Rain, MIL-STD-810, Method 506 is used to evaluate materiel likely to be exposed to rain, water spray, or dripping water during storage, transit, or operation. It can also be used to evaluate seals, enclosures, and covers to prevent ingress of water, access effectiveness of water removal systems, and evaluate the physical deterioration of materials due to exposure to water.
The method is not appropriate, however, for evaluating the effects of flight through rain, evaluation of pressure washers or decontamination devices, or the effects of extended light precipitation. It is also not intended for evaluating equipment to atmospheric effects caused by rain.
Available Procedures for Rain Testing
MIL-STD-810 has three procedures to evaluate materials ability to withstand rain:
- Procedure I – Rain and Blowing Rain is used to evaluate items that will be deployed in conditions that are unprotected from rain. This procedure uses a rainfall drip rate of 4 inches per hour (1.7 mm per minute) as a minimum for testing.
The simulated rain must be comprised of droplets of approximately 500 μm in diameter. Unless otherwise tailored, the test uses a wind velocity of 40 mph (18 m/s). The test item should be stabilized to a temperature 18 °F (10 °C) higher than the water being used for rain.
- Procedure II – Exaggerated uses rain simulated with overlapping pressure nozzles. This method is often used when the test item is too large to be tested with the blowing rain method. While it does not simulate rain, it can be used to a degree of confidence in the watertightness of an item. The test incorporates a 50 psig (276 kPa) pressure with a flow rate of 5.5 gallons per minute (20.8 liters per minute).
- Procedure III – Drip is used to simulate the conditions where items may be exposed to falling water from leakage in a storage area or drops caused by condensation. This test uses a minimum rate of 7 gallons per square foot per hour (280 liters per square meter per hour).
The Challenges of Preventing the Penetration of Water
Wind blown rain creates resonances that can penetrate gasketing materials used in covers, cases, and seals. In many cases, test items that have passed immersion testing can still have ingress problems with blowing rain. These problems create issues for designers in any number of fields where rain exposure is expected. Where MIL-STD testing is not applicable, other standards are available for ingress protection testing such as IEC 60529.
IEC 60529 is typically applied to commercial products and their ability to keep the environment from interfering with the operation of a product. Ratings are defined by the letters IP followed by two digits and an optional letter. It classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures. The standard aims to provide users more detailed information than vague marketing terms such as waterproof.
Detailed Environmental Test Plan Templates
CVG Strategy offers EZ-Test Plan Templates for MIL-STD environmental (climatic/dynamic) and EMI/EMC testing documentation. Our Detailed Environmental Test Plans (DETP)s are written as specified in MIL-STD-810 Task 405. They are available for specific applications such as Ground Mobile, Ground Stationary, and Shipboard Controlled, Shipboard Uncontrolled, and Aircraft Military.
These DETPs include appropriate test methods, (such as Rain MIL-STD-810 Method 506) addendums for product specific information, test labels for photo identification and data sheets for collection of required data. Profile (LCEP).
Our Electromagnetic Interference Test Plans are written as specified by the Department of Defense. They contain the test methodology, addendums for product specific information, test labels for photo identification and data sheets. These plans are available for procedures listed in MIL-STD-461 and are also available for MIL-STD-1275, MIL-STD-704, and MIL-STD-1399-300.
Custom Test Plans are also available for applications not covered in the EZ-Test Plan offerings. These plans can be written for any number of applications and their relevant standards.
Put CVG Strategy’s Experience to Work for You
Companies of all sizes, from start up to established product developers, face challenges in product test and evaluation. This can particularly be the case when a product is developed for a new market sector or expanding sales internationally.
Properly tested products prevent costly product recalls, product redesign, and product liability. They maintain customer satisfaction and keep your company’s reputation in good standing. Contact CVG Strategy to see how our testing services can assist your engineering team with Rain, MIL-STD-810, Method 506, or any other test and evaluation concern.