Flammables in a vessel vapor space is a hazard present in many facilities. In most cases, it is associated with handling flammable liquids; control systems include inert gas (e.g., nitrogen) padding, electrical grounding, hot work permit procedures, etc.

But, a flammable vapor space can also develop in vessels which contain only TRACE amounts of flammable materials! Here are a few of the ways this could occur:

• A reaction involving a chemical with trace quantities of a flammable material; when the main component is consumed in the reaction, these small quantities accumulate in the vessel’s vapor space, or
• A liquid containing small quantities of soluble or entrained flammable impurities flows through a vessel, the flammable material is released and trapped in the vapor space, or
• Adsorption of a liquid which contains trace quantities of a non absorbed flammable impurity which can be left to accumulate in the vapor space.

© AIChE | Messages for Manufacturing Personnel