Advantages and uses of flange-connected plastic-coated steel pipes

Flange-connected plastic-coated steel pipes are a type of pipeline system connected by steel flanges. They are composite pipes that combine the strength of steel pipes and the corrosion resistance of plastic coatings. They are widely used in fields with high requirements for corrosion resistance, high pressure resistance, and long life. This article mainly discusses the advantages and uses of flange-connected plastic-coated steel pipes.

Structural composition:

It consists of plastic-coated steel pipes and flange connectors. Plastic-coated steel pipes are based on high-quality carbon structural steel or low-alloy steel, and the inner and outer plastic coatings are generally polymer materials such as polyethylene and epoxy resin. Flange connectors are usually made of carbon steel or stainless steel, and the two sections of steel pipes are connected together by welding or bolting.

Advantages of flange-connected plastic-coated steel pipes:

1. Corrosion resistance: The plastic coating isolates the medium from the steel pipe, extending its service life.
2. High strength: Steel flange connection, high pressure bearing capacity (up to 10MPa or more).
3. Good sealing: Bolt fastening and sealing gaskets can effectively prevent leakage of pipeline systems and ensure stable delivery of fire water and other media.
4. Convenient installation and maintenance: Flange connection is connected by bolts during installation, which is convenient for disassembly and reassembly, and is convenient for later maintenance, replacement of parts or expansion and transformation of pipeline systems.
5. Adapt to various environments: The plastic coating makes the steel pipe corrosion-resistant, wear-resistant and impact-resistant. The flange connection can withstand high pressure and can be used in fire protection systems with different pressure levels and harsh environments. Different coatings (PE/EP/PO, etc.) can also be selected according to the medium.

Installation points:

• Flange welding: Before welding, ensure that the end face of the steel pipe is flat and free of burrs. Control the current, voltage and welding speed during welding to ensure that the weld is full and defect-free. After welding, check the verticality of the flange and the axis of the steel pipe and the coaxiality of the flange bolt holes at both ends.

• Sealing treatment: Select a suitable sealing gasket, ensure that the gasket is in the correct position and without damage during installation, and tighten the bolts evenly so that the gasket can fully play its sealing role.

• Pipeline pairing: During installation, accurately align the plastic-coated steel pipe to be connected with the flange to align the bolt holes, avoid forced pairing to damage the plastic coating or cause deformation and stress on the flange.

Application areas of flange-connected plastic-coated steel pipes:

1. Municipal water supply and drainage projects

Urban water supply network: The water supply and drainage field can be used for urban tap water transportation. The plastic coating layer (PE/EP) prevents scaling and rust on the inner wall of the pipe to ensure water quality safety.
Sewage treatment system: Acid and alkali resistant, anti-microbial corrosion, suitable for sewage transportation and reclaimed water reuse.
Firefighting pipeline system: The internal and external plastic-coated steel pipes meet the standards, are resistant to high pressure and have excellent fireproof performance. Whether it is a fire hydrant system or an automatic sprinkler fire extinguishing system, it can reliably transport fire water.

Applicable coatings: polyethylene (PE), epoxy resin (EP)

2. Petroleum and chemical industries

Petroleum pipelines: oil-resistant and chemical medium-resistant, suitable for crude oil and refined oil pipelines.
Chemical fluid transportation: resistant to acid, alkali and salt spray corrosion, used in pickling lines, chemical wastewater treatment, etc., can be used to transport corrosive media such as acid, alkali and salt.
Natural gas gathering and transportation: some plastic-coated steel pipes can be used for low-pressure gas transportation (must comply with relevant explosion-proof standards).

Applicable coatings: epoxy resin (EP), polyolefin (PO)

3. Power and energy engineering

Power plant circulating water system: resistant to seawater and chloride ion corrosion, used for cooling water pipelines.
Cable protection sleeve: plastic-coated steel pipe has both mechanical protection and insulation properties (flame-retardant coating required).
Coal mine underground water supply/drainage: impact resistance, anti-static, in line with coal mine safety standards (MT/T 181).

Applicable coatings: epoxy coal tar (suitable for burial), flame-retardant polyethylene (PE)

4. Marine and ship engineering

Seawater desalination pipeline: resistant to chloride ion corrosion, suitable for reverse osmosis (RO) system.
Ship ballast water pipe: meets IMO standards to prevent marine organisms from attaching.
Port terminal water pipe: salt spray resistant, UV resistant, suitable for coastal environment.

Applicable coating: ultra-high molecular weight polyethylene (UHMW-PE), epoxy powder (FBE)

5. Industrial pipeline system

Food/pharmaceutical industry: food-grade epoxy coating on the inner wall, in line with FDA standards, to ensure fluid hygiene.
Paper mill pipeline: acid and alkali resistant, pulp wear resistant, used for slurry transportation.
Heating, ventilation and air conditioning (HVAC): anti-condensation, good thermal insulation performance, suitable for hot and cold water circulation system.

Applicable coating: epoxy resin (EP), polypropylene (PP)

6. Mining and metallurgical industry

Slurry transportation pipeline: strong wear resistance, suitable for gold, iron ore and other slurry transportation.
Blast furnace coal injection pipeline: high temperature resistant, anti-static, to ensure safe production.
Tailings discharge pipe: corrosion resistant, anti-sedimentation deformation, used for mine wastewater treatment.

Applicable coatings: wear-resistant ceramic composite coating, ultra-high molecular weight polyethylene (UHMW-PE)

7. Agricultural irrigation system

High-standard farmland irrigation: resistant to fertilizer and pesticide corrosion, extending the life of the pipeline.
Greenhouse water pipe: anti-ultraviolet aging, suitable for long-term outdoor use.
Applicable coatings: polyethylene (PE), polyvinyl chloride (PVC)

Conclusion:

Flange-connected plastic-coated steel pipes are widely used in municipal, chemical, electric power, marine, industrial, mining, agriculture and other fields, especially for corrosive media, high-pressure environments, and long life requirements. When selecting, the coating material should be matched according to the specific working conditions (medium, temperature, pressure), and ensure compliance with relevant standards such as ASTM, ISO, GB/T.

Read more: How are pipe flanges manufactured? or Pipe elbow and flange welding connection