RIPI has developed the world’s first international standard in the field of spherical tank volume calibration

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Recently, the international standard ISO 23505:2025 \"Petroleum and liquid petroleum products – Calibration of the volume of spherical tanks – Photometric external distance measurement\", developed by the Research Institute of Petrochemical Sciences, was officially released. This standard is the first international standard formulated by China in the field of oil and gas metering; it marks a breakthrough for China in establishing international standards in this area and fills a gap in the standards set by the International Organization for Standardization (ISO) regarding the calibration of spherical tank volumes. Spherical tanks are storage and transportation devices for compressed and liquefied gases such as natural gas and liquefied petroleum gas; they also serve as measuring devices to determine the amount of liquid and gas contained within the tank. The calibration of their volume determines the accuracy with which the quantity of product inside the tank can be measured. Previously, there was a long absence of ISO standards for the calibration of spherical tank volumes; the industry generally used the perimeter measurement method established by the American Petroleum Institute. In this approach, technicians had to climb up to the top of the spherical tank to determine its circumference by measuring its perimeter from above. The accuracy of measurement using this method is difficult to ensure; it is time-consuming and labor-intensive, and its adaptability to the operating conditions of spherical tanks is also poor. As a result, it fails to meet the urgent demands of the modern energy industry for efficient, safe, and precise measurement. Photorelectronic rangefinders are widely used in the field of measurement and are commonly employed in the calibration of vertical tanks. In 2003, the Institute of Rock and Mineral Sciences successfully developed a method for determining the volume of spherical tanks using external photometric rangefinders, which was patented. At the same time, the Institute of Rock Mechanics has collaborated with Yanshan Petrochemical, **the First Large-Capacity Metrology Station** and other entities to work together on turning this invention patent into a **standard**. In May 2005, the standard **“Calibration of the Volume of Spherical Metal Tanks – Total Station External Measurement Method” (GB/T 19780-2005)**, developed under the leadership of the China Academy of Mining and Metallurgy, was officially issued by the General Administration of Quality Supervision, Inspection and Quarantine and the Standardization Administration of China. It has since become the current **standard** for determining the volume of spherical metal tanks in China. The standard established by the Academy of Rock Mechanics is applicable to the calibration of spherical metal tanks with a radius of over one meter, and is particularly suitable for determining the volume of large spherical tanks. This standard employs photometric rangefinders for measurements, and innovatively provides standard methods for determining the position of the sphere’s center, the angle between the tangent line and the direction to the sphere’s center, as well as the radius of the spherical tank. The entire measurement process can be carried out from the ground, thereby completely eliminating the safety risks associated with measurements at high altitudes. Through 20 years of industry practice since the release of this **standard, the scientific validity, advancement, and feasibility of the sphere tank volume calibration method developed by the China Academy of Mining and Metallurgy have been fully demonstrated. In July 2023, the Institute of Rock Mechanics submitted a proposal to ISO to further upgrade the existing **standard into an international standard, thereby helping Chinese methods to gain recognition abroad. Between 2024 and 2025, ISO conducted multiple rounds of discussions and voting on this draft standard, making several revisions to it based on the opinions submitted by various parties. Eventually, an implementable international standard was developed, which received unanimous approval from all stakeholders. In August this year, the ISO standard was successfully released and implemented. “This measurement method is not only efficient and precise, but also easy to operate; it reduces the reliance on the professional skills of calibrators and is thus more suitable for widespread adoption and use in the industry. The new standard addresses many of the shortcomings of traditional measurement methods; it helps to automate and intelligentize the calibration of international spherical tanks, providing a more accurate, efficient, and unified basis for measurement in global energy trade. It helps to ensure fair trade practices and reduce settlement risks, offering the world safe, fast, and precise solutions for spherical tank calibration. ”Zhao Xiaomin, deputy dean of the Institute of Geosciences, explained.