Household appliances inspection

The rice cooker is a kitchen appliance widely used in homes and restaurants. It is mainly used for cooking rice, making soup, steaming vegetables and other cooking tasks. With the development of technology, modern rice cookers use advanced microcomputer temperature control systems, which can accurately control the heating process to ensure that the rice is heated evenly and has a softer taste. In addition, the multifunctional design enables the rice cooker to have a timer, heat preservation and multiple cooking modes to meet the taste and nutrition needs of different users. The inner pot usually uses a high-quality non-stick coating, which is easy to clean and durable. The outer shell design is simple and beautiful, and the operation is intuitive and convenient. At the same time, the rice cooker also pays attention to safety performance, equipped with protection devices such as anti-dry burning and automatic power off to effectively prevent kitchen accidents. Whether it is a fast-paced urban life or a leisurely family gathering, the rice cooker has become an indispensable and important appliance in the modern kitchen with its intelligent, practical and energy-saving characteristics.

Rice Cooker Inspection Requirements

Normal working environment

The appliance should be able to work normally under the following conditions:

--- Indoor or similar indoor environment, the surrounding air should be free of flammable, corrosive gases and conductive dust;

———Ambient temperature: -10℃~40℃, relative humidity: no more than 95%;

———Power supply: rated voltage (1±10%), rated frequency ±1Hz.

Electrical safety

The appliance should meet the applicable requirements of GB4706.1 and GB4706.19.

Electromagnetic compatibility

The equipment should meet the applicable requirements of GB4343.1 and GB17625.1.

Volume deviation

The actual volume of the cooking container should not be less than 95% of the rated volume.

Anti-stick coating

Anti-stick properties

The coating of the cooking container of the utensil shall have appropriate anti-stick properties and after the test, there shall be no food adhering to the surface of the cooking container.

Wear resistance

The coating of the cooking container of the appliance shall have appropriate abrasion resistance and after the test, the cooking container shall not have any exposure of the base material.

Adhesion

The coating of the cooking container shall have adequate adhesion and after the test, the coating shall not fall off completely in the cross-cut area.

Corrosion resistance

The coating of the cooking container of the utensil should have appropriate corrosion resistance. After the test, the surface of the cooking container should be free of defects such as peeling, blistering, cracking, shrinkage holes, erosion points, etc.

Thermal efficiency

For normal pressure appliances with metal cooking containers, the thermal efficiency shall not be less than that specified.

For normal pressure appliances with non-metallic cooking containers, the thermal efficiency shall not be less than that specified.

For normal pressure appliances with the above two types of cooking containers, they should meet the requirements respectively.

Insulation energy consumption

For appliances with thermal insulation function, the thermal insulation energy consumption should not exceed the regulations.

Standby power

For appliances with a standby function, the power in the standby state should not exceed the following values:

--- Heating appliances with electric heating elements: 1.8W;

---Electromagnetic induction heating appliances: 2W.

Note: For appliances with communication protocol functions such as WIFI and Bluetooth, the standby power does not apply to the state when the WIFI, Bluetooth and other communication protocol functions are turned on.

Insulation temperature

For appliances with heat preservation function, the heat preservation temperature should not be lower than 60℃.

life

Coating life

For pressure appliances and normal pressure appliances with a rated pressure ≤ 40 kPa, the coating of their cooking containers should be able to withstand 800 cycles of life test.

For pressure appliances with a rated pressure > 40 kPa, the coating of the cooking container shall be able to withstand a life test of 500 cycles.

After the test, the coating shall meet the following requirements:

--- The number of falling points in any 1cm2 area shall not exceed 3;

———The single point shedding area is not greater than 1mm2.

Opening button and lid opening and closing life

The lid opening button and the lid opening and closing connection device should be able to withstand a 20,000-cycle life test. After the test, the appliance should be able to work normally, the lid opening button should not be badly fastened, broken or disengaged, and the lid should open and close smoothly.

Environmental adaptability

High and low voltage adaptability

The device should have appropriate resistance to voltage fluctuations. During the test, the device should be able to work normally without abnormal operation, failure or alarm, and the product components should not be abnormal.

Temperature adaptability

The equipment should have appropriate high and low temperature resistance. During the test, the equipment should be able to work normally without abnormal operation or failure, and the product components should not be abnormal.

Altitude acclimatization

The equipment should have appropriate altitude adaptability. The equipment should be operated under the highest altitude conditions claimed. During operation, the rice soup should not overflow and drip from the equipment onto the table; the rice after operation should not be undercooked or burnt.

Appointment time deviation

For an appliance that completes cooking by reservation, the time from the start of reservation to the completion of cooking should be within the range of -25min to +5min of the reservation time.

For appliances that are scheduled to start cooking, the time from the start of the reservation to the switching to the cooking state should be within ±5 minutes of the reservation time.

Cooking performance

The rice cooking performance of an electric rice cooker should be judged by evaluating the quality of the rice.

The quality of rice is evaluated through physical and chemical experiments and instrumental analysis, and five indicators are evaluated: rice expansion rate, moisture deviation, moisture content, reducing sugar, and gelatinization degree. All indicators should meet the requirements.

Rice Cooker Inspection Test Method

Test conditions

Test environment

Except for special requirements, the test should be carried out in the following environment:

a) Ambient temperature (20±5)℃, without obvious airflow and heat radiation;

b) Relative humidity 45%~75%;

c) Atmospheric pressure 86kPa~106kPa;

d) Power supply voltage single phase (220.0±2.2)V;

e) Power supply frequency: (50±1) Hz.

Test instruments and meters

Test instruments and meters should meet the following requirements:

a) The accuracy of voltmeter, power meter, energy meter and temperature recorder should not be less than ±0.5%;

b) The instrument resolution for measuring temperature is 0.1°C;

c) When the scale is at full capacity, the relative error shall not exceed ±0.1% and the minimum display (scale) value shall not exceed 5g;

d) The timer resolution is 0.01s and the accuracy is ±2s/h;

e) Thermocouples should use fine-wire thermocouples with a wire diameter not greater than 0.3 mm;

f) Magnetic field strength measuring instrument frequency measurement range: 2kHz~400kHz; resolution 1nT, measurement error ±5%;

g) 0.4 and appropriate range pressure gauge.

Note: Considering the influence of electromagnetic interference, the thermocouple can use platinum resistance or equivalent method.

Test prototype preparation

Before each test, the temperature difference between the cooking container, heating plate or coil plate casing and the ambient temperature is within 5 °C or the appliance has not been powered for at least 6 h.

The initial water temperature of the test water should not deviate from the ambient temperature by more than ±2°C.

Electrical safety

The equipment shall be tested in accordance with the relevant provisions of GB4706.1 and GB4706.19.

Electromagnetic compatibility

The equipment shall be tested in accordance with the relevant provisions of GB4343.1 and GB17625.1.

Volume deviation

Wipe the cooking container dry and weigh its mass m1, place it horizontally, and fill it with water until it is flush with the mouth of the cooking container. Weigh the mass m2 of the cooking container and water, and calculate the actual volume Vc according to the formula. Calculate the volume deviation δ according to the formula.

Anti-stick coating

Anti-stick test

The anti-sticking test of the coating is carried out according to the following steps:

a) Use a soft cloth soaked in vegetable oil to gently wipe the non-stick coating surface of the cooking container, then use warm water and detergent to remove the oil, then rinse with clean water, wipe dry and set aside;

b) Set the high temperature box at 150°C, put the cooking container into the high temperature box, and measure the temperature at the center of the bottom of the inner surface of the cooking container;

c) When the temperature reaches (150±5)℃, crack an egg and quickly put it into the cooking container. After the egg white is basically solidified, use a non-metallic spatula to scoop it out without damage, and wipe the coating surface with a soft cotton cloth with a slight force;

d) Carry out the test three times in succession on the same area, and then observe whether there is any adhesion residue on the coating surface of the cooking container.

Wear resistance test

The wear resistance test of the coating is carried out according to the following steps:

a) Fix the cooking container or the test sheet consistent with the coating process of the cooking container on the test equipment;

b) After wetting a scouring pad with a thickness of (10±1) mm with 5% detergent water, place the scouring pad on the bottom of the force-applying object so that the contact surface between the scouring pad and the bottom of the force-applying object is a square with a side length of (50±1) mm;

c) Apply a downward force of 25 N to the scouring pad, then start the test equipment to make it reciprocate 100 mm at a frequency of 35 times/min. Replace the scouring pad after every 250 times, and test it 500 times in total.

Note: The abrasive material on the surface of the scouring pad is aluminum oxide with a particle size of 400.

Adhesion test

The adhesion test of the coating shall be carried out according to the following steps:

a) Use a paper cutter to evenly scratch 100 1mm×1mm square grids on the bottom of the cooking container. The scratches should go deep into the metal bottom layer.

b) Add no less than 1/4 of the rated volume of pure water into the cooking container and boil for 15 minutes;

c) Pour the purified water out of the container, allow the cooking container to cool naturally to room temperature, and wipe off the water on the coating surface with a paper towel;

d) Use the tape to tightly adhere to the grid area from the diagonal direction of the square, and then quickly pull off the tape at a 90° angle perpendicular to the coating surface;

e) Replace the new tape and repeat step d) for a total of 5 tests.

Note: The tensile strength of the tape is about 82N/100mm.

Corrosion resistance

Acid resistance test

Add acetic acid solution (2%) to the maximum water level of the cooking container, cover it and boil it for 10 minutes. Then set the rice cooker to keep warm for 24 hours. After the test, clean the cooking container, wipe it dry with a soft cloth, and use a 4x magnifying glass to check the changes on the coating surface.

Alkali resistance test

Add sodium carbonate solution (2%) to the maximum water level mark on the cooking container, cover it and boil it for 10 minutes. Then set the rice cooker to keep warm for 24 hours. After the test, clean the cooking container, wipe it dry with a soft cloth, and use a 4x magnifying glass to check the changes on the coating surface.

Salt water corrosion resistance test

Add sodium chloride solution (5%) to the maximum water level of the cooking container, cover it and boil it for 7 hours. During the heating period, add distilled water in time to keep the original solution level unchanged. Then set the rice cooker in the keep warm mode for 16 hours. After the test, clean the cooking container, wipe it dry with a soft cloth and visually inspect the changes on the coating surface.

Insulation temperature

The insulation temperature test is carried out according to the following steps:

a) Fix the thermocouple in a circular area with a diameter of 50 mm and a position (20±5) mm above the bottom of the cooking container, with the axis of the cooking container as the center;

b) cooking the rice in accordance with the maximum amount of rice and rice-to-water ratio specified in the manufacturer's instructions and the working cooking program;

c) Read the temperature 4h, 4.5h and 5h after the appliance enters the insulation state. The arithmetic mean of the three readings is the insulation temperature of the appliance.

life

Coating life

Place the appliance on the test bench and supply power with rated voltage. Add the minimum amount of rice water into the cooking container, start the rice cooking function to conduct a rice cooking test, and cut off the power and cool to room temperature after each cooking. During the cooling period, clean the cooking container and complete the operation of replacing the new rice water load.

For appliances with a rated pressure ≤ 40 kPa and normal pressure appliances, perform 800 cycles continuously.

For instruments with a rated pressure > 40 kPa, perform 500 cycles continuously.

After the test is completed, visually inspect the coating surface of the cooking container.

Note: Appropriate forced cooling measures may be adopted to shorten the cooling time.

Opening button and lid opening and closing life

The appliance opens and closes the lid at a speed of about 10 times/min for a total of 20,000 times. An inspection is carried out after every 2,000 tests and the results are recorded.

After the test is completed, check whether the cooking functions of the appliance can work normally, visually check whether the lid opening button is poorly fastened, broken or disengaged, and whether the lid opens and closes smoothly.

Environmental adaptability

High and low voltage adaptability

Adjust the input voltage of the appliance to 198 V and 242 V respectively, add the maximum amount of rice and the corresponding amount of water specified in the instructions for use into the cooking container, start the appliance to work under the most unfavorable function until the working program is completed.

Temperature adaptability

Add the maximum amount of rice and the corresponding amount of water specified in the instructions for use into the cooking container of the appliance, then place the appliance in an environmental test chamber with an ambient temperature of (-10±2)℃ and (40±2)℃. When the sample temperature is consistent with the ambient temperature, input the rated voltage and start the appliance to work under the most unfavorable function until the working procedure is completed.

Altitude acclimatization

Place the rice cooker horizontally in a high mountain climate test chamber with the altitude of the test chamber set to the highest value specified in the instructions. Add the maximum amount of rice and the corresponding amount of pure water specified in the instructions into the cooking container to test the rice and porridge cooking functions.

During the test, visually inspect the table to see if there is any rice soup dripping onto it.

The rice sample should be divided within 15 minutes after the end of the cooking test. The rice should be divided into three equal parts along the axis of the cooking container and into four equal parts along the circumference of the cooking container to determine whether the rice is undercooked or burnt.

The methods for judging whether the food is undercooked or burnt are as follows:

a) Half-cooked:

---Take out the rice sample blocks and extract a test sample containing about 20 rice grains from each rice sample block;

--- Place the test sample between two pieces of colorless transparent organic glass with mesh grids printed on them. The side length of each grid is 1 mm.

——Apply pressure vertically and evenly to the glass, flatten the test sample as much as possible, and observe and calculate the proportion of the white and translucent parts in the test sample. The white part indicates that the rice is undercooked, and the translucent part indicates that the rice is cooked. The percentage of the white part area to the flattened test sample area indicates the undercooked state of the steamed rice, 0% indicates that the rice is cooked, and 100% indicates that the rice is completely raw.

Determination of raw rice:

● One or two test samples have a degree of undercooking greater than 20%;

●Three or more test specimens have a degree of undercooking greater than 10%.

b) Burnt:

Observe the rice sample close to the bottom of the cooking container. If at least 5 grains turn black or carbonize, it is burnt.

Appointment time deviation

For appliances that are scheduled to complete cooking, add the maximum amount of rice and the corresponding amount of water to the cooking container, set the scheduled time to the maximum time (set to 12 hours if it exceeds 12 hours), start working and start timing, and stop timing after the cooking process is completed. Then calculate the deviation between the actual time and the scheduled time.

For appliances that have a preset cooking mode, when the cooking container is empty, set the preset time to the maximum time (set to 12 hours if it exceeds 12 hours) and start timing until it switches to the cooking state and stops timing. Then calculate the deviation between the actual time and the preset time.