4. Environmental testing standards

4.1 GB/T4796&IEC60721-1 'Classification of Environmental Conditions for Electrical and Electronic Products - Part 1: Environmental Parameters and Their Severity'

GB/T4796 lists the environmental conditions and their severity encountered during transportation, storage, installation, and use of electrical and electronic products. The environmental conditions are classified, severity levels, and specific parameters are provided. These environmental classifications can be used as a comprehensive consideration for designing product environmental tests.

4.1.1 Environmental factors and parameters

1. Overview

The environmental conditions under which products are exposed are usually complex, including multiple environmental factors and corresponding parameters. Therefore, when determining the environmental conditions for a product application, the following two points should be considered:

——List the environmental factors involved;

——Select the appropriate severity level for each parameter.

The impact of the environment on the product under certain application conditions is caused by the following reasons:

——The surrounding medium conditions, usually atmospheric or water (in some cases soil);

——The structural conditions connected to the product;

——External influences.

Therefore, when selecting environmental factors and parameters for the application conditions of a certain product, it is necessary to examine the impact of individual, combined, and sequential environmental factors when these conditions occur.

In terms of application, the environmental factors and parameters used are basically the same as those used in GB2423.5.

2. List of individual environmental factors and their severity

Table 1 of this standard provides the classification, parameters, and severity of individual environmental factors (see Table 1 of GB4796 standard for details):

——Climatic conditions:

1) Cold and hot: including temperature and temperature change rate;

2) Humidity: including relative humidity and absolute humidity;

3) Pressure: including air pressure, water pressure, and pressure change rate;

4) The movement of the surrounding medium, including the movement of the product relative to the surrounding medium: including velocity

5) Precipitation: including rain, drifting snow, and hail;

6) Radiation: including solar radiation, thermal radiation, and ion radiation;

7) Water other than rainwater: including dripping, splashing, spraying, jetting, and water waves, immersion or semi immersion;

8) Moist;

9) Condensation;

10) The formation of ice and frost.

——Biological conditions:

1) Flora;

2) Fauna;

——Chemical active substances:

1) Sea salt;

2) Road salt;

3) Sulfur dioxide;

4) Hydrogen sulfide;

5) Nitrogen oxides;

6) Ozone;

7) Ammonia gas;

8) Chlorine gas;

9) Hydrogen chloride;

10) Hydrogen fluoride;

11) Organic hydrocarbons.

——Mechanically active substances:

1) Sand: including gravel;

2) Dust: including suspended dust and dust deposition;

3) Mud;

4) Smoke moss.

——Polluting liquids:

1) Engine oil;

2) Gearbox oil;

3) Hydraulic oil;

4) Transformer oil;

5) Brake fluid;

6) Cooling liquid;

7) Lubricating grease;

8) Fuel;

9) Battery electrolyte.

——Mechanical conditions:

1) Vibration: including sinusoidal steady-state vibration, with A-type spectrum, B-type spectrum, C-type spectrum, and D-type spectrum; Random steady-state vibration, with G-type spectrum and H-type spectrum; Non steady state vibration, including shock, includes L-type spectrum, I-type spectrum, II-type spectrum, and III-type spectrum;

2) Fall: Free fall;

3) Collision: external collision;

4) Swing and tilt, dynamic;

5) Swing and tilt, static;

6) Steady state acceleration;

7) Static load;

8) Tilt and invert.

——Electrical and electromagnetic interference:

1) Magnetic field: including field strength;

2) Electric field: including field strength and field variability;

3) Harmonics;

4) Signal voltage: including amplitude;

5) Voltage and frequency changes: including voltage fluctuation amplitude, voltage drop or interruption, voltage imbalance, and frequency changes;

6) Induced voltage: including amplitude;

7) Transient: including rise time, duration, amplitude, and rate of current change.

The environmental factors and parameters in Table 1 are used for:

——As a checklist to ensure that all relevant factors and parameters are taken into account;

——Achieve consistency in describing the environment.

The severity levels given in Table 1 for each parameter are for standardization purposes and are limited to the severity grading of the environmental conditions that the product may be subjected to.

It does not involve the severity caused by the stress of the product itself, for example, this severity only involves the temperature of the surrounding medium (air, water, soil, water vapor, ice, oil, etc.) and the temperature of the structure connected to the product, and does not involve the temperature of the hot spot of the product itself.

This severity level is only related to limited environmental conditions, which do not include conditions for benchmark measurement and calibration.

Table 1 of this standard provides the following individual environmental factors and their severity levels

3. Combined environmental factors

The product is simultaneously exposed to several environmental factors and corresponding parameters. When exposed to a combination of environmental factors and a series of environmental factors have different impacts on the product, the impact of the combination of environmental factors is particularly important.

Therefore, when selecting environmental factors for a certain application, it is recommended not only to examine environmental factors, but also to consider a combination of environmental factors as much as possible. The severity level classification of corrosion and aging of metal materials and polymer materials in the atmospheric environment by combining environmental factors is shown in Appendix NA, and the severity level is classified based on the measured values of characteristic changes of standard specimens in Appendix NB.

4. Order of environmental factors

The impact of product exposure to environmental conditions is the result of sequential exposure to two or more factors and parameters. Here are two important examples:

——Thermal shock: Immediately exposing products to low temperatures to high temperature conditions, or vice versa, directly exposing products to high temperatures to water (rain, jet water, waves, immersion), forming thermal shock.

——Ice formation: Immediately exposing the product to temperatures below freezing point before or after exposure to moisture, rain, or other water other than rain can lead to ice formation.

When determining the environmental conditions that a product will be exposed to, these possibilities should be taken into account.

Appendix NA: Environmental Corrosion and Aging Severity Classification of Metals and Polymer Materials

This appendix characterizes the severity level of the atmospheric environment through two methods: metal material environmental corrosion and polymer material environmental aging.

The environmental corrosion of metal materials is mainly affected by environmental factors such as humidity time, concentration of sulfur dioxide and chloride pollutants. The severity of atmospheric corrosion is divided into five levels, as shown in Table NA.1 of the standard.

The environmental aging of polymer materials is mainly affected by environmental factors such as temperature, humidity, and solar radiation intensity. The severity level of environmental aging of polymer materials is also divided into 5 levels, as shown in Table NA.2 of the standard.

Appendix NB: Severity classification based on measured values of characteristic changes of standard specimens

NB. 1 Classification of atmospheric corrosion severity based on metal standard specimens

The severity level of corrosion is evaluated using the corrosion rate of standard metal materials such as carbon steel, copper, zinc, and aluminum in the first year, as shown in Table NB. 1. The corrosion rate in the table is calculated based on uniform corrosion. In addition, if the corrosion rate of the standard sample in a certain atmospheric environment exceeds the upper limit of C5 level, it indicates that the severity of the atmospheric environment exceeds the range of this standard.

NB. 2 Climatic Aging Severity Grading Based on Polymer Standard Specimens

The color change value at the end of the test for polymer standard samples such as PS and PC, corresponding to each aging severity level. To evaluate the short-term severity of a certain area (no more than half a year), it is recommended to use PS as the standard sample for evaluation, and the exposure time is half a year; To evaluate the mid-term severity of a certain area (one to two years), it is recommended to use PC as a standard sample for evaluation, with an exposure time of one year; The specific color difference requirements are shown in Table NB. 2, and the color difference values in the table cannot be extrapolated to estimate long-term aging behavior. If the color difference of the standard sample in a certain atmospheric environment exceeds the upper limit of the W5 level, it indicates that the severity of the atmospheric environment exceeds the range of this standard.