CN111970776A - High-frequency induction heating device for through hole hot-tightening bolt of steam turbine - Google Patents

Abstract

The invention provides a high-frequency induction heating device for through-hole hot-tightening bolts of steam turbines. The water pipe is connected with the high-frequency host, the water-cooled unit connecting cable is connected with the high-frequency host, the high-frequency host is connected with the portable transformer through the water-cooled cable, the high-frequency host is connected with the heating wire rod through the cooling water pipe, and the portable transformer is connected with the heating wire rod. The beneficial effect of the present invention is that: the use of the present invention to heat the through-hole bolts on the joint surface of the cylinder and the like can completely avoid the occurrence of problems in the heating of the resistance rod.

Description

A high-frequency induction heating device for hot-tightening bolts of steam turbine through-holes

technical field

The invention belongs to a heating device for thermally tightening bolts, in particular to a high-frequency induction heating device for thermally tightening bolts through holes in a steam turbine. It can be used in the field of heating and tightening of through-hole hot-tightening bolts on the joint surface of cylinder blocks such as steam turbines in power plants.

Background technique

Under the action of high temperature and high pressure, the mechanical strength of the bolts on the joint surface of the large-capacity steam turbine cylinder block will be weakened, and the tightening force will be reduced. In order to ensure that the bolt tightening force is sufficient to avoid deformation of the cylinder surface and steam leakage during operation, after the steam turbine is closed, the bolts must be stretched to the set pre-tightening force by cold stretching or heating before tightening. The cold drawing method is generally suitable for small size or long thin bolts. For thick bolts with a diameter of M56 and above, heating fastening methods are usually adopted.

The high-medium-pressure and low-pressure inner cylinders of nuclear power, large thermal power and other steam turbines now use high-strength bolts with thick body and high quality, weight and price. bolt.

For a long time, the power station has mostly inserted resistance heating rods in the bolt heating holes, and input DC or AC heating. The heat of the heating rod body is transmitted to the bolt body through radiation, and the bolts are heated slowly. The nut cannot be loosened due to thermal expansion, so it is forced to rework (heat treatment after cooling). , which not only increases the overhaul period but also causes a lot of manpower consumption.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-frequency induction heating device for steam turbine through-hole hot-tightening bolts, which can be used to heat and cool cylinder bolts, which can improve construction efficiency, reduce spare parts loss, and ensure operational safety.

The technical scheme of the present invention is as follows: a high-frequency induction heating device for hot-tightening bolts through a steam turbine, which comprises a power source, the power source is connected to a high-frequency host and supplies power to it, and a control center is connected to the high-frequency host to control the output of its frequency, The water-cooled unit is connected with the high-frequency host through the inlet and outlet water pipes, the water-cooled unit is connected with the high-frequency host by the connecting cable, the high-frequency host is connected with the portable transformer through the water-cooled cable, the high-frequency host is connected with the heating wire rod through the cooling water pipe, and the portable transformer is connected with the heater. Hot wire rod connection.

The portable transformer is connected with a spreader.

The spreader is matched with the beam and moves along the beam.

It also includes a multi-channel thermometer. The multi-channel thermometer is connected with a thermocouple through a high-temperature shielding wire, the thermocouple is arranged on the bolt to be heated, and a digital dial indicator is arranged on the bolt to be heated.

A heating wire rod is sleeved in the through hole of the bolt to be heated.

The heating rod includes a coil housing and manganese zinc ferrite.

The coil shell is connected with manganese-zinc ferrite, the manganese-zinc ferrite has a hollow structure inside, and the manganese-zinc ferrite is connected with the cooling water pipe.

The beneficial effects of the present invention are as follows: the induction heating components adopted in the present invention are based on the principle of electromagnetic induction, the heating coil generates an alternating magnetic field after being energized, and an eddy current is generated in the bolt body to generate heat; the cavity of the heating wire rod passes through cooling water; Centrally heat the diameter of the bolt rod; add a cooling water circulation system to cool the heating rod, high-frequency matching transformer, high-frequency power supply box, etc., take away the heat at the thread, and prevent the nut from snapping. The heating wire rod can be made into a soft and bendable type, which further broadens the applicable surface of this heating method. The use of the present invention to heat the through-hole bolts on the joint surfaces of the cylinder and the like can completely avoid the occurrence of problems in the heating of the resistance rod.

Description of drawings

1 is a schematic diagram of a high-frequency induction heating device for a steam turbine through-hole thermally tightening bolt provided by the present invention;

Figure 2 is a sectional view of the heating process of the hot-tightening bolt;

Figure 3 is a schematic diagram showing the comparison between induction heating and resistance heating;

Figure 4 is a schematic diagram showing the comparison of the total use of induction heating for disassembly and assembly of high-pressure cylinder bolts and resistance heating.

In the picture: 1 high frequency host, 2 power supply, 3 connecting cable, 4 portable transformer, 5 water cooling unit, 6 inlet and outlet water pipes, 7 bolts to be heated, 8 heating wire rods, 9 high temperature shielded wires, 10 multi-channel thermometers, 11 digital dial indicator, 12 spreader, 13 beam, 14 thermocouple, 15 cooling water pipe, 16 water cooling cable, 17 control center, 18 magnetic beam, 20 eddy current, 21 coil shell, 22 manganese zinc ferrite.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

The invention provides a high-frequency induction heating device for steam turbine through-hole hot-tightening bolts based on the principle of high-frequency induction heating. The bolts with through-holes are placed in an alternating magnetic field generated by an induction coil, and eddy currents are generated in the body, and finally are Heating, heating and stretching, through special heating rods, adjusting the power supply frequency and input current to limit the electromagnetic induction area and adjust the magnetic field strength, so that the bolt heated section, internal temperature and temperature difference are all within the pre-control and limit values.

Based on the principle of high-frequency electromagnetic induction, the alternating current is rectified into direct current through a rectifier circuit; the direct current is then converted into a high-frequency current with a frequency of 20 kHz to 40 kHz; when the current passes through the heating rod inserted into the through-hole bolt, an alternating current is generated. Magnetic field; when the magnetic field lines of the magnetic field pass through the bolt body, a strong eddy current is generated, which causes the bolt to heat up quickly; through the special design of the heating wire rod inserted into the through-hole bolt, the magnetic flux generated after the heating coil is energized is constrained and concentrated in the non-threaded bolt. In the auxiliary section, the ineffective heat generation of the tightening nut and the adjacent flange surface is reduced, the heating efficiency is improved, the nut snapping is avoided, the bolt disassembly and assembly speed is accelerated, and the quality of the bolt is guaranteed; the special wire rod, conductive cable, and electric control cabinet are added with circulation The cooling water system ensures that the entire heating system equipment will not be overheated and damaged during long-term operation, improve the reliability of the device, and ensure the safety of personnel.

For different types of bolts, the heating wire rod can be adjusted so that the induction magnetic field is mainly concentrated in all parts from the inner hole of the bolt rod diameter to the outer circular surface, so as to achieve simultaneous heating of all points in the bolt body.

As shown in Figure 1, a high-frequency induction heating device for steam turbine through-hole hot-tightening bolts includes a high-frequency host 1, a power supply 2, a connecting cable 3, a portable transformer 4, a water-cooling unit 5, an inlet and outlet water pipe 6, and a bolt to be heated. 7. Heating wire rod 8, high temperature shielding wire 9, multi-channel thermometer 10, digital dial indicator 11, balancer 12, beam 13, thermocouple 14, cooling water pipe 15, water cooling cable 16, control center 17.

Among them, the power source 2 is connected to the high-frequency host 1 and supplies power to it, the control center 17 is connected to the high-frequency host 1 to control the output of its frequency, the water-cooled unit 5 is connected to the high-frequency host 1 through the water inlet and outlet pipes 6, and the water-cooled unit 5 also passes through The connecting cable 3 is connected to the high-frequency host 1, the high-frequency host 1 is connected to the portable transformer 4 through a water-cooled cable 16, and the portable transformer 4 is connected with a sling 12, which cooperates with the beam 13 and can move along the beam 13 , the high-frequency host 1 is connected to the heating wire rod 8 through the cooling water pipe 15 , and the portable transformer 4 is connected to the heating wire rod 8 .

The multi-channel thermometer 10 is connected to a thermocouple 14 through a high-temperature shielded wire 9 , the thermocouple 14 is arranged on the bolt 7 to be heated, and a digital dial indicator 11 is also arranged on the bolt 7 to be heated.

As shown in FIG. 2 , a heating wire rod 8 is sheathed in the through hole of the bolt 7 to be heated. The heating wire rod 8 includes a coil casing 21 and a manganese-zinc ferrite 22. The coil casing 21 is connected with a manganese-zinc ferrite 22 and a manganese-zinc ferrite The zinc ferrite 22 has a hollow structure, and the manganese-zinc ferrite 22 is connected to the cooling water pipe 15 . A magnetic flux 18 and an eddy current 20 are formed in the bolt 7 to be heated.

The high-frequency induction heating device for the through-hole hot-tightening bolts of a steam turbine of the present invention heats flange bolts such as cylinders, and can achieve the following effects:

(1) Ensure the safety of the operation process

The whole set of heating device is equipped with a complete circulating water cooling system, which cools the cables, transformers and heating coils in the heating process from time to time, so as to avoid the short service life and damage of the transformer if the temperature is too high. Low temperature and not easy to burn, can continuously heat multiple bolts, which is safer than resistance heating.

Through water cooling, the lead wire of the temperature sensor in the heating coil is protected from being overheated and damaged; the water cooling of the coil can effectively avoid accidental burns when the operator pulls and inserts the heating rod.

(2) The maintenance progress is accelerated and the quality of the bolts is guaranteed

Induction heating For each type of bolt, by adjusting the high-frequency power supply box and matching transformer parameters, the optimal power supply frequency and input power can be tailored to achieve rapid heat generation in the same period, short time to reach the expected elongation, and speed up disassembly and assembly progress and shorten the maintenance period. A 728MW unit was overhauled with this device, which shortened the construction period by 3 days compared with the original method of using electric heating rods, and increased power generation ahead of time by nearly 100 million yuan.

The special coil centrally heats the diameter of the bolt and the nut and the adjacent cylinder with little or no heating, reducing thread damage and snapping, avoiding rework affecting the construction period, reducing spare parts, labor consumption, and saving maintenance costs. A 728MW unit has only used this device, and no faults such as bolt snapping have occurred, and the consumption of spare parts has been reduced to nearly zero.

For each type of bolt, the software in the system is used for technical analysis and simulation calculation before heating, and after many heating tests in the laboratory, the monitoring and adjustment parameters in the implementation are fine-tuned and corrected, which can ensure that the bolt is heated 100 times repeatedly. still available.

(3) Automatic heating process, intelligent control and regulation

Monitor and intelligently analyze and adjust the values of the nut surface, the inner and outer walls of the bolt, the cylinder flange, the temperature of the working environment, and the elongation of the bolt, which can further avoid operation and monitoring deviation, speed up the disassembly and assembly, and ensure the performance of bolts and nuts. Quality, and thus reduce the number of operators and workload.

The system device can calculate the relationship curve of the electric power input with time according to the efficacy characteristics of the heating device and the requirements of the heating speed, and preset the programming into the control center. For each type of bolt to be heated, make the above settings in advance. During on-site operations, the staff selects the matching power input mode on the control center panel to heat the bolts according to the disassembly and assembly sequence specified in the project until the bolts are heated and grow to the required length. Each bolt is heated according to the above settings, and the temperature rise rate (bolt elongation rate), temperature difference and maximum thermal stress change closely with the input power adjustment, as shown in Figures 3 and 4.

Claims (7)

1. a high-frequency induction heating device for hot-tightening bolts in a steam turbine through-hole, is characterized in that: it comprises a power supply, and the power supply is connected with the high-frequency host and supplies power to it, and the control center is connected with the high-frequency host to control the output of its frequency, and the water-cooled The unit is connected to the high-frequency host through the inlet and outlet water pipes, the water-cooled unit connecting cable is connected to the high-frequency host, the high-frequency host is connected to the portable transformer through the water-cooled cable, the high-frequency host is connected to the heating wire rod through the cooling water pipe, and the portable transformer is connected to the heating wire. Stick connection. 2 . The high-frequency induction heating device for thermally tightening bolts through holes in a steam turbine according to claim 1 , wherein the portable transformer is connected with a hanger. 3 . 3 . The high-frequency induction heating device for thermally tightening bolts through holes in a steam turbine according to claim 2 , wherein the spreader is matched with the beam and moves along the beam. 4 . 4. The high-frequency induction heating device for hot-tightening bolts of a steam turbine through-hole as claimed in claim 1, further comprising a multi-channel thermometer, and the multi-channel thermometer is connected to a thermocouple through a high-temperature shielding wire, and the thermoelectric The pair is arranged on the bolt to be heated, and a digital dial indicator is arranged on the bolt to be heated. 5 . The high-frequency induction heating device for thermally tightening bolts through holes in a steam turbine according to claim 4 , wherein a heating wire rod is sleeved in the through holes of the bolts to be heated. 6 . 6 . The high-frequency induction heating device for hot-tightening bolts through a steam turbine according to claim 4 , wherein the heating wire rod comprises a coil casing and a manganese-zinc ferrite. 7 . 7. The high-frequency induction heating device for through-hole hot-tightening bolts of steam turbines as claimed in claim 6, characterized in that: the coil casing is connected with manganese-zinc ferrite, and the manganese-zinc ferrite body is a hollow structure, and the manganese-zinc ferrite has a hollow structure. The body is connected to the cooling water pipe.

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