The VSP2 can be thought of as a bench scale chemical reactor contained within a protective containment vessel. Liquid or gaseous reactants can be added to (or withdrawn from) the test cell at any time during an experiment. Tests can be run in true adiabatic mode, with added external heating, or with external cooling. The cylindrical geometry of the test cell is ideal for reactions which require good agitation. Test cells are custom-made in a variety of materials and configurations to better simulate the process conditions.
VSP2 tests can be run in open cell mode (typical for very gassy systems) or in closed cell mode where the thin-walled test cell is kept intact by automatic pressure-balancing. Closed cell operation provides continuous pressure-temperature data during a runaway reaction, information which is necessary for detailed vent sizing calculations and which can be otherwise difficult to determine. Closed cell tests also require less post-test cleanup.
The sample size in the VSP2 (typically 80 ml) provides for a representative sample as well as good accuracy when adding ingredients that make up a small percentage of the mixture (e.g., catalyst additions). Temperature can be measured at up to three locations in the test cell, a useful option when testing solids or immiscible liquids. A baffled test cell with either a “star” stir-bar or a mechanical agitator can be used for optimal mixing of multiphase reactions, such as for emulsions, suspensions, or slurries. For true adiabatic operation (i.e., with low phi-factor and without externally imposed heating) the VSP2 is usually preferred. Polymer and multi-phase systems are particularly well suited to the VSP2 because of the excellent agitation and continuous vapor pressure measurement.
Its versatile and innovative design allows the VSP2 to simulate any number of upset (abnormal) conditions which might lead to a runaway chemical reaction (e.g., loss of cooling, loss of stirring, mischarge of reagents, mass-loaded upset, batch contamination, fire exposure heating, etc.). VSP2 data yield critical rates of temperature and pressure rise during a runaway reaction, thereby providing reliable energy and gas release rates which can be applied directly to full scale process conditions.
The VSP2 typically utilizes a sample size of 40-100 grams in a lightweight metal test cell with a volume of approximately 120 ml. The test cell is surrounded by a heater which is used to maintain adiabatic conditions during an experiment. This test cell and heater assembly is placed in a 4L containment vessel. Tests are typically performed as a closed system, so that vapor pressure data can be directly measured throughout the runaway.
The VSP2 represents Available Best Practice and has its roots in established DIERS technology which is recognized by OSHA as an example of good engineering practice. The VSP2 identifies and quantifies process safety hazards so they can be prevented or accommodated by process design. VSP2 data include adiabatic rates of temperature and pressure change which, due to the low thermal-inertia test design, can be directly applied to process scale to determine relief vent sizes, quench tank designs and other relief system design parameters related to process safety management.
The versatile VSP2 design lets you directly simulate most process upset conditions including:
Many testing configurations to accommodate a range of applications including:
VSP2 data allow you to completely characterize chemical reaction hazards and determine key process safety parameters including: