The explosive range of a mixture of flammable vapors and air lies between the lower and upper explosive limits. These limits are specified as a percentage of __________.
• Explosive (flammable) limits are defined by concentration of fuel in air • Difference between oxygen concentration and fuel vapor concentration in combustion • How "percent" is usually expressed for gas mixtures (think: by volume in air)
• Ask yourself: When we say a mixture is too "lean" or too "rich" to burn, what exactly is there too little or too much of? • In tank atmosphere testing, what are you actually measuring with an explosimeter or gas detector when you read a % of the lower explosive limit? • Which choices describe something that is normally measured as a percent of the gas mixture inside a space, not a property of the liquid itself?
• Make sure the percentage refers to the composition of the gas mixture, not a property of the liquid cargo like flash point • Eliminate any options that are not expressed as a percent of the total gas volume in a space • Check which answer focuses on the amount of fuel vapor in air, rather than on oxygen alone or on the definition using itself (circular definition)
No comments yet
Be the first to share your thoughts!