A steam trap pipe heater

Abstract

A heat tracer for a steam drain pipe comprises a heat tracer inner pipe, an outer heat tracer pipe is arranged outside the heat tracer inner pipe, a chamber is formed between the heat tracer inner pipe and the outer heat tracer pipe, the lower part of the outer heat tracer pipe is welded to the lower part of the inner heat tracer pipe, the upper part of the outer heat tracer pipe is connected to the outer pipe end cover, the outer pipe end cover is located outside the inner heat tracer pipe, the upper half of the outer pipe end cover is a hollow annular chamber, a steam inlet hole is arranged at the edge of the chamber, a plurality of flow guide holes are evenly distributed along the annular direction at the bottom of the chamber, the flow guide holes are communicated with the chamber, a steam outlet hole is arranged at the lower side of the outer heat tracer pipe, and the steam outlet hole is communicated with the chamber. The present invention avoids fatigue failure of the drain pipe weld caused by temperature alternation without significantly affecting the overall efficiency and output of the unit, so as to solve the problem of thermal fatigue of the steam drain pipe.

Description

Technical Field

[0001] The invention relates to the technical field of operation and maintenance of nuclear power and thermal power plants, and in particular to a heat tracer for a steam drain pipe. Background Art

[0002] The steam turbine of a pressurized water reactor nuclear power plant is a saturated steam turbine. The steam extraction humidity of the steam turbine is high. During the operation of the unit, there is a lot of water in the main steam and steam turbine extraction pipes. In order to ensure the safety of steam pipes and equipment and improve the efficiency of the steam system, the water in the steam system must be discharged in time. Therefore, nuclear power plants use a large number of steam traps and steam traps with water-repellent and steam-blocking functions, and a certain amount of steam traps are also set up in the steam system of thermal power plants. The temperature and pressure of the main steam and steam turbine extraction pipes are relatively high, and the pressure and temperature inside the steam trap and the pipes in front of it are relatively high; the water is discharged to the condenser through the steam trap, and the temperature and pressure of the condenser are relatively low. The intermittent opening of the steam trap and the steam trap will cause the subsequent pipelines to alternate between cold and hot to generate thermal stress, causing cracking and leakage in weak links. There have been many steam trap pipe thermal fatigue failure accidents in nuclear power plants and nuclear power plants.

[0003] Controlling the alternating thermal stress of the steam trap and the pipeline after the steam trap below the allowable fatigue stress is an effective way to solve the problem of thermal fatigue failure. At present, the main methods to reduce the thermal fatigue risk of steam trap pipelines are:

[0004] (1) Optimize the structure of the steam trap to improve the fluidity of the steam trap, the stability of the flow field and the uniformity of the temperature distribution;

[0005] (2) Optimize the pipeline structure, improve the support and hanger arrangement, tee and elbow structure, pipeline diameter and wall thickness of the drainage pipeline, and reduce the thermal stress level of the pipeline from the aspects of structural form and spatial layout;

[0006] (3) Optimize pipeline materials. Different materials have different thermal expansion coefficients, elastic moduli, and fatigue strengths under high temperature environments. Selecting more suitable drainage pipeline materials is also an important means to reduce thermal fatigue risks.

[0007] (4) Thermal system optimization: By optimizing the thermal system, reducing the amount of drainage, reducing the frequency of drainage or improving the smoothness of drainage, it is also a means to reduce the risk of thermal fatigue of pipelines.

[0008] The above methods (1), (2), and (4) are mainly used to alleviate pipeline thermal stress to a certain extent. Due to the large workload of the transformation, complex thermal and structural mechanics simulation analysis is required in advance to verify the effectiveness of the implementation plan and ensure that there will be no unacceptable impact on the original system function. Method (3) mainly reduces the risk of fatigue failure by improving the fatigue resistance of the material, and the effect is relatively limited. Summary of the invention

[0009] In order to overcome the above technical problems, the purpose of the present invention is to provide a steam drain pipe heater, which can avoid fatigue failure of the drain pipe weld caused by temperature alternation without significantly affecting the overall efficiency and output of the unit, so as to solve the thermal fatigue problem of the steam drain pipe.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A heater for a steam drain pipe comprises a heater inner tube 1, an outer heater tube 2 is arranged on the outer side of the heater inner tube 1, a chamber is formed between the heater inner tube 1 and the outer heater tube 2, the lower part of the heater outer tube 2 is welded to the lower part of the heater inner tube 1, the upper part of the heater outer tube 2 is connected to the outer tube end cover 3, the outer tube end cover 3 is located on the outer side of the heater inner tube 1, the upper half of the outer tube end cover 3 is a hollow annular chamber, a steam inlet hole is opened at the edge of the chamber, a plurality of guide holes are evenly distributed along the annular direction at the bottom of the chamber, the guide holes are communicated with the chamber, a steam outlet hole is opened on the lower side of the heater outer tube 2, and the steam outlet hole is communicated with the chamber.

[0012] The outer tube 2 of the heater is threadedly connected to the outer tube end cover 3.

[0013] The chambers of the inner tube 1 and the outer tube 2 of the heater are relatively fixed by a support member 8, and a plurality of the support members 8 are distributed in the tube at equal distances.

[0014] A compression cover 4 is provided on the outer tube end cover 3 , and a double wedge-shaped sealing ring 5 is provided between the outer tube end cover 3 , the compression cover 4 and the inner tube 1 of the heater.

[0015] The wedge-shaped surface of one end of the sealing ring 5 is fastened by the upper part of the outer tube end cover 3, and the other end is fastened by the clamping cover 4; the outer tube end cover 3 and the clamping cover 4 are positioned and connected by clamping bolts 6 and clamping nuts 7.

[0016] The clamping cover 4 is positioned and connected to the outer tube end cover 3 of the heater by means of clamping bolts and clamping nuts.

[0017] The inner tube 1, the outer tube 2 and the outer tube end cover 3 of the heater are separable structures. During installation, the outer tube 2 of the heater is welded to the downstream pipeline of the steam trap, and the outer tube end cover 3 is mechanically fastened to the upstream pipeline of the steam trap.

[0018] Beneficial effects of the present invention:

[0019] (1) The heat source of the tracing heat of the present invention comes from the superheated steam of the high-parameter steam system of the power plant, which is discharged to the low-parameter steam-water system of the power plant after cooling. Power is provided by the pressure difference between different systems. There is no need to install active equipment such as pumps, fans, boilers, etc., and the cooled steam returns to the thermal circulation system of the power plant again, which saves energy and is safe and reliable.

[0020] (2) Compared with electric heating heat tracing pipes, this patent does not involve electrical equipment and utilizes the original system steam of the power plant to heat the drain pipes, which greatly reduces the operation and maintenance costs.

[0021] (3) The medium temperature of the high-parameter steam system of a nuclear power plant is very different from the medium temperature of the drain pipe, which is sensitive to thermal fatigue. By extracting steam from the high-parameter steam system to heat the drain pipe, the temperature alternation problem of the weld behind the drain trap caused by intermittent draining can be effectively avoided, thereby fundamentally reducing thermal fatigue stress and protecting the pipe and weld to the greatest extent.

[0022] (4) The present invention adopts a tube-in-tube form, which can fully protect the heated pipe. Before installation, the outer tube, inner tube and outer tube end cover of the heater are independent structures, which are installed separately during installation, which is convenient and simple, and can be disassembled and regularly inspected and maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the heating system principle;

[0024] Figure 2 It is the structural schematic diagram of the heater;

[0025] Figure 3 It is a schematic diagram of the structural section of the heater;

[0026] Figure 4 It is the cross-section diagram at A-A;

[0027] Figure 5 This is the cross-sectional view at B-B.

[0028] 1-heater inner tube (heated drain pipe), 2-heater outer tube, 3-heater outer tube end cover, 4-compression cover, 5-double wedge sealing ring, 6-compression bolt, 7-compression nut, 8-support. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with embodiments.

[0030] like Figure 1 The tracer of the present invention is installed on the steam drain pipe section where fatigue may occur. Superheated steam is introduced from the steam system with high superheat and pressure in the power plant (such as the outlet of the steam-water separation reheater of the nuclear power plant, the main steam pipeline of the thermal power plant, etc.), and then enters the tracer to heat the drain pipeline. The cooled superheated steam is discharged into the low-parameter steam-water system (such as the No. 3 low-pressure extraction pipeline of the nuclear power plant, the cold reheat pipeline of the thermal power plant, etc.). The high-parameter system and the low-parameter system automatically generate steam flow due to the pressure difference, and the cooled superheated steam is discharged into the low-parameter system for waste heat utilization.

[0031] See also Figures 1 to 5A heat tracer for steam drain pipes, which introduces superheated steam from a steam system with high superheat and pressure in a power plant, and then enters the heat tracer to heat the drain pipe. The superheated steam cooled under the pressure difference of the system is automatically discharged into a low-parameter steam-water system for waste heat utilization. The heat tracer structure includes a heat tracer inner tube 1, a heat tracer outer tube 2, a heat tracer outer tube end cover 3, a clamping cover 4, a double wedge-shaped sealing ring 5, a clamping bolt 6, a clamping nut 7, and a support 8. There is a support 8 between the heat tracer inner tube 1 and the outer tube 2.

[0032] The lower part of the outer tube 2 of the heater is welded to the inner tube 1 of the heater (heated drain pipe), and the inlet end of the heater is mechanically fastened to the heated drain pipe, and the fastened end is sealed by a double wedge-shaped sealing ring. The outer tube 2 of the heater is connected to the outer tube end cover 3 by threads; there is a double wedge-shaped sealing ring 5 between the outer tube end cover 3 of the heater and the compression cover 4 and the pipeline; the compression cover 4 and the outer tube end cover 3 of the heater are positioned and connected by compression bolts 6 and compression nuts 7.

[0033] The inner tube 1, outer tube 2 and outer tube end cap 3 of the heater are separable structures. The inner tube 1 and the outer tube 2 of the heater are relatively fixed by the support 8. The support 8 is distributed in the tube at equal distances, so that the inner and outer tubes are basically coaxial and the vibration amplitude of the inner tube under the action of airflow is limited.

[0034] During installation, the support member 8 is directly welded to the inner tube 1 of the heater, and then the outer tube 2 of the heater is installed on the drain pipe after the steam trap, and the outer tube 2 of the heater is welded to the inner tube 1 of the heater.

[0035] The number of the support members 8 is determined according to the length of the steam trap, and multiple support members 8 are distributed at equal intervals in the pipe.

[0036] During installation, the outer tube end cover 3, the double wedge-shaped sealing ring 5 and the compression cover 4 are mounted on the drain pipe in front of the steam trap. The outer tube end cover 3 is installed on the outer tube 2 of the heater through threaded connection so that the weld is inside the heater.

[0037] Finally, the outer tube end cover 3 of the heater and the external pipe are sealed with a double wedge sealing ring 5, and are positioned and connected with a clamping bolt 6 and a clamping nut 7, and a pre-tightening force is applied so that the double wedge sealing ring 5 is subjected to radial and axial forces at the same time to prevent steam leakage.

[0038] The upper part of the outer tube end cover 3 of the heat tracer is a hollow chamber, with a steam inlet hole for introducing superheated steam on the edge, and multiple flow guide holes are symmetrically distributed along the axial direction on the bottom of the chamber, and 8 holes are designed in the figure. This is to ensure that the steam enters the heat exchanger evenly, improve the flow stability and heat exchange uniformity. The lower part of the outer tube end cover 3 of the heat tracer is provided with an internal thread, which is connected to the outer tube through a thread and sealed.

[0039] During operation, high-temperature steam enters the end cover chamber through the steam inlet hole, then evenly enters the heater through the guide hole to heat the pipe, and comes out from the steam outlet hole, so that the heater is always in a heating state.

Claims

1. A steam trap pipe heater, characterized in that: The invention comprises a heat tracer inner tube (1), an outer heat tracer outer tube (2) is arranged outside the heat tracer inner tube (1), a chamber is formed between the heat tracer inner tube (1) and the outer heat tracer outer tube (2), the lower part of the heat tracer outer tube (2) is welded to the lower part of the heat tracer inner tube (1), the upper part of the heat tracer outer tube (2) is connected to the outer tube end cover (3), the outer tube end cover (3) is located outside the heat tracer inner tube (1), the upper half of the outer tube end cover (3) is a hollow annular chamber, a steam inlet hole is provided at the edge of the chamber, a plurality of flow guide holes are evenly distributed along the annular direction at the bottom of the chamber, the flow guide holes are communicated with the chamber, a steam outlet hole is provided at the lower side of the heat tracer outer tube (2), the steam outlet hole is communicated with the chamber; The outer tube (2) of the heater is threadedly connected to the outer tube end cover (3); A compression cover (4) is provided on the outer tube end cover (3), and a double wedge-shaped sealing ring (5) is provided between the outer tube end cover (3), the compression cover (4) and the inner tube (1) of the heater; The inner tube (1) of the heater, the outer tube (2) of the heater and the outer tube end cover (3) are separable structures. During installation, the outer tube (2) of the heater is welded to the downstream pipeline of the steam trap, and the outer tube end cover (3) is mechanically fastened to the upstream pipeline of the steam trap.

2. A steam trap pipe heater according to claim 1, characterized in that: The chambers of the inner tube (1) and the outer tube (2) of the heater are relatively fixed via a support member (8), and a plurality of the support members (8) are distributed in the tube at equal distances.

3. A steam trap pipe heater according to claim 1, characterized in that: The wedge-shaped surface at one end of the sealing ring (5) is fastened to the upper part of the outer tube end cover (3), and the other end is fastened to the pressing cover (4); the outer tube end cover (3) and the pressing cover (4) are positioned and connected by a pressing bolt (6) and a pressing nut (7).

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