What is the primary function of mast riser or king post vents on a tanker?

The primary function of mast riser or king post vents on a tanker is to physically direct the exiting cargo vapors above the deck. These vents are designed to handle the vapors produced by the liquid cargo during loading, unloading, and transportation. By directing the vapors upwards, the vents help to ensure safe dispersion into the atmosphere, reducing the risk of flammable concentrations near the vessel and enhancing safety for crew and cargo operations.

Additionally, this mechanism helps in maintaining the pressure balance within the cargo tanks, allowing for a smooth flow of the liquid cargo without forming vacuum conditions that could potentially damage the tank structure. The design of these vents ensures that any volatile organic compounds or vapors escaping from the tanks do so in a controlled manner, thus also mitigating environmental concerns associated with tanker operations.