The PVC pipe production line is a set of professional continuous production equipment specially designed for manufacturing various PVC series pipes, including PVC-U (unplasticized polyvinyl chloride) pipes, PVC-C (chlorinated polyvinyl chloride) pipes, and other modified PVC pipes. Its core component is the conical twin-screw extruder, which is matched with a full set of auxiliary equipment to realize automatic operation of the entire production process from raw material mixing, extrusion molding to finished product cutting and packaging. With the advantages of stable production, high efficiency, and precise product quality, this production line is widely used in construction water supply and drainage, municipal engineering, agricultural irrigation, electric power communication threading, and other fields, meeting the diverse needs of different industries for PVC pipes.

 

 

    

1. Technological Process (Detailed Version)

The production process of PVC pipes is a continuous and systematic operation, and each link is closely connected to ensure the stability and qualification of the final product. The detailed process flow is as follows:

   

Raw Material Preparation and Mixing: First, select high-quality PVC resin (SG-5 grade for water supply pipes, SG-4 grade for drainage pipes) as the base material, and mix it with various additives in a scientific proportion. The additives include stabilizers (calcium-zinc stabilizer for environmental protection, lead salt stabilizer for cost-effectiveness), lubricants (to reduce friction between materials and equipment, ensuring smooth extrusion), plasticizers (for modified PVC pipes, not required for PVC-U pipes), and fillers (calcium carbonate, with addition amount ≤10% for water supply pipes and ≤20% for drainage pipes to reduce production costs without affecting product performance). All raw materials and additives are put into the high-speed mixer for full mixing.

    

High-speed Mixing and Cold Mixing: The high-speed mixer heats and stirs the mixed raw materials at a high speed. The hot mixing temperature is controlled at 80–130℃, which can make the additives fully dissolve and disperse evenly in the PVC resin, and remove the moisture in the raw materials. After hot mixing, the materials are quickly transferred to the cold mixer for cooling, and the temperature is reduced to ≤40℃ to prevent the raw materials from agglomerating due to high temperature and ensure the fluidity of the materials during feeding.

 

    

Conveying and Feeding: The cooled mixed materials are conveyed to the feeding hopper of the extruder through a closed screw conveyor or vacuum conveyor, which avoids material pollution and ensures continuous and stable feeding. The feeding process is equipped with a level sensor to automatically supplement materials when the material level is insufficient, realizing unattended feeding.

   

Forced Feeding: The materials in the feeding hopper enter the forced feeder, which uses a spiral feeding structure to push the materials into the extruder barrel at a uniform speed. This can effectively solve the problem of uneven feeding caused by the light weight of PVC materials, ensuring stable material supply for the extruder and improving the stability of product quality.

   

Extrusion Molding: The materials enter the conical twin-screw extruder, which is the core equipment of the entire production line. The conical twin-screw rotates at a certain speed, and through the combined action of shearing, extrusion, and heating, the solid materials are gradually melted, plasticized, and homogenized to form a molten material with uniform texture and good fluidity. The molten material is extruded into the extrusion mold under a certain pressure (20–30 MPa) to form a pipe blank with a certain shape and size.

   

Sizing and Shaping: The extruded pipe blank first passes through the sizing sleeve, which determines the outer diameter of the pipe. Then it enters the vacuum sizing tank. The vacuum sizing tank maintains a negative pressure of -0.06~-0.08 MPa. Under the action of negative pressure, the pipe blank is closely attached to the inner wall of the sizing sleeve, so that the outer diameter of the pipe is fixed, and the dimensional tolerance is controlled within ±0.3 mm, ensuring the roundness and dimensional accuracy of the pipe.

   

Cooling Setting: After vacuum sizing, the pipe enters the cooling water tank for rapid cooling. The cooling method adopts a combination of spray cooling and immersion cooling, and the water temperature is controlled at 15–20℃. The length of the cooling water tank is not less than 6 meters, which can ensure that the pipe core is fully cooled to ≤40℃, so that the pipe shape is fixed, internal stress is reduced, and the toughness and strength of the pipe are improved.

   

Printing: The cooled pipe passes through the printing machine, which uses inkjet printing technology to print the product specification, execution standard, production date, manufacturer's name, and other information on the surface of the pipe. The printing content is clear, wear-resistant, and not easy to fall off, which is convenient for product traceability and quality inspection.

   

Hauling: The printed pipe is pulled by the haul-off machine at a uniform speed. The haul-off machine adopts a crawler-type or three-jaw-type structure, which is equipped with variable frequency speed regulation function. The hauling speed is adjustable and stable, and the hauling force is evenly distributed, which can avoid the pipe from being stretched or deformed. The hauling speed directly determines the wall thickness of the pipe, so it needs to be strictly matched with the extrusion speed.

   

Fixed-length Cutting: The pipe pulled by the haul-off machine enters the cutting machine for fixed-length cutting. The cutting machine adopts a planetary saw or lift-knife type structure, which can realize synchronous tracking cutting with the pipe movement. The standard cutting length is 4 meters or 6 meters, and the cutting length can be adjusted according to customer needs. The cutting surface is flat, smooth, and free of burrs, ensuring the convenience of pipe connection.

   

Belling (Optional): For pipes that need to be connected by socket, the cut pipe enters the belling machine for belling processing. The belling machine can form R-type or straight mouth bell ends, and the inner diameter of the bell end is matched with the outer diameter of the pipe, ensuring tight connection and no water leakage.

   

2. Core Equipment and Detailed Functions

  

2.1 Mixing System (High-speed Mixer + Cold Mixer)

The mixing system is the first link of the production line, which directly affects the plasticization effect of the materials and the quality of the final product. It is composed of a high-speed mixer and a cold mixer, which work together to complete the mixing and cooling of raw materials.

Formula Requirements: The formula of the mixed materials is strictly formulated according to the use of the pipe. For PVC-U water supply pipes, SG-5 PVC resin is selected, matched with calcium-zinc stabilizer (environmental protection and non-toxic), appropriate lubricants, and calcium carbonate (addition amount ≤10%); for PVC-U drainage pipes, SG-4 PVC resin is selected, matched with lead salt stabilizer (low cost and good stability) or calcium-zinc stabilizer, lubricants, and calcium carbonate (addition amount ≤20%). The proportion of each additive is strictly controlled to ensure the mechanical properties, corrosion resistance, and service life of the pipe.

   

Working Principle: The high-speed mixer is equipped with a high-speed rotating stirring blade, which generates high shear force when rotating, so that the raw materials and additives are fully mixed. At the same time, the electric heating device outside the mixer heats the materials to 80–130℃, which promotes the dissolution and dispersion of the additives and removes the moisture in the materials. After hot mixing, the materials are quickly transferred to the cold mixer. The cold mixer is equipped with a cooling water jacket, which cools the materials to ≤40℃ through water circulation, preventing the materials from agglomerating and ensuring the fluidity of the materials.

   

Key Parameters: The rotating speed of the high-speed mixer is 800–1200 r/min, and the mixing time is 5–8 minutes; the rotating speed of the cold mixer is 200–300 r/min, and the cooling time is 5–7 minutes.

  

2.2 Extruder (Core Equipment: SJSZ Conical Twin-screw Extruder)

The extruder is the core of the entire PVC pipe production line, which is responsible for melting, plasticizing, and extruding the mixed materials into pipe blanks. The SJSZ conical twin-screw extruder is widely used in PVC pipe production due to its excellent plasticization performance, low energy consumption, and stable production.

   

Equipment Structure: The conical twin-screw extruder is composed of a barrel, a conical twin-screw, a feeding device, a heating device, a cooling device, and a transmission system. The screw is conical, and the diameter of the screw gradually increases from the feeding end to the extrusion end, which can gradually increase the pressure of the materials during the extrusion process, ensuring full plasticization of the materials. The barrel is divided into three sections: feeding section, plasticizing section, and homogenizing section, each of which is equipped with an independent heating and cooling device to accurately control the temperature.

    

Key Parameters: The length-diameter ratio of the screw is 25–30, which is suitable for the plasticization of PVC materials; the power of the extruder is 30–160 kW, which varies according to the production capacity and pipe caliber; the extrusion pressure is 20–30 MPa, which ensures that the molten material can be smoothly extruded into the mold.

    

Temperature Control: The temperature of each section of the extruder is strictly controlled to prevent the PVC material from decomposing due to overheating (PVC decomposes at above 190℃). The specific temperature setting is as follows: feeding section 140–160℃ (mainly to preheat the materials and facilitate feeding), plasticizing section 160–180℃ (to melt and plasticize the materials fully), homogenizing section and machine head 170–185℃ (to ensure the uniformity of the molten material and smooth extrusion).

    

Working Principle: When the extruder works, the conical twin-screw rotates in the barrel, and the materials are pushed forward under the action of the screw. During the pushing process, the materials are subjected to the shearing force of the screw and the barrel, and the heating of the heating device, so that the solid materials are gradually melted into a molten state, and the additives are fully mixed with the PVC resin to form a uniform molten material. The molten material is extruded into the extrusion mold at a certain pressure and speed to form a pipe blank with a certain shape.

   

2.3 Extrusion Mold

The extrusion mold is the key equipment that determines the shape, size, and surface quality of the PVC pipe. It is designed according to the caliber and wall thickness of the pipe, and its structure and precision directly affect the product quality.

    

Structure Design: The extrusion mold adopts an annular flow channel design, and the flow channel is designed with a gradual shrinkage angle of 8°–12°, which can make the molten material flow evenly in the flow channel, reduce the pressure loss, and ensure that the wall thickness of the pipe blank is uniform. The mold is composed of a mold body, a core rod, a sizing sleeve, and other parts. The core rod and the mold body form an annular gap, which is the flow channel of the molten material.

    

Material Selection: The mold is made of 40Cr alloy steel, and the surface of the flow channel is chrome-plated with a chrome layer thickness of 0.05–0.1 mm. This material has good wear resistance, corrosion resistance, and high hardness, which can extend the service life of the mold and ensure the smoothness of the pipe surface.

   

Precision Control: The dimensional precision of the mold is strictly controlled, and the coaxiality of the core rod and the mold body is ≤0.02 mm, which ensures that the wall thickness of the pipe blank is uniform, and the outer diameter and inner diameter tolerance meet the national standard requirements.

   

2.4 Vacuum Sizing and Cooling System

The vacuum sizing and cooling system is used to fix the shape and size of the pipe blank, reduce the internal stress of the pipe, and improve the dimensional accuracy and mechanical properties of the pipe.

    

Vacuum Sizing Tank: The vacuum sizing tank is equipped with a vacuum pump, which can maintain a stable negative pressure inside the tank. The negative pressure range is -0.06~-0.08 MPa. When the pipe blank passes through the sizing tank, the negative pressure makes the pipe blank closely attach to the inner wall of the sizing sleeve, so that the outer diameter of the pipe is fixed. The sizing sleeve is made of copper or stainless steel, with high dimensional precision and good heat conductivity. The outer diameter tolerance of the pipe after sizing is ±0.3 mm, which meets the national standard requirements. For small-caliber pipes (20–63 mm), the vacuum degree can be appropriately reduced to -0.02~-0.04 MPa; for large-caliber pipes (110–315 mm), the vacuum degree needs to be increased to -0.04~-0.06 MPa to ensure the sizing effect.

    

Cooling Water Tank: The cooling water tank is divided into multiple sections, each of which is equipped with an independent water circulation system and temperature control device, realizing segmented temperature control. The cooling water temperature is controlled at 15–25℃, and the front section of the water tank (close to the sizing tank) has a slightly higher water temperature (20–25℃) to avoid the pipe from being brittle due to rapid cooling; the rear section has a lower water temperature (15–20℃) to ensure that the pipe core is fully cooled. The length of the cooling water tank is not less than 6 meters, and the pipe is cooled by spray and immersion, which can make the pipe cool evenly and reduce internal stress. After cooling, the temperature of the pipe core is ≤40℃, and the shape of the pipe is fixed.

   

2.5 Haul-off Machine

The haul-off machine is used to pull the cooled pipe at a uniform speed, ensuring the continuity of the production line and the stability of the pipe size. It is an important auxiliary equipment for the production line.

   

Type and Structure: The haul-off machine mainly adopts two types: crawler-type and three-jaw-type. The crawler-type haul-off machine is suitable for pipes of various calibers, with large hauling force and uniform force; the three-jaw-type haul-off machine is suitable for small-caliber pipes, with compact structure and high precision. The haul-off machine is equipped with a variable frequency speed regulation system, which can adjust the hauling speed according to the extrusion speed, ensuring that the hauling speed is consistent with the extrusion speed, avoiding the pipe from being stretched or deformed.

    

Key Parameters: The hauling speed range is 1–20 m/min, which can be adjusted according to the pipe caliber (10–20 m/min for small caliber, 0–15 m/min for large caliber); the hauling force is 5–50 kN, which varies according to the pipe size and wall thickness. The haul-off machine is equipped with a pressure adjustment device, which can adjust the clamping force of the crawler or three-jaw to avoid damaging the pipe surface.

   

2.6 Cutting Machine

The cutting machine is used to cut the continuous pipe into fixed-length finished products, which requires flat cutting surface, no burrs, and accurate cutting length.

   

Type and Working Principle: The cutting machine mainly adopts planetary saw and lift-knife type. The planetary saw cutting machine is suitable for large-caliber pipes (above 110 mm). The saw blade rotates around the pipe while moving forward, realizing synchronous tracking cutting with the pipe, and the cutting surface is flat; the lift-knife type cutting machine is suitable for small-caliber pipes (below 63 mm), and the knife blade moves up and down to cut the pipe, with fast cutting speed and high efficiency. The cutting machine is equipped with a length measurement device, which can accurately control the cutting length, and the standard cutting length is 4 meters or 6 meters, which can be adjusted according to customer needs.

   

Key Requirements: The cutting blade is made of high-speed steel or carbide, which has high hardness and wear resistance, ensuring smooth cutting; the cutting process is synchronized with the pipe movement, avoiding the pipe from being deformed during cutting; the cutting surface is free of burrs, and the verticality of the cutting surface is ≤0.5 mm/m.

  

2.7 Auxiliary Equipment

In addition to the above core equipment, the PVC pipe production line is also equipped with a series of auxiliary equipment to ensure the smooth operation of the production line and the quality of the products.

   

Printing Machine: The printing machine adopts inkjet printing technology, which can print the product specification, execution standard (such as GB/T 10002.1-2006 for PVC-U water supply pipes), production date, batch number, manufacturer's name, and other information on the surface of the pipe. The printing ink is resistant to water, corrosion, and friction, and the printing content is clear and durable, which is convenient for product traceability and quality inspection.

   

Belling Machine: The belling machine is an optional equipment, mainly used for processing the bell end of the pipe to facilitate the socket connection of the pipe. It can process R-type or straight mouth bell ends, and the inner diameter of the bell end is matched with the outer diameter of the pipe. The belling temperature is controlled at 160–180℃, and the belling time is adjusted according to the pipe caliber, ensuring that the bell end is firm and not easy to fall off.

   

Stacker: The stacking rack is used to automatically stack the cut or belled pipes, reducing manual labor intensity. It is equipped with a hydraulic lifting device and a turning device, which can automatically adjust the stacking height and angle, and stack the pipes neatly. The stacking capacity is 500–2000 pieces per hour, which is suitable for different production capacities.

  

3. Products and Application Fields (Detailed Introduction)

  

3.1 Types of Products

The PVC pipe production line can produce various types of PVC pipes, which are divided according to the use and material, mainly including the following types:

   

PVC-U Water Supply Pipe: It is made of unplasticized PVC resin, with the characteristics of non-toxic, tasteless, corrosion-resistant, high pressure resistance, and smooth inner wall (low flow resistance). It is suitable for building indoor water supply, municipal water supply, and rural water supply projects. The caliber ranges from 20 mm to 630 mm, and the working pressure ranges from 0.6 MPa to 1.6 MPa.

   

PVC-U Drainage Pipe: It is also made of unplasticized PVC resin, with the characteristics of light weight, corrosion resistance, good drainage performance, and easy installation. It is suitable for building indoor drainage, municipal sewage discharge, and rainwater drainage projects. The caliber ranges from 50 mm to 1600 mm, and it is mainly used for non-pressure drainage.

   

PVC Electrical Conduit: It is made of modified PVC resin, with the characteristics of flame retardant, insulation, corrosion resistance, and impact resistance. It is suitable for threading of electrical wires and cables in buildings, protecting the wires and cables from damage. The caliber ranges from 16 mm to 110 mm, and it is divided into rigid conduit and flexible conduit.

   

PVC-C Power Pipe: It is made of chlorinated polyvinyl chloride resin, with the characteristics of high temperature resistance, high pressure resistance, corrosion resistance, and good insulation performance. It is suitable for power communication threading, such as buried power cable protection, communication cable protection, etc. The caliber ranges from 50 mm to 200 mm, and it can be used in harsh environments such as high temperature and humidity.

  

4.2 Application Fields

PVC pipes produced by the production line have the advantages of light weight, corrosion resistance, low cost, easy installation, and long service life, and are widely used in various fields:

   

Building Industry: It is mainly used for indoor water supply and drainage, electrical threading, and floor heating pipelines. PVC-U water supply pipes are used for indoor tap water supply, PVC-U drainage pipes are used for indoor sewage and rainwater drainage, and PVC electrical conduits are used for threading of wires and cables in walls and ceilings.

   

Municipal Engineering: It is used for municipal water supply and drainage, sewage treatment, and rainwater collection. PVC-U water supply pipes are used for municipal water supply pipelines, PVC-U drainage pipes are used for municipal sewage and rainwater drainage pipelines, and PVC-C power pipes are used for buried power cable protection.

   

Agricultural Field: It is used for agricultural irrigation, water supply for farmland, and drainage of paddy fields. PVC pipes have the characteristics of corrosion resistance and light weight, which are suitable for outdoor use in rural areas, and can save water and improve irrigation efficiency.

   

Electric Power and Communication Field: PVC-C power pipes and PVC electrical conduits are used for threading of power cables and communication cables, protecting the cables from external damage, and ensuring the normal operation of power and communication systems.

   

Other Fields: It is also used for industrial water supply and drainage, chemical pipeline transportation (non-corrosive media), and landscape water supply and drainage, etc.