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rain testing

MIL-STD 810 Rain Testing

The purpose of rain testing is to determine the cause of water ingress related to rain, and its effects on materials. It helps determine the effectiveness of protective covers, cases, and seals in preventing rain ingress. It also demonstrates the ability of the material to perform during and after exposure to water.

Water enclosure testing will also show any physical deterioration of the material caused by the rain. The effectiveness of any water removal system can also be determined. Additionally, the effectiveness of protection offered to a packaged material is tested.

Keystone Compliance is an ingress protection lab with significant MIL-810H rain and MIL-810G rain experience. Our test engineers have an in-depth knowledge of the requirements of ingress protection testing. Below is a summary of Method 512.7, as derived from the MIL-STD 810H rain testing section. It also includes information from the MIL-STD 810G rain section.

How Should Method 512.7 Be Applied?

Rain Testing is used to evaluate material exposed to rain, water spray, or dripping water during storage, transit, or operation. If the material configuration is the same, the immersion test is normally considered to be more severe. Rain testing is not necessary if material has previously passed immersion testing and the configuration is unchanged.

There are documented situations in which rain tests revealed problems not observed during immersion tests due to differential pressure. Immersion tests may be better for material likely to be placed on surfaces with significant amounts of standing water. In most cases, perform both tests if appropriately identified in the life cycle profile.

What are the Limitations of This Method of IP Code Testing?

Weapon systems may be required to operate during weather encounters to include high speed flight through hydrometeors. In such cases, a tailored approach must be used, based on system configuration, trajectories, and system specific statistically based weather occurrence. Traceability must be addressed between realistic flight through weather and ground test methods to ensure adequate performance characterization is achieved. Ground testing may include nylon bead, single water drop, or whirling-arm impact, ballistic gun ranges, and sled track facilities.

Due to limitations of test facilities, it may be difficult to determine atmospheric rain effects on electromagnetic radiation and propagation. This Method is not intended for use in evaluating the adequacy of aircraft windshield rain removal provisions. Nor does it address pressure washers or decontamination devices. It may aid in determining the effects of extended rain exposure, or exposure to light condensation drip rates from overhead surfaces.

What are the  Effects of Rain Environments?

Rain water falling, upon impact, or deposited as pooled water has a variety of effects on material. Consider the following typical problems to help determine if this Method is appropriate for the material being tested. This is not intended to be all-inclusive, and some of the examples may overlap the categories.

In the Atmosphere

There are a variety of effects that could result from exposure to wet atmospheric environments. There could be interference with radio communication, or limited radar effectiveness. Restricted visibility and decreased lift from wing surface could lead to limited aircraft operations or damage to an aircraft in flight.

Water Enclosure Ingress in wet atmospheres may also affect munitions launch and flight. It could lead to degradation or negation of optical surveillance, and decreased effectiveness of personnel in exposed activities. It could also lead to premature functioning of some fuses, and inhibited visibility through optical devices.

On Impact

The effects of rain upon direct impact of a material includes surface erosion.

After Deposition and/or Penetration

After deposition and/or penetration, there are several possible effects that could result from exposure to these environments. Some materials may not be as strong, or may have increased potential for corrosion, erosion, or fungal growth. Additionally materials may weigh more as a result of water ingress.

Electrical or electronic apparatus may become inoperative or unsafe. There may be further malfunction of electrical material. Freezing inside material may cause delayed deterioration and malfunction by swelling or cracking of parts. Additionally, there is potential for modified thermal exchange and slower burning of propellants.

What Are the Different Procedures for Rain Compliance Testing?

Procedure I, Rain and Blowing Rain, is useful for out-of-doors materials that are unprotected from rain or blowing rain. The accompanying wind velocity can vary from almost calm to extremely high. For large material this test may not be adequate. In this case consider Procedure II.

Procedure II, Exaggerated, is best for large (shelter-size) material, when a blowing-rain facility is not available or practical. This procedure is not intended to simulate natural rainfall but does provide confidence in the watertightness of material.

Procedure III, Drip, is best for material normally protected from rain, that may be exposed to condensation or leakage. This comes from upper surfaces. The drip test will vary based on material that may experience falling water or subjected to heavy condensation or leaks.

What is the Rainfall/Drip Rate for Each Procedure?

The rainfall rate used in Procedure I may be tailored to the expected deployment locale and duration. A minimum rate of 1.7 mm/min (4 in/hr) is recommended. This rate is not uncommon, and provides a reasonable degree of confidence in the material.

Procedure II generally uses a 276 kPa nozzle pressure with a flow rate of 5.5 gal/min. This should produce water droplets traveling at approximately 64 km/h (40 mph). Procedure III has a requirement for a volume of water greater than 7 gal/ft2/hr dripping through a predetermined hole pattern.

Procedure II has an alternative requirement for items exposed only to 3.5 gal/ ft2/hr. When the duration of the test is extended, reduce the drip rate so there is an equal volume of water.

How Should the Wind Velocity be Measured for the Best Rain Testing?

High rainfall intensities accompanied by winds of 18 m/s are not uncommon during storms. This is the recommended velocity, unless otherwise specified.. Where facility limitations preclude the use of wind, use Procedure II.

What Rain Testing Lab Should you Trust to Get Ip Code Certifications for your Product?

Keystone Compliance has been recognized as one of the best rain labs in the country. We employ experienced test engineers who understand the requirements of MIL-810 rain compliance standards. Our enclosure testing lab is fully equipped with the appropriate devices.

Are you looking for a rain laboratory to perform compliance testing for your product?  Keystone Compliance is equipped to provide rain certifications for commercial, military, and aerospace products. Contact us to learn why so many manufacturers rely on Keystone Compliance to meet their compliance testing needs.

There have been several versions of rain testing procedures in MIL-STD-810 rain testing. Below is a list of each version and the appropriate method number: