PE (polyethylene) material is widely used in the field of water supply pipe manufacturing due to its high strength, corrosion resistance, and non-toxicity. Because it will not rust, it is an ideal pipe to replace ordinary iron water supply pipes. PE water supply pipes implement national product standards: GB/T 13663.1-2017, GB/T 13663.2-2018 "Polyethylene (PE) Pipe System for Water Supply Part 2: Pipes".

Pipeline development: my country's plastic pipes are developing rapidly and their quality is constantly improving. Among them, polyethylene PE pipes are widely used in building water supply, building drainage, buried drainage pipes, building heating, gas pipelines, electrical and telecommunications protective casings, industrial pipes, agricultural pipes, etc. due to their unique advantages. They are mainly used in urban water supply, urban gas supply and farmland irrigation.

Features and benefits:

Corrosion resistance

(1) Polyethylene has excellent corrosion resistance, good hygienic properties and long service life

Polyethylene is a non-inert material. It can resist corrosion from a variety of chemicals except for a small amount of strong oxidants, and is not easy to breed bacteria. It is well known that the reason why steel pipes and cast iron pipes are replaced by plastic pipes is not only because plastic pipes have lower water delivery energy consumption, lower living energy consumption, lighter weight, less water flow resistance, easier and faster installation, lower cost, longer life, and heat preservation function, but also because plastic pipes are better than steel pipes and cast iron pipes in corrosion resistance and not easy to breed microorganisms.

The service life of polyethylene pipes is more than 50 years, which has not only been confirmed by international standards and some advanced foreign standards, but also has been proven in practice.

Another reason why polyethylene can be promoted and applied is that polyvinyl chloride is increasingly under pressure from environmental protection. The first is the hygienic performance of polyvinyl chloride itself: As we all know, the production of polyvinyl chloride pipes under regular production and strict control can ensure hygienic performance and is allowed to be used in the field of drinking water. However, some people are still worried that problems may occur in places where control is not strict: such as excessive vinyl chloride monomer in polyvinyl chloride resin, and the misuse of toxic additives in the formulation of polyvinyl chloride pipes for water supply. Polyvinyl chloride pipes and fittings for drainage that are not guaranteed to be non-toxic are misused in water supply pipes and fittings, etc. The second is the recycling of polyvinyl chloride pipes: polyvinyl chloride and polyethylene are thermoplastics. In theory, they can be used, but countries have proved that the proportion of old plastic products that can be recycled is limited. The main treatment method is incineration to recover energy. Because polyvinyl chloride contains chlorine, it may produce harmful substances if it is not well controlled during incineration, while polyethylene only contains hydrocarbons, and generates water and carbon dioxide after incineration.

Flexibility

Polyethylene has unique flexibility and excellent scratch resistance

The flexibility of polyethylene pipe systems has great technical and economic value. The flexibility of polyethylene is an important property that greatly increases the value of this material for pipeline projects. Good flexibility allows polyethylene pipes to be coiled and supplied in longer lengths, avoiding a large number of joints and fittings. At the same time, flexibility, light weight and excellent scratch resistance allow it to adopt a variety of installation methods that can reduce the impact on the environment and social life and are cost-effective, such as trenchless construction technology. Trenchless construction technology refers to the construction technology of laying, replacing or repairing various underground pipelines without trenching (grooving) on the surface using various rock and soil drilling techniques. Various trenchless construction technologies are very suitable for the use of polyethylene pipes, such as horizontal directional drilling and guide drilling methods for laying new pipelines, expansion methods for replacing old pipelines in situ, and interlaced lining methods for repairing old pipelines and various improved lining methods (folding deformation method, hot drawing method and cold rolling method).

PE's unique flexibility also enables it to effectively resist underground movement and end loads. On the surface, in terms of strength and rigidity, plastic buried pipes are not as good as cement pipes and metal pipes, but in practical applications, plastic buried pipes are "flexible pipes". Under correct design and laying construction, plastic buried pipes and surrounding soil share the load. Therefore, plastic buried pipes do not need to achieve the same strength and rigidity as "rigid pipes" to meet the requirements of mechanical properties in buried use. At the same time, the pressure relaxation characteristics of polyethylene can effectively consume stress through deformation. Its actual axial stress level is much lower than the theoretical calculated value, and its elongation at break is generally greater than 500%. The bending radius can be as small as 20 to 25 times the pipe diameter. It is a high-toughness material with a strong adaptability to uneven foundation settlement. These characteristics make it the best pipeline to resist earthquakes, foundation settlement and temperature expansion. For example, in the 1995 Kobe earthquake in Japan, PE water pipes and gas pipes were among the pipeline systems that survived.

Low temperature resistance

Polyethylene has outstanding low temperature resistance

The low-temperature brittle point of PE pipe is -70℃, which is better than other pipes. PVC-U pipes are prone to brittle cracks during outdoor construction in winter. An experience summarized in the pilot project of laying PVC-U buried water supply pipes in Beijing, my country is that it is not suitable to lay PVC-U pipes at temperatures below zero. There is also an obvious evidence that in order to improve the toughness and low-temperature impact resistance of PP, ethylene and propylene monomers can be copolymerized to form random copolymer polypropylene (PP-R). It generally adopts the process route and method of iPP to copolymerize the mixed gas of propylene and ethylene to obtain a copolymer with propylene and ethylene segments randomly distributed in the main chain (i.e. PP-R pipe material). The ethylene content in PP-R pipe material is mostly around 3%. However, the improved low-temperature resistance of PP-R is still unsatisfactory, and its brittle point is about -15℃, which is much higher than the brittle point temperature of polyethylene pipe -70℃.

Fracture toughness

Polyethylene has good rapid crack growth fracture toughness

When rapid crack growth damage occurs, the crack can quickly expand at a speed of 100 to 45 m/s for hundreds of meters to more than ten kilometers, causing damage to long-distance pipelines, large-scale leakage accidents, and subsequent combustion and explosion (natural gas transmission) or flood (water transmission) accidents. The probability of such an accident is small, but once it occurs, the harm is extremely great. For the sustainable development of plastic pressure pipes, the importance of preventing rapid crack growth damage has exceeded the requirements for long-term life strength performance. The reason is: at the same SDR (ratio of pipe diameter to its thickness), the calculated long-term life-long-term strength has nothing to do with increasing pipe diameter (in fact, large-diameter pipes may be safer than small-diameter pipes), but the risk of rapid crack growth increases with the increase of pipe diameter. In the existing large varieties of plastic pipes, such as polyethylene, polypropylene, polyvinyl chloride pipes, etc., when a certain pipe diameter is reached, the allowable pressure determined by preventing rapid crack growth damage is always lower than the allowable pressure determined by long-term strength issues. That is to say, after the allowable pressure is determined according to the requirement of preventing rapid crack growth damage, the long-term service life (such as 20°C, 50 years) requirement can be met automatically; materials with poor fracture toughness due to rapid crack growth will be eliminated, regardless of whether their long-term strength performance is good or bad. For example, polyvinyl chloride (PVC-U) gas pipes have basically been replaced by polyethylene (PE) gas pipes. The trend of polyvinyl chloride (PVC-U) water pipes being replaced by polyethylene (PE) pipes in Europe has become clear.

my country has not yet established a test device to monitor rapid crack growth damage. my country's plastic pressure pipe standards do not address this issue, which shows that my country's plastic pressure pipe level is at least one stage behind the world's general level.

Terms of Use:

General Provisions

① Pipes and fittings should have product quality inspection reports from the quality inspection department and certificates from the manufacturer.

② When storing, handling and transporting pipes, they should be tied with non-metallic ropes and the ends of the pipes should be sealed.

③ Pipes and fittings must not be dropped or violently impacted during storage, handling and transportation.

④ When storing, handling and transporting pipes and fittings, they must not be exposed to the sun or rain; they must not come into contact with oils, acids, salts or other chemicals.

⑤ The storage period of pipes and fittings from production to use should not exceed one year.

Material acceptance

① Acceptance of pipes and fittings must be carried out. First, the relevant materials such as product instructions, product certificates, quality assurance, and various performance inspection and acceptance reports must be inspected.

② When accepting pipes and fittings, samples should be taken from the same batch, and the specifications, dimensions and appearance performance should be checked in accordance with the current national standard "Polyethylene (PE) Materials for Water Supply". If necessary, a comprehensive test should be carried out.

Storage

① Pipes and fittings should be stored in a well-ventilated warehouse or simple shed with a temperature not exceeding 40°C.

② Pipes should be stacked horizontally on flat supports or on the ground. The stacking height should not exceed 1.5 meters. When the pipes are bundled into 1mx1m square bundles and supported on both sides, the stacking height can be appropriately increased, but should not exceed 3m. Pipes should be stacked neatly layer by layer to ensure that they will not collapse and are easy to take and manage.

③ When pipes and fittings are temporarily stacked outdoors, they should be covered.

④ When storing pipes, pipes of different diameters and wall thicknesses should be stacked separately.

Handling

① When transporting pipes, non-metallic ropes must be used for lifting.

② When transporting pipes and pipe fittings, they should be placed carefully and arranged neatly. Do not drop or drag them along the ground.

③ When transporting pipes and fittings in cold weather, violent impact is strictly prohibited.

transportation

① When transporting pipes by vehicle, they should be placed on the bottom of a flat car. When transporting by ship, they should be placed in a flat cabin. During transportation, straight pipes should be supported along their entire length, and coils should be neatly stacked. Straight pipes and coils should be tied and fixed to avoid collisions. There should be no sharp objects that may damage the pipes when stacked.

② When transporting pipe fittings, they should be neatly stacked layer by layer in boxes and securely fixed.

③ Pipes and fittings should be covered during transportation to avoid exposure to the sun and rain.

Connection technology:

PE water pipe connection method

There are many ways to connect polyethylene pipes to other pipes, pipes to PE pipes, pipes to fittings, and polyethylene pipes to metal pipes. Different connection methods have their own advantages and limitations. Users can choose the appropriate connection method according to the pipe diameter, working pressure, use site and other environments. The most commonly used connection methods for urban water supply polyethylene pipes are: hot melt connection, electric fusion connection, socket-type flexible connection, flange connection, steel-plastic transition joint connection, etc.

1. Hot melt connection

Hot melt connection is to use a special heating tool to heat the parts of polyethylene pipes or fittings to be connected under pressure, melt them, remove the heating tool, apply pressure to connect the two molten surfaces together, and keep them under stable pressure for a period of time until the joint cools down. Hot melt connection includes hot melt butt connection, hot melt socket connection, and hot melt saddle connection.

2. Electric fusion connection

The electric fusion connection is to use a special electric fusion pipe fitting with an embedded resistance wire to closely contact the connection part of the PE pipe or pipe fitting and energize it. The PE pipe heats the connection part through the embedded resistance wire, so that it melts and connects together until the joint cools down. The electric fusion connection can be used to connect polyethylene pipes or socket fittings of different types and different melt flow rates. The electric fusion connection is divided into electric fusion socket connection and electric fusion saddle connection.

3. Socket-type flexible connection

The socket-and-spigot flexible connection of polyethylene pipes is a new type of connection method developed with reference to the socket-and-spigot flexible connection principle of cast iron pipes and polyvinyl chloride pipes (PVC-U). The PE pipe is a polyethylene pipe with a reinforced polyethylene socket welded on one end. The socket-and-spigot flexible connection is to directly insert one end of the polyethylene pipe into the special socket of the pipe or pipe fitting, and the locking ring in the socket is pressed to resist pulling and the rubber sealing ring is pressed to seal, so as to achieve the purpose of connecting the PE pipe and the pipe fitting.

4. Flange connection

Flange connection is mainly used for the connection between polyethylene pipes and metal pipes or valves, flow meters, pressure gauges and other auxiliary equipment. Flange connection mainly consists of polyethylene flange connectors, steel or aluminum back pressure slip-on flanges, steel or aluminum flanges, gaskets or sealing rings, bolts, nuts, etc. Flange connection is achieved by tightening bolts and nuts to make the flange connectors and flanges in close contact.

5. Steel-plastic transition joint connection

Steel-plastic transition joint connection is to connect polyethylene pipes and metal pipes by using steel-plastic transition joints prefabricated by cold pressing or other methods. There are anti-pulling locking rings and sealing rings in the steel-plastic transition joints, which are usually required to have good sealing performance and anti-pulling and pressure resistance performance greater than the polyethylene pipes in the system.

The above is the connection method of PE pipes. It should be noted that it is strictly forbidden to directly make pipe threads on polyethylene pipes and fittings in any form and use threaded connections; it is strictly forbidden to use open flames to bake polyethylene pipes and fittings and connect directly.

The connection technology of polyethylene is very mature and reliable. Statistics show that the leakage rate of polyethylene pipes is less than 0.2%, which is much lower than the 2-3% of ductile iron pipes. This has greatly improved the safety and economic benefits of pipelines. This is also a very important reason why polyethylene pipes are widely used in gas pipelines.

Bonding method

1. Before bonding pipes and fittings, wipe the socket side and the outside of the plug with a dry cloth. If there is oil on the surface, wipe it clean with acetone.

2. The cross section of the pipe should be flat, perpendicular to the pipe axis and chamfered; before bonding, the insertion mark should be drawn and a trial insertion should be carried out. The trial insertion depth can only be 1/3 to 1/2 of the original depth. It is strictly forbidden to use the bonding method when the gap is too large.

3. When applying adhesive, apply it to the inside of the socket first, then to the outside of the plug, and finally to the socket.

When applying the coating, apply an appropriate amount evenly from the inside to the outside along the axial direction without missing any part or applying too much (200g/m2).

4. After applying the adhesive, the applied external force should be kept constant within 1 minute to keep the straightness and correct position of the interface.

5. After bonding, wipe off the excess adhesive in time. Do not apply force or forced loading during the curing time.

6. Adhesive joints must not be constructed in rain or water, and must not be operated below 5°C.

7. Connection procedure: preparation → cleaning the working surface → trial insertion → brushing adhesive → bonding → maintenance.

Welding steps of PE water supply pipe

PE water supply pipe is made of special polyethylene as raw material and extruded by a plastic extruder. It is used in urban water supply pipe network, irrigation and water diversion projects and agricultural sprinkler irrigation projects. It is particularly suitable for plastic pipes that are resistant to acid, alkali and corrosion. Since PE pipes are connected by hot melt and electric hot melt, the integration of the interface and the pipe is realized, and the hoop stress and axial impact stress generated by pressure can be effectively resisted. Moreover, PE pipes do not add heavy metal salt stabilizers, the material is non-toxic, does not scale, and does not breed bacteria, avoiding secondary pollution of drinking water. The welding of PE water supply pipes can be divided into the following steps, which are very important. Everyone must pay attention.

(1) When welding PE water supply pipes, align the axes of the two pipes and first spot weld the ends of the two pipes.

(2) When welding the PE water supply pipe to the flange, the water supply pipe should be inserted into the flange first, and then spot welded and aligned with a square ruler. After leveling, weld again. The flange should be welded on both sides, and the inner welding should not protrude from the closed surface of the flange.

(3) When the wall thickness of the PE water supply pipe is more than 5mm, the groove should be cut to ensure sufficient penetration. The groove can be formed by gas welding cutting or groove machine processing, but the slag and iron oxide should be removed and polished with a file until the metal is exposed.

(4) When cutting the steel pipe, the cut surface should be perpendicular to the center line of the pipe to ensure the concentricity of the pipe after welding.

(5) The flange should be perpendicular to the center line of the pipe, and the surfaces should be parallel to each other. The flange gasket should not protrude into the pipe. The bolt specifications for connecting the flange should match the flange, and the length of the screw protruding from the nut should not be greater than 1/2 of the screw diameter.

(6) When welding the water supply pipe, the pipe joints must be cleaned of rust, dirt and grease.

(7) Flange gaskets should be selected according to the drawings and specifications. Rubber gaskets are used for cold water systems and asbestos rubber gaskets are used for hot water systems.

Butt fusion installation:

Butt fusion is to use a butt fusion welding machine to heat the pipe ends (the temperature of hot fusion is 210+10℃). After the pipe ends are melted, they are quickly fitted together, maintaining a certain pressure, and cooling to achieve the purpose of welding. Applicable pipe diameter range: dn≥90mm

Steps:

1. Place the two PE pipes to be connected on the hot melt fixture at the same time (the clamp block can be replaced according to the diameter of the pipe to be installed), and lift the other end of each pipe to the same horizontal plane with a pipe bracket.

2. Use an electric rotary cutter to cut the ends of the pipes flat to ensure that the contact surfaces of the two pipes are fully aligned.

3. Heat the electric heating plate to 210°C, place it between the two pipe ends, and operate the electric hydraulic device to make the two pipe ends completely contact and heat with the electric heating plate at the same time.

4. Remove the heating plate and operate the hydraulic device again to fully connect the two melted pipe ends and lock the hydraulic device (to prevent rebound).

5. Keep it cool for a while and then release it. The operation is completed.

6. After the construction is completed, it must pass the pressure test and acceptance before it can be buried and put into use.

Technical requirements:

Although HDPE pipes have been successfully used in many fields, the following points still need to be noted during use:

1. Welding: When hot-melt connection is performed, the temperature must reach 210±10℃, and care should be taken to avoid over-burning.

2. Buried: When working in a pipe trench, necessary safety measures must be considered.

3. Test: Water is recommended as the pressure test medium. During the test, measures should be taken to prevent the pipeline from moving or being damaged.

4. Positioning: Polyethylene materials cannot be controlled by magnetic positioning equipment. Other methods can be used to detect polyethylene pipelines, including tracer wires, marking tapes, detection tapes, line markings, electronic marking systems and voice-controlled pipeline tracing methods.

5. Gas pressure: HDPE pipes cannot be used in the field of high-pressure gas transportation.

6. Application scope: HDPE pipes are not recommended in some occasions. Please consult the supplier about its chemical corrosion resistance.

7. Static electricity: HDPE pipes contain high static electricity. Appropriate measures should be taken to eliminate static electricity in situations with flammable and explosive gases.

8. Impact performance: HDPE pipes have good impact resistance. When hitting the pipe with a hammer, it should be noted that the pipe will produce a certain rebound force.

9. Coil: The coiled small-diameter HDPE pipe stores energy like a spring. If the packaging tape is cut, a large rebound force will be generated.

10. Storage: If pipes must be stored in piles, avoid stacking too high and stack them in straight rows. If the pipes are not stacked properly, the pipes may deform.

11. Weight: Although HDPE pipes are lighter than other traditional pipes, they still have a certain weight, so care should be taken during transportation and construction.

12. Unloading: Correct unloading facilities must be used and all tools used for handling should be checked to ensure they meet the requirements.

Materials used:

ABS (Acrylonitrile Butadiene Styrene)

Unplasticized polyvinyl chloride (UPVC)

CPVC (Post-Chlorinated Polyvinyl Chloride)

PP (Polypropylene)

PE (Polyethylene), also known as LDPE, MDPE, and HDPE (low, medium, and high density)

Installation process:

(1) Heat the pipes and fittings at the same time, then insert the sockets. After the sockets are in place, wait for a moment and let go. Do not twist during the heating, socketing and cooling process;

(2) Heat the hot melt machine die head to about 20°C;

(3) Use pipe shears to cut the pipe according to installation requirements;

(4) Natural cooling;

(5) Mark the pipe at the depth where the socket is to be inserted;

(6) The construction is completed and put into use after passing the pressure test acceptance.

Construction steps:

1. Material preparation: Place the pipe or pipe fitting on a flat surface and place it on the butt joint machine, leaving a cutting allowance of 10-20 mm.

2. Cutting: Cut off impurities and oxide layers on the end faces of welded pipe sections and pipe fittings to ensure that the two butt ends are flat, smooth and free of impurities.

3. Alignment: The end faces of the two welded pipe sections must be completely aligned, and the smaller the misalignment, the better. The misalignment cannot exceed 10% of the wall thickness. Otherwise, the butt joint quality will be affected.

4. Heating: The docking temperature is generally between 210-230℃. The heating time of the heating plate is different in winter and summer. The best melting length of the two end surfaces is 1-2mm.

5. Fusion butt welding: It is the key to welding. The butt welding process should always be carried out under molten pressure, and the curling width should be 2-4mm.

6. Cooling: Keep the docking pressure unchanged and allow the interface to cool down slowly. The cooling time is based on the fact that the curled edge feels stiff and no heat can be felt when touched.

7. Docking is completed: After cooling, loosen the slips, remove the docking machine, and prepare for the next interface connection.

National Standard:

The main differences between this standard and ISO 4427:1996 are as follows: 1. This standard only covers pipes made of PE 63, PE 80, and PE 100 materials, and does not cover pipes made of PE 32 and PE 42 materials; 2. This standard adds a chapter on definitions; 3. The performance requirements for pipes are added.

The main differences between this standard and ISO 4427:1996 are:

1. This standard only includes pipes made of PE 63, PE 80, and PE 100 materials, and does not include pipes made of PE 32 and PE 42 materials;

2. This standard adds a chapter on definitions;

3. The "elongation at break" item has been added to the performance requirements for pipes;

4. Added a chapter on "Inspection Rules";

The differences between this standard and GB/T 13663-1992 are:

GB/T 13663-1992 "High-density polyethylene (HDPE) pipes for water supply" was not formulated in accordance with international standards.

From the date of implementation of this standard, it will replace GB/T 13663-1992

Appendix A of this standard is a suggestive appendix.

This standard was proposed by the State Bureau of Light Industry.

This standard is under the jurisdiction of the National Technical Committee on Standardization of Plastic Products.

Scope of application

This standard specifies the product specifications, technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of polyethylene pipes for water supply (hereinafter referred to as "pipes") made of polyethylene resin as the main raw material through extrusion. This standard also specifies the basic performance requirements of raw materials, including the classification system.

This standard applies to water supply pipes made of PE63, PE 80 and PE 100 materials (see 4.1). The nominal pressure of the pipes is 0.32MPa~1.6MPa, and the nominal outer diameter is 16mm~1000mm.

The pipes specified in this standard are suitable for general-purpose pressure water transportation at temperatures not exceeding 40°C, as well as the transportation of drinking water.

Reference standards

The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards.

GB/T 2918-1998 Standard environment for conditioning and testing of plastic specimens (idt ISO 291:1997)

GB/T 3681-1983 Test method for natural weather exposure of plastics

GB/T 3682-1983 Test method for melt flow rate of thermoplastics

GB/T 6ill－1985 Determination of the damage resistance time of thermoplastic pipes under long-term constant internal pressure (eqv ISO/DP 1167:1978)

GB/T 6671.2-1986 Determination of longitudinal shrinkage of polyethylene (PE) pipes (idt ISO 2506:1981)

GB/T 8804.2-1988 Test method for tensile properties of thermoplastic pipes Polyethylene pipes (eqv ISO/DIS 3504-2)

GB/T 8806-1988 Plastic pipe size measurement method (eqv 1974)

GB/T 13021～1991 Polyethylene pipes and fittings - Determination of carbon black content - Thermal gravimetric method (NEQ 1986)

GB/T 17219-1998 Safety evaluation standard for drinking water transmission and distribution equipment and protective materials

GB/T 17391-1998 Test method for thermal stability of polyethylene pipes and fittings (eqv 1991)

GB/T 18251-2000 Determination of dispersion of pigments and carbon black in polyolefin pipes, fittings and compounds

GB/T 18252-2000 Plastic piping systems - Determination of the long-term hydrostatic strength of thermoplastic pipes by extrapolation

definition

3.1 Definition

3.1.1 Geometric Definition

3.1.1.1 Nominal outside diameter dn: the specified outside diameter in millimeters.

3.1.1.2 Average outer diameter dem: the value obtained by dividing the measured value of the outer circumference of the pipe by 3.142 (pi), accurate to 0.1 mm, with the second non-zero digit after the decimal point rounded up.

3.1.1.3 Minimum average outer diameter dem,min: The minimum value of the average outer diameter specified in this standard, which is equal to the nominal outer diameter dn, in millimeters.

3.1.1.4 Maximum average outer diameter dem,max: the maximum value of the average outer diameter specified in this standard.

3.1.1.5 Outside diameter at any point dey: The outside diameter measured through the cross section of the pipe at any point, accurate to 0.1mm, with the second non-zero digit after the decimal point rounded up.

3.1.1.6 Out-of-roundness: The difference between the maximum outside diameter and the minimum outside diameter measured at the same cross section of the pipe.

3.1.1.7 Nominal wall thickness en: the specified value of the pipe wall thickness, in millimeters, equivalent to the minimum wall thickness ey,min at any point.

3.1.1.8 Wall thickness ey at any point: The measured value of the wall thickness of the pipe at any point, accurate to 0.1 mm, with the second non-zero digit after the decimal point carried forward.

3.1.1.9 Minimum wall thickness ey,min: The minimum value of the wall thickness at any point on the circumference of the pipe specified in this standard.

3.1.1.10 Maximum wall thickness ey, max: The maximum value of the wall thickness at any point on the circumference of the pipe determined based on the tolerance of the minimum wall thickness (ey, min).

3.1.1.11 Standard Dimension Ratio (SDR): The ratio of the nominal outer diameter of the pipe to the nominal wall thickness. SDR = dn / en

3.1.2 Definitions related to materials

3.1.2.1 Compound material: Granules made from polyethylene base resin with necessary antioxidants, UV stabilizers and pigments added.

3.1.2.2 σlpl1: The hydrostatic intensity corresponding to 20°C, 50 years, and 97.5% probability prediction, in MPa.

3.1.2.3 Minimum required strength (MRS): σlpl rounded to the next smaller value in the priority number R10 or R20 series.

3.1.2.4 Design stress σs: The allowable stress under specified application conditions, MRS divided by the coefficient C, rounded to the next smaller value in the priority number R20 series, that is: σs = [MRS] / C ……………… (1)

3.1.2.5 Total service (design) factor C: A total factor with a value greater than 1 that takes into account the service conditions and the properties of components such as fittings in the piping system that are not reflected in the lower limit of the prediction.

3.1.3 Definitions related to conditions of use

3.1.3.1 Nominal pressure (PN): The nominal pressure PN in this standard is equivalent to the maximum working pressure of the pipe at 20°C, in MPa.

3.1.3.2 Maximum Operating Pressure (MOP): The maximum effective pressure of the fluid allowed to be used continuously in the piping system, expressed in MPa.

symbol

3.2 Notation

C: total usage (design) factor;

dem: average outer diameter;

dem,max: maximum average outer diameter;

dem,mix: minimum average outer diameter;

dn: nominal outer diameter;

ey: wall thickness at any point;

ey,min: minimum wall thickness;

ey,max: maximum wall thickness;

ft: reduction factor of temperature to pressure;

ty: wall thickness tolerance at any point of the pipe;

σlpl: hydrostatic strength corresponding to 20℃, 50 years, 97.5% probability prediction;

σs: design stress;

Abbreviations

3.3 Abbreviations

MFR: melt flow rate;

MOP: Maximum operating pressure;

MRS: minimum required strength;

PE: Polyethylene;

PN: nominal pressure;

SDR: Standard Size Ratio.

Material naming

4.1 Naming

The polyethylene pipe materials in this standard are named as follows:

4.1.1 Determine the hydrostatic strength σlpl of the material at 20℃, 50 years and 97.5% predicted probability in accordance with GB/T18252.

4.1.2 According to Table 1, convert the minimum required strength (MRS) based on σlpl, and multiply the MRS by 10 to obtain the material grade.

4.1.3 Name the materials according to material type (PE) and classification number according to Table 1.

Table 1 Nomenclature of materials

The polyethylene pipe is produced by using mixed materials, the mixed materials are blue or black, and the basic performance should meet the requirements of Table 2. The blue pipe material should ensure that the weather resistance of the pipe made of this material meets the requirements of Table 12. For PE63 grade materials, polyethylene pipes can also be produced by adding masterbatch to pipe grade base resin. The material performance requirements are tested by sampling from the pipe.

Clean recycled materials produced when producing pipes according to this standard can be mixed into new materials for recycling as long as pipes that meet this standard can be produced.

Table 2 Basic performance requirements of materials

Product Specifications

5.1 The pipes in this standard are designed with an expected service life of 50 years.

5.2 For conveying water at 20℃, the minimum C can be Cmin=1.25. The maximum allowable values of design stress for different grades of materials obtained by formula (1) are shown in Table 3.

Table 3 Maximum allowable values of design stress for different grades of materials

The relationship between the nominal pressure (PN) of the pipe, the design stress σs, and the standard dimension ratio (SDR) is: PN = 2σs/(SDR-1)……………………………….(2)

Where: PN and σs are both in MPa.

For pipes made of PE63 and PE100 grade materials, the nominal outer diameter and wall thickness determined by the design stress in Table 3 according to the selected nominal pressure shall comply with the provisions of Table 4, Table 5 and Table 6 respectively. The designer and user of the pipeline system can adopt a larger total use (design) factor C, in which case pipes with higher nominal pressure grades can be selected.

PEM tubes are lightweight and strong, making them easy to transport and store. Transportation is mainly by truck, and the standard loading volume is as follows.

PE water pipe construction and installation: management/storage

Product Management

A. Pipes with the largest diameter are often piled at the bottom.

B. The inside and outside of the PEM pipe are very smooth. In order to prevent it from sliding, it must be securely fixed during loading.

C. Small diameter straight pipes or light pipes can be loaded and unloaded by hand. Construction and installation: Management/storage

custody

A. PEM pipes should be kept in a clean place.

B. To prevent direct sunlight during long-term storage, place it indoors or cover it with a cloth.

C. When stacking pipes on the ground for storage, remove stones or other sharp objects and make the ground flat before stacking.

D. PEM tubes should be kept away from heat sources.

E. Please note that the pipe may be deformed in case of excessive loading or stacking.

The loading column number limit is as follows

6. Technical requirements

6.1 Color

The color of municipal drinking water pipes is blue or black, and the black pipe should have a co-extruded blue stripe. There should be at least three stripes along the longitudinal direction of the pipe. Other water pipes can be blue and black. Pipes laid in the sun (such as above-ground pipes) must be black.

6.2 Appearance

The inner and outer surfaces of the pipe should be clean and smooth, without any defects such as bubbles, obvious scratches, dents, impurities, uneven colors, etc. The pipe ends should be cut flat and perpendicular to the pipe axis.

6.3 Pipe size

6.3.1 Pipe length

6.3.1.1 The length of straight pipe is generally 6m, 9m, 12m, which can also be agreed upon by both parties. The maximum deviation of length is +0.4%, -0.2% of the length.

6.3.1.2 The diameter of the coil rack should not be less than 18 times the outer diameter of the pipe. The coil expansion length shall be agreed upon by the supplier and the buyer.

6.3.2 Average outer diameter

The average outer diameter of the pipe shall comply with the requirements of Table 8. For fine tolerance pipes, Grade B shall be used, and for standard tolerance pipes, Grade A shall be used. The use of Grade B or Grade A shall be determined by the supplier and the buyer. If there is no clear requirement, Grade A shall be used.

Table 8 Average outer diameter

6.3.3 Wall thickness and deviation

The minimum wall thickness ey,min of the pipe is the nominal wall thickness en. The wall thickness tolerance at any point of the pipe shall comply with the provisions of Table 9.

Table 9 Wall thickness tolerance at any point

6.4 Hydrostatic strength

The hydrostatic strength of the pipe shall comply with the requirements of Table 10.

Table 10 Hydrostatic strength of pipes

The 80°C hydrostatic strength (165h) test only considers brittle failure. If ductile failure occurs within the required time (165h), select a lower failure stress and the corresponding minimum failure time according to Table 11 and retest.

Table 11 Re-test requirements for hydrostatic strength at 80°C (165h)

6.5 Physical properties

The physical properties of the pipe should meet the requirements of Table 12. When the recycled material is added to the mixed material for extrusion, the difference between the melt flow rate (MFR) (5kg, 190℃) measured on the pipe and the measured value on the mixed material should not exceed 25%.

Table 12 Physical performance requirements of pipes

6.6 Hygienic performance

The sanitary properties of pipes used for drinking water distribution should comply with the requirements of GB/T 17219.

Pipeline connection:

6.1. General Provisions:

6.1.1. The connection of pipes, pipe fittings and pipe accessories shall be made by hot-melt connection (hot-melt butt connection, hot-melt socket connection, hot-melt saddle connection) or electric-melt connection (electric-melt socket connection, electric-melt saddle connection) and mechanical connection (locking and non-locking socket connection, flange connection, steel-plastic transition connection). Manual hot-melt socket connection shall not be used for pipes with a nominal outer diameter greater than or equal to 63mm, and hot-melt butt connection shall not be used for pipes with a wall thickness of less than 6mm. Threaded connection and bonding shall not be used for polyethylene pipes and pipe fittings.

6.1.2. All pipeline connections should use corresponding special connection tools. Open flame heating is strictly prohibited during connection.

6.1.3. Pipeline connections should use pipes, fittings and pipe accessories of the same grade and pressure level (the connection between pipes and pipe accessories of different grades should be tested to determine whether the connection quality can be guaranteed before connection).

6.1.4. When polyethylene pipes and fittings are connected with metal pipes and pipeline accessories, when steel spray-coated or ductile iron transition fittings are used, the pressure rating of the transition fittings shall not be lower than the nominal pressure of the pipes.

6.1.5. When performing hot melt or electric melt connection operations in cold climates (below -5°C) or windy conditions, protective measures should be taken or the process parameters of the connection equipment should be adjusted.

6.1.6. When connecting pipelines, special cutting knives or pipe cutting tools should be used to cut the pipes. The cut section should be flat, smooth, and free of burrs, and should be perpendicular to the pipe axis.

6.1.7. After the pipeline is connected, the appearance quality of the joint should be checked in time, and those that do not meet the standards must be reworked.

6.2. Hot melt connection:

6.2.1. The temperature control of the hot melt connection tool should be accurate, the temperature distribution of the heating surface should be uniform, and the heating surface structure should meet the welding process requirements. Clean cotton cloth should be used to wipe off dirt on the heating surface before and after hot melt connection.

6.2.2. The heating time, heating temperature, applied pressure, pressure holding and cooling time of hot melt connection shall comply with the regulations of the hot melt connection tool manufacturer and the polyethylene pipe, pipe fittings and pipeline accessories manufacturer. The connector shall not be moved or any external force applied to the connector during the pressure holding and cooling period.

6.2.3. Butt-melt connection shall also comply with the following provisions:

6.2.3.1. The connecting ends of the two parts to be connected should extend out of the welding machine fixture to a certain free length, and the two corresponding parts to be connected should be aligned so that they are on the same axis. The misalignment should not be greater than 10% of the wall thickness.

6.2.3.2. Dirt on the connection surfaces of pipes, fittings and pipeline accessories should be wiped clean with a clean cotton cloth, and the connection surfaces should be milled to make them perpendicular to the axis.

6.2.3.3. The sections of the parts to be connected should be heated using a hot melt butt connection tool.

6.3.3.4. After heating, the parts to be connected should be quickly separated from the heating tool, and the uniformity of melting of the heated surface of the parts to be connected and whether there is any damage. Then, use uniform external force to make the connection surface completely contact, and turn the edges to form a uniform flange. The height and width of the flange should comply with relevant regulations.

6.3.3.5. When pipes and fittings of different SDR series are welded together, it is advisable to make the wall thickness of the weld the same through mechanical processing.

6.3.3.6. During welding, each weld should have a detailed original welding record, which should at least include the ambient temperature, welder code, weld number, pipeline specification type, welding pressure, drag pressure, pressurization time, heating plate temperature, switching time, heat absorption time, cooling time, etc.

6.3.3.7. Hot-melt butt connection of polyethylene (PE) water supply pipes should use pipes from the same manufacturer, material and brand, pipes and fittings, and fittings. Polyethylene pipes of different SDR series should not be connected by hot-melt butt connection.

6.2.4. Welding quality inspection:

6.2.4.1. Necessity of testing;

6.2.4.2. Inspection method: The quality inspection of welding joints is divided into destructive test and non-destructive test. Non-destructive test is generally used at the construction site. The main means of non-destructive test is visual inspection, which can also be called appearance inspection. The main standards are as follows:

The curling should be uniform, smooth and full, with similar curling sizes on both sides; the weld should be smooth and symmetrical, and the height difference of the curling and any side of the flange should not be greater than 0.1 < its wall thickness; the cut flange should not have defects such as unfusion, notches, holes, etc., and the misalignment of the cut pipe ends should not exceed 10% of the wall thickness.