Reliable explosion protection in an oil tanker vapor recycle plant – Case Study


Courtesy of Siemens Industry, Inc. - Process Analytics

In-situ gas analyzer monitor oxygen in real-time


The world-class transshipment and storage facility Kiire, Japan, contains 46 million barrels of crude oil in 57 storage tanks, an amount equal to Japan’s two week demand. Continuous loading and unloading of oil tankers generates odorous gases and additionally results in losses of volatile hydrocarbons into the surrounding environment. Recently, the terminal operator decided to implement a new Tanker Vapor Recycle (TVR) plant that treats the malodorous vapors exhausted from the hold of a carrier during loading and unloading. The plant improves the facility’s environmental profile by ensuring the reliable elimination of malodorous vapors, collecting previously lost volatile hydrocarbons, and helping to retrieve the equivalent of 17 million liters of crude oil per year.


In the Tanker Vapor Recycle plant, a gaseous mixture containing combustible components as well as oxygen in varying concentrations is processed. Gas mixtures consisting of combustible, oxidizing, and inert gases in principle are flammable under certain conditions such as gas composition, temperature and pressure. To protect the plant from the danger of explosion, the oxygen concentration must be monitored continuously. The measured concentration values are used to immediately start preventive measures at the occurrence of a critical gas composition.

The in-situ laser gas analyzer was selected to perform this O2 monitoring application.


The gas analyzer main requirements have been:

  • To deliver the measuring values in real-time for immediate reaction in case of sensing an explosive gas mixture
  • To provide correct O2 concentration values even under strongly varying gas composition, because with different types of crude oil, the HC concentrations in the vapor varies also.
  • To withstand the harsh environmental conditions at the measuring location
  • To be approved for installation in hazardous areas by the Japanese Institution of Industrial Safety (TIIS), an authority for test and certification of electrical apparatus
  • Transmission of the measured data directly to the control system of the plant

Following an extensive evaluation and test phase, it became obvious that only an in-situ measuring principle based analyzer could meet the demands. And with the TIIS approval as mandatory requirement in mind, the in-situ laser gas analyzer was considered to be by far the best choice to solve this application.

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