The Advanced Reactive System Screening Tool (ARSST™) is a low thermal-inertia (low Φ-factor) adiabatic screening calorimeter suitable for the acquisition of critical design and safety data. This user-friendly and affordable device quickly and safely identifies and quantifies reactive chemical hazards during process upset conditions. Results include rates of energy and gas release as well as total adiabatic temperature rise, and these data are directly scalable to process conditions without complicated manipulation.
Introducing the ARSST
The ARSST is a perfect tool for basic process safety screening tests, particularly in cases where there is only limited information available on the material being tested. The ARSST represents Minimum Best Practice for identifying potentially dangerous chemical reactivity so that it can be prevented or safely mitigated.
ARSST technology was initially invented as a short-cut to more elaborate VSP2 testing, and as such, ARSST tests can be performed easily with minimal specialized training. Consumables are inexpensive, and these tests can be set up in about 20 min. The sample size is relatively small at several grams, an advantage during early process development when material can be scarce.
The small sample size is also beneficial when working with energetic materials or hazardous decomposition products that require special clean-up procedures, for example, gas scrubbing and acid neutralization. An ARSST test generally requires around a 10 ml sample, though previous studies have seen samples as small as 1 g successfully tested. For sample addition a fill tube can be used to add liquid directly to the ARSST test cell during a test. A magnetic stirrer is used to agitate the samples.
ARSST tests are generally conducted in ‘open cell’ mode which enables use of the light-weight glass test cell. Vaporization (boiling) is suppressed by imposing a nitrogen gas ‘pad’ in the containment vessel. A pad pressure of 20 bar (300 psi) is generally sufficient to ensure there is negligible reactant loss during the test. Numerous benchmark exercises have been undertaken through organization such as DIERS, showcasing the excellent agreement between open cell ARSST data and closed cell VSP2 data. This agreement is particularly robust in terms of the data required for vent sizing.
Where an ARSST test results in the generation of non-condensable gas, this gas will accumulate in the surrounding containment vessel (350 or 450 ml). The molar rate of gas generation can be easily estimated by leveraging the measured pressure rise rate and the ideal gas law.
Open cell testing is advisable when working with gassy systems that may pose challenges to a lightweight closed cell, circumventing concerns about high pressures, solution effects and gas volume uncertainty. In the Fauske thermal hazards lab the ARSST is typically the instrument of choice for gassy decompositions due to there being less material to accommodate and clean up post-test.
Image Credit: Fauske & Associates
Benefits of the ARSST
The ARSST represents an ideal tool for both industry and virtually any university chemistry or chemical engineering lab working in unit operation studies or other research areas. Users are able to rapidly acquire reliable adiabatic data suitable for use in a range of safety applications including vent sizing, thermal stability, reaction chemistry and characterization of material compatibility. This device is user-friendly and can quickly generate the needed test data for use with established DIERS vent sizing methods, such as in the Fauske FERST software.
Features and Applications
The ARSST design allows users to directly simulate the majority of process upset conditions, including:
- Loss of agitation or cooling
- Mischarge or accumulation of reactants
- Contamination of batch
- Thermally initiated decomposition
- Fire exposure or other external heating
Image Credit: Fauske & Associates