Tank gauging and calibration
Published by Poppy Clements,
Assistant Editor
Tanks and Terminals,
Tank gauging is a verification and measurement process used to determine the exact capacity of a tank or container. This procedure is essential in various environments, including the oil and gas industry, chemical industry, agriculture, maritime transportation, etc.
Triangulation for external dimensions
It is important for several reasons:
- It ensures the accuracy of measurements of the quantity of liquid or gas stored in the tank.
- It helps to ensure compliance with safety, environmental protection, and trade regulations.
- It is crucial for an efficient inventory management, logistical planning, and accurate product billing.
- It helps minimise the risks of errors and economic losses associated with incorrect estimates of tank capacity.
Tank gauging and calibration are two essential processes in the field of legal metrology (the science of measurement applied to commercial transactions and the ones regulated by laws and standards). Calibration involves the assessment and adjustment of measuring instruments, while tank gauging aims to verify the continuous compliance of these instruments with legal or regulatory standards.
Bending and theodolite calculation for measuring the shells
Regulations and standards associated with these activities may vary from country to country, but there are also recognised international standards.
Tank gauging typically involves the following four major steps:
- Preparation: before starting the tank gauging process, the tank is emptied of any residual content and cleaned in order to ensure accurate measurements.
- Measurement: precise measurement techniques are used to assess the tank's capacity. This may involve the use of measurement devices such as level gauges, pressure sensors, volumetric measurements, laser levels, theodolites, etc.
- Calculation: data collected during the measurement process are analysed and used to calculate the exact capacity of the tank. Corrections may be applied to take account of factors such as temperature, pressure, and density of the tank's contents.
- Reporting: a detailed report is typically produced to document the results of tank gauging, including the measured capacity of the tank, the methods used, measurement conditions, applied corrections, etc.
Standard gauges
All instruments used for commercial transactions need to be checked periodically in order to ensure that the selected device is measuring accurately. And if necessary, to be set as close as possible to zero at the usual rate of use.
This is true in all countries where volumetric meters/counters are used for commercial transactions.
The traditional method used to check the accuracy of meters at different flow rates has been the standard-gauge, which is a base linked to the primary-gauge-standards and avoids any systematic bias. This old and robust method has its benefits and disadvantages:
Benefits
- Good measurement accuracy.
- Insensitive to flow rate and product viscosity.
- Temperature correction of the measurement envelope is easy to achieve.
Disadvantages
- Constraining implementation for the operator, with unavailability of loading docks.
- Heavy, cumbersome equipment that is difficult to use and to transport (return to laboratory).
- Requires product to be returned to the storage tank after calibration which creates additional pollution and safety risks.
- Requires the availability of warehouse operators for product movement.
- Needs to be instrumented like tanks (earthing, overfill protection, steam, etc.).
- Often owned and maintained by the depot, for use by an outside service provider.
Points taken inside the Tank by the RST
Alternative technology
All instruments used for commercial transactions need to be checked periodically in order to ensure that it is measuring accurately. And if necessary, to be set as close as possible to zero at the usual rate of use.
This is true in all countries where volumetric meters/counters are used for commercial transactions.
In order to modernise the profession and facilitate the operator's work, Alma invented an approved pilot-meter to provide an alternative to standard gauges: MASTER ETALCOMPT API.
It is firmly rooted in Anglo-Saxon verification methods and simplifies the logistics of periodic connection to international laboratories.
Benefits
- The direct use in the series between loading arms and tanks.
- Decreases instance of loading docks being unavailable for operation, with very little disruption (pressure loss).
- Decreases the amount of product returned to the storage tanks (less risk of pollution and safety issues).
- Very low internal volume, facilitating multi-product use.
- Extremely compact, making it easy to use and return to the laboratory.
- No additional equipment required (earthing, overflow protection, steam).
- Lower carbon footprint.
- Equipment is owned by the service provider, who is responsible for its use and maintenance.
The Master Etalcomp Api
Disadvantages
- There are some interferences to manage with the tanker driver.
- It can, in some cases, reduce normal loading rates.
- Upstream organisation is required to limit quality changes and manage trucks presence.
Since creating a first approved and functional version of this pilot-meter, ALMA has been in the process of approving an optimised version. Optimisation is based essentially on iso-functionality, reduced space requirements, improved ergonomics, simplified design, and lower costs.
In addition to the ability of being able to be inserted between a loading arm and a tank, a technology like the MASTER ETALCOMPT API is also approved for the upstream use of loading arms and useful for top loading arms. It can also be used for in-line or line-transfer counting in a range from 15 to 150 m3/h and for viscosities from 0.6 to 13 cst.
Read the article online at: https://www.tanksterminals.com/special-reports/23082024/tank-gauging-and-calibration/
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