Product structure:

High-density polyethylene outer protective tube (referred to as the outer tube) by high-density polyethylene resin with antioxidant and color masterbatch through extrusion production.

Product Description:

1. Performance of external protection pipe: the product is black (yellow for one-step production process and special requirements of users; Yellow or colorless transparent pipes have a very fast light aging speed and are generally not used). It has high strength, good toughness, good sealing, corrosion resistance, low temperature resistance, impact resistance, easy welding, easy construction and service life.

Long advantages. In the insulation pipe production and district heating engineering, has been widely used at home and abroad.

2, the role of external protection pipe: external protection pipe is a two-step production of prefabricated insulation pipe (pipe) supporting products, mainly used for the outer protective layer of insulation materials. The outer protective tube provides effective protection for the polyurethane insulation layer, and can play the role of waterproof, anti-corrosion, anti-aging, impact resistance, etc.

3. The use temperature of the external protection pipe: the thickness of the insulation layer of the insulation pipe should ensure the normal use of the external protection in the temperature range of -50 ℃ ~ 50 ℃.

4. Production Capacity: At present, our company has 9 external protection pipe production lines, 8 of which have been put into production and 1 of which is currently being set. The largest extrusion pipe diameter is φ1845mm, which can produce and DN90-DN1800mm 5000km of various types of high-density polyethylene outer protective pipes annually.

high density polyethylene outer tube specification table:

high density polyethylene:

1, features: high density polyethylene (High Density Polyethylene, referred to as "HDPE"), is a high crystallinity, non-polar thermoplastic resin. HDPE is an opaque wax-like material, the appearance was milky white, in the meager section was a certain degree of translucent.

2. Commonly used polyethylene model: Our company's external protection pipe uses PE80 grade high-quality pipe special high-density polyethylene resin as the main raw material, which has high mechanical strength and excellent corrosion resistance.

Main polyethylene resin raw material model and manufacturer list:

3. The resin raw materials selected for insulation pipes, pipe fittings and interface plates are all products of the same batch, which ensures that the on-site interface is firmer, effectively ensures the consistency of melt flow rate and adhesive force, and solves the problem that raw materials of the same batch are easy to crack. Traceability of products is realized.

4. Material density: GB/T29047-2012 standard stipulates that the density of polyethylene resin should be greater than 935kg/m3, and the resin should be added with antioxidants, ultraviolet stabilizers, carbon black and other additives required for the production and use of outer protective pipes. (or color masterbatch prefabricated from black and white carbon)

5, carbon black content: the added carbon black density should meet the requirements of 1500kg/m3~2000kg/m3. The carbon black content of the outer protection pipe shall be 2.5%± 0.5%(mass percentage), the carbon black shall be evenly distributed in the base metal, and the outer protection pipe shall not have chromatic aberration stripes. In the production of the outer protective tube of our company, color masterbatch is added to the raw material to control the color of the outer protective tube. Generally, 50Kg of color masterbatch is added to every 1000Kg of raw material (Note: the highest carbon black content in the color masterbatch is 50%).

6. Melt flow rate: The melt mass flow rate (MFR) of the high-density polyethylene resin used for the outer protective pipe and its welding should be 0.2g/10min-1.4g/10min (test condition: 5kg,190 ℃). When the two outer protective pipes are welded, the difference between the melt flow rates shall not be greater than 0.5g/10min.

7. No more than 15% (mass percentage) of recycled materials can be used, but the recycled materials should be clean and undegraded materials produced in the pipeline production process of the manufacturer's factory. Feeding, mixing, drying and feeding: the feeding requirements are uninterrupted. After adding the masterbatch according to the proportion, stirring and coupling shall be uniform to ensure the consistent color tone of the product. I have color difference and no uneven color band.

The vacuum feeding used by the feeding machine of our company can ensure uniform feeding. The feeding hopper has a drying function, which can effectively dry the moisture in the raw materials, improve the dryness of the raw materials and ensure the extrusion quality.

Spiral extrusion:

Spiral extrusion is used to realize the production of outer protective tube. At the same time, the extrusion temperature should be strictly controlled in the production process of outer protective tube. The temperature of the extruder head should not be lower than 220 ℃ and the temperature should be evenly distributed.

Our company external protection pipe production equipment for high-speed single screw extruder, screw length diameter ratio of 33:1.

Our company's external protection pipe production line process: the use of automatic feeding drying device, spiral die extrusion, vacuum sizing, corona treatment, spray cooling, automatic cutting and other processes to effectively control the product quality.

Diameter forming:

The outer protection pipe production line adopts vacuum sizing technology to ensure the accuracy of the outer protection pipe diameter. The vacuum degree of the sizing sleeve is adjusted according to the specifications and models of the outer protection pipe. A lower vacuum degree should be adopted on the premise of ensuring the roundness of the outer protection pipe.

The outer protection pipe production line adopts vacuum sizing technology to ensure the accuracy of the outer protection pipe diameter, with a maximum sizing rate of 1.6 meters and an accuracy of 0.1mm.

Production process inspection: during the production process of the external protective tube, the wall thickness and circumference of the external protective tube shall be detected to monitor the stability of the production and operation of the equipment so as to ensure the stable and controllable product quality.

Spray cooling: the cooling method of the outer protection pipe is circulating cold water with 360-degree annular nozzle. After cooling, the surface temperature of the outer protection pipe shall reach about 20 ℃. The product temperature during extrusion is about 70-80°C.

Corona treatment:

Our company's outer protection pipe production line is equipped with online corona equipment, which can carry out online corona treatment on the inner wall of the outer protection pipe. Corona process is to apply 5-10 kVA high-frequency high-voltage electricity on the treatment device. The original reason for generating partial high-voltage discharge between electrodes is to carry out corona treatment on the inner wall of polyethylene pipe. Corona discharge will produce fine and dense purple-blue sparks. As high-voltage discharge is carried out in air, various plasmas generated after air ionization accelerate and impact the inner wall of outer protective tube under the action of strong electric field, the energy of these plasma particles is close to the chemical bond energy of the plastic molecules, so that the chemical bonds of the molecules on the surface of the plastic can be induced to break and degrade, so that the molecules on the inner surface of the outer tube can be rearranged and the surface roughness can be increased.

In corona discharge, a large amount of ozone is also generated. Ozone is a strong oxidant, so that the plastic surface molecules oxidation, such as peroxygen compounds. In addition, corona treatment also has the functions of removing oil, water vapor and dust. After the above physical and chemical modification, it can significantly improve the wettability and adhesion of the plastic surface, improve the adhesion between the inner wall of the outer protective pipe and the insulation layer, and make the steel pipe, polyurethane insulation layer and polyethylene outer protective pipe in the directly buried prefabricated insulation pipe reach a trinity structure. The surface tension inside the outer sheath tube after the corona treatment reached 50dyn/cm2. The corona process makes the bonding force between PE outer protective pipe and polyurethane insulation layer greater than 0.4MPa.

Pulling out by traction: the formed outer guard shall be pulled out by automatic traction machine, and the traction speed shall be consistent with the extrusion speed.

Cutting to length: the automatic cutting saw controlled by the computer system is used to complete the cutting, and the equipment automatically cuts after the operator inputs the cutting size.

Both ends of the outer protection pipe shall be cut flat and perpendicular to the axis of the outer protection pipe, and the angle error shall not be greater than 2.5 °. The common cutting size of the outer protective tube produced by our company is 11.65m.

Finished product testing:

1. Appearance inspection of finished products: the outer protective tube shall be black (except for other colors required by customers), and its inner and outer surfaces shall be visually inspected without grooves affecting its performance, bubbles, cracks, depressions, impurities, uneven colors and other defects.

2. Density inspection: Take the corresponding sample and use the solid density tester to carry out the density test of the outer protection pipe. The density of the outer protection pipe ≥ 940 kg/m is qualified.

The detection value in the product type inspection report (2014BQ055) of our company is 949.8kg

3. Inspection of tensile yield strength and elongation at break: Take the corresponding sample and carry out tensile test on the sample with an electronic universal tensile testing machine. The tensile yield strength of the outer protective tube ≥ 19Mpa and the elongation at break ≥ 350 are qualified. The detection value in our product type inspection report (2014BQ055) is 20.7MPa; the detection value in our product type inspection report (2014BQ055) is 711%.

4. Inspection of outer diameter and wall thickness: the outer diameter and minimum wall thickness of the outer protective tube shall comply with the following table:

Outer diameter and minimum wall thickness of outer protective tube Unit: mm

Product identification, warehousing and delivery:

The finished pipe that has passed the inspection shall be marked with the site code (such as Lanzhou: LZ, Baotou: BD, Tangshan: TS), production date, specification, length and pipe number on the inner wall of the pipe end.

After inspection, the product is put into storage and transferred to the customer for sequential use or delivery.