The right to define weights, volumes or lengths to serve as references for material goods and coinage accepted as payment for these goods is one of the privileges that have reserved most jealously the rulers of ancient societies.
The units of mass, volume and length today maintain their importance to us because they determine the price the seller will demand and the buyer will pay in any business transaction involving property. In the past, diversity of interests and regional and historical differences introduced different systems of units. However, the increasing importance of trade led to the harmonization of these measurement systems. This development culminated with the introduction of SI units (m, kg, s), each country has since been employed as a basis for their own legal metrics.
Below illustrates an example of the principle of custody transfer operation under the laws of the Federal Republic of Germany. Other countries have their own rules, but the principles are formulated according to internationally accepted principles OIML committee.
The aim of the legal control of weights and measures
The purpose of the legal control of weights and measures is to protect citizens from the consequences of incorrect measurements in commercial transactions or in government contracts, and propose weights and measures standards in all aspects of the labor, and environmental health.
The legislation formulated to achieve these ends apEcación establishes requirements on the measurement equipment and procedures adopted for measurement and verification. In Germany, for example, these requirements are regulated by the directives of the EEC and the EC, the "Eichgesetz" (Standards Act), the "Eichordnung" (Ordinance standards), and verification requirements and standards articulated by the Physical-Technical Federal Institute (Physikalisch-Technische Bundesanstalt, PTB). This is the highest technical authority of the country in control of weights and measures and safety engineering, and service in relation to standards, weights and measures. The measures defined as a means to achieve these objectives can be divided into preventive and repressive:
- Preventive: upo certification, initial calibration, sealed
- Dams: recalibrated periodically during the life cycle, market control measures warning or punishment for infractions
Custody transfer operations in everyday life
Accountants to ensure compliance with the regulations of custody transfer with us on many aspects of our daily lives that often we hardly notice them:
- Scales in stores and markets (food, etc.).
- Pumps at service stations (fuel, lubricants, etc.).
- Domestic water meters (water, hot water, etc.).
- Accountants in wastewater systems (treatment plants, sewage pumping stations, etc.).
- Weighbridges (debris from construction sites, waste, etc.).
For liquid measuring devices, OIML makes a clear distinction between meters for 'water' and counters for liquids, "other than water." Other devices are designed for gas flow measurement. The variety of custody transfer meters is correspondingly wide.
Recalibrated periodically during the life cycle, exceptions to the rule of a calibration validity is generally limited to two years. However, the "Eichor-dnung" (Ordinance standards) German includes a long list of exceptions in the section entitled "General Rules". Important time limits applied to the flow meters are recounted in the list in Appendix B:
■ Measuring systems for liquefied gases with counters - 1 year
■ Measurement systems for volumetric meters milk - 1 year
■ Hot para.agua volumetric meters - 5 years
■ Volumetric meters for cold water - 6 years (sewage)
These times are not valid for direct measurement systems mass flow. Coriolis flowmeters in general need to be calibrated every twelve months when used for measuring liquids other than water.
Accountants are not subject to mandatory periodic calibration (Schedule A of the Ordinance standards):
■ Special volumetric meters and counters for wastewater.
■ Accountants in business transactions carried out by distribution lines between fixed partners.
■ Counters for:
- water with a maximum flow rate of at least 2,000 m3 / h,
- other liquids than water with a maximum flow rate of at least 600 m3 / h,
- heat energy at a rate of at least 10 MW.
