Basic knowledge of pipes and fittings

Thread Content

1. Steel pipes Steel pipes are divided into two types: seamless steel pipes and welded steel pipes according to their manufacturing methods. Seamless steel pipes are made of high-quality carbon steel or alloy steel, and are divided into hot-rolled and cold-rolled (drawn). Welded steel pipes are made of steel plates rolled into tubular shapes and welded with butt seams or spiral seams. In terms of manufacturing methods, they are divided into welded steel pipes for low-pressure fluid transportation, spiral seam electric welded steel pipes, direct coil welded steel pipes, electric welded pipes, etc. Seamless steel pipes can be used for various liquid and gas pipelines, etc. Welded pipes can be used for water pipes, gas pipes, heating pipes, etc. 1 Welded steel pipe 1.1 Welded steel pipe and galvanized welded steel pipe for low-pressure fluid transportation Welded steel pipe for low-pressure fluid transportation is made of carbon mild steel. It is the most commonly used small-diameter pipe in pipeline engineering. It is suitable for transporting water, gas, steam and other media. According to its different surface quality, it is divided into galvanized pipes (commonly known as white iron pipes) and non-galvanized pipes (commonly known as black iron pipes). The ones with a zinc protective layer on the inner and outer walls are about 3%-6% heavier than the non-galvanized ones. According to the different wall thickness of the pipe, it is divided into: There are three types: thin-walled tubes, ordinary tubes and thickened tubes. Thin-walled pipes are not suitable for transporting media and can be used as casing. 1.2 Straight seam rolled electric welded steel pipes Straight seam rolled electric welded steel pipes can be divided into electric welded steel pipes and straight seam rolled welded steel pipes that are rolled and welded by steel plates on site. Several tube wall thicknesses can be made. 1.3 Spiral seam welded steel pipe Spiral seam welded steel pipe is divided into two types: automatic submerged arc welded steel pipe and high frequency welded steel pipe. A Spiral seam automatic submerged arc welded steel pipes are divided into two categories: Class A pipes and Class B pipes according to the pressure of the conveying medium. Class A pipes are generally welded with ordinary carbon steel Q235, Q235F and ordinary low alloy structural steel 16Mn. Class B pipes are welded with Q235, Q235F, Q195 and other steels and are used as low-pressure fluid transport pipes. B Spiral seam high-frequency welded steel pipes. Spiral seam high-frequency welded steel pipes. There is no unified product standard. They are generally made of ordinary carbon steels Q235, Q235F and other steels. 2 Seamless steel pipes Seamless steel pipes are divided into hot-rolled pipes and cold-drawn (rolled) pipes according to the manufacturing method. The maximum nominal diameter of cold-drawn (rolled) pipes is 200mm, and the maximum nominal diameter of hot-rolled pipes is 600 mm. In pipeline engineering, when the pipe diameter exceeds 57mm, hot-rolled pipes are often used, and when the pipe diameter is less than 57mm, cold-drawn (rolled) pipes are often used. There are three types of seamless steel pipes commonly used in pipeline engineering:: 2.1 General seamless steel pipe General seamless steel pipe, referred to as seamless steel pipe, is made of ordinary carbon steel, high-quality carbon steel, ordinary low alloy steel and alloy structural steel. It is used to make liquid pipelines or structures and parts. Seamless steel pipes are supplied according to outer diameter and wall thickness. They have a variety of wall thicknesses under the same outer diameter and can withstand a wide range of pressures. Generally, the length of steel pipes is 3~12.5m for hot-rolled pipes and 1.5~9m for cold-drawn (rolled) pipes. 2.2 Seamless steel pipes for low and medium pressure boilers Seamless steel pipes for low and medium pressure boilers are made of No. 10 and No. 20 high-quality carbon steel and have a working temperature of 2. Cast Iron Pipe Cast iron pipe is made of pig iron. According to their different manufacturing methods, they can be divided into: Sand molded centrifugal socket straight pipes, continuous cast iron straight pipes and sand molded iron pipes. According to the different materials used, it can be divided into: Gray iron pipe, ductile iron pipe and high ferrosilicon pipe. Cast iron pipes are mostly used in pipeline projects such as water supply, drainage and gas. 1 Water supply cast iron pipe 1.1 Sand-type centrifugal cast iron straight pipe Sand-type centrifugal cast iron straight pipe is made of gray cast iron and is suitable for transporting pressure fluids such as water and gas. 1.2 Continuous cast iron straight pipe Continuous cast iron straight pipe is a continuously cast gray cast iron pipe, which is suitable for transporting pressure fluids such as water and gas. 2 Drainage cast iron pipes, ordinary drainage cast iron socket pipes and fittings. Flexible anti-seismic interface drainage cast iron straight pipes. These cast iron pipes are sealed with rubber rings and fastened with bolts. They have good flexibility and elasticity under internal water pressure. It can adapt to large axial displacement and lateral flexural deformation, and is suitable for indoor drainage pipes in high-rise buildings, especially in earthquake areas. Three non-ferrous metal pipes 1 Aluminum and aluminum alloy pipes Aluminum and aluminum alloy refer to industrial pure aluminum containing 98% aluminum and aluminum alloys with aluminum as the main body and additional alloying elements such as copper, magnesium, manganese, zinc, chromium and so on. Aluminum and aluminum alloy pipes are formed by drawing or extruding industrial pure aluminum or aluminum alloys. Aluminum has good acid corrosion resistance. 2 Copper and copper alloy tubes Copper tubes are mainly made of pure copper and phosphorus deoxidized copper, called copper tubes or red copper tubes. Brass tubes are made of ordinary brass, lead brass and other brass. 3 Lead and lead alloy pipes 4. Plastic pipes Plastic pipes are generally made of plastic resin as raw material, adding stabilizers, lubricants, etc., and are extruded in a pipe making machine by a plastic method. Because of its light weight, corrosion resistance, beautiful appearance, no bad odor, easy processing, and convenient construction, it has been increasingly widely used in construction projects. It is mainly used for tap water supply system piping, drainage, exhaust and sewage sanitary pipes, underground drainage pipe systems, rainwater pipes, and wiring pipes for wire installation in housing buildings. Plastic pipes are divided into two categories: thermoplastic pipes and thermosetting plastic pipes. The main resins used in thermoplastic pipes are polyvinyl chloride resin (PVC), polyethylene resin (PE), polypropylene resin (PP), polystyrene resin (PS), propylene-butadiene-styrene resin (ABS), polybutylene resin (PB), etc. ； The main resins used in thermosetting plastics are unsaturated polyester resin, epoxy resin, furan resin, phenolic resin, etc. Table 1 lists the characteristics and main uses of these plastic pipes (see Table 1). Table 1 Comparison of characteristics and main uses of several commonly used plastic pipes Name Features Connection methods Main uses PVC pipes have good tensile and compressive strength, but their flexibility is not as good as other plastic pipes. They have excellent corrosion resistance and are the cheapest among all types of plastic pipes. However, they are brittle at low temperatures. Bonding, socket rubber ring connections, and flange threaded connections are used in residential life, industry, mining, and agriculture for water supply and drainage, irrigation, gas supply, exhaust pipes, wire conduits, rainwater pipes, industrial anti-corrosion pipes, etc. CPVC pipes have outstanding heat resistance and thermal deformation. Temperature is 100℃, excellent chemical resistance, bonding, flange thread connection hot water pipe PE pipe is light weight, good toughness, good low temperature resistance, non-toxic, cheaper, high impact strength, but low compressive and tensile strength Hot melt welding, flange thread Connecting drinking water pipes, rainwater pipes, gas pipes, industrial corrosion-resistant pipes, PP pipes have good corrosion resistance, good strength, high surface hardness, surface smoothness, and certain high temperature resistance. Hot melt welding, flange thread connection, chemical sewage, sea water , oil and irrigation pipes, used for indoor concrete floors as heating pipes for heating systems. ABS pipes have excellent corrosion resistance, are lighter in weight, and have higher heat resistance than PE and PVC, but are more expensive. Bonding and flange threaded connections for sanitary ware are used for sewer pipes and water supply pipes. , sewage pipes, underground cable pipes, high anti-corrosion industrial pipes and other PB pipes. The strength is between PE and PP, and the flexibility is between LDPE and HDPE. Its outstanding features are creep resistance (cold deformation), repeated winding, temperature resistance, and chemical resistance. It can also be used for hot-melt welding, flange threaded connection of water supply pipes, hot and cold water pipes, gas pipes, and underground buried high pipes. GRP pipes have excellent corrosion resistance, light weight, high strength, and good design performance. Socket rubber ring connections and flange connections are widely used in petrochemical pipelines and large pipes. Caliber water supply and drainage pipes 1. Rigid polyvinyl chloride pipes and fittings for building drainage Rigid polyvinyl chloride (UPVC) pipes and fittings for building drainage are made of PVL resin as the main raw material, adding special additives, and extruded and injection molded in a pipe making machine. 1.1 Features (1) Excellent physical properties. UPVC pipes and fittings are corrosion-resistant, have high impact strength, low fluid resistance, no scaling, smooth inner walls, are not easy to block, and meet the requirements for flame retardant performance of building materials, are resistant to aging and have a long service life. The indoor and buried service life can reach more than 50 years, and the outdoor use can reach 50 years. (2) Light weight, easy to transport, store and install, which is helpful to speed up the project progress and reduce construction costs. (3) Save construction costs. Using UPVC pipes and fittings is cheaper than using cast iron piping systems of the same specifications and is easy to maintain. 1.2 Purpose: It is suitable for drainage systems in buildings. It can also be used for industrial drainage systems under the heat resistance and conditions of chemical resistance of the pipe. It can be used continuously at temperatures below 60°C and intermittently at temperatures below 80°C. 2 Rigid polyvinyl chloride plastic pipes and fittings for water supply Rigid polyvinyl chloride plastic pipes and fittings for water supply are made of food hygiene grade polyvinyl chloride resin as the main raw material, adding non-toxic special additives, and are mixed, plasticized, extruded or injected. Product complies with * * Drinking water hygiene standards, using socket bonding, elastic sealing rings, metal variable joints and other connection methods. 2.1 Features (1) Excellent physical properties, UPVC water supply pipes and fittings have high impact strength, smooth surface, low fluid resistance, water delivery capacity is 120% of the same type of steel pipes, and are not easy to scale, and the water delivery capacity will not be reduced after long-term use. (2) Corrosion-resistant, non-rusting, not corroded and damaged by the corrosiveness and material action of soil and water, and generally has a service life of more than 50 years. (3) The thermal conductivity is small and it is not easy to freeze and crack when used in winter. (4) It is light in weight, easy to transport, store and install, and has high labor efficiency, which is helpful to speed up the project progress and reduce construction costs. 2.2 Purpose It is mainly used in indoor water supply systems of residential buildings, replacing traditional white iron pipes and fittings, and can be used in systems such as drainage, sewage discharge, and transportation of corrosive fluids. It can also be used to transport water supply pipes in buildings (overhead or buried) with temperatures below 45°C. 3 Composite foamed rigid polyvinyl chloride pipe Composite foamed rigid polyvinyl chloride pipe is co-extruded from three layers of PVC formula. Through this modified PVC inner and outer skin layer and honeycomb structure core layer, the composite foamed rigid PVC pipe not only has the characteristics of traditional PVC solid wall pipes that are superior to cast iron and copper pipes, but also has characteristics that traditional PVC solid wall pipes, cast iron pipes and steel pipes cannot match. Composite foamed rigid polyvinyl chloride pipe is a new type of plastic pipe developed in China in recent years. 3.1 Features The product has the characteristics of light weight, low cost, low fluid resistance, acid and alkali resistance, long service life, high mechanical strength, good sound insulation performance, strong electrical insulation, simple construction, heat and cold resistance, etc. 3.2 Purpose It is suitable for low-pressure water supply pipes, drainage and sewage pipes, indoor air conditioning and ventilation pipes, exhaust pipes, wire and cable sheathing pipes, hot and cold fluid conveying pipes and chemical and pharmaceutical industrial pipes in industrial and residential buildings. 4 Rigid polyvinyl chloride electrical special pipes and joints are made of polyvinyl chloride resin as raw material, mixed with special additives, plasticized and extruded. 4.1 Features: It has the characteristics of good flame retardant performance, corrosion resistance, weather resistance, light weight, beautiful appearance, low cost, supporting products and convenient construction. 4.2 Purpose: It is suitable for electric chlorine installation casings in various buildings for indoor and outdoor (exposed or concealed) applications. It plays the role of beautifying the indoor environment, fire prevention, safety, insulation and wire decoration. 5 Soft polyvinyl chloride plastic pipes are made of polyvinyl chloride resin as raw material, with plasticizers, stabilizers and other auxiliary agents, and are made by mixing and discharging. 5.1 Features It has the advantages of light weight, corrosion resistance, good electrical insulation performance, and convenient construction. 5.2 Purpose: It is suitable for electrical bushings and fluid delivery pipes. Electrical bushings can be used to protect wires and cables at normal temperatures, and liquid delivery pipes can be used to transport certain liquids and gases. 6 Polyethylene plastic pipes are made of polyethylene resin as raw material, mixed with a certain amount of additives, and processed by extrusion molding. 6.1 Features It has the characteristics of light weight, corrosion resistance, non-toxic, easy to bend, and convenient construction. 6.2 There are two varieties: high-pressure (low-density) polyethylene and low-pressure (high-density) polyethylene. The former is softer in nature, with lower mechanical strength and melting point. ； The latter has higher density, greater rigidity, higher mechanical strength and melting point. 6.3 Usage Suitable for industrial and residential use as drinking water pipes, rainwater pipes, gas pipes, industrial corrosion-resistant pipes, transporting liquids, gases, edible media, etc. It can also be used as medical hoses. 7 Polyethylene corrugated pipes are made of high-density polyethylene resin as raw material, mixed with a certain amount of additives, and plasticized. 7.1 Features It has the characteristics of light weight, corrosion resistance, aging resistance, high product strength, good bending performance and convenient construction and installation. 7.2 Application: Suitable for cable casings, underground cable pipes, agricultural irrigation pipes, ventilation pipes, water pipes, etc. 8 Polypropylene plastic pipes are made of polypropylene resin as raw material, added with appropriate stabilizers, and processed by extrusion molding. 8.1 Features It has the characteristics of light weight, corrosion resistance, high heat resistance, and convenient construction. 8.2 Purpose It is suitable for transporting fluid media (including corrosive fluid media) in chemical, petroleum, electronics, medicine, catering and other industries and various civil buildings. It can also be used as water pipes, agricultural drainage and irrigation pipes, sprinkler irrigation pipes and electrical insulating pipes. 9 Acrylonitrile-butadiene-styrene pipe (ABS) pipe ABS pipe is made of acrylonitrile-butadiene-styrene terpolymer as the main material and formed by extrusion. ABS for pipes and fittings with a minimum content of 6% butadiene, 15% acrylonitrile, and 25% styrene or its substitutes. 9.1 Features ABS plastic pipe is lightweight, has high impact strength and surface hardness, and can maintain toughness, solidity and rigidity in the range of -40℃~100℃. Its corrosion resistance and impact resistance are better than those of polyvinyl chloride pipes. ABS tubes can retain heat better than copper tubes and brass tubes and have extremely high toughness, and can avoid damage from severe cold, weather, loading, unloading, and transportation. When subjected to a high yield strain, it can return to its original size without damage. Therefore, it can replace stainless steel pipes, copper pipes and other pipes. 9.2 Purpose ABS pipes are suitable for domestic water supply, sewage, ventilation systems, irrigation systems, submersible pump devices, drinking water pipelines, gas distribution pipelines, well casings, underground electrical pipelines, and can also be used as industrial pipe devices for transporting corrosive salt water solutions, organic matter containing fluid corrosives (such as crude oil and food), and pure chemicals or other sensitive products.