Stainless steel pipe fitting method and installation

Stainless steel has a unique corrosion resistance that reacts with the oxidant to form a thin, dense oxide film that prevents oxidation from proceeding further. For other types of metal pipes, almost no passivation function, which is one of the main reasons why the corrosion resistance of stainless steel pipe materials exceeds that of ordinary metal pipes.

Rust steel pipe parts are recognized as healthy materials and are widely used in food processing and transportation pipelines, including pharmaceutical industry, beverages, brewing, etc. The stainless steel pipe material has superior performance and effectively reduces the transportation cost. It will not scale during the long-term transportation process, and the inner wall is smooth and clean, and the transportation energy consumption is low. It is the water pipe material with the lowest transportation cost so far.

First, the classification and use of stainless steel pipe fittings

1, stainless steel pipe classification

Stainless steel pipe fittings are one kind of pipe fittings. They are made of stainless steel, so they are called stainless steel pipe fittings. They include: stainless steel elbows, stainless steel tees, stainless steel crosses, stainless steel reducers, stainless steel caps, etc.

According to the connection method, it can be divided into four types: socket type stainless steel pipe fittings, threaded stainless steel pipe fittings, flanged stainless steel pipe fittings and welded stainless steel pipe fittings. The stainless steel elbow is used for the turning of the pipe; the flange is used to connect the pipe to the pipe, the pipe is connected to the pipe end, the stainless steel tee is used for the collection of the three pipes; the stainless steel pipe is used for the collection of the four pipes. Place; stainless steel reducer for the connection of two pipes of different pipe diameters.

2, the use of stainless steel pipe fittings

Stainless steel pipe fittings can be plated with paint or oxidation resistant metals (eg, zinc, nickel, and chrome) to ensure the carbon steel surface, but as is known, this protection is only a film. If the protective layer is destroyed, the underlying steel will begin to corrode, resist air, steam, water and other weakly corrosive media and corrosive steels such as acid, alkali, salt and other chemical etching media.

The most used parts for stainless steel pipe fittings are pressure vessel and chemical. The general refinery equipment factory has a large demand. Other aspects, such as chemical, food, beverage, pharmaceutical and other industries can be applied. It is mainly used in industrial transportation pipelines such as petroleum, chemical, medical, food, light industry, mechanical instrumentation, and mechanical structural components.

Second, the characteristics of stainless steel pipe fittings

1, life

Stainless steel tubing has the longest life. From the analysis of the use of stainless steel abroad, the service life of stainless steel water pipes can reach 100 years, at least 70 years, as long as the life of buildings.

2, corrosion resistance

One of the most outstanding advantages of stainless steel tubing is its excellent corrosion resistance, which is the best among all kinds of tubing. Because stainless steel can passivate with the oxidant, a tough and dense chromium-rich oxide protective film Dr2O3 is formed on the surface, which effectively prevents the further oxidation reaction. Other metal pipes, such as galvanized water pipes and copper pipes, have little passivation ability. This is the key reason why the corrosion resistance of copper pipes of galvanized pipes is far less than that of stainless steel pipes.

Stainless steel does not have uniform corrosion like carbon steel, no need to protect the coating when used; stainless steel water pipes have no restrictions on the chemical composition of water, because stainless steel is very good in water with various oxygen content, temperature, pH and hardness. Corrosion resistance; stainless steel water pipes can withstand high flow rates, even at flow rates greater than 40 m / s, still maintain a very low corrosion rate, no more than 0.003 mm / year, especially suitable for high-rise water supply.

3, heat and insulation

The thermal conductivity of stainless steel pipes is 1/25 of that of copper pipes, which is 1/4 of ordinary steel pipes, and is especially suitable for hot water transportation. The most commonly used stainless steels in the water industry are 304 and 316 stainless steels, which are suitable for most water treatment and transfer conditions.

4, strength

The strength of the material determines whether the water pipe is strong and crash resistant, safe and reliable. Safety and reliability are the most important requirements for building water supply. In the case of impact by external force, the possibility of leakage of stainless steel water pipes is extremely small. The working pressure of high-rise water supply system is generally greater than 0.6Mpa; the pressure on pipes is higher. Due to its excellent mechanical properties, thin-walled stainless steel pipes can withstand high water supply pressures up to 10Mpa, which is especially suitable for high-rise water supply.

Third, how to distinguish between true and false stainless steel pipe fittings

1. Compare the project's teeth and teeth:

2. The standard is sharp and the teeth are even and bright.

3, feel: the tooth front is smooth, the processing depth is standardized, the core is evenly walled, and the flow parts are unblocked.

4, mechanical treatment before leaving the factory, the surface is free of clips and debris.

5, low carbon content, corrosion resistance, oxidation resistance, strong toughness, strong pressure resistance.

6, rough, the tooth front is unfavorable and thick, the tooth distance is not standardized, the tooth front is damaged, easy to leak

7, the thread can not see the luster, the gray hand feels poor,

8, core , the wall thickness is uneven, easy to block after the fluid.

9, rough, surface untreated, easy to be oxidized

10, high carbon content, not resistant to corrosion, poor toughness, weak tensile strength.

Fourth, the installation skills of stainless steel pipe fittings

There are 9 main precautions for the installation of stainless steel pipe fittings:

1. Stainless steel material is lifted and cannot be in direct contact with other metals. Non-metallic materials such as wood or rubber sheets should be added.

2. Pipe cutting is not allowed to be cut with ordinary grinding wheel. Stainless steel special grinding wheel or plasma cutting should be used.

3. When the stainless steel pipe and pipe fittings are positioned and welded, the inside of the weld should be filled with argon.

4. The arcing and arcing and arcing are carried out by reflow method. The arc should be filled with arc pits. The arcing must be completed in the groove. It is forbidden to arc and arc on the surface of the pipe and pipe base material. If the arcing and arcing are found, defects such as pores and cracks should be cleaned in time.

5, stainless steel pipes, pipe fittings and stainless steel pipes, pipe fittings and non-stainless steel pipes, pipe joints, welded butt joints before welding, the inside of the pipe and the cavity should be filled with argon gas protection, in order to carry out tungsten argon arc welding.

6. The arcing and arcing of multiple multi-layer welding should be staggered from each other.

7. When the stainless steel material is continuously welded, the interlayer temperature does not exceed 60 °C.

8. The welds at the pipe joints are to be pickled and passivated after welding.

9. The hydraulic test of stainless steel pipe fittings has certain requirements on water temperature and water quality. The water temperature should not be less than 5 °C; the chloride ion content in water must be greater than 25Pmm.

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