Insulation recovery method for electric heater
By combining gas welding flame heating with power regulation, the problem of low insulation in armored electric heaters was solved, achieving restoration of insulation performance and extension of service life.
Patent Information
- Application Number
- CN202511388002.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2025-12-12
AI Technical Summary
The lack of effective insulation restoration methods for armored electric heaters in the existing technology leads to frequent failures and increases repair costs and time.
A combination of gas welding flame heating and power regulation is used to remove moisture from the magnesium oxide layer and improve its insulation performance through heating and power drying techniques.
It improves the insulation performance of armored electric heaters, extends their service life, and reduces repair costs and cycles.
Smart Images
Figure CN121126589A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electric heater repair, and in particular to a method for restoring the insulation of an electric heater. Background Technology
[0002] A sheathed high-resistance alloy electric heater (referred to as a sheathed electric heater) typically consists of a hot end, a connector, a cold end, and a cable joint. The hot end of this heater uses a nickel-chromium alloy (such as Cr20Ni80) as the heating element, while the cold end uses a copper core as the non-heating element. The nickel-chromium wire in the hot end and the copper wire in the cold end are mated within the connector. Both the hot and cold ends are encased in a stainless steel shell, which is filled with compacted magnesium oxide powder. The magnesium oxide powder provides excellent insulation and thermal conductivity.
[0003] Armored electric heaters are primarily used in nuclear power plants for heating and temperature control of equipment such as sodium pipes and containers, ensuring stable system pressure, preventing thermal stratification, and guaranteeing safe reactor operation. They are resistant to high temperatures and radiation, and have excellent sealing properties, making them suitable for the confined and harsh environment inside the nuclear island. They are a key component for the safe operation of nuclear power plants. In existing technologies, for fast reactor nuclear power units that extensively utilize armored electric heaters, frequent failures and defects occur. For faults involving low insulation in armored electric heaters, the common approach is "replacement only" or "return to factory for repair," which undoubtedly increases repair costs and time. Currently, there is a lack of a method for insulation restoration of armored electric heaters. Summary of the Invention
[0004] This invention provides a method for restoring the insulation of an electric heater, which addresses the problem of the lack of restoration methods for low insulation in armored electric heaters in the prior art.
[0005] The technical solution of the present invention is as follows:
[0006] This invention proposes a method for restoring the insulation of an electric heater, the method comprising:
[0007] Step 1: When the insulation resistance of the electric heater to ground is lower than the set value, disconnect the power supply to the electric heater;
[0008] Step 2: Use a gas welding flame to heat the outside of the heater, driving the moisture absorbed by the cold end of the electric heater from the connector to the terminal.
[0009] Step 3: Use an insulation resistance tester to measure whether the insulation resistance of the electric heater to ground meets the standard;
[0010] Step 4: If the insulation resistance to ground of the electric heater does not meet the standard, use a power regulator to supply a small current to the electric heater;
[0011] Step 5: Heat the electric heater for a certain period of time A using a power regulator, and measure the insulation resistance to ground of the electric heater using an insulation resistance tester. If the insulation resistance to ground of the electric heater increases, increase the current of the power regulator and heat it again for a certain period of time A, and measure the insulation resistance to ground of the electric heater again using an insulation resistance tester.
[0012] Step Six: If the insulation resistance to ground of the electric heater meets the standard, increase the current of the power regulator again and heat for a certain period of time B to complete the insulation restoration of the electric heater.
[0013] In some embodiments, the insulation resistance of the heater to ground in step one of the method is set to 1MΩ. Disconnecting the power supply to the electric heater specifically includes: disconnecting the power supply to the electric heating end and disconnecting the connection between the electric heater terminator and the upstream cable.
[0014] In some embodiments, the heating direction in step two is that the gas welding flame starts heating from the connector and slowly moves towards the nearby cold end terminator.
[0015] In some embodiments, step two involves heating and baking with an oxy-acetylene torch for 20-30 minutes.
[0016] In some embodiments, whether the ground insulation resistance meets the standard in step three specifically refers to whether the ground insulation resistance reaches 1MΩ.
[0017] In some embodiments, step four involves using a power regulator to supply a small current to the electric heater. Specifically, the power regulator draws power from a maintenance power source near the electric heater, and a lead wire from the power regulator is used to supply power to the electric heater that needs to be heated. The small current is 0.5 times the rated current of the heating wire.
[0018] In some embodiments, in step five, the electric heater is heated for a certain period of time A using a power regulator, and the insulation resistance to ground of the electric heater is measured using an insulation resistance tester. If the insulation resistance to ground of the electric heater increases, the current of the power regulator is increased to heat it again for a certain period of time A, which is 2-4 hours. If the insulation resistance to ground of the electric heater increases to 0.5MΩ, the current of the power regulator is increased by 0.7-0.8 times the rated current to heat it again for 2-4 hours.
[0019] In some embodiments, if the insulation resistance to ground of the electric heater meets the standard in step six, the current of the power regulator is increased again to heat for a certain period of time B to complete the insulation restoration of the electric heater. Specifically, if the insulation resistance to ground of the electric heater reaches 1MΩ or above, the current of the power regulator is increased again to the rated current and heated for 4 hours to complete the insulation restoration of the electric heater.
[0020] In some embodiments, if the insulation resistance to ground of the hot end of multiple electric heaters in a heating section of the electric heating system is unqualified in step six, the electric heaters are dried using a normal power supply, provided that the busbar of the electric heating system is safe.
[0021] The implementation of this invention has the following beneficial effects:
[0022] This invention proposes a method for restoring the insulation of an electric heater. The invention uses heating and electric drying techniques to remove moisture from the magnesium oxide layer inside the armored electric heater, thereby improving the insulation performance of the armored electric heater, avoiding frequent replacement of the electric heater, extending the service life of the electric heater, and reducing the repair cost and repair cycle of the electric heater. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of an electric heater used in an embodiment of the present invention to provide an insulation restoration method for an electric heater.
[0024] Figure descriptions: 1. Hot end; 2. Connector; 3. Cold end; 4. Terminator. Detailed Implementation
[0025] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] like Figure 1 As shown, the single-core armored electric heater consists of a hot end 1 and two cold ends 3 on either side. One end of the cold end 3 is connected to the hot end 1 via a connector 2, and the other end of the cold end 3 is equipped with a terminator 4. The terminator 4 is crimped to the upstream cable via screws. The low insulation of the heating wire may be due to a defect in either the cold end 3 or the hot end 1, allowing moisture to enter the magnesium oxide layer inside the casing. To address moisture in the cold end 3, a gas welding flame can be used to heat the exterior of the heater, paying attention to the heating direction. This will drive the moisture absorbed by the magnesium oxide from the connector 2 towards the terminator 4. Heating for several minutes can effectively improve the insulation level to the required 1MΩ or higher. If drying the cold end 3 does not improve the insulation level, it can be determined that a defect in the hot end 1 is causing moisture to enter the magnesium oxide layer inside the casing.
[0027] In this situation, a temporary power supply or a power regulator (with adjustable voltage and current) can be used to apply a small current to the heating wire, starting with 0.5 times the rated current of the heating wire. This will heat the nickel-chromium wire in heating end 1, effectively drying and removing moisture from the magnesium oxide layer. Once the insulation has improved, the current can be gradually increased to the rated current until the insulation reaches a satisfactory level. If the insulation of heating end 1 of multiple heating wires in a heating section is substandard, the mains power supply can be used directly for heating and drying, provided the safety of the electric heating system busbar is ensured.
[0028] like Figure 1 As shown, this invention proposes a method for restoring the insulation of an electric heater, the method comprising:
[0029] Step 1: When the insulation resistance of the electric heater to ground is less than 1MΩ, first disconnect the power supply of the electric heating section and disconnect the connection between the electric heater terminal 4 and its cable.
[0030] Step 2: Use a gas welding flame to heat the exterior of the cold end 3, hot end 1, and connector 2 of the electric heater, driving the moisture absorbed by the magnesium oxide layer from connector 2 to terminal 4. The heating direction is that the gas welding flame starts heating from connector 2 and slowly moves towards the closer cold end 3 and terminal 4. Heat and bake for 20-30 minutes.
[0031] Step 3: Use an insulation resistance tester to measure whether the insulation resistance of the electric heater to ground reaches 1MΩ. If the insulation resistance value to ground exceeds 1MΩ, it proves that the insulation failure of the electric heater is caused by moisture entering the magnesium oxide layer at the cold end of the casing.
[0032] Step 4: If the insulation resistance to ground of the electric heater does not meet the standard, it means that drying the cold end 3 cannot improve the insulation level. This indicates that a defect in the hot end 1 is causing moisture to enter the magnesium oxide layer inside the casing. Since the hot end 1 is fixed to pipes or other equipment and wrapped with insulation materials, it is not suitable to use gas welding flames or other methods to heat the outside of the electric heater. A small current, 0.5 times the rated current of the heating wire, can be supplied through a power regulator. Specifically, the power regulator draws power from the maintenance power supply near the electric heater. A lead wire from the power regulator is connected to the electric heater to be heated. The power regulator starts supplying power at 0.5 times the rated current, causing the nickel-chromium wire inside the hot end 1 to heat up, thus drying and removing moisture from the magnesium oxide layer.
[0033] Step 5: Heat the heater for 2-4 hours using a power regulator. Use an insulation resistance tester to measure the insulation resistance of the electric heater to ground. If the insulation resistance of the electric heater to ground rises to 0.5MΩ, increase the current of the power regulator to 0.7-0.8 of the rated current of the heating wire, heat for another 2-4 hours, and measure the insulation resistance of the electric heater to ground again using an insulation resistance tester.
[0034] Step Six: If the insulation resistance to ground of the electric heater reaches 1MΩ or higher, increase the current of the power regulator to the rated current again and heat for 4 hours to finally raise the insulation to a qualified level, completing the insulation restoration of the electric heater. If the insulation resistance value to ground of the hot end of multiple electric heaters in a heating section is unqualified, the electric heaters can be dried directly using the normal power supply, provided that the safety of the electric heating system busbar is ensured.
[0035] This invention proposes a method for restoring the insulation of an electric heater. The invention uses heating and electric drying techniques to remove moisture from the magnesium oxide layer inside the armored electric heater, thereby improving the insulation performance of the armored electric heater, avoiding frequent replacement of the electric heater, extending the service life of the electric heater, and reducing the repair cost and repair cycle of the electric heater.
[0036] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.
Claims
1. A method for restoring the insulation of an electric heater, characterized in that, The method includes: Step 1: When the insulation resistance of the electric heater to ground is lower than the set value, disconnect the power supply to the electric heater; Step 2: Use gas welding flame to heat the outside of the heater, and drive the moisture absorbed by the cold end (3) of the electric heater from the connector (2) to the terminal (4); Step 3: Use an insulation resistance tester to measure whether the insulation resistance of the electric heater to ground meets the standard; Step 4: If the insulation resistance to ground of the electric heater does not meet the standard, use a power regulator to supply a small current to the electric heater; Step 5: Heat the electric heater for a certain period of time A using a power regulator, and measure the insulation resistance to ground of the electric heater using an insulation resistance tester. If the insulation resistance to ground of the electric heater increases, increase the current of the power regulator and heat it again for a certain period of time A, and measure the insulation resistance to ground of the electric heater again using an insulation resistance tester. Step Six: If the insulation resistance to ground of the electric heater meets the standard, increase the current of the power regulator again and heat for a certain period of time B to complete the insulation restoration of the electric heater.
2. The method for restoring insulation of an electric heater according to claim 1, characterized in that, In the method described in step one, the insulation resistance of the heater to ground is set to 1MΩ. The specific steps of disconnecting the power supply to the electric heater include: disconnecting the power supply to the electric heating end (1) and disconnecting the connection between the electric heater terminal (4) and the upstream cable.
3. The method for restoring insulation of an electric heater according to claim 2, characterized in that, In step two, the heating direction is such that the gas welding flame starts heating from the connector (2) and slowly moves towards the closer cold end (3) terminal (4).
4. The method for restoring insulation of an electric heater according to claim 3, characterized in that, In step two, the gas welding flame is used to heat and bake for 20-30 minutes.
5. The method for restoring insulation of an electric heater according to claim 4, characterized in that, In step three, whether the insulation resistance to ground meets the standard specifically refers to whether the insulation resistance to ground reaches 1MΩ.
6. The method for restoring insulation of an electric heater according to claim 5, characterized in that, In step four, a small current is supplied to the electric heater using a power regulator. Specifically, the power regulator draws power from a maintenance power source near the electric heater, and a lead wire from the power regulator is sent to the electric heater that needs to be heated. The small current is 0.5 times the rated current of the heating wire.
7. The method for restoring insulation of an electric heater according to claim 6, characterized in that, In step five, the electric heater is heated for a certain period of time A using a power regulator. An insulation resistance tester is used to measure the insulation resistance of the electric heater to ground. If the insulation resistance of the electric heater to ground increases, the current of the power regulator is increased to heat it again for a certain period of time A, which is 2-4 hours. If the insulation resistance of the electric heater to ground rises to 0.5MΩ, the current of the power regulator is increased to 0.7-0.8 times the rated current of the heating wire, and the heating is continued for another 2-4 hours.
8. The method for restoring insulation of an electric heater according to claim 7, characterized in that, If the insulation resistance to ground of the electric heater meets the standard in step six, the current of the power regulator is increased again to heat for a certain period of time B to complete the insulation restoration of the electric heater. Specifically, if the insulation resistance to ground of the electric heater reaches 1MΩ or above, the current of the power regulator is increased again to the rated current and heated for 4 hours to complete the insulation restoration of the electric heater.
9. The method for restoring insulation of an electric heater according to claim 7, characterized in that, If the insulation resistance to ground of the hot end (1) of multiple electric heaters in a heating section of the electric heating system is not qualified in step six, the electric heaters shall be dried by the normal power supply, provided that the busbar of the electric heating system is safe.