According to GOST 15467-79, product quality should be understood as a combination of its properties, thanks to which it is able to satisfy, in accordance with its purpose, certain needs.
The term “production” according to GOST R ISO 9000-08 (clause 3.4.2) is here considered as the result of a process that is a combination of various activities interconnected and interacting with each other and converting inputs into outputs (clause 3.4.1 of the same GOST). Thus, the definition of product quality should be carried out in the areas of assessment:
- its compliance with the requirements (expectations or needs that are established and are mandatory or are only anticipated - the definition follows from paragraph 3.1.2 of GOST 9000-08);
- ability to satisfy needs, that is, to determine the set or level of required characteristics and its usefulness.
Section 4 of GOST 15467-79 establishes that product quality assessment should be carried out by applying the following methods:
- differential, based on individual quality indicators, each of which characterizes a single product property (for example, water hardness characterizes the content of Ca and Mg salts that can form deposits or scale in equipment);
- integrated - comprehensive quality indicators are used (for example, for surface water the 1st, 2nd, 3rd, 4th or 5th quality class can inform that the water is conditionally clean, slightly polluted, polluted, dirty or extremely dirty);
- mixed - assessment is carried out using single and complex indicators (for water in surface sources, single indicators, such as hardness, and complex indicators, such as quality class, are regulated);
- statistical - mathematical statistics are applied (the order of use in the control of product quality is regulated by a series of GOSTs R 50779).
Verification of compliance with established requirements is carried out for each quality indicator before sending products to the consumer. This procedure is called acceptance for external or operational control for the internal consumer.
The scope of control, including methods for evaluating product quality, such as differential, complex or mixed, for which tests are carried out, is prescribed in the technical conditions or contracts (agreements). If the specification does not reflect the true quality requirement, then it cannot be guaranteed. For example, for vessels operating under high pressure, regulatory documents should regulate not only the material from which the apparatus is made, its design and dimensions, but also such operations as manufacturing, installation, commissioning, technical diagnosis, operation and repair. That is, all requirements, the mandatory observance of which guarantees the reliability and safety of the pressure vessel.
The ability (in accordance with its purpose) to meet certain needs can be considered by the example of mandatory requirements for the quality of chemically treated water intended for steam generation. Such water in technological documentation is usually called chemically purified (desalted) or nutritious (supplied to the power of boilers in which steam is generated).
Evaluation of product quality is carried out according to certain indicators: the requirements are established depending on the parameters of the steam (low, high or medium pressure). For example, for boilers with a working pressure of 9 kgf / cm², 18 kgf / cm² and 50 kgf / cm², the feed water hardness should be no higher than 70 µmol / kg, 15 µmol / kg and 5 µmol / kg, respectively. Copper compounds, in terms of Cu, are not regulated for the first two cases, and for boilers with a working pressure of 50 kgf / cm², their content in feed water should not exceed 20 μg / kg.
Product quality assessment is carried out by competent laboratories, the general requirements for which are established by GOST R ISO / IEC 17025-09. The standard is established by 15 requirements for quality management in a testing or calibration laboratory and 10 technical requirements. Only at their implementation the laboratory can be certified within the framework of the QMS operating in the organization or accredited by an independent body. The last option to confirm competence is, of course, more significant.
A management system refers to an organization’s structure used to manage processes or activities that transform resource inputs into a product or service that meets the organization’s goals. For example, satisfying quality with customer requirements, observing safety rules, or achieving environmental goals.
Product quality assessment in many foreign companies is based on statistical process control, based on the Six Sigma method. For statistically controlled processes, the probability of an unexpected failure is limited to six standard deviations from the normal distribution, i.e. less than 4/1000000000. The introduction of this method allows us to guarantee high and stable product quality.