Our Solutions: Testing
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Gas & vapour testing
Gases, vapours and similar substances have the potential to create risk for fire and explosions. Understanding the properties related to the risk of these hazardous materials is essential to optimising safety for your processes.
Sigma-HSE’s gas & vapour testing labo0ratory offers comprehensive standard and custom testing packages to aid you in the identification of potentially hazardous gases and vapours in your work environment.
We offer a wide range of gas & vapour tests.
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ASTM D 93 / ISO 2719 / ASTM D 3828
The flashpoint is conducted to determine the lowest temperature at which a liquid will liberate sufficient vapour that will briefly ignite (flash).
Flashpoint measures the response of the test specimen to heat and ignite under controlled laboratory conditions. It is only one of a number of properties that must be considered in assessing the overall ﬂammability hazard of a material. Flash point is used in shipping and safety regulations to deﬁne ﬂammable and combustible materials and classify them. Flash point can indicate the possible presence of highly volatile and ﬂammable materials in a relatively non-volatile or non-ﬂammable material.
There are several closed cup methods used at sigma to determine a flashpoint
A test specimen (75 ml) is introduced into the test cup of the apparatus and the lip assembly attached and the 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 ignition source application at 1 °C intervals, for temperatures up to 110 °C, and 2 °C for temperatures above 110 °C. Further trials on fresh material are conducted starting 23 ± 5 °C, below that of the lowest ignition temperature observed in the initial trial. The flash point is the lowest temperature at which the application of a flame results in an ignition of the 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 ﬂash point (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) an ignition source is applied, and a determination 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 adjusted 5°C lower or higher depending on whether or not a ﬂash occurred previously. A fresh test specimen is introduced and tested. This procedure is repeated until the ﬂash point 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 even very small quantities of material with a low flashpoint 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.
The auto-ignition temperature (AIT) test is conducted to determine the lowest temperature at which a substance will produce hot-flame ignition in the air at a specific atmospheric pressure, without the aid of an external energy source such as a spark or flame. It is the lowest temperature at which a combustible mixture should be raised, so that the rate of heat evolved by the exothermic oxidation reaction will overbalance the rate at which heat is lost to the surroundings and cause ignition.
The test is predominantly conducted on liquids, however gases and solids capable of full vaporisation so they can be tested using the method below:
Working through a range of material concentrations, the material is injected into a heated and thermally stabilised, 500 ml round bottom flask. Once an ignition temperature is observed, the flask temperature is reduced, and the material concentration is varied until an AIT is established.
The AIT is required to define the maximum permitted surface temperature of electrical and non-electrical equipment used in areas where potential testing material is present. This allows for the correct and appropriate designation of equipment based on their temperature or “T” Class.
Many products are incorrectly given an AIT based either on untrustworthy literature or on its worst-case component (component with the lowest AIT). Other inert or less sensitive components within the product can greatly affect the overall AIT of the product. These products will usually produce a higher AIT.
ASTM E681 / ASHRAE 34
This test is conducted to determine the lower and upper flammable concentration limits of chemicals that have sufficient vapour pressure to form flammable mixtures in atmospheric pressures at specific temperatures.
This test can be conducted on vaporised liquids and gaseous materials. Refrigerant gases are tested to ASHRAE 34, using the method detailed within ASTM E681, with specific ignition criteria and air moisture content.
Lower limit of flammability or lower flammable limit (LFL) is the minimum concentration of a combustible substance that can propagate a flame in a homogeneous mixture of the combustible material and the air, under the specified conditions of the test. Generally, 1% v/v of the material is added to a glass vessel under a vacuum. Air is allowed back into the system and the material and air is mixed before an electrical ignition source is activated, and observations for flame propagation are observed. The material is then incrementally increased in 1% steps until ignition is observed and the LFL defined.
Upper limit of flammability or upper flammable limit (UFL) is the maximum concentration of a combustible substance that can propagate a flame in a homogeneous mixture of the combustible material and air, under the specified conditions of the test. Once the UFL has been established, a theoretical UFL is calculated, and testing is started at a concentration above.
The material is added to a glass vessel under a vacuum, air is allowed back into the system and the material and air is mixed before an electrical ignition source is activated, and observations for flame propagation are observed. The material is then incrementally decreased in 1% steps until ignition is observed and the UFL defined.
To ensure that avoiding a flammable atmosphere as a ‘basis of safety’ is accurately conducted and monitored, making sure flammable limit alarms and detection systems are correctly set. Blended materials cannot simply be based upon worst case constituent values, therefore testing of the product is essential.
Can’t find the tests you need?
From flashpoint testing to auto-ignition temperature, Sigma-HSE is your process safety solution provider for gas & vapour testing. Our dedicated team of experts are committed to helping you ensure and maintain compliance by testing potentially combustible gases & vapours and then providing you with comprehensive and actionable testing data.
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