EXTERNAL PUBLICATIONS

SUMMARY

A wide range of industrial equipment may process or store significant quantities of flammable material. This equipment has the potential for release of flammable material followed by an explosion unless effective control measures are in place. Releases can occur from leaks or as part of the equipment design specification. Under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR), duty holders must: identify zones in the vicinity of equipment where releases could produce flammable atmospheres; and control the risks by avoiding ignition sources so far as is reasonably practicable. The likelihood of a flammable atmosphere forming in a zone is used to determine how stringent the controls on ignition sources must be. This process is called area classification. It is often based on mathematical models of releases. However, there was a lack of suitable models for indoor releases of pressure liquefied flammable liquids. These produce ‘flashing’ liquid releases where the liquid turns to gas on release.

This report describes the development of a mathematical model for flashing liquid releases and includes a review of the scientific literature, models and guidance. The model is an extension to HSE’s QUADVENT model and can be used for both indoor and outdoor release scenarios. The report describes the application of the model to typical industrial scenarios for LPG (liquefied petroleum gas) systems and ammonia-based industrial refrigeration plants. The researchers identify that the zoning distances calculated for LPG systems using the model are broadly consistent with those set out in guidance by industry bodies. This report will be of interest to hazardous area classification specialists.

This Research Report and the work it describes were funded by the Health and Safety Executive. Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.