CARGO GRADES
| GRADE A | Flammable liquid with a Reid vapor pressure of 14 pounds per square inch absolute (PSIA) or more. |
| GRADE B | Flammable liquid with a Reid vapor pressure of more than 8-1/2 psia but less than 14 psia. |
| GRADE C | Flammable liquid with a Reid vapor pressure of 8-1/2 psia or less and a flash point of 80°F or below. |
| GRADE D | Combustible liquid with a flash point above 80°F but below 150°F. |
| GRADE E | Combustible liquid with a flash point of 150°F or above. |
RELEVANT DEFINITIONS
Reid Vapor Pressure: Equilibrium exerted by vapor over liquid at 100°F, expressed as pounds per square inch absolute (PSIA) as defined in 46 CFR 30.10-59.
Vapor Density: This is actually a specific gravity rather than a true density because it equals the ratio of the weight of a vapor or gas (with no air present) compared to the weight of an equal volume of air at the same temperature and pressure. Values less than 1 indicate that the vapor or gas tends to settle. However, temperature effects must be considered.
Flash Point: The lowest temperature at which the vapors of a liquid may be ignited momentarily. Values given in the data sheets are open cup except when designated "(cc)," which indicates the closed cup value. In general the open cup value is about 10° to 15°F above the closed cup value.
Flammable Limits: The range of gas or vapor concentrations (percent by volume in air) which will burn or explode if an ignition source is present. Limiting concentrations are commonly called the "lower explosive limit" (LEL) and the "upper explosive limit" (UEL). Below the LEL the mixture is too lean to burn, and above the UEL, the mixture is too rich to burn.