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Regulations
In most Countries around the world there exists some kind of Government Weights & Measures Department (W&M) which is responsible for ensuring that "trade is conducted on the basis of fair and accurate measure" Usually this Government department is divided into two main areas, Enforcement and Equipment Approval / Standards Maintenance.
The Enforcement division has two main functions:
- The control of Equipment used for trade purposes
- The control of trading activities which rely on weight or measure
The Approvals division is normally responsible for the maintenance of National standards and the Type Approval (Pattern Approval) of weighing equipment for use in trade applications.
The weights & measures regulations and legislation normally requires a scale to be type approved by the government testing laboratory before it can be used for trade purposes. This is sometimes called "Type Approval" or "Trade Approval" or "First of a Kind Approval"
Once a machine is type approved it can then be used in trade applications, each individual machine in trade applications must then be tested for compliance to the type approval and for calibration accuracy. This testing is carried out by the Government Weights & Measures department or in some circumstances by a private testing laboratory approved by the Weights & Measures Department.
To be approved a private laboratory must have the resources and equipment available to calibrate the scales, it must be qualified in the specialised field of scale testing and it must be inspected and audited by the Government Weights & Measures department or similar controlling body.
Scale Requirements
The owner or user of scale equipment must not only ensure the equipment is suitable for the intended purpose but satisfy themselves the scale is performing correctly and meets any applicable regulations.
After determining what level of performance and accuracy the user requires of a scale for any given application, it must be determined what regulations, if any the scale must comply with. Broadly speaking, the scale application will fall into one of two areas '- "Trade Approved" and "Non Trade" depending on the intended use of the scale.
If a financial charge is made based on the weight derived from the scale then it is being "used for trade" and the scale must be trade approved. Examples of trade use include charging for produce (meat, vegetables etc.) based on scale weight, such as a retail store. Charging a passenger for the weight of excess baggage or charging for transportation of freight based on the weight.
Not all scale applications are considered "used for trade." If a charge is not being made based on the scale weight then it is not a trade application. This does not necessarily mean that the scale should be any less accurate, just that it does not fall under the relevant Government regulations for Trade Approval. Examples include weighing baggage or cargo into a container for loading onto an aircraft, weighing ingredients for a batching process, weighing turbine blades to balance a jet engine or simple weighing people at a hospital.
The use of scale equipment which complies with a developed country's Weights & Measures Regulations will ensure the scale is "capable" of a certain level of performance. However, just because a scale does not comply with the local regulations does not necessarily mean the scale performance will be low. Perhaps it has never been submitted for approval or maybe it is not designed to meet the Weights & Measures Regulations.
In summary, you must decide what a scale is to be used for, what level of accuracy and performance is required, is it a "Trade Use" application and finally what steps will be taken to ensure the scale is calibrated and performing to the required standard.
Standards
Most countries (excluding USA) have adopted the OIML standards as the basis for their Weights & Measures regulations. The OIML deals with the performance of weighing equipment, the standards scales must meet for the particular trade use and forms the basis of the W&M regulations. OIML originates in Europe and is a committee made up of representatives from a number of different countries, including most of Europe, Australia, and parts of Asia. The deliberations of the OIML committee produces the OIML recommendations.
OIML is a very thorough organisation and is more stringent than other standards around the world, such as National Institute of Standards & Technology (NIST) of USA.
Quality Assurance
To be certain of the results from any test laboratory, Inspection or Calibration Body it is important that the tests or calibration results meet certain standards. These standards must be recognised standards by both Industry and Government.
To prove that an Inspection Body or Test Laboratory meets these standards requires an independent organisation, free of commercial motivation to audit the Inspection Body or Test Laboratory. A successful audit and ensuing Accreditation of an Inspection Body provides authoritative confirmation that an inspection body's operations and procedures comply with international quality systems and performance standards and that inspection personnel are competent.
Most countries now have independent organisations set up by their governments to provide auditing and accreditation services to private companies seeking accreditation and recognition for their testing, inspection and calibration services.
These organisations include UKAS of United Kingdom, A2LA of USA, HOKLAS of Hong Kong, IANZ of New Zealand, RvA of The Netherlands, NATA of Australia,, SINGLAS of Singapore etc. All the above organisations have Mutual Recognition Agreements (MRA) between themselves. This means they have inspected and audited each other and are satisfied that they are all working to the same standards. That is they will accept a laboratory accredited by any one of the above organisations as the same as there own.
These organisations are independent accreditation authorities that will inspect, audit and monitor the performance and capability of a laboratory inspection or calibration body (e.g. ATRAX) to ensure their testing (test methods and results) comply with International Standards. Approval is an assurance of the laboratory's competence to perform certain tests. It is official recognition of the laboratory's credibility and acceptance of their test results and calibration procedures.
Countries Without Weights & Measures Regulations
Although there is no legal requirement to do so it is safe practise for a company to select weighing equipment that is Type Approved in some other reputable country, a country with an advanced weights & measures system. This at least ensures that the equipment design has been thoroughly tested and should perform accurately and consistently.
How can a company ensure there scales are calibrated correctly? In the absence of any Government test facility available to them local companies have had to rely on other methods to satisfy themselves there scales are calibrated and weighing correctly. This has typically involved having there local scale supplier calibrate the scales in the presence of a third party, typically a surveyor of some sort. This surveyor will normally prepare a report stating the scales were calibrated and the test witnessed.
Unfortunately this method is lacking in several areas. The surveyor is normally guided by the scale company performing the test and the test is conducted with equipment supplied by the scale supplier. The surveyor has no specific training or knowledge of weighing equipment, instead they are a general surveyor involved with a range of differing equipment and tasks. The surveyor has no credentials established by a qualified third party for this work, and is unable to give any real assurance the equipment is properly calibrated.
The scale company's method of test and calibration is not challenged or qualified by an independent and qualified third party. There is no certainty the test weights used are correct and there fore there is no traceabilty to the test. There is no objective proof that the scales are calibrated correctly or weighing correctly.
Many organisations now recognise the need for calibration test results that are correct and can be validated. In particular, organisations that are involved in Airports have placed importance on knowing there test results are correct and traceable. They have taken the responsible position of demanding certainty and not relying on best efforts alone. To achieve this they have embraced the independent accreditation system and are requiring accredited companies be used to inspect, test and calibrate any equipment that requires this type of work.
The use of an approved company to test and calibrate your weighing equipment, provides the scale owner with the most comprehensive protection and assurance that the equipment is calibrated correctly and performing to specification. For a responsible company in a high profile airport site there is no serious alternative.
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