Measuring the energy content and quality of LNG along the supply chain is an important part of maintaining U.S. leadership as a global natural gas producer and exporter, according to a recent release from the American Petroleum Institute (API).

To that end, API said it has taken the significant step of publishing the first edition of a standard ensuring accuracy in measuring LNG energy content and other attributes, while conforming to the latest international requirements set by the International Organization for Standardization (ISO).

The new API Manual of Petroleum Measurement Standard (MPMS), entitled Refrigerated Light Hydrocarbon Fluids—Sampling of Liquified Natural Gas—Continuous and Intermittent Methods, is focused on helping suppliers, operators and customers of LNG terminals and storage facilities accurately measure the quality of LNG and relay that information effectively to buyers at the point of transfer.

When transferring LNG to a buyer, it is common practice to determine the quantity of fuel being transferred by assessing the amount of energy contained within the LNG cargo. In other words, relaying how many British thermal units (BTUs) or Joules per kg of energy have been purchased provides the buyer information about both the quantity and quality of the fuel that has changed custody. The best means of ensuring this is done correctly is through representative and accurate sampling.

The LNG measurement standard, which is being incorporated as Chapter 8.6 in API’s MPMS, outlines good procedural steps required to accurately measure the LNG and convey this information along the supply chain.

The API MPMS standard adds that all LNG sampling devices must ensure that the LNG quantity being analyzed at the transfer point must be representative of the entire LNG cargo being transferred, loaded or unloaded.

LNG is a complex mixture of low-molecular-weight hydrocarbons with nitrogen as a principal inert impurity, along with methane as a major component. The minor hydrocarbon component concentrations can vary with the source of the raw gas, the liquefaction pre-treatment, the liquefaction process, and the storage conditions. Each of these factors underscore the need for representative sampling measures, a prerequisite for ensuring the correct composition of the LNG being transferred has been properly identified and relayed to the buyer and seller.

At the same time, the standard also emphasizes the need for strict safety measures to prevent injuries when conducting LNG sampling.

The standard was published on May 29 by API’s Global Industry Services (GIS) division and is made available through Contact API at for information or questions.