In order to ensure a better use environment for PVC pipes, PVC pipe manufacturers can avoid external loading and achieve the expected service life, so the pipes are arranged and laid reasonably. In order to ensure the scientific rationality of the installation, the installation design principles must be followed when installing the PVC pipe.
1. The pipeline is generally suitable for open installation. In places where the pipeline may be collided, it is more suitable to conceal or take protective measures. The exposed water pipe is more suitable to be arranged on the wall, corner or column near the sanitary appliance or equipment with large water volume. PVC water supply pipes cannot pass through bedrooms, storage rooms, flue ducts and air ducts.
2. Lay the water supply pipe in a place exposed to sunlight outdoors. At this time, light materials should be used for heat insulation. When the pipeline is darkly applied, it is strictly forbidden to touch organic chemicals such as waterproof paint to avoid affecting the water quality and damaging the pipeline. When the pipeline passes through the roof and basement, metal waterproof flexible casing and effective waterproof measures should be set up.
3. When PVC water supply pipes are laid in parallel with other pipes in the same ditch (rack), they are suitable for laying along the side of the ditch (rack), and when laid up and down in parallel, they cannot be laid on the hot water pipe or steam pipe, and the plane position Should be staggered; when laying across other pipelines, protective measures or metal casings should be used.
4. The PVC water supply pipeline should be far away from the heat source. The net distance between the standpipe and the stove side should not be less than 400mm, and the net distance from the heating pipeline should not be less than 200mm, and the outer wall temperature of the pipe should not be higher than 40℃ due to the heat source radiation. The installation of PVC pipes does not follow the steps blindly. In order to ensure the long-term use of PVC pipes and reduce the occurrence of failures, all pvc pipe manufacturers need a certain design when installing. The design of the above principles is summarized because of these factors.
With the development of extension springs application technology, more requirements are put forward for extension springs materials. The first is the forward fatigue life under high stress and the anti-slack function; the second is the corrosion resistance, non-magnetic, electrical conductivity, wear resistance, heat resistance and other aspects according to different uses. Therefore, in addition to the development of new varieties of extension springs materials, favorable results have been achieved in terms of strict control of chemical composition, reduction of non-metallic impurities, and improvement of surface quality and dimensional accuracy.
(1) Development of the production process of extension springs steel. In order to advance the quality of extension springs steel, the industry has generally selected out-of-furnace refining technology, continuous casting process, new rolling and online automatic detection and control equipment.
In order to ensure the chemical composition of steel and reduce the content of gases and various non-metallic inclusions, a large-capacity electric furnace or converter is used for smelting, and a ladle outside the furnace is used for refining to reduce the oxygen content (mass fraction) to (0.0021~0.0010)%. Produce ultra-pure steel, and then greatly advance the planning and operating stress of extension springs.
The continuous casting production process has been selected in the production of extension springs steel. Continuous casting can reduce the segregation of steel, reduce secondary oxidation, improve surface decarburization, and make the arrangement and function stable and uniform through techniques such as electromagnetic mixing and low-temperature casting.
The use of a split full continuous rolling mill can improve the dimensional accuracy and surface quality, and at the same time, the steel can be arranged uniformly along the length. In the rolling process, in order to ensure the surface quality of the product, online automatic detection and control are selected. In order to adapt to the production of variable cross-section extension springs flat steel, a new austenite rolling process has been developed, that is, the steel is heated and then rapidly cooled to the metastable austenite zone for plastic processing and quenching. This process allows the steel to advance its strength without reducing its plasticity. In addition, the function of extension springs steel is advanced by online heat treatment and surface hardening treatment after rolling.
(2) The development of alloy steel The primary function of alloying elements is to advance mechanical functions, improve process functions and give certain special functions. SiCr steel has been used for valve extension springs and suspension special-shaped springs. Si is an anti-stress slack alloy element. The addition of V and Mo to SiCr steel constitutes SiCrV and SiCrMo steels, which can improve fatigue life and anti-slack function. At the same time, the SiCr drawn wire has better anti-laundering function when working at high temperatures than piano wire and important-purpose carbon extension springs. With the high-speed miniaturization of engines, Ti alloys with good anti-vibration performance, light weight and small elastic modulus have been widely used, and their strength can reach 2000MPa.