Miss Guo: 18851200191 (if you can’t enter the group, please add the group owner’s wechat) Abstract: This paper introduces the characteristics, technical parameters and industry standards of the steel wire mesh skeleton reinforced polyethylene composite pipeline system, This paper further introduces its application structure design method, external pressure load resistance and hydraulic mechanics, including the treatment of construction interface, pipe fitting characteristics and protection during construction, so as to facilitate technicians and design and construction personnel to preliminarily understand the system application knowledge of steel mesh skeleton reinforced polyethylene composite pipeline
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Moreover, due to the reinforcement of high-strength steel wire mesh, its pressure resistance and resistance to rapid crack growth are significantly enhanced compared with HDPE pipe, For example, the maximum pressure of PSP composite pipe below DN250 can reach 3.5Mpa, and the wall thickness of the pipe is significantly lower than that of HDPE pipe
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Generally, electric melting connection is mostly used below 2.5MPa, and metal pipe fittings are generally used for crimping connection in the field of high working pressure (above 2.5MPa)
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one point three The standard production length of PSP composite pipeline is generally 9m and 12m
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one point four Allowable pressure and safety factor the allowable internal pressure of PSP composite pipeline is related to product design, and the safety factor is generally 3.0; According to GB / t32439-2015 standard, the maximum pressure (PN) of 20 ℃ continuous water transmission can be divided into six pressure levels: 0.8, 1.0, 1.6, 2.0, 2.5 and 3.5Mpa
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The pressure grades of the pipes and fittings within these size ranges are different, and different wall thickness sizes are selected according to different application working pressures
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Other dimensions can also be determined by the supplier and the demander through negotiation
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CJ / T189 standard specifies 1.25mpa, and some special fields may need 3.0MPa design
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Therefore, The bending load effect of the pipeline does not control the safety of the pipeline and may not be included in the structural design
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Overview: the steel wire mesh skeleton polyethylene composite pipeline is a three-layer integrated structure, the inner layer is high-density polyethylene material, the middle layer is the pressure bearing layer integrated by the steel wire mesh skeleton and special adhesive resin, the outer layer is high-density polyethylene protective layer, and the inner layer, steel wire mesh reinforcement layer and outer layer are integrated with the adhesive resin of high-density Polyethylene Grafted with maleic anhydride, Referred to as PSP composite pipe or SRTP pipe, as shown in Figure 1
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The common methods for determining the nominal pressure design of PSP pipeline are as follows: where: according to the relevant provisions of relevant cjj101-2016 standards, the standard value of design internal water pressure of PSP composite pipe should be selected according to the standard value of pipeline working pressure plus 0.5MPa
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For PSP pipeline with concrete protective shell structure, The concrete protective structure shall bear all external loads
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The steel wire strength can reach 2000mPa, the dip angle of steel wire is generally 54.7 ° ~ 60 °, the number of steel wire layers is generally even, the winding direction of steel wire is left-hand and right-hand, and there is no need to weld between steel wire meshes, which greatly improves the production efficiency
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The hydrostatic pressure bearing capacity of PSP pipeline is designed through burst pressure test combined with corresponding instability pressure design method
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The allowable deviation of length is + 0.5%, and no negative deviation is allowed
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At the same time, the stress relaxation effect of steel mesh skeleton polyethylene composite pipe weakens the circumferential bending stress effect of the pipe wall under the combined action of long-term internal pressure and external soil load
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1 structural diagram of steel wire mesh skeleton polyethylene composite pipe because its inner and outer layers are made of high-density polyethylene, it has the same characteristics as high-density polyethylene pipe, such as corrosion resistance, chemical resistance, light weight and good flexibility
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According to relevant standards, the ratio of structural stiffness of PSP pipeline to the stiffness of soil around the pipe is less than 1, which shall be designed according to flexible pipeline
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PSP composite pipe is produced by continuous extrusion method and steel wire continuous winding composite process
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It can also be 18m if transportation conditions permit
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one point five The PSP pipeline with external load bearing capacity is reinforced by continuous steel wire mesh, and its matrix structure stiffness is low
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Generally, if the medium transmission temperature exceeds 20 ℃, corresponding pressure reduction coefficient shall be carried out to correct its nominal pressure, which is described in detail in the corresponding product standards
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The nominal pressure of the pipe shall be based on the predicted short-time burst pressure Pb of the pipe and obtained after considering various coefficients
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1 product features and parameters 1.1 technical parameters and industry standard PSP composite pipe is an outer diameter series plastic pipe, The national standards, industrial product standards and design and construction specifications commonly used in the field of DN50 ~ DN800mm diameter are as follows: CJ / t189-2007 – steel wire mesh skeleton polyethylene composite pipes and fittings GB / t32439-2015 – steel wire mesh skeleton polyethylene composite pipes for water supply cjj101-2016 – Technical Specification for buried plastic pipeline engineering cecs181:2005 steel wire mesh skeleton plastics (polyethylene) for water supply ）Technical specification for composite pipe engineering 1.2 Size range the nominal outer diameter of the existing steel wire skeleton polyethylene composite pipe is DN50 ~ DN800mm
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The reinforcement of PSP is high-strength copper plated steel wire mesh formed by dip angle staggered winding
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Cjj101-2016 standard introduces in detail the recommended calculation and design methods for external load action of pipeline, including the ultimate bearing capacity strength of pipe wall under load, the maximum circumferential bending stress of pipe wall under external load, and the maximum vertical allowable deformation (generally 5%) of pipeline under earth pressure and ground load
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The nominal pressure grade of the pipeline can be selected according to more than 1.2 times of the standard value of the designed internal water pressure
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It is generally composed of core pipe extrusion, steel wire winding composite, rubber layer extrusion, outer layer composite, traction and length counting cutting
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Because there is no affinity between steel wire mesh and high-density polyethylene, it is necessary to use a maleic anhydride grafted high-density polyethylene resin between polyethylene and steel wire to realize multi-layer bonding, so as to achieve better interfacial peel strength
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According to the existing relevant standards, PSP composite pipes and fittings are applicable to the pipeline system with medium temperature ≤ 60 ℃
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Fig
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The PSP composite pipe designed according to this method will not have structural failure caused by steel wire fracture, and the minimum number of steel wires can also be verified according to the requirements of GB / t32439-2015 standard
PSP composite pipe has high production efficiency, strong structural designability, and has the advantages of strong bearing capacity, good corrosion resistance, excellent wear resistance, high cost performance, light weight and convenient transportation and installation
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The unique structure of PSP not only integrates the advantages of high strength of steel pipe and corrosion resistance of plastic pipe, but also overcomes the defects of easy delamination of metal plate skeleton reinforced plastic composite pipe
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one point six PSP pipe is mainly made of high-strength steel wire, high-density polyethylene and adhesive resin.
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Since its inception in the early 21st century, it has been used in municipal engineering, civil fire protection, oilfield water conservancy transportation, medical and chemical industry, agricultural water-saving irrigation, coal mining industry Slurry transportation engineering and submarine water conveyance engineering are widely used
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Therefore, the pipeline shall not adopt rigid pipeline foundation
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For the pipeline with nominal diameter less than 630mm, the cross-sectional area of the pipeline is relatively small and the constitutive relationship of soil is easy to form, so the external pressure load effect is low
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PSP composite pipes are usually connected by electric melting pipe fittings and metal flange or grooved pipe fittings by crimping mechanical connection
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The temperature and pressure reduction coefficient of commonly used PSP composite pipes for water supply is shown in Table 1
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