Manual tank gauging is a critical process for oil and gas measurement technicians to support the integrity of your company.

Accurate measurement of crude oil helps to reduce uncertainty of measurement, allows your company to adhere to third-party contracts, and supports the fair treatment of all involved parties in the oil and gas value chain.

Many measurement technicians have a basic understanding of how to perform manual tank gauging through learned experience or training on company/vendor equipment. However, we believe it is important to gain an understanding of the industry standards for manual tank gauging to increase the accuracy of measurement.

This way, measurement technicians can confidently and safely perform required tasks to increase the reliability of measurement to support your company and additional stakeholders in the value chain.

The Industry Standard for Manual Tank Gauging

Guidance on manual tank gauging can be found in the API Manual of Petroleum Measurement Standards (API MPMS). Specifically, Chapter 3 describes the standard practice for the manual gauging of petroleum and petroleum products in fixed or floating roof tanks and marine tank vessels.

This standard includes the following key elements for a measurement technician:

• The procedures for manually gauging the liquid level of petroleum and petroleum products.
• The procedures for manually gauging the level of free water that may be found with the petroleum or petroleum products.
• The methods used to verify the length of gauge tapes under field conditions.
• The influence of bob weights and temperature on the gauge tape length.
• The influences that may affect the position of the gauging reference point

Gaining an understanding of these key elements will help a measurement technician understand how to account for variances, environmental conditions, and other variables that may affect the accuracy of the measurement.

Additional factors to consider, which are contained elsewhere in the API MPMS, include temperature, API gravity, and suspended sediment and water of the tank contents.

Overall, Chapter 3 of the API MPMS is significant to help measurement technicians understand how to complete an accurate gauge reading of petroleum and free water. These readings are then used with tank capacity tables to determine the total observed volume (TOV) of the petroleum contained in the tank.

The total observed volume is used with various correction factors to calculate the gross standard volume (GSV) and the net standard volume (NSV) in order to generate an accurate reading. This reading is then used to generate a measurement ticket that is the referential record used throughout the value chain.

Manual Tank Gauging in Alignment with BLM Onshore Orders

If your company is involved in the production of oil and gas on federal or Indian lands, you will need to also have an understanding of the measurement standards utilized by the Bureau of Land Management (BLM), as contained in the BLM Onshore Orders.

The published measurement rules that became effective in January 2017 contain designated oil measurement rules. Specifically, 43 CFR 3174.5 and 3174.6 outline the procedures for manual tank gauging. Measurement technicians need to understand the following elements to support accurate measurement of product on BLM designated land.

– 3174.5 outlines the general requirements for oil measurement by tank gauging.

• Understand the measurement objective of accurately computing the total NSV drawn from a tank.
• Understand how to use oil tank equipment.
• Understand tank calibrations, including how to identify when a tank needs to be recalibrated.

– 3174.6 outlines the procedures for oil measurement by tank gauging.

• Understand how to isolate the tank to allow contents to settle.
• Understand how to determine opening oil temperatures before, during, or after sampling.
• Understand how to take oil samples, which must yield a representative sample of the oil and its physical properties.
• Understand how to determine observed oil gravity using a properly calibrated hydrometer or thermohydrometer.
• Understand how to measure the opening tank fluid level after taking samples.
• Understand how to determine the S&W (sediment and water) content of the oil in the tank.
• Understand how to transfer oil, close the tank valve, and seal the valve.
• Understand how to determine closing oil temperature.
• Understand how to take the closing tank gauge.
• Understand how to complete the measurement ticket.

Many of the procedures contained in 3174.6 include references to API standards that measurement technicians need to understand. Becoming familiar with these standards and how the standards apply to each step in the manual tank gauging process will increase your ability to consistently generate an accurate and reliable measurement.

Receive Training on Manual Tank Gauging

Oil and gas measurement professionals can grow in their understanding of the manual tank gauging requirements and procedures through dedicated education and training.

Gas Certification Institute (GCI) provides a training class, Fundamentals of Crude Measurement, that includes a specific focus on manual tank gauging.

Our fundamental training class is based on the API Manual of Petroleum Measurement Standards. We teach directly from API MPMS to provide measurement professionals with a deeper understanding of manual tank gauging through education on the industry standards, best practices, and safety procedures that support this critical and difficult task.

To register for our next Fundamentals of Crude Measurement class, visit our Training Schedule page to view registration information. You will return to the field with greater confidence to complete measurement tasks and to support the integrity of your company.