CN211554158U - Test device for evaluating durability of metal tubular electric heating element - Google Patents
Test device for evaluating durability of metal tubular electric heating element Download PDFInfo
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- CN211554158U CN211554158U CN201921545861.2U CN201921545861U CN211554158U CN 211554158 U CN211554158 U CN 211554158U CN 201921545861 U CN201921545861 U CN 201921545861U CN 211554158 U CN211554158 U CN 211554158U
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Abstract
The utility model discloses a test device for evaluating the durability of a metal tubular electric heating element, which comprises a test groove with a cover, a test circuit and a monitoring system, wherein 4 holes with different sizes are arranged on the cover of the test groove with the cover, an electric heating pipe sample, a reflux condenser, a stirrer and a thermometer are respectively arranged on the cover, and a water outlet is arranged at the lower part of the side wall of the test groove; the test circuit comprises a test power supply, an isolated voltage regulator and a fuse protector; the two poles of the test power supply are connected with the input end of the isolated voltage regulator, the fuse is connected to the zero line of the leading-out end of the isolated voltage regulator, and the electric heating pipe sample is connected; the monitoring system comprises a voltmeter connected in parallel to the test circuit and an ammeter connected in series to the test circuit. The test device can better simulate the working state of the electric heating pipe and check the durability of the electric heating pipe.
Description
Technical Field
The utility model relates to a metal tubulose electric heating element durability test equipment specifically indicates a test device of evaluation metal tubulose electric heating element durability.
Background
The metal tubular electric heating element (electric heating tube for short) is the core part of electric water heater and other household appliances. The metal tubular electric heating element for the household appliance is used for heating water. In the using process, the water contains corrosive media such as chloride ions, and the long-term use can cause the heating pipe to corrode and perforate, leak and even explode the pipe. The corrosion perforation of the electric heating pipe can also cause electric leakage, which brings safety risks such as electric shock of personnel. The corrosion hidden trouble of the electric heating pipe is difficult to detect when the electric heating pipe leaves factory and is the main reason influencing the long-term reliability of the electric heating pipe, which troubles the industry for many years. At present, no effective detection method exists in the industry.
The electric heating tube uses a metal tube as a shell, an alloy electric heating wire as a heating element, a leading-out rod is arranged at one end or two ends, and an insulating material is filled in the metal tube to fix the heating element. Corrosion of an electrical heating tube refers to corrosion of the metal tube housing. At present, the shell of the electric heating tube in the household appliance is mostly made of austenitic stainless steel. The main corrosion modes of austenitic stainless steels in tap water are pitting, intergranular corrosion and stress corrosion. The stress corrosion of austenitic stainless steel often originates from pitting corrosion on the surface, extends inwards in a stress concentration area to form deeply-developed through cracks, and is a main reason for generating corrosion perforation, leakage and tube burst of an electric heating tube. The electric heating tube shell is made of austenitic stainless steel seamless steel tubes through cold bending forming, and machining stress can be generated in the cold bending and assembling processes, so that stress corrosion of the electric heating tube shell cannot be ignored. Method for measuring the susceptibility of austenitic stainless steel materials to stress corrosion, which is currently most commonly used YB/T5362 method for testing the stress corrosion of stainless steel in boiling magnesium chloride solution, requires that the stainless steel material be made into a sample with residual stress, such as a U-shaped sample, and be continuously boiled in 42% boiling magnesium chloride solution for 24 hours or more, and the test temperature is kept at 143 ℃. After the test is finished, whether the sample generates the stress corrosion cracks, the time for generating the stress corrosion cracks and the length of the cracks are observed under a microscope to judge the stress corrosion sensitivity of the material. However, the stress of the electric heating tube is introduced when the electric heating tube is manufactured into a finished product, factors influencing the durability of the electric heating tube not only include material factors, but also influence caused by post-processing and assembly processes, and the durability of the electric heating tube cannot be fully reflected only by examining the stress corrosion sensitivity of the material of the shell of the electric heating tube.
Secondly, in order to protect electric appliance products such as a water heater and the like and ensure the safety of the products, a control circuit of the electric heating pipe is provided with an automatic power-off function. That is, the electric heating pipe is heating water to a certain temperature, for example, the electric heating pipe in the electric water heater can automatically cut off the power after heating the water in the water tank to 70-90 ℃, and the electric heating pipe in the hot water kettle sets that the power is automatically cut off after boiling the water (100 ℃). When the water temperature is reduced to a certain temperature, the electric heating pipe can be automatically restarted and reheated, so that the water can be ensured to be always kept at a proper temperature. This design makes it impossible to use YB/T5362 "method for testing the stress corrosion of stainless steel in boiling magnesium chloride solution" when evaluating the durability of an electric heating tube because the electric heating tube cannot heat the test solution to 143 ℃. In addition, when the stress corrosion sensitivity of the stainless steel material is examined, the sample size is small, the required solution is less, and the sample size is usually 500-1000mL, and the examination can be completed in a glass instrument with a reflux condenser. The test solution is maintained in a saturated state by refluxing and condensing the water vapor evaporated from the test solution back into the test solution. And because the test solution is not much, only a small amount of magnesium chloride crystals can be separated out on the tube wall of the glass instrument in the test process, and the test environment cannot be polluted. However, the electric heating tube has a large size, and the durability evaluation test cannot be completed in a glass instrument. If a saturated magnesium chloride solution is adopted when the durability of the electric heating tube is evaluated, water in the test solution is evaporated in the test process, and a large amount of magnesium chloride crystals can be separated from the saturated magnesium chloride to pollute the test environment.
Therefore, it is necessary to develop a test apparatus suitable for evaluating durability of an electric heating tube from the viewpoint of the overall product, and to propose a related test method. The device and the method are very important and urgent to help enterprises to randomly check the product performance before leaving factories and help professional organizations to evaluate the safety and reliability of electric heating tube products.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide an evaluation metal tubulose electric heating element durability's test device can simulate electric heating pipe's operating condition betterly, examines electric heating pipe's durability.
The above object of the present invention is achieved by the following technical solutions: a test device for evaluating the durability of a metal tubular electric heating element is characterized in that: the testing device comprises a testing groove with a cover, a testing circuit and a monitoring system, wherein,
the test tank with the cover is characterized in that 4 holes with different sizes are formed in the tank cover of the test tank with the cover, an electric heating pipe sample, a reflux condenser, a stirrer and a thermometer are respectively installed on the holes, the electric heating pipe sample, the reflux condenser, the stirrer and the thermometer are all deep into the test solution in the tank, a gap is reserved between the reflux condenser and the liquid level of the test solution, and a water outlet is formed in the lower portion of the side wall of the test tank; the electric heating tube sample is directly used for heating the test solution; the reflux condenser reduces the water vapor volatilized from the test solution through cold tap water flowing outside the reflux condenser in the test process, so that the water vapor is condensed again and flows back to the test tank; the stirrer is used for stirring the test solution to ensure that the temperature difference of the test solution at different positions in the test tank is within +/-3 ℃; the thermometer is used for observing the test temperature in the test process; the water outlet is convenient for emptying the test solution in the test tank after the test is finished;
the test circuit comprises a test power supply, an isolated voltage regulator and a fuse protector; the two poles of the test power supply are connected with the input end of the isolated voltage regulator, the fuse is connected on the zero line of the leading-out end of the isolated voltage regulator, and the electric heating tube sample is connected, so that the voltage at the two ends of the electric heating tube sample can be adjusted by adjusting the isolated voltage regulator, and the purpose of controlling the temperature of the test solution is achieved; the test power supply can select instrument parameters according to the type of the tested electric heating tube sample; the fuse is used for protecting a test circuit and avoiding safety accidents caused by overload;
the monitoring system comprises a voltmeter connected in parallel to the test circuit and an ammeter connected in series to the test circuit and is used for monitoring the change conditions of current and voltage in the test circuit in the test process.
The utility model discloses in, the core component of taking lid test groove as whole durability test device makes with the glass steel, and the size is recommended to be: phi 500cm x 600 cm.
The utility model discloses in, the outlet is seted up in test groove lateral wall lower part from bottom surface 3cm high department.
In the utility model, the stirrer is made of polytetrafluoroethylene.
Compared with the prior art, the utility model discloses following beneficial effect has:
(1) the utility model discloses examine electric heating pipe's durability from the product angle. The test device simulates the real working state of the electric heating pipe.
(2) The utility model discloses reduced test solution concentration, can not produce a large amount of magnesium chloride crystallization in the process of the test, the pollution test environment.
(3) The utility model discloses refer to GB/T17897 corrosion stainless steel ferric trichloride corrosion test method of metal and alloy, change test solution, change the test parameter and can examine the resistance to pitting corrosion of electric heating pipe.
(4) The utility model discloses refer to GB/T4334 corrosion stainless steel intercrystalline corrosion test method of metal and alloy, change test solution, change the test parameter and can examine the resistant intercrystalline corrosion behavior of electric heating pipe.
(5) The device designed by the utility model is easier to manufacture and has low price; the utility model discloses a test result repeatability that the method was obtained is stronger, and the comparability of test result between the different mechanisms is stronger.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic view of the overall structure of the device for testing the durability of the metal tubular electric heating element of the present invention;
FIG. 2 is a schematic structural diagram of a mounting element with a cover test chamber in the device for testing the durability of a metal tubular electric heating element according to the present invention;
FIG. 3 is a plan view of a test chamber with a cover in the device for testing the durability of a metal tubular electric heating element according to the present invention.
Description of reference numerals:
101. a test cell with a cover; 102. A test circuit; 103. A monitoring system; 1. An electric heating tube sample;
2. a reflux condenser; 3. A stirrer; 4. A thermometer; 5. A water outlet; 6. A test power supply;
7. an isolated voltage regulator; 8. A fuse; 9. A voltmeter; 10. And (4) an ammeter.
Detailed Description
A test device for evaluating the durability of a metal tubular electric heating element as shown in fig. 1 to 3 comprises a test tank with a cover 101, a test circuit 102 and a monitoring system 103, wherein,
the test cell 101 with a lid, which is a core member of the entire durability test apparatus, is made of glass fiber reinforced plastic and has a size recommended as follows: phi 500cm is multiplied by 600 cm; 4 holes with different sizes are formed in the test tank cover, an electric heating pipe sample 1, a reflux condenser 2, a stirrer 3 and a thermometer 4 are respectively installed on the test tank cover, the electric heating pipe sample 1, the stirrer 3 and the thermometer 4 are all deep into the test solution in the tank, a gap is reserved between the reflux condenser 2 and the liquid level of the test solution, and a water outlet 5 is formed in the position, 3cm away from the bottom surface, of the lower portion of the side wall of the test tank; the electric heating tube sample 1 was used directly to heat the test solution; the reflux condenser 2 reduces the water vapor volatilized from the test solution through cold tap water flowing outside the reflux condenser pipe in the test process, so that the water vapor is condensed again and flows back to the test tank; the stirrer 3 is made of polytetrafluoroethylene and is used for stirring the test solution to ensure that the temperature difference of the test solution at different positions in the test tank is within +/-3 ℃; the thermometer 4 is used for observing the test temperature in the test process; the water outlet 5 is convenient for emptying the test solution in the test tank after the test is finished;
the test circuit 102 comprises a test power supply 6, an isolated voltage regulator 7 and a fuse 8; the two poles of the test power supply 6 are connected with the input end of the isolated voltage regulator 7, the fuse 8 is connected on the zero line of the leading-out end of the isolated voltage regulator 7, and the electric heating tube sample 1 is connected, so that the voltage at the two ends of the electric heating tube sample 1 can be adjusted by adjusting the isolated voltage regulator 7, and the purpose of controlling the temperature of the test solution is achieved; the test power supply 6 can select instrument parameters according to the type of the tested electric heating tube sample 1; the fuse 8 is used for protecting the test circuit and avoiding safety accidents caused by overload;
the monitoring system 103 comprises a voltmeter 9 connected in parallel to the test circuit and an ammeter 10 connected in series to the test circuit, and is used for monitoring the change conditions of current and voltage in the test circuit in the test process.
The test method for evaluating the durability of the metal tubular electric heating element by using the test device comprises the following steps:
step 1: analytically pure MgCl was used in reference to YB/T5362 stress corrosion test method of stainless steel in boiling magnesium chloride solution2Preparing a test solution by using a reagent and deionized water or distilled water, wherein the mass concentration of the test solution is 25-40%; filling the prepared test solution into a test groove 101 with a cover, wherein the volume of the test solution is not more than 90% of the volume of the test groove;
step 2: covering a cover of the test tank 101 with the cover, sequentially installing the electric heating pipe sample 1, the reflux condenser 2, the stirrer 3 and the thermometer 4 on the test tank cover, and sealing the installation hole by using silicon rubber to reduce the evaporation of water in the test solution in the test process as much as possible;
and step 3: connecting a test circuit 102 to an electric heating pipe sample 1, and then connecting a monitoring system 103;
and 4, step 4: connecting a running water cooling loop on the reflux condenser 2, and opening the stirrer 3; opening a switch of the isolated voltage regulator 7, and switching on a test circuit; adjusting an isolated voltage regulator 7 to heat the test solution by the electric heating tube sample 1, adjusting the isolated voltage regulator 7 after the test solution is heated to a set test temperature, and adjusting the voltage at two ends of the electric heating tube sample 1 to stabilize the temperature of the test solution within a range of +/-3 ℃ of error of the test temperature, wherein the set test temperature is within a range of 70-95 ℃;
and 5: continuously monitoring the voltage value and the current value in the test circuit 102 through a voltmeter 9 and an ammeter 10 of a monitoring system 103 in the test process;
step 6: keeping the test parameters in the step 4 unchanged, and continuously testing until the test current in the monitoring system 103 changes suddenly; once the test current changes suddenly, the current in the loop increases by more than 20% of the working current, the switch of the isolated voltage regulator 7 is turned off, the test circuit 102 is cut off, the test time is recorded, and the durability test of the electric heating tube sample 1 is completed.
In the step 1, the electric heating tubeThe portion of sample 1 submerged in the test solution can be used to calculate the test area. The ratio of the volume of the test solution to the test area of the electric heating tube sample 1 should be controlled every 1cm2The test area should be not less than 20mL of test solution. If the surface area of the electric heating pipe sample is too large, the test groove can be replaced to a larger size so as to meet the proportion of the test solution to the test area of the electric heating pipe.
In the step 6, deionized water or distilled water can be added at random according to the liquid level change of the test solution in the test process so as to ensure that the concentration of the test solution is controlled within the test concentration range.
As a specific example, the durability of an electric heating tube for an electric water heater, which is made of a 310 stainless steel seamless steel tube, is examined, and the power of the electric heating tube is 2200W. The specific test steps are as follows:
1) solution preparation
A35% test solution was prepared from an analytically pure magnesium chloride reagent meeting GB/T672 magnesium chloride hexahydrate (magnesium chloride) requirements and deionized water. The prepared MgCl2The test solution was transferred to a test cell with a lid and a test cell volume of phi 500cm × 600 cm.
2) Test sample mounting
An electric heating pipe sample, a reflux condenser, a stirrer and a thermometer are sequentially arranged on a test tank cover, and the silicon rubber is used for sealing the mounting hole, so that the evaporation of water in the test solution in the test process is reduced as much as possible.
3) Test of
The test power supply is connected with the input end of the isolated voltage regulator, and the zero line at the output end of the isolated voltage regulator is connected with the fuse and the ammeter and then is connected to one of the leading-out rods of the electric heating pipe. The fire wire end of the isolated voltage regulator is directly connected with the other leading-out rod of the electric heating pipe. The monitoring voltmeter is then connected in parallel to the circuit.
The tap water cooling circuit on the reflux condenser was connected, the stirrer was switched on, and the test solution was stirred at low speed. And opening the switch of the isolated voltage regulator, and switching on the test circuit. And adjusting the isolated pressure regulator to 220V to heat the test solution by the electric heating tube sample, and after the test solution is heated to 90 ℃, adjusting the isolated pressure regulator to 157V to stabilize the temperature of the test solution at 90 +/-3 ℃. And after the test is continued for 158 hours, the monitoring ammeter monitors that the current in the test circuit is suddenly increased, the test is stopped, and the test time is recorded.
4) Analysis of test results
After the test is finished, sampling is carried out on the corrosion part on the electric heating pipe, and the microscopic appearance of the section is observed by using a scanning electron microscope. The cause of the failure is determined.
The above embodiments of the present invention are not right the utility model discloses the limited protection scope, the utility model discloses an embodiment is not limited to this, all kinds of basis according to the above-mentioned of the utility model discloses an under the above-mentioned basic technical thought prerequisite of the utility model, right according to ordinary technical knowledge and the conventional means in this field the modification, replacement or the change of other multiple forms that above-mentioned structure made all should fall within the protection scope of the utility model.
Claims (5)
1. A test device for evaluating the durability of a metal tubular electric heating element is characterized in that: the test device comprises a test groove with a cover (101), a test circuit (102) and a monitoring system (103), wherein,
4 holes with different sizes are formed in a cover of the test tank (101) with the cover, an electric heating pipe sample (1), a reflux condenser (2), a stirrer (3) and a thermometer (4) are respectively installed on the holes, the electric heating pipe sample (1), the stirrer (3) and the thermometer (4) are all deep into the test solution in the tank, a gap is reserved between the reflux condenser (2) and the liquid level of the test solution, and a water outlet (5) is formed in the lower portion of the side wall of the test tank;
the test circuit (102) comprises a test power supply (6), an isolated voltage regulator (7) and a fuse (8); the two poles of the test power supply (6) are connected with the input end of the isolated voltage regulator (7), the fuse (8) is connected on the zero line of the leading-out end of the isolated voltage regulator (7), and the electric heating pipe sample (1) is connected finally;
the monitoring system (103) comprises a voltmeter (9) connected in parallel to the test circuit and an ammeter (10) connected in series to the test circuit and used for monitoring the change conditions of current and voltage in the test circuit in the test process.
2. A test device for evaluating durability of a metal tubular electric heating element according to claim 1, characterized in that: the material of the test tank with the cover (101) is made of glass fiber reinforced plastics.
3. A test device for evaluating durability of a metal tubular electric heating element according to claim 1, characterized in that: the size of the test tank (101) with the cover is phi 500cm multiplied by 600 cm.
4. A test device for evaluating durability of a metal tubular electric heating element according to claim 1, characterized in that: the water outlet (5) is arranged at the position of the lower part of the side wall of the test tank, which is 3cm away from the bottom surface.
5. A test device for evaluating durability of a metal tubular electric heating element according to claim 1, characterized in that: the stirrer (3) is made of polytetrafluoroethylene.
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| CN201921545861.2U CN211554158U (en) | 2019-09-17 | 2019-09-17 | Test device for evaluating durability of metal tubular electric heating element |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110632417A (en) * | 2019-09-17 | 2019-12-31 | 威凯检测技术有限公司 | Test device and method for evaluating durability of metal tubular electric heating element |
| CN112305358A (en) * | 2020-10-29 | 2021-02-02 | 威凯检测技术有限公司 | Accelerated life test method for daily tubular electric heating element for heating water |
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2019
- 2019-09-17 CN CN201921545861.2U patent/CN211554158U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110632417A (en) * | 2019-09-17 | 2019-12-31 | 威凯检测技术有限公司 | Test device and method for evaluating durability of metal tubular electric heating element |
| CN110632417B (en) * | 2019-09-17 | 2024-08-20 | 威凯检测技术有限公司 | Test device and method for evaluating durability of metal tubular electric heating element |
| CN112305358A (en) * | 2020-10-29 | 2021-02-02 | 威凯检测技术有限公司 | Accelerated life test method for daily tubular electric heating element for heating water |
| CN112305358B (en) * | 2020-10-29 | 2023-09-12 | 威凯检测技术有限公司 | Accelerated life test method of daily tubular electric heating element for heating water |
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