In municipal engineering, the installation of HDPE (high-density polyethylene) pipes must follow strict specifications to ensure their durability, sealing and safety. The following are key precautions:

 

Preliminary preparation

Material acceptance

Check the quality certification documents of pipes and fittings (such as certificates of conformity, test reports) to ensure compliance with national standards such as GB/T 19472.2.

Appearance inspection: no cracks, scratches, depressions or bubbles, and the port is flat and burr-free.

Check whether the specifications (such as SDR value, ring stiffness grade) are consistent with the design requirements.

Trench excavation

Trench bottom width: When the pipe diameter is ≤DN500, the trench width is ≥ the outer diameter of the pipe + 0.5m; when the pipe diameter is larger, sufficient operating space must be reserved.

Slope and base: Slope according to design requirements (such as 1:0.33), the base must be flat and free of gravel and hard objects, and the over-excavated part should be backfilled and compacted with sand and soil.

Groundwater level: If groundwater is encountered, it is necessary to take precipitation measures or replace the gravel layer with anti-floating pipes.

 

Pipeline installation

Connection method

Hot-melt butt welding (applicable to large-diameter pipes):

Clean the heating plate, control the temperature (200~220?), and perform the welding pressure and time according to the manufacturer"s parameters.

Check the uniformity of the flange after butt welding to avoid false welding.

Electrofusion connection (with socket pipe fittings):

Ensure that the oxide layer is scraped off the pipe end, the insertion depth is clearly marked, and the power-on time/voltage meets the requirements of the pipe fittings.

Mechanical connection (flange or clamp): Check whether the sealing ring is installed in place and the bolts are tightened symmetrically.

Main points for laying

Flexible foundation: Lay a 10~15cm medium-coarse sand cushion layer, and fully support the 120° range below the pipe.

Bending radius: Cold bending is allowed, but the curvature radius ≥ 25 times the pipe diameter (such as DN400 pipe requires R ≥ 10m).

Snake laying: When the temperature changes greatly, reserve 2%~3% of the expansion and contraction to avoid thermal expansion and deformation of the straight line.

 

Backfill requirements

Backfill in layers

Backfill on the pipe side: use sand or fine soil with a particle size of ≤10mm, symmetrically compact in layers (each layer ≤20cm), and the compaction degree ≥90%.

50cm above the top of the pipe: direct mechanical rolling is prohibited, and manual compaction is adopted.

Upper backfill: compact in layers according to the requirements of roads or greening to avoid settlement.

Special area treatment

Add steel casing protection when crossing the road, and seal and prevent seepage at both ends of the casing.

Soft soil foundation needs to be replaced or reinforced with gravel piles to prevent uneven settlement of the pipeline.

 

Quality and safety control

Testing items

Pressure test: inject water to stabilize the pressure for 1h, and the pressure drop is ≤0.05MPa to be qualified (refer to GB 50268).

Water-tight test: non-pressure pipelines are tested in sections according to the specifications, and the allowable water seepage is ≤Q=0.0046Di (m³/24h·km).

Electrofusion joint inspection: Detect the fusion quality by X-ray or ultrasonic.

Safety measures

Groove support: set baffles or slopes when the depth is ≥1.2m, and set warning lights at night.

Lifting operation: use nylon slings to avoid scratches on pipes, and keep personnel away from the radius of the boom.

 

Prevention of common problems

Leakage: strictly check the quality of the interface to avoid socket failure or incorrect welding parameters.

Deformation: control the compaction degree during backfilling to avoid overloaded vehicles rolling over inadequate backfill sections.

Through standardized construction and full-process quality control, HDPE pipes can give full play to their advantages of corrosion resistance, good flexibility, and long life (more than 50 years), and are suitable for municipal scenarios such as water supply and drainage, rainwater and sewage pipe networks.

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HDPE (high-density polyethylene) wear-resistant pipe for mining is widely used in mining transportation systems due to its excellent wear resistance, corrosion resistance and lightweight characteristics, especially in the transportation of high-wear ore sand, tailings and other materials. However, there are still problems such as bend wear and connection leakage in actual applications. The following are the key technologies and solutions for HDPE wear-resistant pipe for mining:

 

1. Wear resistance optimization

The wear resistance of HDPE pipe depends on the molecular weight. The wear resistance of ultra-high molecular weight polyethylene (UHMW-PE) pipe is higher than that of ordinary HDPE. Its wear resistance is 4-7 times that of steel pipe, and it has self-lubricating properties, which can reduce the adhesion of ore sand.

UHMW-PE pipe advantages:

Strong impact resistance, suitable for high-wear slurry transportation.

Low friction coefficient, reducing material flow resistance.

Excellent low temperature resistance, suitable for cold mining environment.

 

2. Bend wear solution

When conveying ore sand, the elbow part is prone to local wear due to eddy currents and impact. In a case of an iron mine, a 45° welded elbow suffered penetrating damage within 1 month because the ore sand formed a high-speed vortex on the inside of the elbow.

Improvement measures:

Reduce the elbow angle: Change the 45° elbow to two 22.5° elbows to reduce fluid impact.

Use large curvature radius elbows: Use the flexibility of HDPE to directly bend and lay to reduce welding joints.

Enhance the wear-resistant layer of the elbow: Add UHMW-PE lining or ceramic coating to the wear-prone parts.

 

3. Connection method optimization

Traditional HDPE pipe docking is prone to leakage, affecting the transportation efficiency. The new combination flange connection technology can improve the sealing performance:

Combination flange connection:

The split flange plate (first combination plate + second combination plate) is used for easy installation.

Interference fit of docking seat + sealing gasket prevents slurry leakage.

 

4. Construction and maintenance suggestions

Construction points:

Use hot melt or electric fusion welding to ensure the strength of the interface.

Avoid dragging and collision of pipelines to prevent mechanical damage.

Maintenance measures:

Regularly check the wear of elbows and joints.

Clean up the sludge deposits in the pipeline to prevent blockage.

 

5. Industry application cases

Nuclear power plant water supply system: The Catawba Nuclear Power Plant in the United States uses HDPE pipes instead of carbon steel pipes. It has no corrosion problems in 20 years of operation and the flow rate has increased by 15-25%.

Mine tailings transportation: After an iron mine switched to UHMW-PE pipes, it solved the problems of blockage and corrosion and extended its service life.

 

HDPE wear-resistant pipes for mining can effectively cope with the challenges of high-wear transportation by optimizing materials (such as UHMW-PE), improving elbow design, and enhancing connection sealing. In the future, with the advancement of polymer material technology, the application of HDPE pipes in the mining field will be further expanded.

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HDPE pipe (high-density polyethylene pipe) is widely used in water supply, drainage, gas, agricultural irrigation and other fields due to its excellent corrosion resistance, flexibility and weather resistance. So, how long is the service life of HDPE pipe? What factors affect its durability in practical applications? The following is a detailed answer for you:

 

Service life of HDPE pipe: up to 50 years or more

Under normal working conditions, the design life of HDPE pipe is usually 50 years or more. Under low pressure, stable temperature, good installation and maintenance environment, its life can be even longer. Compared with metal pipes (such as cast iron or steel pipes), HDPE pipes are not easy to corrode and are not affected by water quality or soil pH, so they are regarded as "long-term solutions" in many projects.

 

3 factors affecting the durability of HDPE pipes

1. Working pressure and temperature conditions

The long-term performance of HDPE pipes is closely related to the pressure and temperature they withstand:

The higher the pressure, the greater the internal stress on the material, which will accelerate aging, especially when operating at high pressure for a long time;

The increase in temperature will also accelerate the movement of polyethylene molecules, thereby affecting the mechanical properties and anti-aging properties of the pipe;

In standard design, the working temperature of 20? is generally used as the benchmark. For every 10? increase in temperature, the life span may be reduced by half.

Suggestion: Select HDPE pipes with corresponding pressure levels (such as PN6, PN10, PN16, etc.) and SDR coefficients according to the usage scenario to avoid overload operation.

2. Ultraviolet (UV) irradiation and environmental factors

Although HDPE has a certain UV resistance, long-term exposure to strong sunlight will cause ultraviolet rays to break the molecular chains on the surface of HDPE, forming cracks, which will affect the structural strength.

In addition, other environmental factors such as:

Contact with acidic and alkaline soils or chemicals;

Underground movement (such as earthquakes, landslides);

Pipeline laying depth and whether external protection is in place;

will also indirectly affect its life span.

Recommendation: When laying outdoors, an anti-ultraviolet protective layer should be added or black HDPE pipes should be used; when laying underground, the site selection, backfilling and support should be reasonable.

3. Raw material quality and production process

The raw material quality of HDPE pipes is the fundamental guarantee of their durability:

Using PE100 or higher grade raw materials (rather than recycled materials) can ensure higher crack resistance and impact resistance;

Whether the production process is standardized, whether the wall thickness is uniform, and whether it has passed ISO or CE quality certification;

Whether the quality of welding connection is good, weld defects will also become the source of early failure.

Recommendation: Purchase HDPE pipe products from well-known brands with qualification certification to avoid low-priced and low-quality pipes.

Overall, under appropriate application conditions, HDPE pipes can fully reach or even exceed a service life of 50 years. However, its durability is still significantly affected by three major factors: working pressure and temperature, environmental exposure conditions, and raw materials and production processes. Scientific selection and standardized construction are the key to ensuring its long-term stable operation.

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HDPE Pipeline Construction Specifications: Burial Depth, Support and Backfill Requirements

HDPE (High-density Polyethylene) pipeline construction must follow strict specifications to ensure its long-term stability and performance. The following are key construction requirements, including the key points of burial depth, support and backfill:

 

1. Burial Depth Requirements

Minimum Cover Thickness:

Under the roadway: ≥1.0m (need to be combined with load calculation, and additional protection measures if necessary).

Non-roadway (green belt, sidewalk, etc.): ≥0.7m.

Frozen areas: need to be buried below the freezing line, or insulation measures must be taken.

Special load areas (such as heavy vehicle traffic areas): The burial depth needs to be determined through structural calculations, and a concrete protective layer or casing may need to be added.

 

2. Trench Excavation and Support

Trench Width:

Single pipe: outer diameter of pipe diameter + 0.5m (≥0.25m on each side).

Multiple pipes in parallel: pipe spacing ≥0.3m, and the total width must meet the backfill compaction requirements.

Slope or support:

Loose soil: need to be sloped (such as 1:1 slope) or use steel sheet piles or channel steel for support.

Rock formation: need to lay a 10~15cm sand cushion at the bottom of the trench to prevent scratching the pipe.

Base treatment: ensure it is flat and free of sharp objects, compact or replace sand and gravel if necessary.

 

3. Pipeline installation and support

Foundation cushion:

General soil: 10cm thick medium-coarse sand or gravel cushion.

Soft soil foundation: needs to be replaced or reinforced (such as crushed stone + geotextile).

Pipeline connection:

Hot-melt butt or electric fusion connection, must be strictly operated according to process parameters (temperature, pressure, time).

After connection, it needs to be cooled and fixed to avoid stress.

Pipeline fixing:

Concrete piers or special clamps are required at elbows, tees and other parts to prevent displacement.

Expansion joints are set every 50 meters for long straight sections (especially in areas with large temperature differences).

 

4. Backfill requirements

Layered backfill:

30cm above the bottom of the pipe to the top of the pipe: use medium-coarse sand or fine soil (particle size ≤10mm), compact in layers (15~20cm per layer), and the compaction degree is ≥90%.

Pipe top 30cm or more: original soil can be used for backfilling, but stones, frozen soil, etc. need to be removed, and the compaction degree should be ≥85% (≥95% under the roadway).

Notes:

Backfilling should be carried out symmetrically to prevent the pipeline from shifting.

Unilateral dumping or mechanical direct rolling of the pipeline is prohibited.

Density testing is required after backfilling.

 

5. Special working condition treatment

High water level areas: anti-floating measures (such as weight blocks and anchors) need to be taken.

Crossing roads/structures: steel casing or concrete protection box needs to be added.

Drainage of trenches: avoid water accumulation during construction, and set up drainage ditches and water collection wells when necessary.

 

6. Acceptance criteria

Appearance inspection: no scratches or deformation of the pipeline, no leakage at the joints.

Pressure test: water supply pipelines need to undergo water pressure test (1.5 times the working pressure, no leakage after 30 minutes of stable pressure).

Elevation and coordinates: meet the design requirements, deviation ≤±50mm.

 

According to the specification

Domestic standard: "GB 50268-2008 Water supply and drainage pipeline construction and acceptance specification"

International reference: ISO 4427 (HDPE water supply pipe), ASTM F714 (polyethylene pressure pipe)

Before construction, it is necessary to adjust the plan in combination with the specific engineering geology, load conditions and design documents, and consult professional engineers when necessary.

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How is the corrosion resistance of HDPE pipe? Analysis of chemical industry application

HDPE (high-density polyethylene) pipe is widely used in the chemical industry due to its excellent corrosion resistance. The following is a detailed analysis of its corrosion resistance characteristics and chemical industry applications:

Corrosion resistance characteristics of HDPE pipe

Strong chemical inertness

HDPE is a non-polar polymer material that shows strong resistance to most acids, alkalis, salts, organic solvents and other chemical substances, especially at room temperature:

Acids: hydrochloric acid (HCl), sulfuric acid (H?SO?, concentration ≤50%), phosphoric acid (H?PO?), etc.

Alkali: strong alkaline solutions such as sodium hydroxide (NaOH) and potassium hydroxide (KOH).

Salts: sodium chloride (NaCl), ammonium chloride (NH?Cl), etc.

Organic solvents: polar solvents such as alcohol and glycerin (but poor tolerance to non-polar solvents such as gasoline and benzene).

No risk of electrochemical corrosion

Unlike metal pipes, HDPE does not suffer from electrochemical corrosion (such as pitting and intergranular corrosion), and is suitable for use in highly corrosive environments such as moisture and salt spray.

Environmental stress cracking resistance (ESCR)

Through modification (such as PE100 grade materials), HDPE pipes can resist stress cracking and extend their service life in chemical media.

Limitations

Strong oxidants: such as concentrated nitric acid (HNO?) and concentrated sulfuric acid (>50%) will slowly oxidize HDPE.

Halogenated hydrocarbons: such as carbon tetrachloride (CCl?) may cause swelling.

High temperature effects: Long-term exposure to environments above 60°C or certain chemical media may reduce performance.

 

Application scenarios in the chemical industry

Corrosive media transportation

Acid and alkali solutions: waste acid (dilute sulfuric acid, hydrochloric acid) and alkali (NaOH) transportation in electroplating plants.

Brine/brine: brine pipelines and seawater desalination systems in the chlor-alkali industry.

Chemical wastewater: collection and discharge of corrosive wastewater containing heavy metal ions, sulfides, etc.

Environmental protection and waste gas treatment

Waste gas scrubber pipeline: resistant to corrosive condensate formed by acidic gases such as SO? and HCl.

Sewage treatment plant: aeration pipeline, sludge transportation pipeline (resistant to hydrogen sulfide corrosion).

Chemical equipment matching

Storage tank lining: as the inner lining of metal storage tanks, prevent chemicals from directly contacting metals.

Underground pipeline: replace steel pipelines to avoid soil electrolytic corrosion (pay attention to ultraviolet protection).

Special process requirements

Electrolysis workshop: brine pipeline of ion membrane electrolyzer (resistant to chloride ion corrosion).

Pharmaceutical industry: high-purity water or solvent transportation (no metal ion precipitation pollution).

 

Selection and construction considerations

Material grade selection

PE80/PE100: Chemical industry recommends PE100, with higher density and chemical resistance.

UV-resistant version: Carbon black or UV stabilizer needs to be added for outdoor use.

Connection method

Hot-melt connection: No leakage risk, suitable for high-pressure systems.

Electrofusion connection: Ensure sealing under complex working conditions.

Temperature and pressure design

Chemical pipelines need to adjust the pressure level according to the medium temperature (such as derating above 40°C).

Compatibility test

For special media (such as organic solvents), it is recommended to conduct long-term immersion experiments to verify the stability of the material.

 

Advantages compared with other materials

Feature	HDPE Pipe	PVC Pipe	Stainless Steel Pipe	FRP Pipe (Fiberglass)
Acid Resistance	?????	?????	????? (304)	?????
Alkali Resistance	?????	?????	?????	?????
Soil Corrosion Resistance	?????	?????	?????	?????
Cost	Low	Lowest	High	Medium-High
Ease of Installation	High	High	Medium	Low

The advantages of HDPE pipes in the chemical industry are their comprehensive corrosion resistance, light weight and low cost, and they are particularly suitable for the transportation of corrosive media at medium and low pressures and room temperatures. However, for high temperature (>60°C), strong oxidants or non-polar solvents, it is necessary to carefully evaluate or select modified HDPE (such as cross-linked polyethylene PEX) and other materials (such as PTFE-lined steel pipes). In practical applications, it is recommended to combine parameters such as medium concentration, temperature, and pressure, and refer to chemical pipeline design specifications such as "HG/T 20538-2016" for selection.

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