ISO 6551 is an International Standard that establishes guidelines for ensuring the fidelity and security of pulsed data cabled transmission systems utilized for the metering of fluids (see the note), the main objective being to ensure the integrity of the primary indication (see 2.2.5).
In order to achieve different levels of security (see the note and clause 3) that can be applied to such systems, criteria and recommendations for the design, installation, use and maintenance of the relevant equipment are laid down.
Note: Compliance with the requirements of ISO 6551 does not increase the basic precision of measurement, either in the electrical or electronic section of the system or in the overall system which includes the meter(s).
ISO 6551 on the fidelity and security of pulsed data cabled transmission systems is useful for:
Quantitative measurements are required at many stages in the production, transportation, refining, and marketing of petroleum and its products. They form the basis of royalty, fiscal, and custody transfer accounting and provide the means of stock and loss control.
The use of agreed standardized measurement equipment and procedures obviates disputes over quantities, enabling these to be determined with an accuracy mutually acceptable to all parties to a transaction and at the most economical cost for the method of measurement selected.
During the last decade, there has been a rapid increase in the use of electrical or electronic data-transmission systems designed to facilitate the determination of physical quantities such as length, mass, volume, etc. Such systems can be vulnerable to disturbances arising from the environment in which they are used, and also from functional failures, all or any of which may affect the integrity of the resulting measurement.
The purpose of ISO 6551 is to assist manufacturers and users of electrical or electronic pulsed data transmission systems used in the metering of fluids to meet certain criteria for the design, installation, use, and maintenance of such equipment. The object is to establish and maintain the credibility of indicated data against influences acting to impair the fidelity of the system.
ISO 6551 recommends solutions for fidelity and security problems which constitute good practice in this field at this time, but it is not claimed that the recommendations are wholly comprehensive.
The recommendations are, however, considered to be practicable and to satisfy the immediate needs of industries associated with meter proving and the metering of hydrocarbons and hydrocarbon products in the bulk commercial, royalty metering, revenue accounting, and custody transfer fields in general.
ISO 6551 is recommended for general adoption but it must therefore be read and interpreted in conjunction with legal metrology (weights and measures), safety, and other regulations in force in a particular country in which it is intended to apply it.
Note: Clauses have been included on safety and other precautions that constitute good practice. Although every care is taken to include such clauses wherever necessary, it is impossible to cover all contingencies. In the designing of measurement and sampling operations, attention should also be given to general codes of safe practice for petroleum operations. The operator or other user of this measurement standard should work according to accepted safe practices and comply with all relevant regulatory requirements.