NB/T 10309-2019Corrosion resistant metallic tube electric heating elements (English PDF)

3.1 Corrosion resistant metallic tube electric heating elements

Daily-use tubular electric heating element that uses anti-corrosion metal pipe as the outer shell and can meet the technical requirements of this standard.

3.2 Corrosion resistant metallic tube

The pipe body and the pipe surface material are the same or the pipe body and the pipe surface material are different, but the pipe surface is a metal pipe with certain corrosion resistance.

3.3 Tube body

Metal pipes directly wrapped with insulating filler materials.

3.4 Tube surface

The heat exchange surface in direct contact with the heated medium.

3.5 Corrosion resistance

The ability of the element to resist the corrosion and destruction of the heating medium.

5.1 Basic requirements

The components should meet the technical requirements of Chapter 5 in JB/T 4088-2012.

5.2 Anti-corrosion requirements

5.2.1 Carry out the pretreatment of the samples including electric strength, leakage current and salt spray test according to the requirements of 6.2.1~6.2.4, and then press

GB/T 17897-2016 4.1 Method A, the test temperature is (50±1) °C, and the test shall be carried out continuously for 6 h.

5.2.2 The leakage current of the components at operating temperature, after salt spray test and after corrosion test shall not exceed 0.75 mA.

5.2.3 The insulation of the component should be able to withstand the corresponding electric strength test, and there should be no breakdown during the test.

The test voltages corresponding to different rated voltages are shown in Table 1.

5.3 Dry heating and quenching test requirements

The components should be able to withstand 6 cycles of dry burning and rapid cooling tests.

Whether the test is qualified is determined by the following methods.

a) During the test, no phenomena that affect safety, such as melting, spraying flames, and releasing harmful gases, shall occur;

b) After the test, the component works at the working temperature, and the test voltage is adjusted to make the input power equal to 1.15 of the maximum rated input power After reaching a steady state, measure the leakage current according to 13.2 of GB 4706.1-2005, and the measured leakage current should not More than 0.75 mA; the component should withstand the voltage of the basic sine wave with a frequency of 50 Hz or 60 Hz for 1 min, different amounts The test voltage corresponding to the constant voltage is shown in Table 1. The setting current of the electric strength test equipment is 5 mA.

5.4 Voltage increase test requirements

The components should be able to withstand a voltage increase test of 2.5 times the rated voltage.

Whether the test is qualified is determined by the following methods.

a) During the test, no phenomena that affect safety, such as melting, spraying flames, and releasing harmful gases, shall occur;

b) After the test, the component works at the working temperature, and the test voltage is adjusted to make the input power equal to 1.15 of the maximum rated input power After reaching a steady state, measure the leakage current according to 13.2 of GB 4706.1-2005, and the measured leakage current should not More than 0.75 mA; the component should withstand the voltage of the basic sine wave with a frequency of 50 Hz or 60 Hz for 1 min, different The test voltage corresponding to the rated voltage is shown in Table 1. The setting current of the electric strength test equipment is 5 mA.

5.5 Anti-dry burning test requirements

The components should be able to withstand the corresponding dry burning test.

Whether the test is qualified is determined by the following methods.

a) During the test, no phenomena that affect safety, such as melting, spraying flames, and releasing harmful gases, shall occur;

b) After the test, the component works at the working temperature, and the test voltage is adjusted to make the input power equal to 1.15 of the maximum rated input power After reaching a steady state, measure the leakage current according to 13.2 of GB 4706.1-2005, and the measured leakage current should not More than 0.75 mA; the component should withstand the voltage of the basic sine wave with a frequency of 50 Hz or 60 Hz for 1 min, different The test voltage corresponding to the rated voltage is shown in Table 1. The setting current of the electric strength test equipment is 5 mA.

Note 1. For components with a surface load > 10 W/cm², this requirement does not apply.

Note 2. This requirement does not apply to components whose tube body material is copper or aluminum.

6.1 General requirements for testing

6.1.1 The relevant tests involving energization of components should be carried out under the following conditions.

a) The ambient temperature is (20±5)°C, the relative humidity is not more than 90% (when the temperature is 25°C), and the atmospheric environment is at an altitude of 2 000 m Below, no wind, no strong radiation, or other conditions stipulated in technical documents;

b) The deviation of the power supply voltage does not exceed ±1%;

c) The components can be installed in the water heater or under simulated end-use conditions;

d) In all tests, the measuring instrument or measuring device should not significantly affect the measured value;

e) For components with current protection or one-time temperature protection device, the protection device should be removed or short-circuited;

f) Unless otherwise specified, a component with multiple rated voltages or one (multiple) rated voltage ranges shall be within the specified range The most unfavorable voltage is tested;

g) There should be no flammable and explosive materials and gases in the test site;

h) The test personnel should make appropriate safety protection, and should use appropriate devices to fix and protect the components to avoid the test process Due to high temperature or insufficient electrical protection, it may cause personal injury or damage the surrounding environment;

i) There should be no people frequently in the test site;

j) Test conditions required by users.

6.1.2 The accuracy or error of test instruments and meters shall meet the following requirements.

a) The accuracy of electrical measuring instruments used for type testing should not be less than 0.5; for ex-factory inspection, it should not be less than 1.0;

b) For temperature measuring instruments, the allowable error is within ±1%;

c) The accuracy of the time measuring instrument is within 0.1 s;

d) For measuring tools for measuring length, the allowable error is within ±0.5% of the measured length;

e) For humidity measuring instruments, the allowable error is within ±6% RH of the measured humidity.

6.1.3 The test carried out in the corrosive heating medium shall meet the following requirements.

a) In a test, only components composed of the same type of anti-corrosion material can be tested in the same container;

b) When the component is immersed in the solution, the effective heating surface should be completely immersed in the test solution, and the test requirements should be ensured throughout the test. The required conditions exist;

c) The concentration of the solution should be consistent during the test.

6.1.4 During the test, the container used to hold the corrosive solution shall meet the following requirements.

a) The container in contact with the test solution should not be affected by corrosive agents and avoid changing the properties of the solution;

b) It is recommended to use inert plastic or glass in places that do not need to withstand high temperatures;

c) The metal structural material of the container should be selected from alloys with corrosion resistance to the test environment or a suitable anti-corrosion coating should be selected.

6.2 Anti-corrosion test

6.2.1 Cold electric strength test

According to the provisions of 16.3 in GB 4706.1-2005, the components should withstand a basic sine wave with a duration of 1 min and a frequency of 50 Hz or 60 Hz The test voltage is determined according to Table 1. The setting current of the electric strength test equipment is 5 mA, and it is judged whether the test result meets the requirements of 5.2.2. Claim.

~ 6.2.5 During the test, the leakage current and electric strength test of the components shall meet the requirements of 5.2.2 and 5.2.3.

6.2.2 Leakage current measurement at operating temperature

Install the components on the water heater or simulate the end-use state into a special container, and continue to heat under normal working conditions 10 h. Adjust the test voltage to make the input power equal to 1.15 times the maximum rated input power. After reaching a steady state, press GB 4706.1-2005 In 13.2, measure the leakage current to determine whether the measurement result meets the requirements of 5.2.2.

Immediately after the test, according to the provisions in 13.3 of GB 4706.1-2005, the components should be subjected to a duration of 1 min with a frequency of 50 Hz or 60 Hz The basic sine wave voltage, the test voltage is determined according to Table 1, the setting current of the electric strength test equipment is 5 mA, and the test result is judged to be Whether it meets the requirements of 5.2.3.

6.2.3 Electric strength test at working temperature

6.2.4 Salt spray test

After the test in 6.2.3, the components are taken out separately, and they are naturally dried indoors for 0.5 h to 1 h. According to the requirements of GB/T 2423.17-2008, use The salt solution with a concentration of (5±1)%, a temperature of (35±2)°C, and a PH value of 6.5 to 7.2 is subjected to a 48-hour salt spray test. Then clean, room Naturally dry for 0.5 h to 1 h, measure the leakage current according to 13.2 of GB 4706.1-2005, and judge whether the measurement result meets the requirements of 5.2.2.

At the same time, in accordance with the provisions of 13.3 in GB 4706.1-2005, the components should withstand the basic sinusoidal frequency of 50 Hz or 60 Hz lasting 1 min.

The voltage of the wave, the test voltage is determined according to Table 1, the setting current of the electric strength test equipment is 5 mA, and it is judged whether the test result conforms to 5.2.3 Requirements.

6.2.5 Corrosion test

After the 6.2.4 test, according to the method A of 4.1 in GB/T 17897-2016, the surface of the element or the main element The heat-conducting surface is completely immersed in the FeCl3 solution at the test temperature (50±1) °C and the concentration is 6%, and the corrosion test is continuously carried out for 6 h. According to GB 4706.1 -In 2005, 13.2 measure the leakage current, and judge whether the measurement result meets the requirements of 5.2.1.

At the same time, in accordance with the provisions of 13.3 in GB 4706.1-2005, the components should withstand the basic sinusoidal frequency of 50 Hz or 60 Hz lasting 1 min.

The voltage of the wave, the test voltage is determined according to Table 1, the setting current of the electric strength test equipment is 5 mA, and it is judged whether the test result conforms to 5.2.3 Requirements.

6.3 Dry heating and rapid cooling test

Connect the power supply, adjust the voltage to make the surface load of the component reach 8 W/cm², and dry it for 10 min at this voltage, and then heat it within 2 s Design the surface of the component in contact with the liquid or the main heat-conducting surface of the component to be completely immersed in a container filled with (20±5)°C tap water for cooling 1 min. After 6 cycles of dry heating and rapid cooling, judge whether the test result meets the requirements of 5.3.

6.4 Voltage increase test

6.4.1 Put an appropriate amount of room temperature water into a container with a water inlet and a water outlet, so that the surface of the component or component main The required heat-conducting surface can be completely immersed in water. Take corresponding measures to keep the water temperature below the boiling point during the test.

6.4.2 Connect the power supply and adjust the voltage so that the input voltage reaches the rated voltage. After the component is maintained at the rated voltage for 10 minutes, adjust the voltage to 20 The rate of V/5min is increased step by step and stops after 2.5 times the rated voltage.

6.4.3 After the test, judge whether the result meets the requirements of 5.4.

6.5 Anti-dry burning test

6.5.1 The components are dry-burned in air for 30 minutes under rated voltage conditions.

6.5.2 After the test, the component is cooled to room temperature, and then the surface of the component designed to be in contact with the liquid or the main thermal conductive surface of the component is completely immersed 10 min in water.

6.5.3 After the test, judge whether the result meets the requirements of 5.5.

7.1 Inspection classification

Inspection is divided into factory inspection and type inspection.

7.2 Factory inspection

in JB/T 4088-2012 is applicable.

7.3 Type inspection

7.3.1 Type inspection shall be carried out when the following situations occur.

a) Trial-produced new products;

b) When there are major changes in design and process or materials;

c) Stop production for more than one year, then resume production;

d) For continuous batch production, at least once a year.

7.3.2 The samples for type inspection shall be randomly selected from the products that have passed the factory inspection and packaged.

7.3.3 The products for type inspection are divided into four groups with three pieces in each group. The inspection items, technical requirements and test methods of type inspection are shown in Table 2.

7.3.4 Products after type inspection shall not be delivered as finished products.

7.3.5 In the inspection items 1, 2, 3, 4, 5, 6, and 7 of Table 2, as long as one item is unqualified, the type inspection shall be deemed unqualified.

8.1 Product mark

8.1.1 There should be a permanent mark on the component, and the content of the mark should include.

a) Manufacturer's name or code or trademark;

b) Product model;

c) Factory year and month;

d) Rated voltage and rated power.

8.1.2 All components that are welded with flanges or fastening devices and used to heat the liquid, and whose joints are installed below the liquid level, shall have signs of withstanding water pressure.

8.1.3 There should be a durable and obvious mark on the outside of the packing box. The content of the mark includes.

Serial number group inspection item technical requirements test method First group Cold electric strength test 5.2.3 6.2.1

8.2 Packaging

8.2.1 The components should be packed in a packing box with suitable padding, and there should be a number of certificates, packing quantity, and instructions for use in the box.

8.2.2 If the shell of the component is made of No. 10 steel or similar materials and has not been processed by electroplating or painting, the shell should be coated with anti-rust oil.

8.2.3 If the manufacturer and the customer have an agreement, follow the packaging agreement.

8.3 Transportation

The components should be protected from shock, vibration and direct rain and snow during transportation.

8.4 Storage

The components should be stored in a warehouse with good ventilation, no corrosive gas, and no rain or snow.