The inspection method of electric heaters for railway passenger cars usually follows a series of strict standards and procedures to ensure their quality and safety. The following is the inspection method of electric heaters for railway passenger cars compiled according to the relevant implementation rules issued by the National Railway Administration:

1. Sampling
Sampling plan: A one-time sampling inspection plan is adopted to randomly select a certain number of samples as a sample. The specific sampling quantity and requirements are determined according to the railway product supervision and random inspection plan.
Sampling location: Samples can be taken at the manufacturer or user.
Sampling requirements: The inspection agency commissioned by the National Railway Administration organizes personnel to take samples. The samples to be inspected should be products produced within two years, inspected and qualified by the manufacturer, and not used.
2. Inspection conditions
Inspection environmental conditions: Carry out in accordance with the test conditions specified in the standards.
Main instruments and equipment for inspection: including steel tape measure, digital push-pull force gauge, insulation resistance tester, withstand voltage tester, program-controlled ground resistance tester, leakage current tester, power analyzer, etc., to ensure that all instruments and equipment are in normal working condition and have metrological verification/calibration certificates.
3. Inspection content and inspection method
The inspection items of railway passenger car electric heaters usually include but are not limited to the following aspects:

Appearance and size inspection: Check whether the appearance of the heater is intact and whether the size meets the requirements.
Marking: Check whether the marking of the heater is clear and accurate, including information such as model, production date, manufacturer, etc.
Tensile test: Tensile tests are performed on certain parts of the heater to ensure its structural strength.
Insulation resistance test: An insulation resistance tester is used to measure the insulation resistance of the heater to determine whether its insulation performance is good.
Dielectric strength test: Including cold dielectric strength test and wet hot dielectric strength test, use a withstand voltage tester to test the heater at a specified voltage and time to check whether it flashes or breaks down.
High-voltage circuit leakage current test: During the dielectric strength test, measure the leakage current of the high-voltage circuit of the heater to ensure that it meets the specified requirements.
Grounding resistance test: Use a programmable grounding resistance tester to measure the grounding resistance of the heater to ensure that its grounding performance is good.
Leakage current test: Under rated working voltage, measure the leakage current of the heater to determine whether it exceeds the specified range.
Power test: Measure the actual power of the heater to verify whether it meets the design requirements.
Temperature check: Check the temperature change of the heater during operation through a temperature sensor or digital thermometer.
Noise test: Use a sound level meter to measure the noise level of the heater during operation.
Flame retardant test: Pour a certain amount of gasoline on the electric heating plate or electric heating tube of the heater, and observe whether there is an open flame at the rated voltage to check its flame retardant performance.
Over-temperature protection performance test: Check whether the heater is equipped with an over-temperature protector, and conduct the test under the set conditions to verify the working performance of the over-temperature protector.
IV. Inspection procedure
Preparation before inspection: After receiving the inspection sample, the inspection agency shall check the integrity of the seal and seal of the sample, inspect the sample, and record its appearance, status, and other information.
Inspection operation: The inspector shall conduct the inspection according to the prescribed inspection method and inspection conditions, and fill in the original inspection record truthfully.
Processing after the inspection: After the inspection, the condition of the inspected samples and the status of the instruments and equipment should be carefully checked and recorded. For qualified samples, they should be returned to the manufacturer after the results of the supervision and random inspection are announced; for unqualified samples, they should be returned 3 months after the results of the supervision and random inspection are announced, or the situation should be explained to the manufacturer if they cannot be returned.
V. Determination of inspection results
According to the data and results of the inspection records, the samples are individually judged according to the prescribed judgment scheme. Usually, the judgment scheme for Class A and Class B unqualified is [n; Ac, Re], where "n" is the number of Class A and Class B unqualified inspection samples, "Ac" is the qualified judgment number, and "Re" is the unqualified judgment number.

In summary, the inspection method of railway passenger car electric heaters involves sampling, inspection conditions, inspection content and methods, inspection procedures, and the determination of inspection results. Through these inspection methods and procedures, it can be ensured that the quality and safety of railway passenger car electric heaters meet relevant regulations and requirements.