Flash Point Testing

Our test method adheres to ASTM D93 / ISO 2719 / ASTM D 3828, and uses the same quality system as our accredited methods. 

Flash point measures the response of the test specimen to heat and an ignition source under controlled laboratory conditions. It can be performed as a closed or open cup method. It is only one of a number of properties that must be considered in assessing the overall flammability hazard of a material.

A flash point is used in shipping and safety regulations to define flammable and combustible materials and classify them. Flash point data will also indicate the possible presence of highly volatile and flammable materials in a relatively non-volatile or non-flammable substance.

There are several closed cup methods used at Sigma-HSE to determine the flash point of a gas or vapour. This includes Seta-Flash Point testing and Pensky Martens closed cup methods. We do not currently perform the open cup methods.

A test specimen (75 ml) is introduced into the test cup of the apparatus and the lip assembly is attached. A sample is heated at a rate of 1.0 to 1.6°C per minute with continual stirring at 250 rpm. A small flame with a diameter of 3.2 to 4.8 mm is directed into the cup containing the sample, at regular intervals, with simultaneous interruption of stirring.

Testing is started at 23 ± 5 °C below the expected flashpoint (or at ambient if unknown) with the source of ignition applied at 1 °C intervals, for temperatures up to 110 °C, and 2 °C for temperatures above 110 °C. Further trials on fresh materials are conducted starting 23 ± 5 °C, below that of the lowest ignition temperature observed in the initial trial. The flashpoint is the lowest temperature at which the application of a flame results in the ignition of vapour above the sample.

A test specimen (2ml for temperatures up to and including 100 °C, 4 ml for temperatures above 100 °C) is introduced into the test cup of the apparatus that is maintained at the expected flashpoint (or ambient temperature if the expected flashpoint is not known). After a specified time (1 minute for temperatures up to and including 100 °C, 2 minutes for temperatures above 100 °C) a source of ignition is applied, and a determination is made whether or not a flash occurred.

The test specimen is removed from the test cup; the test cup and cover are cleaned, and the test temperature is adjusted to 5°C lower or higher depending on whether or not a flash occurred. A fresh test specimen is introduced and tested. This procedure is repeated until the flashpoint is established within 5°C. Finally, the procedure is then repeated at 1°C intervals until the flash point is determined to the nearest 1°C.

Many products containing small quantities of materials with a low flashpoints can still dominate the flammability characteristics, especially flashpoint. Even in an aqueous solution, materials of high volatility will be driven off at low temperatures. Equally, a mixture of materials with similar volatility characteristics and differing individual flashpoints can produce an averaging scenario.

Therefore, assumptions are far from ideal when assessing liquid mixtures for flammability. Testing is the only way to confidently ensure a flammable atmosphere is either avoided or understood, and there the only way to apply appropriate safety measures.