June 23, 2009
The relatively new concept of validation likely will be used more and more by customers and certifying agencies to ascertain that all conceivable means were used to guarantee that a manufactured product indeed meets all requirements, including hidden characteristics not readily verifiable. This article gives an overview of typical applications.
Has a customer ever asked you to validate a manufacturing process or procedure, or have you asked for validation from a supplier? In either case, you need to know what validation means for you, your customers, and your suppliers.
A client recently wrote: "We are seeking validated information proving that a change in manufacturing procedure will provide a product that is equal to or superior to that supplied previously. We know that the benefits of the proposed change are significant with respect to component cost reduction and labor saved. However, we are poorly equipped to offer evidence acceptable to the customer."
If some essential properties or characteristics change during service time, possibly because of intervening deterioration processes, you should be able to determine the consequences for both the original and the modified product.
Or if the actual service conditions cannot be described adequately, and the projected future behavior of the component is not known in sufficient detail, then screening tests perhaps can evaluate the results of the proposed change—how the new part will perform and last relative to the original part.
Designing and running accelerated endurance tests with carefully selected parameters (moderately exceeding the norm to make up for the reduced time) can help you determine which of the proposed solutions creates a better-performing, longer-lasting part.
Will the proposed change improve or worsen availability and functionality?
Validation—the process of checking if something satisfies certain criteria—depends much upon service conditions and time between failures (TBF), prescribed by the application requirements.
The concept should be used with precise reference to the discipline to which it is applied because it may mean different things in different situations.
In engineering or as part of a quality management system, validation confirms that the needs of an external customer or user of a product, service, or system are met.
In regard to welding, validation generally is a part of the quality management system. It is required to prove the reliability of the organization providing goods or services and it is considered an essential ingredient for ensuring the integrity of materials, processes, and manufactured items.
The validation process is designed to demonstrate that the entire inspection activity and indeed the whole quality assurance system continuously meet all requirements.
Validation relates to meeting the requirements of official agencies that enforce adherence to specific codes, or of external customers as applicable, for example, to nondestructive testing equipment, methods, procedures and inspectors.
In the case of nondestructive testing as a whole system applied to welded structures, there is consensus as to what validation means. It answers the question: "Will the service offered provide complete, valid, and true results consistently?"
As a matter of fact, it's been shown that NDT can miss important clues if it's performed nonchalantly by unscrupulous or inferior organizations.
The adequacy of NDT equipment and its current operational order and calibrations, preparation and skill of personnel, the application of suitable methods and procedures, and the interpretation of results with respect to applicable standards all must be validated by an unbiased and reliable external agency.
The company providing the welding declares the quality assurance requirements, means, and procedures within its quality manual. The company and all subcontractors should be ready to submit documentation that specifies how all fixed procedures and established written instructions are implemented to the satisfaction of the customer or certifying agency.
The definition of validationis not yet standardized, so different meanings can be found. Neither the American Welding Society nor ASM International provides a universally accepted definition for the term. You also may find different meanings in other situations.
In open literature, reference can be found to validation of a welding schedule as a process whereby experienced welders are asked to determine the productivity of the baseline welding procedure.
Validation of welding parameters is used to describe the assessment of a welding procedure specification (WPS) generally in an experimental situation, as opposed to a production environment.
In research work, the term validationis used for the purpose of determining if a model proposed for explaining a certain result or for simulation of a certain process can be used for predictions, as in the following sentence: "Thermal cycles measured with thermocouples embedded in specimens are employed to validate a numerical thermo-metallurgical model of an electron beam welding process."
Any manufacturing facility doing welding must demonstrate to the customer or to the appointed authority that welding equipment is in good operating condition and is being subjected to scheduled maintenance, controls, and periodic calibration. Within this restricted scope, validation of welding equipment simply means calibrating instruments and verifying that they are suitable for use in the specified application.
In brief, validation could be thought of as proof of the pudding before the eating.