Cargo Properties and Hazards Flashcards

A cargo's Reid Vapour Pressure (RVP) is a standardized measure of what property?

Answer: Its volatility at a standard temperature of 100°F (37.8°C)

Reid Vapour Pressure (RVP) is a common measure of the volatility of petroleum products. It is specifically defined as the absolute vapor pressure exerted by a liquid at 37.8°C (100°F) under specific test conditions. A higher RVP indicates a more volatile cargo that will vaporize more easily.

A gas detector in a cargo tank reads a hydrocarbon concentration well above the Upper Flammable Limit (UFL). What is the primary hazard associated with this atmosphere?

Answer: The atmosphere is too rich to burn, but the introduction of air can bring it into the flammable range.

An atmosphere with a hydrocarbon concentration above the Upper Flammable Limit (UFL), also called the Upper Explosive Limit (UEL), is considered 'too rich' to burn because there is insufficient oxygen for combustion. The primary danger is that if air is introduced into the tank (e.g., during ventilation), the mixture can be diluted into the flammable range (between the LFL and UFL), creating a significant explosion hazard if an ignition source is present.

What does the Threshold Limit Value - Time-Weighted Average (TLV-TWA) for a chemical cargo represent?

Answer: The average airborne concentration to which nearly all workers may be repeatedly exposed over a lifetime without adverse effect.

The TLV-TWA is the time-weighted average concentration for a conventional 8-hour workday and 40-hour workweek, to which it is believed that nearly all workers may be repeatedly exposed, day after day, for a working lifetime without adverse health effects. The 15-minute limit is the STEL, the immediate danger is the IDLH, and the absolute ceiling is the TLV-C.

Which of the following cargoes presents a significant hazard due to its tendency to polymerize, a reaction that can be accelerated by heat and generate more heat in a dangerous feedback loop?

Answer: Styrene Monomer

Styrene Monomer is a well-known example of a cargo that can self-react through polymerization. This process is exothermic (releases heat), and the increased temperature can accelerate the reaction rate, potentially leading to a 'runaway polymerization' that generates large amounts of heat and gas, which can over-pressurize and rupture a cargo tank. To prevent this, such cargoes are carried with an inhibitor and their temperature is carefully monitored.

During a pre-transfer conference, you are informed that the cargo to be loaded has a specific gravity of 1.05. What is the most important operational consideration based on this property in the event of a spill into the water?

Answer: The cargo is heavier than water and will sink, making containment and recovery difficult.

Specific gravity is the ratio of a substance's density to the density of a reference substance, typically water. Water has a specific gravity of 1. A cargo with a specific gravity greater than 1, like 1.05, is denser than water and will sink if spilled. This makes traditional spill response methods like booming and skimming ineffective.

To minimize the hazard of static electricity generation when starting to load a static accumulator cargo into a non-inerted tank, what is the most critical operational procedure?

Answer: Introduce a small amount of water into the tank before loading begins.

Static accumulator cargoes are poor conductors and can build up a static charge during pumping, which can lead to a dangerous spark. To mitigate this risk, it is standard procedure to load at a reduced rate (typically around 1 m/s) until the filling pipe outlet and any other structures on the tank bottom are well submerged. This reduces splashing and turbulence, which are primary causes of static generation. Introducing water or loading at a high rate would increase the hazard.