An LPG / LNG Ullage Survey is a specialized marine cargo inspection process conducted on vessels carrying Liquefied Petroleum Gas (LPG) or Liquefied Natural Gas (LNG). The purpose of this survey is to accurately determine the quantity of cargo onboard by measuring the empty space (ullage) within the cargo tanks.

During the survey, trained inspectors use calibrated instruments to measure the distance from the top of the tank to the surface of the liquid cargo. These measurements are then corrected for temperature, pressure, and density to calculate the precise volume and mass of the cargo.

This process is essential for:

• Verifying cargo quantities during loading and discharge operations
• Ensuring compliance with international maritime standards
• Detecting any discrepancies or potential cargo losses
• Supporting commercial transactions between buyers and sellers

Given that LPG and LNG are stored under pressurized and cryogenic conditions, ullage surveys require strict safety procedures, specialized equipment, and adherence to industry guidelines such as those set by organizations like the International Maritime Organization (IMO).

Overall, an LPG/LNG ullage survey plays a critical role in maintaining transparency, safety, and accuracy in the transportation of liquefied gas cargoes.