Water Reactivity 1

Some materials, when in contact with water emit gases that could be flammable. This test is intended to determine whether the reaction of a substance with water leads to the development of a dangerous amount of gases which may be flammable. The test applies to both liquid and solid substances. The “Dangerous When Wet” (DWW) test is a classification criterion used for certain substances or chemicals that possess the potential to react dangerously or release flammable gases when they come into contact with water. This test determines whether a substance exhibits hazardous properties when wet, particularly concerning its reactivity with water or moisture.

Testing Principle and Methodology

The standard recommendation is to test the material in its commercial form, that is as received. In case of uncertainty on how to perform the testing please contact Prime Process Safety Center for guidance. At Prime Process Safety Center, we would need 100g of the material to perform the testing. The test is generally conducted by addition of distilled water to the material to observe any evolution of gas and possible subsequent ignition.

Applicable Standard

The test is conducted according to the UN/DOT, section 33 ‘’Classification Procedures, Test Methods and Criteria relating to class 4’’.

Test Method

The test consists of two parts. The screening part where a small amount of the material to be tested, typically about 2 mm in diameter is brought into contact with distilled water and an observation is made of any evolution of gas and subsequent ignition of the gas. If the gas ignites during the screening test, no further test is necessary, and the material is classified as Division 4.3. If the material does not ignite after a series of screening tests, the final stage of the test is performed to determine the rate of emission of the flammable gas.

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Data Interpretation

A substance is classified as Division 4.3 if;

  • Spontaneous ignition occurs in any step of the test procedure.
  • There is an evolution of a flammable gas at a rate greater than 1 Liter per kilogram of the substance per hour.

Packing group I is assigned to any substance which reacts vigorously with water at ambient temperatures and generally demonstrates a tendency for the gas produced to ignite spontaneously, or which reacts readily with water at ambient temperatures such that the rate of evolution of the flammable gas is equal to or greater than 10 litres per kilogram of substance over any one minute period.

Packing group II is assigned to any substance which reacts with water at ambient temperatures such that the maximum evolution of flammable gas is equal to or greater than 20 litres per kilogram of substance per hour and which does not meet the criteria for packing group I.

Packing group III is assigned to any substance which reacts slowly with water at ambient temperatures such that the maximum evolution of flammable gas is greater than 1 litres per kilogram of substance per hour and which does not meet the criteria for packing group II.

When to perform the Dangerous When Wet Test

The “Dangerous When Wet” (DWW) test is typically performed on substances or materials known or suspected to react dangerously when exposed to water or moisture. The test helps in identifying and classifying substances that exhibit hazardous properties upon contact with water. Instances where the test is recommended are

  • when New Substance Identification is required,
  • during classification and Labeling,
  • during Safety Data Sheets (SDS) Creation,
  • Risk Assessment and Safety Protocols,
  • Transportation and Handling Precautions, and
  • Environmental Impact Assessment.

Why work with Prime Process Safety Center

  • Prime Process Safety Center is a leader in process safety testing with very experienced laboratory personnel. At Prime Process Safety Center our ultimate goal is to provide accurate, reliable and defensible data that meets industry and regulatory standards. We understand the need for the quality of your data, and we work assiduously to achieve just that.
  • We are knowledgeable and experienced in performing dangerous when wet test, ensuring accurate and reliable results.
  • We have state-of-the-art dangerous when wet test equipment, providing precise and sensitive measurements.
  • We follow strict testing protocols and quality control measures to ensure consistent and reliable test results.
  • Our team can interpret and analyze the data obtained from the tests, providing valuable insights and recommendations for your specific application or research.

FAQs

What is the "Dangerous When Wet" (DWW) classification?

Answer: The DWW classification refers to substances or materials that pose hazards or react dangerously when they come into contact with water or moisture. This classification identifies materials that exhibit hazardous properties upon wetting.

Why is a substance classified as "Dangerous When Wet"?

Answer: A substance receives the DWW classification if it reacts violently, produces flammable or toxic gases, or poses other hazards upon contact with water. The classification warns handlers about potential risks associated with moisture exposure.

How is the DWW test performed on substances?

Answer: The DWW test involves exposing a sample of the substance to controlled amounts of water or moisture to observe its reactions. The test determines if the material exhibits hazardous properties, such as reactivity, flammability, or gas generation, when wet.

What types of substances are typically classified as "Dangerous When Wet"?

Answer: Substances classified as DWW can include reactive metals like sodium or potassium, chemicals generating flammable gases upon contact with water, pyrophoric materials spontaneously igniting, and other materials reacting dangerously when exposed to moisture.

What precautions should be taken for substances classified as "Dangerous When Wet"?

Answer: Handling, storage, transportation, and disposal procedures for DWW materials should involve specific precautions, including appropriate packaging, labeling, training for personnel, avoiding contact with water or moisture, and implementing emergency response plans.