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As we all know, the valve in the pipe network system is called the "important throat", in the event of failure problems will easily affect the design function to achieve or even lead to leakage, ranging from a certain amount of Economic losses, heavy then have a serious impact on the follow-up of production operations. According to the statistics of relevant domestic production accidents, 35% of production accidents are caused by valve failures.
Valves are the main fluid control components in the thermal power plant's water and steam system and are used to regulate the flow or pressure of the medium. Features include shutting down or turning on media, controlling flow, changing flow, changing media flow, preventing media backflow, controlling pressure or relieving pressure. The valve plays an important controlling role in the plant's system.
The correct installation of the valve, the correct operation, timely maintenance, can effectively prevent the valve running, run, drip, drain, reduce material consumption, energy consumption, to ensure the safe and effective operation of production equipment. Now on the valve installation process and technology talk about some experience.
First, the main technical performance of the valve 1 strength performance. The so-called strength of the performance refers to the normal operation of the pipeline system, the valve pressure on the media capacity. In the course of normal use, since the valve is a mechanical component under internal pressure and plays a very important role in the thermal power plant, it is necessary to ensure that the valve has enough strength so as to ensure the long-term performance of the piping system use.
2 sealing performance. Valve sealing performance refers to the ability of the valve to prevent media leakage. This is the valve in the actual use of the process, the most important technical performance indicators. If the piping system is in use, the valve sealing performance is not good enough, making the media pipeline leaks, then this not only brought some economic losses to the enterprise, but also may cause serious environmental impact on the surrounding influences. Therefore, when we seal the valve, we must proceed from the following three parts, effectively improve the sealing of the valve to ensure the normal operation of the pipeline system.
(1) the valve in the opening and closing parts and the contact between the seat part of a certain seal.
(2) To ensure the tightness between packing and valve stem and packing.
(3) Make the appropriate seal at the connection between the valve body and the stem, and check the tightness of the seal.
At present, there are mainly two forms of leakage occurring during the normal operation of the pipeline system, namely, the leakage and the leakage of the pipeline system respectively. Leakage due to the main parts of the valve itself connected parts of the problem, making the medium leak from the valve to the valve. The internal leakage is due to the valve closed due to lax, this leakage is mainly due to operator negligence caused. Therefore, the pipeline system operation process, we must ensure that the valve has a reliable seal.
Second, the valve of the internal process Once the valve is opened, the valve and valve seat contact between the sealing surface will therefore be separated accordingly the sealing surface of such valves mechanical wear will be smaller than other types of valves, Then the sealing effect is relatively good. However, the separate sealing surface increases the possibility of dust particles adhering to the surface. This can be avoided by replacing the valve disc with a ceramic ball or steel ball. For most of the globe valves, the valve flap and seat are convenient for replacement and repair, and usually do not need to disassemble the whole valve. Therefore, this type of valve for pipe and valve is connected between the welding site environment is more applicable. Compared with other types of valves, the minimum flow resistance of the stop valve to be larger, if the valve stem and the corresponding valve body structure according to the actual flow of fluid to the inlet and outlet channels, the minimum flow resistance of the globe valve can be more Good improvement. In addition, the closing valve also has a smaller closing stroke and opening stroke, the sealing surface can withstand frequent opening and closing, it is also more suitable for high-frequency opening and closing the scene of the operating environment.
Power plant gate valve is mainly used to cut off the internal fluid medium. According to the actual structure of the gate, gate valve can be divided into wedge, parallel gate valve, and one of the parallel gate valve and parallel single gate and parallel double gate. For a gate valve, when the valve is fully open, the pressure loss of the fluid operation is minimal; however, when the valve is in a partially throttled state, ie, the gate is partially open, high-speed fluid flow causes the gate to vibrate , While the vibration of the valve seat and the connection between the gate seal will form a certain degree of damage. Therefore, if the gate valve is used for throttling, the gate will be eroded. Therefore, the gate valve is not usually used to regulate the flow, and is mainly used for blocking, that is, an operating environment that does not require frequent switching.
In addition to the cut-off valve, gate valve, the power plant with more valves and check valves , also known as check valve, check valve . As the name implies, the check valve is used to prevent the backflow of fluid valve, mainly used in the pipeline convection to have the design requirements and only allows one-way flow of the operating environment, when the fluid flow direction and the design or requirements of the opposite direction of flow, The valve disc will have a certain impact on the valve so that it immediately cut off the flow. Check valve is divided into swing Kai, lift and butterfly three types. Among them, butterfly check valve sealing is poor, in practical applications has been very small. Swing check valve, is based on the hinge mechanism, the valve design in the hinge mechanism around the valve seat outside the fixed axis for rotational movement to achieve the opening and closing of the function, to ensure that the valve flap can accurately exercise To the seat sealing surface, so that both form a good contact and seal. As for the lift check valve, the valve flap is along the centerline of the valve for lifting movements, and its function is mainly to rely on the pressure of the fluid operation will lift the valve, and the pressure of the fluid back to promote Valve flap down to the seat to cut off, to prevent the function of reflux.
Third, the valve installation process 1 before installation, the appearance of the valve inspection, no cracks, trachoma, mechanical damage. Check the nameplate intact, and meet the requirements. Remove the residue from the valve. Turn the valve stem to see if it is flexible and easy to install, to avoid invalid work. After the inspection is completed, clean the pipe connected to the valve, the available compressed air to blow away the pipe slag and other debris.
2. Installation, should be strictly in accordance with the installation instructions provided by the manufacturer. When installing the threaded valve, seal packing should be wrapped around the pipe thread, to avoid the accumulation of the valve, affecting the flow of media. When installing the flange valve, pay attention to the symmetrical tightening according to the specified torque so as to avoid uneven tightening torque and damage to the valve. Valve in the body direction signs, the valve should flow into and out of the correct direction of installation. For example, check valves, stop valves, throttle valves , pressure relief valve , if fitted anti-flip, will lose the valve in the piping system function, or even dangerous. Valve insulation installation. Where the transport medium prone to condensation in the ambient temperature caking phenomenon, should be combined with pipelines, with heat tracing, to prevent freezing valve.
3. After installation, the valve should be checked. All valves should be the appearance of inspection, inspection items include: valve type, size, nameplate, number, quality assurance level, the material should be consistent with drawing design requirements. External and visible surfaces, threads, sealing surface should be no damage, corrosion phenomenon, casting the body should be no blisters, shrinkage, porosity, cracks and other harmful defects, forged valve should be no cracks, wrinkles, heavy skin, rust, Depression and so on. The batch of valves to the scene, the batch should be based on the same manufacturer, the same size, the same model in proportion to spot checks strength test and tightness test.
4. For the pipeline transporting flammable and explosive gases, purge and purge the pipeline with nitrogen before the pipeline is put into production, to prevent the medium of transmission and the oxygen in the pipeline from forming the explosion limit and avoid the explosion phenomenon .
5. Attention to the site material storage. First, all kinds of material valves should be stacked separately, carbon steel valves allow open storage, but to padded flat wood and tarpaulin, all valves to check the closure of the two ports, small pipe fittings and valves on the shelves . Second, all stored materials should be clearly marked, indicating the specifications, materials, certificate number, quantity and so on. Third, taking into account the on-site transport routes, product protection and other factors, the valve before the installation, the valve engineer to confirm the need to disassemble certain parts of the valve. The disassembled parts shall be uniformly registered, protected and managed by the valve team according to the valve name, specifications and valve position numbers so as to avoid disorder and unnecessary damage.
IV Conclusion Now the valve in the process of using, there are still many problems, which not only affects the normal operation of the pipeline system, but also may cause pollution to the surrounding environment, serious case may also be a safety accident. Therefore, when installing and constructing, the construction personnel must strictly check the quality of each part of the valve and adopt certain protective measures for some important parts. Only in this way can the normal operation of the pipeline system be ensured.
Discussion on Installation Technology and Technology of Boiler Pipeline Valve in Power Plant
Abstract: With the continuous improvement of science and technology, the types of boiler pipe valves are gradually increasing. Because of their different structural forms, driving methods and manufacturing materials, etc., the practical application of boiler pipe valves Also have different effects. Based on this, this paper analyzes the actual process of power plant pipeline valves, with a view to provide reference for the subsequent research on power plant pipeline valves.