UN Transportation Testing

Recommendations on the Transport of Dangerous Goods, UN Manual of Test & Criteria – UN Test O.1

The Oxidising Solids – UN Test 0.1 is primarily conducted for the purposes of transportation testing. Mixtures of a reference oxidiser (potassium bromate) / cellulose (fuel) and the mixtures of the substance and cellulose (fuel) that are to be tested are prepared in specific ratios. Using a conical funnel, the mixtures are formed into a truncated conical pile which is covered by a looped ignition wire that rests on a low-heat conducting plate. Power is then applied to the ignition wire and is maintained for the duration of the test.

A recorded burning time is taken from when the power is switched on, to the flash point when the main reaction (e.g. flame, incandescence or glowing, spontaneous combustion) ends. This test is performed on the cellulose ratio five times.

Each controlled substance is also subject to five tests, with each reference mixture ratio required to identify and make a packing group assignment to determine if the substance should not be classified in Division 5.1. The test method is identical to that detailed within CLP/GHS regulatory procedures and therefore, the test results and data thus gathered can be used for both applications.

Materials and substances that are classified for transportation alongside oxidizing substances, such as oxidising solids, are usually based on either guesswork or comparative studies. These are often incorrect and large costs associated with sustainable transport with classified oxidised substances and materials can be avoided. If a product contains a known oxidising constituent, it doesn’t simply mean the blend of oxidizing substances should also be classified.

Recommendations on the Transport of Dangerous Goods, UN Manual of Test & Criteria – UN Test N.4

The same test method is un manual of tests conducted to determine whether a solid material should be classified, for example, transportation as a Self-Heating Solid of UN Class 4, Division 4.2. The same test technique applies to classification under CLP as a Self-Heating Solid (H.251 & H.252)

The sample container, in its commercial form, is filled to the brim of the wet test basket and the basket is tapped several times. More material is added, if the material is seen to have settled. The wet test basket is housed in the hot wire mesh cover and placed into the centre of a preheated, hot air, circulating oven, set to the required test temperature.

The initial test is conducted using a 100 mm cube sample, at a temperature of 140 °C. The sample temperature and oven temperature are continually monitored, using inconel sheathed thermocouples over a test period of 24 h (unless ignition is detected earlier). If ignition is not observed, then the material is not classified as a self-heating solid. If ignition is observed, then the material is classified, and further testing is required to designate the correct packing group and/or define the classification exemption conditions.

Although the material may be self-heating if transported within specified volume restrictions, exceptions can be made and therefore huge costs are avoided. These exemptions can only be determined through testing.

Recommendations on the Transport of Dangerous Goods, UN Manual of Test & Criteria – UN Test N.1

The Readily Combustible Solids or Flammability of Solids (Burning Rate) – UN Test N.1 is conducted to determine whether a solid material should be classified for transportation as a flammable, or readily combustible, substance of UN Class 4, Division 4.1. The same test technique has the ability to be applied to the classification of CLP as a Flammable Solid (H.228)

A powder train strip is formed using a triangular cross-sectioned mould onto a heat-resistant, non-porous plate. Using a butane flame, one end of the powder train the strip is ignited and an initial time taken to burn over a marked 200 mm length is recorded.

If the burning rate test time is equal to, or less than 120s, then further trials are conducted over fresh powder strips. The burning time and burning rate test over a length of 100 mm are measured.

If the time taken is equal to or less than 45 s (2.2 mm.s-1) then the material is classified as a ‘Flammable or Combustible Solid, of UN Class 4, Division 4.1. During the 100 mm trials, a section of the material past the 100 mm mark is subjected to wetting and observations are made to whether the wetted zone, stops flame propagation for at least 4 minutes.

If the wetted zone fails to stop propagation, the material is designated to packing group 2. If it succeeds, a packing group 3 designation is given.  The preliminary screening test method is identical to that detailed within CLP/GHS’ regulatory requirements and procedures and therefore, the test data as gathered and carried out by the preliminary screening test can be used for both applications.

Materials that are being classified for the transport and packaging of dangerous goods as a flammable solid, based on either guesswork or comparative studies are often incorrect and the large costs associated with classified flammable materials can be avoided. Because a product, contains a known flammable constituent, doesn’t simply mean the blend should also be classified.