The manufacturing process of sanitary pipe fittings also includes steps such as forming, cleaning and degreasing of pipe fittings. The following is a detailed introduction:
1. Material selection
Raw material selection: Usually high-quality stainless steel materials such as 304 and 316L stainless steel are used. These materials have good corrosion resistance, hygiene and mechanical properties, and can meet the strict requirements of sanitary pipe fittings in food, beverage, pharmaceutical, bioengineering and other industries.
Cutting and blanking: According to product specifications and size requirements, stainless steel plates or pipes are cut into suitable blanks using cutting equipment. Common cutting methods include laser cutting, plasma cutting, sawing, etc. Laser cutting has high precision and smooth cuts, and is suitable for cutting various shapes; plasma cutting has fast speed and is suitable for cutting thick plates; sawing is often used for cutting pipes, and the cutting surface is relatively flat.
2. Forming processing
Stamping: For some simple-shaped pipe fittings, such as elbows and tees, stamping technology is often used. Through the action of the mold and the punch, the blank is plastically deformed under a certain pressure to obtain the desired shape. This method has high production efficiency, good dimensional accuracy and surface quality.
Spinning: For some round pipe fittings or heads, spinning is a common method. The blank is fixed on the spinning machine, and the blank is gradually formed through rotation and roller extrusion. The surface of the spinning pipe fittings is smooth and the wall thickness is uniform.
Pipe bending: The straight pipe is bent by special pipe bending equipment to manufacture elbows, bends and other pipe fittings. In the process of pipe bending, it is necessary to control the parameters such as bending radius, angle and speed to prevent deformation and cracking of pipe fittings. In order to ensure the bending quality, it is sometimes necessary to pre-bend the pipe fittings or add auxiliary measures such as mandrels.
3. Welding process
Welding method: Tungsten inert gas arc welding (TIG) is mainly used. This welding method has the advantages of stable arc, concentrated heat, high welding quality and beautiful weld formation. It can effectively reduce the mixing of impurities and heat-affected zones during welding and ensure the hygienic performance of pipe fittings. For some thicker pipe fittings, MIG or plasma arc welding may be used for base and filler welding.
Welding preparation: Before welding, the welding parts of the pipe fittings need to be cleaned to remove impurities such as oil, rust, and moisture to prevent defects such as pores and slag inclusions during welding. At the same time, appropriate welding materials, such as welding wire and welding rod, should be selected according to the material and specifications of the pipe fittings, and the parameters of the welding equipment, such as welding current, voltage, welding speed, and gas flow, should be adjusted.
Weld seam treatment: After welding, the weld seam needs to be ground and polished to make the weld seam flush with the surface of the pipe fitting and the surface roughness meets the sanitary requirements. For some important pipe fittings, non-destructive testing of the weld seam, such as radiographic testing and ultrasonic testing, may also be required to ensure that the internal quality of the weld meets the standards.
Machining: Machining the connection parts and sealing surfaces of the pipe fittings to ensure the dimensional accuracy and connection performance of the pipe fittings. Common machining processes include turning, milling, drilling, tapping, etc. Through these processing techniques, various types of connection interfaces can be processed, such as threaded connection, clamp connection, flange connection, etc., to meet different installation and use requirements.
4. Surface treatment
Pickling and passivation: Pickling and passivation are an important part of the surface treatment of sanitary pipe fittings. Through pickling, impurities such as scale and rust on the surface of the pipe fittings can be removed, so that the metal color of the pipe fitting surface can be exposed; then passivation treatment is carried out to form a dense passivation film on the surface of the pipe fittings to improve the corrosion resistance and oxidation resistance of the pipe fittings. The surface of the pipe fittings after pickling and passivation should present a uniform silver-white color without obvious corrosion marks and passivation spots.
Electrolytic polishing: Electrolytic polishing is a treatment method to further improve the surface finish and corrosion resistance of pipe fittings. In the electrolytic cell, the pipe fittings act as anodes, and the microscopic protrusions on the surface of the pipe fittings are preferentially dissolved through the action of the electrolyte, thereby achieving the effect of flattening and polishing. The surface roughness of the pipe fittings after electrolytic polishing can reach Ra0.2μm or less, with good self-cleaning and corrosion resistance.
Cleaning and degreasing: Use special cleaning equipment and cleaning agents to thoroughly clean the pipe fittings to remove impurities such as oil, dust, and metal chips on the surface. For some pipe fittings used in the food, pharmaceutical and other industries, degreasing treatment is also required to ensure that there is no grease residue on the surface of the pipe fittings to meet hygiene requirements. After cleaning and degreasing, the pipe fittings should be rinsed with deionized water or distilled water and dried to prevent rust on the surface of the pipe fittings.
5. Quality inspection
Appearance inspection: Mainly check the surface quality of the pipe fittings, including surface roughness, weld quality, scratches, bumps, deformation and other defects. The surface of the pipe fittings should be smooth, burr-free, without obvious welding spatter and oxidation color, and the weld should be uniform and flat, without defects such as pores, slag inclusions, and cracks.
Dimensional accuracy measurement: Use measuring tools such as calipers, micrometers, gauges, etc. to measure the key dimensions of the pipe fittings, including pipe diameter, wall thickness, length, bending radius, connection size, etc. The dimensional deviation of the pipe fittings should comply with relevant standards and design requirements to ensure the installation and use performance of the pipe fittings.
Pressure test: Perform pressure test on pipe fittings to check the sealing and strength of pipe fittings. Common pressure test methods include hydraulic test and air pressure test. During the test, fill the pipe fittings with liquid or gas at a certain pressure for a period of time to observe whether the pipe fittings have leakage, deformation and other phenomena. The pressure of the pressure test is usually about 1.5 times the working pressure of the pipe fittings, but it must not be lower than the minimum value specified in the relevant standards.
Material detection: Use spectral analysis, chemical analysis and other methods to detect the material of the pipe fittings to ensure that the chemical composition of the pipe fittings meets the design requirements. At the same time, the organizational structure and grain size of the pipe fittings can also be checked by metallographic analysis and other means to evaluate the performance and quality of the pipe fittings.
6. Packaging and labeling
Packaging: Pack the qualified pipe fittings to prevent damage and contamination during transportation and storage. Generally, plastic film, plastic bags, paper boxes, wooden boxes and other packaging materials are used for packaging. For some high-precision and easily damaged pipe fittings, foam, sponge and other cushioning materials are added to the packaging to protect the pipe fittings from collision and extrusion.
Labeling: Mark the relevant information of the product on the surface of the pipe fitting or on the packaging, such as product model, specification, material, production batch, production date, implementation standard, inspection pass mark, etc. The labeling should be clear, accurate and firm to facilitate users to identify and trace the quality information of the product.