The development of PEX plumbing and heating systems, energy-saving technologies, automation of Housing, gave an impetus to expand the nomenclature of various devices used to control flow of the working medium transported by pipelines. Such devices used to disable, distribution, control, mixing or reset a flow, united under the concept of Taco valves.
Market saturation foreign and domestic models, a wide variety of conditions in which the Taco mixing valves work, the specific requirements for it, questions of reliability and durability, the presence of a large number of construction types complicate the choice of PEX fittings for the concrete conditions of exploitation in modern systems.
The vast majority of mixing valves installed on the pipelines, and a much smaller portion is mounted directly on the boilers, machines, plants and aggregates.
The main parameters of valves are:
diameter nominal bore;
nominal pressure;
medium temperature;
working pressure
test pressure.
And the first three characteristics are common to valves and piping.
Nominal bore diameter (D y) – Nominal internal diameter of the pipeline, which is installed PEX fittings. Different types of reinforcement are the same diameter nominal bore have different flow areas.
Nominal pressure – the maximum operating pressure at 20 ° C, at which the long-term operation of valves and connecting parts of pipelines.
Operating temperature – the highest long-term temperature pumped through a pipeline environment (excluding short-term increases in temperature, acceptable technical conditions).
Operating pressure – the maximum overpressure at which the long-term operation of valves and connecting parts of pipelines at operating temperature ongoing protection.
Pressure test – too much pressure at which the valves and PEX fittings of the piping shall be hydraulically tested for strength and permeability of the material body parts of at or below 5 ° C and not above 70 ° C, if the normative and technical documentation is not specified the exact meaning of this temperature .
Boundary deviation values test pressure should not exceed 15%. Nominal pressure is the only parameter PEX fitting, which ensures its durability and accounted for as operating pressure and operating temperature. Nominal pressure corresponds to the allowable working pressure of the product at normal temperatures. With increasing temperature, the mechanical properties of structural materials deteriorate. Therefore, for valves with a high operating temperature allowable working pressure is lower than conventional. This reduction depends on the material details of fixtures and the temperature dependence of the strength properties of the material. The higher operating temperature, the lower the maximum operating pressure at the same relative pressure.
