Wear & Corrosion Resistant Pipe for Chemical Industry

 

UPE (Ultra-High Molecular Weight Polyethylene) conveying pipes are a type of corrosion-resistant pipeline product using ultra-high molecular weight polyethylene as the pipe body material. They are specifically designed for conveying acids, alkalis, salt solutions, and various chemical media in the chemical industry. The molecular weight of UPE typically ranges from 1.5 million to 5 million, far exceeding that of ordinary polyethylene. Its ultra-long molecular chain structure endows the material with a series of performance characteristics distinct from conventional plastic pipes.

 

The suitability of UPE for conveying chemical media stems from the chemical inertness of its molecular structure. Polyethylene molecules are composed of carbon and hydrogen elements and do not contain polar groups, thus exhibiting good resistance to most acid, alkali, and salt solutions. Under normal temperature conditions, UPE shows good corrosion resistance to hydrochloric acid, sulfuric acid (concentration below 70%), nitric acid (concentration below 30%), sodium hydroxide, potassium hydroxide, sodium chloride, and many other salt solutions. This characteristic makes it one of the preferred materials for conveying corrosive chemical media.

 

II. Chemical Corrosion Resistance

 

Acid Resistance: UPE exhibits good resistance to inorganic acids at room temperature. It demonstrates good chemical stability in media such as hydrochloric acid (any concentration), phosphoric acid, and hydrofluoric acid (concentration below 60%). UPE remains stable with sulfuric acid at concentrations below 70% and temperatures not exceeding 60°C. It is also suitable for use with nitric acid at concentrations below 30% at room temperature. Note that strong oxidizing acids (such as concentrated sulfuric acid and concentrated nitric acid) may oxidize UPE under high temperature or high concentration conditions; therefore, specific concentration and temperature conditions must be evaluated during selection.

 

Alkali Resistance: UPE exhibits excellent resistance to alkaline media such as sodium hydroxide, potassium hydroxide, and ammonia. Within the temperature range of room to 60°C, UPE maintains stable performance in various alkaline solutions, making it suitable for alkaline solution transportation in chlor-alkali industries, alkali production industries, and wastewater treatment.

 

Salt Resistance: UPE exhibits excellent corrosion resistance to various salt solutions such as sodium chloride, potassium chloride, sodium sulfate, and magnesium sulfate. In fields such as salt chemical industry, seawater desalination, and lithium extraction from salt lakes, UPE pipes can be used to transport brine, brines, and high-salinity wastewater.

 

**Organic Solvent Resistance:** UPE is resistant to some organic solvents such as alcohols, esters, and ketones, but its resistance to non-polar solvents such as aliphatic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons is limited. When transporting mixed media containing such solvents, the risk of swelling and seepage must be assessed.

 

**Application Boundaries:** The chemical corrosion resistance of UPE is affected by the concentration of the medium, temperature, and contact time. Increased temperature generally reduces the material's corrosion resistance. Under high-temperature (above 80°C) or high-concentration strong oxidizing media conditions, a specific immersion test is recommended to verify its suitability.

 

**III. Physical and Mechanical Properties:**

**Abrasion Resistance:** UPE has a high level of abrasion resistance among plastic materials, superior to polytetrafluoroethylene (PTFE), nylon, and ordinary polyethylene. When transporting slurries or suspensions containing solid particles, UPE pipes can effectively resist particle erosion and extend the service life of the pipeline.

 

** Impact Resistance: UPE maintains high impact resistance even at low temperatures. Its impact strength remains a high proportion of its normal temperature value at -40℃, making it suitable for outdoor pipeline installations in cold regions.

 

Friction Coefficient: UPE pipes have smooth walls and a low friction coefficient, resulting in low fluid resistance and helping to reduce energy consumption during transport. The low friction coefficient also helps reduce media adhesion and deposition on the pipe wall.

 

Temperature Range: The standard operating temperature range for UPE pipes is -40℃ to +80℃. Outside this temperature range, the mechanical and chemical properties of the material may change, requiring specific evaluation.

 

IV. Connection Methods and Construction Considerations

 

Connection Methods: UPE pipelines are primarily connected via flanges, butt welds, and socket welds. Flange connections facilitate disassembly and maintenance, suitable for pipe sections requiring frequent disassembly and assembly; butt welds provide joints with the same strength as the pipe body, suitable for long-distance pipelines; socket welds are suitable for small-diameter pipes.

 

Thermal Expansion Compensation: UPE has a higher coefficient of linear expansion than metal pipes. In operating conditions with significant temperature variations, pipeline design must consider thermal expansion compensation measures. Expansion joints, bend compensation, or sliding supports can be used to absorb thermal displacement.

 

Support and Fixation: The spacing between pipeline supports should be determined based on the pipe diameter and medium temperature. UPE pipes have lower rigidity than metal pipes; therefore, the support spacing should be appropriately reduced to prevent pipe sagging and deformation.

 

Construction Precautions: During the cutting and welding of UPE pipes, the environment should be kept clean to prevent impurities from entering the pipeline system. Welding operations should be performed by qualified personnel, and welding parameters need to be adjusted according to pipe specifications and site conditions.

 

V. Application Scenarios

Acid Transportation: In industries such as metallurgy, electroplating, and battery manufacturing, UPE pipelines are used to transport acids such as sulfuric acid, hydrochloric acid, and nitric acid, as well as pickling waste liquids.

 

Alkali Transportation: In industries such as chlor-alkali industry, papermaking, and textile printing and dyeing, UPE pipelines are used to transport alkaline solutions such as sodium hydroxide and potassium hydroxide.

 

Salt solution transportation: Used in salt chemical industry, seawater desalination, lithium extraction from salt lakes, and other fields to transport brine, brines, and high-salinity wastewater.

 

Chemical wastewater treatment: Used in wastewater treatment systems of chemical industrial parks to transport corrosive wastewater containing acids, alkalis, and salts.

 

Slurry transportation: Used in mining, metallurgy, and other industries to transport acidic or alkaline slurries containing solid particles.