Basic concepts for the purposes of these regulations and technical uses the following basic concepts: Valves (valves) – technical device installed on the pipelines and tanks intended for their protection or management (overlap, management, distribution, mixing, ) flow of the working medium (liquid, gas, gas-liquid, powder, suspensions, etc.) by area change flow area or flow direction, valves and fittings – designed to shut off the flow of the working environment with a normalized integrity valves; protective fittings – valves, designed for automatic protection of equipment and pipelines from impermissible overpressure in the protected facility by dumping excess of the working environment; fixture – designed to control parameters of the working environment by changing the cross-section area of reinforcement; reverse fixture – designed to automatically prevent backflow of the working environment fittings; fittings shut-off – stop driving fittings with a minimum response time, due process requirements, distribution and mixing valves – valves, designed to distribute medium flow in certain directions, or for mixing flows; fittings – valves, designed to separate working environments that are in different phase states, pressure Nominal (PN) – the highest operating pressure, expressed in kg/cm2 at a temperature of operating environment 293 K (20 C) at which the predetermined period of service (resource) body parts of valves that have specific dimensions, based on the calculation of strength at the chosen materials and their characteristics of strength at 293 K (20 C) operating pressure (PP) – The highest overpressure, which allows continuous operation Fixtures for the chosen materials and a given temperature, pressure design – (P) – Too much pressure to which calculates the strength, the pressure test (RPR; Ph) – positive pressure, which should be carried out hydraulic test fittings for strength and density of water at a temperature of at least 278 K (5 C) and not more than 343 K (70 C) if the documentation otherwise indicated temperature. . For more information see Mike Wirth.