IEC 68-2-18 Test R and Guidance: Water Testing

Foreword

The purpose of this test method is to provide procedures for evaluating the ability of electrical and electronic products to withstand exposure to falling drops (precipitation), impacting water (water jets), or immersion during transportation, storage, and use. The tests verify the effectiveness of covers and seals in ensuring that components and equipment continue to function properly during or after exposure to standardized water exposure conditions.

Scope 

This test method includes the following procedures. Refer to Table 1 for the characteristics of each test.

Test Method Ra: Precipitation

•  Method Ra 1: Artificial Rainfall

        This test simulates exposure to natural rainfall for electrical products placed outdoors without protection.

• Method Ra 2: Drip Box

        This test applies to electrical products that, while sheltered, may experience condensation or leakage leading to water dripping from above.

Test Method Rb: Water Jets

• Method Rb 1: Heavy Rain

        Simulates exposure to heavy rain or torrential downpours for products placed outdoors in tropical regions without protection.

• Method Rb 2: Spray

        Applicable to products exposed to water from automatic fire suppression systems or wheel splash.

           Method Rb 2.1: Oscillating Tube

           Method Rb 2.2: Handheld Spray Nozzle

• Method Rb 3: Water Jet

        Simulates exposure to water discharge from sluice gates or wave splash.

Test Method Rc: Immersion

Evaluates the effects of partial or complete immersion during transportation or use. 

• Method Rc 1: Water Tank
• Method Rc 2: Pressurized Water Chamber

Limitations

• Method Ra 1 is based on natural rainfall conditions and does not account for precipitation under strong winds.
• This test is not a corrosion test.
• It does not simulate the effects of pressure changes or thermal shock.

Test Procedures

General Preparation

Before testing, specimens shall undergo visual, electrical, and mechanical inspections as specified in the relevant standards. Features affecting test results (e.g., surface treatments, covers, seals) must be verified.

Method-Specific Procedures

Ra 1 (Artificial Rainfall):

• Specimens are mounted on a support frame at a defined tilt angle (refer to Figure 1).
• Test severity (tilt angle, duration, rainfall intensity, droplet size) is selected from Table 2. 
• Specimens may be rotated (max. 270°) during testing. Post-test inspections check for water ingress.

Ra 2 (Drip Box):

• Drip height (0.2–2 m), tilt angle, and duration are set per Table 3.
• Uniform dripping (200–300 mm/h) with 3–5 mm droplet size is maintained (Figure 4).

Rb 1 (Heavy Rain):

• High-intensity rainfall conditions are applied per Table 4.

Rb 2.1 (Oscillating Tube):

• Nozzle angle, flow rate, oscillation (±180°), and duration are selected from Table 5.
• Specimens rotate slowly to ensure full surface wetting (Figure 5).

Rb 2.2 (Handheld Spray):

• Spray distance: 0.4 ± 0.1 m; flow rate: 10 ± 0.5 dm³/min (Figure 6).

Rb 3 (Water Jet):

• Nozzle diameters: 6.3 mm or 12.5 mm; jet distance: 2.5 ± 0.5 m (Tables 7–8, Figure 7).

Rc 1 (Water Tank):

• Immersion depth and duration follow Table 9. Water may include dyes (e.g., fluorescein) to detect leaks. 

Rc 2 (Pressurized Chamber):

• Pressure and time are set per Table 10. Post-test drying is required.

Test Conditions

• Water Quality: Filtered, deionized water (pH 6.5–7.2; resistivity ≥500 Ω·m).
• Temperature: Initial water temperature within 5°C below specimen temperature (max. 35°C for immersion).

Test Setup 

• Ra 1/Ra 2: Nozzle arrays simulate rainfall/dripping (Figures 2–4). Fixtures must allow drainage. 
• Rb 2.1: Oscillating tube radius ≤1000 mm (1600 mm for large specimens).
• Rb 3: Jet pressure: 30 kPa (6.3 mm nozzle) or 100 kPa (12.5 mm nozzle).

Definitions

• Precipitation (Falling Drops): Simulated rain (droplets >0.5 mm) or drizzle (0.2–0.5 mm).
• Rainfall Intensity (R): Precipitation volume per hour (mm/h).
• Terminal Velocity (Vt): 5.3 m/s for raindrops in still air.
• Calculations:

          Mean droplet diameter: D _v≈1.71 R^0.25 mm.  

          Median diameter: D ₅₀ = 1.21 R ^0.19mm.  

          Rainfall intensity: R = (V × 6)/(A × t) mm/h (where V = sample volume in cm³, A = collector area in dm², t = time in minutes).  

Note: All tests require post-exposure inspections for water penetration and functional verification. Equipment specifications (e.g., nozzle types, flow rates) are critical for reproducibility.