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MIL-STD 202 Sand and Dust Testing

The dust test is used to ascertain the ability of equipment to resist the effects of a dry dust and sand laden atmospheres. Use this Method to evaluate mechanical, optical, electrical, electronic, electrochemical, and electromechanical devices exposed to sand or dust atmospheres. This test simulates the effect of dust particles up to 150 microns in size, which may penetrate into cracks, crevices, bearings, and joints.

The damage these particles may cause includes fouling moving parts and making relays inoperative. They may also form electrically conductive bridges with resulting “shorts.” The may also act as a nucleus water vapor, and hence a source of possible corrosion and malfunction .

Keystone Compliance is a sand and dust testing lab with significant understanding of MIL-202 sand and dust testing. Our test engineers are experts in MIL-STD 202H sand and dust testing and MIL-STD 202G sand and dust testing. Below is outlined the requirements of solid particle enclosure testing. The following information is extremely technical in nature, and derived from MIL-202H sand and dust and MIL-202G sand and dust.

What Equipment Should a Sand and Dust Laboratory Have?

Ingress protection labs should have a chamber and accessories to control dust concentration, velocity, temperature, and humidity. Adequate circulation of the dust laden air is necessary. Therefore no more than 50% of the cross-sectional area and 30% of the volume of the chamber is occupied by the test item.

The chamber must be able to maintain and verify the dust concentration in circulation. A minimum acceptable means for doing this is by use of a properly calibrated smoke meter and standard light source. The dust-laden air is introduced into the test space so as to allow it to become approximately laminar in flow, before striking the test item.

What Dust is Required for Sand and Dust Ingress Testing?

The dust used in the dust test lab, for ingress protection testing, should be a fine sand of angular structure. It should have the following size distribution, determined by weight using the U.S. Standard Sieve Series:

Exactly 100 percent of this dust shall pass through a 100-mesh screen.
Around 98 plus or minus 2 percent of the dust shall pass through a 140-mesh screen.
Around 90 plus or minus 2 percent of the dust shall pass through a 200-mesh screen.
Around 75 plus or minus 2 percent of the dust shall pass through a 325-mesh screen.

What is the Proper Procedure for Dust and Sand Ingress Testing?

Place the test item in the sand test lab’s chamber, positioned as near the center of the chamber as possible. If more than one item is being tested, there should be at least 4 inches between test items or other material able to furnish protection. Also, no surface of the test item should be closer than 4 inches from any wall of the test chamber. Orient the item to expose the most critical or vulnerable parts to the dust stream, this may change during the test if specifically required.

Step 1: Set the chamber controls to maintain an internal chamber temperature of 23°C and a relative humidity of less than 22%. Adjust the air velocity to 1,750 plus or minus 250 feet per minute. Adjust the dust feeder to control the dust concentration at 0.3 plus or minus 0.2 grams per cubic foot. Maintain these conditions for 6 hours without operating the test item.

Step 2: Stop the dust feed and reduce the air velocity to 300 plus or minus 200 feet per minute. Raise the internal chamber air temperature to 63°C. Adjust humidity control to maintain a relative humidity of less than 10%. Hold these conditions for 16 hours.

Step 3: While holding chamber temperature at 63°C adjust the air velocity to 1,750 plus or minus 250 fpm. Maintain a relative humidity of less than 10%. Adjust the dust feeder to control the dust concentration at 0.3 plus or minus 0.2 grams per cubic foot. Maintain these conditions for 6 hours without operating the test item.

Step 4: Turn off all chamber controls and allow the test item to return to standard ambient conditions. Remove accumulated dust from the test item by brushing, wiping, or shaking. Be careful avoid introducing additional dust into the test item. Under no circumstances, should dust be removed by air blast or vacuum cleaning.

NOTE: This test specimen may be operating during either or both of the 6-hour test periods (step 1 or 3) if required component specification. When component specifications reference test conditions A, B, or C of the previous version of this test, steps 1 – 4 are used unless otherwise specified.

What are the Effects of Sand and Dust Environments on Materials?

Blowing sand and dust environments are typical of hot-dry regions, but exist seasonally in other regions. Naturally-occurring sand and dust storms are important, but the induced environment created by operation can be more severe. The best particle enclosure ingress testing occurs in ingress protection labs. The following paragraphs contain a few examples of the effects of sand and dust on materials.

These environments may cause abrasion and erosion of surfaces, and the penetration of particles through seals. They may degrade the performance of electrical circuits, and cause water. Particles may obstruct openings and filters, causing a fire hazard due to restricted ventilation or cooling. They may also interfere with matting and moving parts.

Particle ingress may reduce heat transfer, or interfere with optical characteristics. Materials may experience increased chafing between non-mating contacting surfaces. Issues with static/dynamic balance may arise due to increased weight. Sand and dust may also lead to attenuation of signal transmission.

Which Laboratories Will Provide the Best Sand and Dust Testing for my Product?

Keystone Compliance has been recognized as one of the best sand and dust labs in the country. We employ experienced test engineers to provide quality sand and dust compliance testing. Our enclosure testing lab is equipped to provide sand and dust 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.

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