Steel-lined Plastic Pipe

Product Introduction

Steel-lined plastic pipe (plastic-lined composite pipe) uses carbon steel pipe as the base material, with a PE, PO, or PP thermoplastic lining applied internally via rotational molding / cold drawing. The exterior retains the mechanical strength of the steel pipe, while the inner plastic layer isolates corrosive media, combining the high strength of steel with the acid and alkali corrosion resistance of plastic. The complete set of lined pipe fittings includes: lined elbows, lined tees, lined crosses, lined reducers, and lined flanges—the entire piping system is fully lined with an anti-corrosion layer, with no exposed metal contacting the media. All connections are flanged; field welding is strictly prohibited (welding will burn and damage the internal plastic lining). The smooth inner surface resists scaling, is hygienic and non-toxic, and withstands weak acids, weak alkalis, salt solutions, and wastewater media. Widely used in chemical plants, power plant chemical water systems, wastewater treatment, pharmaceuticals, water supply and drainage, and desulfurization and denitrification pipelines.

Complete Fittings List (Fully Lined)

• Lined 90°/45° elbows: change pipeline direction, flanged connection, complete internal lining layer
• Lined tees (equal / reducing): for flow branching and merging
• Lined crosses (equal / reducing): for four-way media distribution
• Lined reducers (concentric / eccentric): for pipe diameter transitions; eccentric preferred for horizontal liquid service
• Lined flanges: fully lined on the inner face of the flange, with gaskets matched to the anti-corrosion service conditions

Application Scenarios

1. Chemical industry: pipelines for dilute acids, alkali solutions, salt solutions, and chemical wastewater
2. Power plants: chemical water, desulfurization and denitrification process pipelines
3. Environmental wastewater treatment: sewage, reclaimed water, and exhaust gas scrubbing circulation pipelines
4. Pharmaceutical and food industries: pure water and process media delivery (food-grade PE lining)
5. Municipal water supply and drainage: drinking water and industrial circulating water pipelines

Technical Parameters

1. Base steel pipe material: Q235B, 20# seamless steel pipe
2. Lining material selection
   • PE (polyethylene): -25~80°C, for water supply and drainage, wastewater, and food media; cost-effective
   • PO (polyolefin): -20~90°C, acid and alkali resistant, can withstand negative pressure; mainstream choice for chemical desulfurization wastewater
   • PP (polypropylene): -10~100°C, chemical corrosion resistant; for pharmaceutical and chemical pipelines
3. Lining thickness: 2-5 mm, customized according to DN specification; bubble-free, no blistering, no delamination
4. Nominal diameter: DN25-DN1000
5. Nominal pressure: standard PN10, PN16; up to PN25 on request
6. Working temperature: -20°C to 90°C (PO/PE), PP up to 100°C; do not exceed temperature limits
7. Connection method: flanged connection (all flanges in the fitting set are fully lined); welding is not permitted
8. Length: standard single pipe 6 m; custom short sections and fitting stub pipes available
9. Inspection: spark testing of lining for leaks, thickness measurement, and visual inspection for cracks or delamination

10. Important Selection & Installation Notes

    1. ❗Field welding of pipes and fittings is strictly prohibited—high temperatures will burn and destroy the internal plastic lining; all connections must be flanged;
    2. Do not select PE for high-temperature media; prioritize PO or PP materials;
    3. For negative pressure conditions, use PO lining; PE is not suitable for high negative pressure;
    4. Use PTFE gaskets to match the application; avoid ordinary rubber gaskets that may be corroded by the media.