reduction; steam temperature change causes thermoelectric potential change of thermocouple, which is amplified by electronic temperature regulator and transmitted to servo motor for temperature adjustment and fine adjustment; When the load changes, the action of the pressure reducing valve can quickly keep up, but the reaction of the temperature sensor (thermocouple) is not timely enough, so the dynamic contact device DL from the pressure regulator to the temperature regulator is added, so that the feed water distribution valve and the pressure reducing valve play a coarse adjustment role at the same time.

Note:

 Our company can undertake the design and manufacture of automatic control equipment according to user requirements to achieve the purpose of process control. Users can also solve automatic control equipment by themselves.

Electric actuators:

 Pressure relief valve, water distribution valve, regulating valve equipped with actuators if the angle of travel electric actuator, the general device does not provide, but users need my company complete, we can supply complete sets;

If the above valves are equipped with linear actuators, the user can also specify the actuator manufacturer, but the actuator connection size and thrust force must be provided.
 

III. Use and maintenance of temperature and pressure reducer (temperature and pressure reducer) Installation

 After  arrival, the temperature and pressure reducing device must be properly kept, and moisture corrosion and foreign matters must not enter the device; the spring safety valve has been set to the specified starting pressure and has been lead sealed at the time of delivery, so it is not necessary to disassemble and install it directly; Impulse type safety valve, pressure reducing valve, feedwater distribution valve (or regulating valve), check valve, stop valve and throttle valve must be disassembled on site, anti-rust oil must be removed, packing must be installed, packing gland must be compressed, and the valve must be completely clean (30% of valve accidents are caused by dirty valve). All connecting pipes, pressure gauge elbows, desuperheaters and steam pipelines must be clean. If the user requirements for the above valve installation without disassembly, then our company according to assembly without disassembly, valve to the site can be installed directly without disassembly;

Before installation, the pipe of desuperheater must be kept clean, and the desuperheating water nozzle must not be blocked. The diameter of the nozzle is small, and it is easy to be blocked by foreign matters. If the nozzle hole is blocked, the operation condition is not good, and even the overheating pipe explosion may endanger the safety of personnel and equipment;

 Check   whether the DKJ actuator or straight stroke actuator of pressure reducing valve and feed water distribution valve (regulating valve) is consistent with the model required in the drawing. The connection between valve and angular stroke actuator shall make the full stroke of valve correspond to the crank rotation of actuator 900. When the lever of pressure reducing valve and feed water distribution valve (regulating valve) is in the middle position, the crank mechanism shall be parallel to it, so that the valve disc displacement of valve can be proportional to the displacement of actuator. The distance between the valve and each stroke actuator shall not exceed 5M, and the crank rotation angle shall not exceed 900.

 No safety valve shall be installed during hydrostatic test, and the flange opening shall be blocked by blocking plate. The thickness of blocking plate shall be consistent with that of flange. The two shall be connected by bolts. After hydrostatic test, the blocking plate shall be removed and then the safety valve shall be installed. The blocking plate shall be taken care of by the user.

 For assembly and welding on installation site, attention must be paid to the material of connecting pipes. Alloy steel must be preheated before welding, annealed after welding, and 100% nondestructive damage control shall be carried out. Heat treatment shall not be carried out if the wall thickness of steel pipe is less than 20mm, and heat treatment shall be carried out if the wall thickness is greater than 20mm, but 100% nondestructive inspection shall be carried out;

 For the feed water distribution valve (regulating valve) and pressure relief valve lever hole is not enough when the application can be another hole, in order to match with the actuator mechanism, valve and actuator between the connecting rod by the user according to the field situation from the amount.

IV. Commissioning, operation and maintenance of temperature and pressure reducer (temperature and pressure reducing device)

 Closed circuit valve and stop valve (No. 8 and No. 12) shall be closed before operation of temperature and pressure reducing device. The pipeline before closed circuit valve (No. 12) shall be flushed clean. After flushing, open pressure reducing valve (No. 3) by 10-20%;

 Open drain valve (No. 14) and then open desuperheating water valve (No. 8) to check whether desuperheating system is normal;

After inspection, warm up the pipe. First open the closed valve (No. 12) and preheat the whole device with steam pressure not exceeding 0.0196-0.049MPa. The preheating time shall not be less than 30 minutes.(It is also allowed to preheat with other heat sources). After preheating, gradually open the closed valve (No. 12) to boost the pressure at the rate of 0.098-0.147MPa per minute, and gradually close the drain valve (No. 14). At the same time, manually operate the DKJ actuator, open all throttle valves to drive the pressure reducing valve and feedwater distribution valve (or regulating valve) to steadily increase the outlet steam parameters and keep them within the specified range; When the pressure rises to 75% of the safety valve opening pressure value, you can move the safety valve handle (referring to the spring safety valve) to open the valve, and the opening height is 1/4d.(d is the diameter of the throat of the safety valve) exhaust steam to the outside and clean the impurities in the safety valve. When the pressure reaches the preset opening pressure, set the safety valve. For impulse safety valve, lift the lever of impulse safety valve (No. 5) by hand when the pressure reaches 50% of the rated opening pressure, check the flexibility and tightness of the action of the main safety valve, and set the safety valve when the pressure reaches the specified pressure (according to the safety monitoring procedures of pressure window). Please refer to the instruction manual;

 Under rated pressure, steam traps (No.13 and No.15) shall be put into operation, stop valve (No.14) shall be closed, automatic control shall be put into operation after drainage and adjustment work is completed, please refer to relevant equipment instructions for installation, calibration, operation and maintenance of automatic control equipment; when inlet steam flow of desuperheating and pressure reducing device decreases, throttle valve (No.7) at inlet of desuperheating water shall be gradually reduced to increase resistance drop;

 The device shall be inspected regularly, and the worn parts such as pressure reducing valve, water supply distribution valve, regulating valve, stop valve, check valve and throttle valve shall be repaired or replaced in time, otherwise leakage and vibration of equipment will be caused, and noise of equipment operation will be increased;

The desuperheating water nozzle of the desuperheater must be unblocked, because there is only one hole at its outlet. If the desuperheating water cannot be sprayed or the amount of water sprayed is reduced after blocking, the desuperheating effect will be affected or the thermometer will be burned and the thermal equipment will be damaged. Therefore, once blocking is found during commissioning, it must be stopped and repaired in time;

 All kinds of electric actuators equipped with valves shall be debugged in strict accordance with the installation and debugging instructions of the electric actuator manufacturer.