The Vent Sizing Package 2 (VSP2™) is the most widely used low thermal-inertia (low phi-factor) adiabatic safety calorimeter. The VSP2 is designed for laboratory simulation of runaway chemical reactions, which are typically unintended and often unknown. The VSP2 is fundamentally different from a reaction calorimeter, which is typically operated under isothermal conditions (where thermal inertia does not matter) and measures heat flow and gas evolution, usually for the intended process chemistry. VSP2 results include adiabatic rates of energy and gas release as well as total adiabatic temperature rise, and these data are directly applicable to process conditions.
The commercial version of the original DIERS bench-scale apparatus, invented at FAI in the 1980's, the VSP2 sees daily use in FAI’s own fully equipped thermal hazards laboratory and in the top process safety laboratories around the world. Although originally conceived as a means to develop the runaway reaction data for pressure relief design (vent sizing) the versatile VSP2 provides a plethora of data for safe process design.
Introducing the VSP2
The VSP2 is essentially a 120 ml bench-scale chemical reactor housed within a protective 4-liter containment vessel. The instrument is able to run experiments in true adiabatic mode or with controlled application of external heating (e.g., fire simulation) or cooling. The operator can add or withdraw liquid or gaseous reactants at any point during an experiment.
The reactants are well mixed in a 120 ml thin-wall cylindrical test cell which is ideal for reactions requiring good agitation (e.g., emulsions and suspensions). Each test cell is tailor-made with appropriate materials (typically stainless steel or Hastelloy) and configured to mimic process conditions. The VSP2’s sample size is typically 40-80 ml. This ensures a representative sample and good accuracy when adding ingredients such as catalysts that make up a relatively small percentage of the mixture.
Image Credit: Fauske & Associates
VSP2 Benefits
VSP2利用创新的自动压力平衡系统来防止在失控反应期间高压薄壁测试池破裂。测试电池被加热器组件包围，因此在整个实验过程中，反应物保持绝热。在VSP2测试中，本质上所有反应能量都保留在反应质量中，而不是被重容器吸收或丢失到环境中。闭孔操作在失控的反应过程中产生连续的压力温度数据。此信息是执行详细的通风尺寸计算的关键。
The VSP2’s versatile and innovative design enables the accurate simulation of virtually any upset (abnormal) condition with the potential to lead to a runaway chemical reaction, so that process changes can be implemented to prevent an accident or to mitigate the possible consequences.
Image Credit: Fauske & Associates
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The most important VSP2 data are the adiabatic rates of temperature and pressure change, which can increase exponentially with temperature, and which are critical input for any emergency relief system (ERS) design. The versatile design lets users directly simulate process upset conditions which might be identified during a Process Hazard Analysis (PHA), including:
- Loss of agitation or cooling
- Mischarge or accumulation of reactants
- Contamination of batch
- Resident incubation time
- Thermally initiated decomposition
A wide range of possible testing configurations allows for:
- Solids, liquids or two-phase mixtures
- 原位液体/气体采样或给药
- Closed or open (vented) tests
- 缩放的排列模拟
- Determination of two-phase flow regimes
VSP2 data empowers users to comprehensively characterize chemical reaction hazards and determine essential process safety parameters. For example:
- Required size of emergency relief system (ERS)
- Adiabatic temperature and pressure rise rates (dT/dt, dP/dt)
- 绝热温度升高（Δtad）
- Vapor pressure data
- Heat of reaction or mixing
- 最大时间率（TMR）
- Temperature of no return (TNR)
- 自加工分解温度（SADT）