Product structure:

High density polyethylene outer protective tube (referred to as outer protective tube) is produced by extrusion of high density polyethylene resin with antioxidant and color masterbatch.

Product description：

1, outer tube performance: the product is black (one-step production process and user special requirements for yellow; Yellow or colorless transparent pipe light aging speed is particularly fast, generally not used), with high strength, good toughness, good sealing, corrosion resistance, low temperature resistance, impact resistance, easy welding, easy construction, service life

Long and equal advantages. It has been widely used in the production of insulation pipes and district heating projects at home and abroad.

2, the outer protective pipe function: The outer protective pipe is a two-step production of prefabricated insulation pipe (pipe in 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, anti-impact and so on.

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

4, production capacity: At present, our company has 9 outer protective pipe production lines, 8 have been put into production, and 1 is in the fixed; The largest extrusion pipe diameter of φ1845mm, can produce DN90-DN1800mm various types of high-density polyethylene outer protective pipe 5000km per year.

High density polyethylene outer tube specification sheet:

High density polyethylene:

1, Features: High Density Polyethylene (HDPE, referred to as "HDPE"), is a high crystallinity, non-polar thermoplastic resin. HDPE is an opaque waxy material with a milky white appearance and a certain degree of translucency in a thin cross-section.

2, commonly used polyethylene model: Our company's outer protective pipe selection PE80 grade high-quality pipe special high-density polyethylene resin as the main raw material, with high mechanical strength and excellent corrosion resistance.

List of main polyethylene resin raw material models and manufacturers:

3. The resin raw materials selected for insulation pipes, pipe fittings and interface plates are all products of the same batch to ensure that the site interface is more solid, effectively ensure the consistency of melt flow rate and the consistency of adhesive relay, and solve the problem that the raw materials are not easy to crack in the same batch; The product traceability is realized.

4, material density: GB/T29047-2012 standard specifies that the density of polyethylene resin should be greater than 935kg/m3, resin should be added to the outer protective tube production and use of antioxidants, ultraviolet stabilizer, carbon black and other additives. (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 protective tube should be 2.5%±0.5%(mass percentage), the carbon black should be evenly distributed in the base material, and the outer protective tube should not have color streaks. In the production of the outer protective tube, the color masterbatch should be added to the raw material to control the color of the outer protective tube. Generally, 50Kg of the color masterbatch should be added to every 1000Kg of raw material (note: the maximum carbon black content in the color masterbatch is 50%).

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

7, can use not more than 15%(mass percentage) of the recycled material, but the recycled material should be the manufacturer's factory pipe production process generated clean, non-degraded material. Feeding mixing, drying feeding: feeding requirements are uninterrupted, mixed evenly after adding the color masterbatch in proportion, to ensure that the product tone is consistent, my color difference, no uneven color bands appear.

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

Spiral extrusion:

The extruder head temperature should be not lower than 220℃ and the temperature should be evenly distributed.

Our company's outer protective pipe production equipment for high-speed single screw extruder, screw length to diameter ratio of 33:1.

Our company's outer protective pipe production line process: automatic feeding and drying device, spiral mold extrusion, vacuum sizing, corona treatment, spray cooling, automatic cutting and other processes to effectively control product quality.

Sizing molding:

The outer protection pipe production line adopts vacuum sizing technology to ensure the diameter accuracy of the outer protection pipe. The vacuum degree of the sizing sleeve is adjusted according to the specifications and models of the outer protection pipe. Under the premise of ensuring the

roundness of the outer protection pipe, a lower vacuum degree should be adopted.

The outer protection pipe production line adopts vacuum sizing technology to ensure the diameter accuracy of the outer protection pipe. The maximum sizing rate is 1.6m and the accuracy is 0.1mm.

Production process inspection: The wall thickness and perimeter of the outer protective tube should be tested during the production process to monitor the stability of the production and operation of the equipment to ensure the stable and controllable quality of the product.

Spray cooling: The cooling method of the outer protection pipe adopts circulating cold water cooling of the 360-degree annular arrangement nozzle, and the surface temperature of the outer protection pipe should reach about 20℃ after cooling. Extrusion temperature of the product is about 70-

80℃.

Corona treatment:

Our company's outer protective tube production line is equipped with online corona equipment, which can carry out online corona treatment on the inner wall of the outer protective tube. Corona process is to apply 5-10 kVA high frequency and high voltage electricity on the treatment device, the local high voltage discharge between the electrodes is the original corona treatment of the inner wall of the polyethylene pipe, corona discharge will produce small dense purple and blue sparks, because the high voltage discharge is carried out in the air, the various plasma generated after air ionization under the action of a strong electric field, Accelerating and impacting the inner wall of the outer protective tube, the energy of these plasma particles is close to the chemical bond energy of the plastic molecules, so that the chemical bond of the plastic surface molecules can be broken and degraded, so that the molecules on the surface of the outer protective tube can be rearranged and the surface roughness can be increased.

During corona discharge, a large amount of ozone is also produced. Ozone is a strong oxidizing agent that oxidizes the surface molecules of plastics and produces peroxygenic compounds. In addition, corona treatment has the effect of removing oil, water, gas and dirt, etc., after the above physical and chemical modification, it can significantly improve the wettability and adhesion of the plastic surface, improve the adhesion of the inner wall of the outer protective tube and the insulation layer, so that the steel pipe, polyurethane insulation layer and polyethylene outer protective tube in the directly buried prefabricated insulation tube reach a trinity structure. After corona treatment, the surface tension in the outer sheath reaches 50dyn/cm2. Corona technology makes the bonding force between PE outer protective tube and polyurethane insulation layer greater than 0.4MPa.

Traction and pull out: The automatic traction machine is used to pull out the formed outer protection, and the traction speed should be consistent with the extrusion speed.

Size cutting: The automatic cutting saw controlled by computer system is used to complete the cutting, and the equipment automatically cuts after the operator enters the cutting size.

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

Finished product inspection:

1, the appearance of the finished product inspection: the outer protection pipe should be black (there are other color exceptions required by customers), its internal and external surfaces should not affect the performance of the groove, there should be no bubbles, cracks, dents, impurities, color inequality defects.

2, density test: Take the corresponding sample, use the solid density tester for the outer protective tube density test, the outer protective tube density ≥940kg/m³ is qualified.

The test value in our product type inspection report (2014BQ055) is 949.8kg

3. Test of tensile yield strength and elongation at break: take the corresponding sample, use the electronic universal tensile testing machine to carry out tensile test on the sample, and the tensile yield strength of the outer protective tube is ≥19Mpa, and the elongation at break is ≥350%. The test value in our product type inspection report (2014BQ055) is 20.7MPa; The test value in our product type inspection report (2014BQ055) is 711%.

4, outer diameter and wall thickness inspection: outer diameter and minimum wall thickness of the outer protection pipe should meet the requirements of the following table:

Outer diameter and minimum wall thickness unit: mm

Product identification, warehousing, delivery:
Qualified finished pipes are required to indicate the site code (such as Lanzhou: LZ, Baotou: BD, Tangshan: TS), production date, specifications, length and pipe number on the inner wall of the pipe end.

After the inspection, the products are stored in the warehouse, and then used or delivered to the customer.