Industry standard for buried polyethylene structural wall piping systems

1. Overview of standard projects

In recent years, my country’s large-diameter plastic pipes have developed very rapidly, and there has been an upsurge in investing in the production of large-diameter plastic pipes in various places. In the field of underground drainage pipes, various plastic structural wall pipes are being developed. Double-walled corrugated pipes, annular ribbed pipes (reinforced pipes), winding pipes, etc. made of PVC-U, PE, PP and other materials have been widely used.
Polyethylene winding structural wall pipes and polyethylene double-wall corrugated pipes have the characteristics of light weight, low inner wall roughness, large water transport capacity with the same pipe diameter; resistance to acid and alkali corrosion, no leakage, aging resistance, and long service life; the material is hygienic and No pollution and other characteristics. It is an alternative product that uses plastic instead of steel and plastic instead of cement. It has been widely used abroad. In the past few years, it has been widely used in municipal drainage and sewage, building outdoor drainage, industrial drainage and sewage and other fields.
my country has introduced the production of plastic double-wall corrugated pipe equipment since the 1980s. In recent years, the production scale has begun to expand and its application has developed rapidly. At the same time, with the development of domestic large-diameter polyethylene buried drainage structure wall pipes, some production enterprises have formed large-scale Scale production capacity. If there are no unified national standards for the production, inspection and use of pipes and fittings, this will undoubtedly cause confusion to the engineering design, construction and use departments. Therefore, there is an urgent need to formulate national standards for polyethylene wrapped structural wall piping systems.
The National Plastic Products Standardization Technical Committee (SAC/TC48) Plastic machining Pipes, Fittings and Valves Sub-Technical Committee (TC48/SC3) began in 2000 to draft and prepare the national standard for buried polyethylene structural wall piping systems, and has successively investigated Production enterprises, design and application departments; at the same time, relevant domestic and foreign standards have been collected and studied. According to the Notice No. 59 [2001] of the State Administration of Quality and Technical Supervision on the issuance of the “2001 Development and Revision of National Standards Project (I)”, the 14th project plan is to develop a national standard [Polyethylene (PE) for Buried Use ) structural wall ductwork]. SC3 organized enterprises and related scientific research and testing units to establish a standard drafting group. After careful and meticulous preparation, it selected domestic representative enterprises and determined in April 2001 that the product standard was divided into two parts and the Product drafting unit:
Part 1: Polyethylene double-wall corrugated pipes, Anhui Guotong High-tech Pipe Industry Co., Ltd. Shanxi Plastics General Factory Jiangsu Galaxy Group Company Lanzhou Dingtai Large Plastic Industry and Trade Co., Ltd. Sinopec Wuhan Branch Scientific Research Institute
Part 2: Polyethylene wound structural wall pipes, Shijiazhuang Baoshikara Large Diameter Plastic Pipe Co., Ltd., Jiangsu Lixing Plastic Pipe Industry Co., Ltd., Hangzhou Hanyi Plastic Pipe Co., Ltd., Dalian Donggao New Pipe Co., Ltd.
After the work of the standard drafting group, the standard was officially approved and released by the National Standardization Management Committee of the General Administration of Quality Supervision, Inspection and Quarantine on March 15, 2004, and was officially implemented on October 1, 2004.

2. Relevant standards at home and abroad

In the early days of drafting standards, ISO did not have relevant product standards. The international standards organization once had standard documents ISO/DP 9970 and ISO/DP 9971 plastic lightweight pipes (structural pipes). Later, the standard work was transferred to the European standards organization CEN/TC155 [Plastic Piping Systems Technical Committee]. In accordance with the national guidelines for drafting national standards, SC3 and the standard drafting unit decided to refer to and adopt the draft European standard prEN 13746-1: 2001 Plastics piping systems for non-pressure underground drainage and sewrage –Structured -wall piping systems of unplasticized poly after research. (vinyl chloride ) (PVC-U), polypropylene(PP), and polyethylene(PE) Part 1: Specification for pipes, fittings and the system
[Plastic piping systems for underground pressureless drainage and sewerage—polyvinyl chloride (PVC-U), poly(PP) and polyethylene (PE) structural wall piping systems Part 1: Specification for pipes, fittings and systems]. Since this European standard includes various structural wall pipes of polyvinyl chloride, polyethylene and polyethylene materials in one standard, the text structure is relatively complex and inconvenient to use. However, my country’s standards are generally divided into materials and structures. Product Standards. Therefore, when formulating the standard, we excerpted the PE structural wall pipe and used it as a reference to formulate the national standard for this product.
GB/T 19472-2004 also involves some basic standards and method standards, mainly including the following:
GB/T 2918-1998 Standard environment for conditioning and testing of plastic specimens
GB/T 3682-2000 Determination of melt mass flow rate and melt volume flow rate of thermoplastic plastics
GB/T 6111-2003 Thermoplastic pipes for fluid transportation – Internal pressure resistance test method
GB/T 6671-2001 Determination of longitudinal shrinkage of thermoplastic pipes
GB/T 8804.3-2001 Thermoplastic pipes – Determination of tensile properties – Part 3: Polyolefin pipes
GB/T 8806-1988 Plastic pipe size measurement method
GB/T 9647-2003 Determination of stiffness of one ring of thermoplastic pipes
GB/T 14152-2001 Test method for external impact resistance of thermoplastic pipes – Clockwise rotation method
GB/T 17391-1998 Test method for thermal stability of polyethylene pipes and fittings
GB/T 18042-2000 Thermoplastic pipes – Test method for creep ratio
HG/T 3091-2000 Rubber seals, water supply, drainage and sewage pipe interface seals, material specifications
ISO 12091 Structural wall thermoplastic pipes Oven testing
ISO 13968:1997 Plastic pipes and conveying systems Determination of ring flexibility of thermoplastic pipes
EN 1277 Thermoplastic piping systems for non-pressurized buried underground applications. Test methods for tightness of elastomeric sealing ring connections.

3. Product application scope and characteristics

Buried drainage pipeline systems are generally gravity flow systems, which do not have high requirements for internal pressure resistance, but have high requirements for the ability to withstand external loads (ring stiffness). At the same time, the two structural wall pipes included in this product standard are suitable for underground drainage, buried farmland drainage and other projects where the long-term temperature is below 45°C; after taking into account the chemical resistance of the material, they can also be used for industrial drainage and sewage discharge. pipeline. Double-walled corrugated pipes can also be used as communication casing.

4. Product Type

GB/T19472.1 stipulates a structural form of double-wall corrugated pipe; according to the actual production situation in my country at that time, GB/T19472.2 stipulates two major types of structural forms, Type A: with flat inner and outer surfaces, The outer walls are connected by internal spiral ribs, or the inner surface is smooth, the outer surface is flat, and the spiral hollow tube is embedded in the wall; Type B: The inner surface is smooth and the outer surface is a hollow spiral rib. Two structures of wound pipe.
With the development of production and technology, some new structural wall pipes have been developed at home and abroad, such as steel strip-reinforced spiral pipes. SC3 will gradually formulate relevant product standards based on the needs of production and use. Currently, there is a plan for the light industry standard plan Q 2004-088T [Steel Strip Reinforced Plastic Wound Structural Wall Pipe], which was drafted by Fujian Yatong New Material Technology Co., Ltd.
In GB/T19472-2004, except for the schematic diagram of typical pipe fittings given in Appendix B (informative appendix) of the wound pipe, other pipe fittings are not specified. Pipe series with outer diameters can be connected with solid-wall pipe fittings, and pipes and fittings from manufacturers can be used with each other. Therefore, from the perspective of standardization, socialized mass production and connection, we hope that double-wall corrugated pipes produced in series with outer diameters will not be excluded.
Due to reasons such as molding, the size series of pipes specified in the GB/T19472.2 double-wall corrugated pipe standard coexist with the outer diameter and the inner diameter. However, the inner diameter series is prone to sealing problems when connecting pipes. We hope to produce Manufacturers pay attention to this in practical applications. GB/T18477-2001 only stipulates PVC-U double-wall corrugated pipes with a series of outer diameters. Therefore, SC3 organized Zhejiang Yonggao Plastic Industry Development Co., Ltd. and other units to promptly revise QB/T1919 [PVC-U double-walled corrugated pipes] Corrugated pipes], the outer diameter and inner diameter series coexist to solve the size problem of GB/T18477. After the national standard is revised, SC3 is preparing to abolish QB/T1919.

5. Requirements for raw materials

The PE structural wall pipes for underground drainage and sewage in GB/T19472 are mainly designed to withstand external loads. Although they do not withstand internal pressure, they also have certain requirements for raw materials. The performance of raw materials specified in the standard is mainly as follows:
Double-wall corrugated pipe plastic parts: The raw materials used in the production of pipes should be mainly polyethylene (PE) resin, which can be added to improve the processing performance of the pipe or other materials. The polyethylene (PE) resin content should be 80% (W/W) above. According to the provisions of prEN13476, some calcium carbonate fillers can be added, but there are requirements for the particle size and particle size distribution of calcium carbonate, whether it is activated, etc.; adding an appropriate amount of fillers that meet the standard requirements is helpful for improving the modulus and rigidity of the product. Promotional effect, but blindly pursuing cost reduction and adding fillers will be counterproductive, such as ring flexibility will be greatly reduced. In addition, the elastic modulus of raw materials is more important for structural wall pipe products. Therefore, in the two-part product standard, an informative appendix is given on the elastic modulus requirements of raw materials and test methods.
Raw materials should meet the requirements of Table 1.
Table 1 Material properties of PE pipes
Serial No. Item Requirements Inspection Method
1 Internal pressure resistance (80℃, ring stress 3.9Mpa, 165h) Note)
Internal pressure resistance (80℃, ring stress 2.8Mpa, 1000h) Note) No damage, no leakage GB/T 6111-2003
Using A-type sealing head
2 Melt mass flow rate (5kg, 190℃) MFR≤1.6g/10min GB/T 3682-2000
3 Thermal stability (200℃) OIT≥20min GB/T 17391-1998
4 Density ≥930kg/m3 (basic resin) GB/T 1033-1986
Note: Tests were carried out on solid wall pipes machined from the corresponding extrudates.
The table only gives the basic requirements for raw materials for pipes required by this standard. As a raw material manufacturer, it is not enough to meet the above requirements. There should also be other requirements for the production of PE resin such as moisture content.
1) For the internal pressure resistance test of raw materials, the raw materials should be extruded into solid-wall pipes for hydraulic testing in accordance with the requirements of GB/T6111-2003. The conditions of the hydraulic test reflect that the raw material requirements are basically above PE63 grade resin (GB/T13663-2000 [PE pipes for water supply]). The conditions for the internal pressure test of the pipe are: internal pressure resistance (80°C, ring stress 3.5 MPa, 165h); internal pressure resistance (80℃, ring stress 3.2Mpa, 1000h). In the ISO international standard for PE structural wall pipes led by South Korea, South Korea has initially proposed the requirement for resin production above PE80. Currently, the international standard is still in use In the early stages of drafting, SC3 will pay attention to the development of the standard.
2) The melt flow rate reflects the molecular weight and fluidity of the resin.
3) Thermal stability (oxidation induction time OIT) is an indicator to evaluate the material’s ability to resist thermal degradation during processing, storage, welding and use.
4) Conventional density is a measure of the packing density of macromolecules. It is formed by cooling after processing or by annealing and crystallizing at moderate temperatures. Due to the addition of additives and pigments, the test density of the raw resin may be different from the test density of the pipe. However, the standard requires that the base resin should be ≥930kg/m3, that is, resin with a medium density of PE or above.
5) Recycled materials are allowed to be clean recycled materials from the same type of pipes produced by our factory that meet the requirements of this section, but the pipe products produced should still meet the requirements of this standard.
As explained above, the production of structural wall PE pipe systems still requires necessary performance requirements for raw materials. It cannot be produced with just any resin, let alone some domestic production companies that use recycled PE pipes or other products to produce structural walls. Pipeline, this will definitely damage the long-term development of the entire industry.

6. Size range

With the development of production and technology, PE structural wall pipes have a series of advantages such as light weight, large size range, and convenient construction. The inner diameter and outer diameter series of the pipe in the GB/T19472.1 double-wall corrugated pipe standard have reached 1200mm, which is basically consistent with prEN 13476; the inner diameter of the pipe in GB/T19472.2 has reached 3000mm, exceeding the size of prEN 13476 (1200mm) For large-diameter winding pipes, attention should be paid to the minimum joint length and minimum welding length when connecting. The current standards are not detailed enough. At the same time, due to the weight of large-diameter pipes, the ring stiffness level may be lower. Manufacturers, The design application and construction party should be comprehensively determined based on the specific project.
The standard also stipulates requirements such as the minimum average inner diameter, the maximum average outer diameter, the minimum laminated wall thickness, and the minimum inner wall thickness, which are basic requirements for pipeline quality and connections.