3LPP Coating Line Three Layer Polypropylene DN219-1720 mm

The anti-corrosion coating processing line includes:
-steel pipe transmission system
-Internal and external shot blasting system
-dust collection system
-pipe heating system
-electrostatic spraying system
-PE coating system
-water cooling system
-end cutting system
-hydraulic and pneumatic system
-testing system
-electronic control system

Pipe is blasted to Sa 2.5 or better and the surface profile checked, since adhesion on PP systems is less forgiving of a weak profile. Internal air purging and end masking follow. Induction heating brings the wall to the coating window, which for polypropylene sits higher than for polyethylene and is held more tightly. Epoxy powder is applied electrostatically, the copolymer adhesive is extruded through its own head, and the polypropylene topcoat is laid by spiral wrap from the side extruder. Cooling is deliberately staged: the pipe passes through successive water spray zones rather than a single drench, so that the temperature gradient through the coating stays inside the limit the material can tolerate. Joint cutting, end bevelling and holiday detection close the cycle.

1. Pipe diameter: DN219-1720 mm (8 to 68 inch)
2. Processing capacity: ≥250m²/h
3. Cleaning level: ≥Sa2.5
4. Materials for production: epoxy powder, adhesive, polyethylene

Standards Compliance

Three-layer polypropylene coating is normally specified under ISO 21809-1 or a project derivative of it, with layer thicknesses and test frequencies named by the owner. GB/T 23257 covers domestic Chinese requirements and includes provisions for PP systems. Steel surface preparation follows ISO 8501-1. Where a project cites an owner specification, our quotation lists the clauses we meet and any we do not, in writing, before the order.

Applications

Oil gathering and transport lines carrying warm crude; steam injection and thermal recovery lines; heavy oil field surface pipe; high-temperature hot water transmission; industrial process lines where the design temperature exceeds the polyethylene limit. Buyers specifying this line are usually working from a design temperature, not a material preference, and the conversion is best done early: the topcoat material drives the extruder profile, the die and the cooling schedule, so a late change from PE to PP is a redesign rather than an option.

Service & Support

Site supervision by 2 to 3 engineers across 15 to 30 days, with the first trial pipe coated jointly and sectioned for inspection. Training covers the PP to PE structure switch, which is the operation most likely to cause trouble if performed by memory rather than from the recipe. English documentation covers layout drawings, foundation, electrical, PID and manuals. Emergency spares leave by air within 72 hours. Warranty: 12 months machine, 24 months drive train, and a two-year package of wear parts on request.

Why Choose Qingdao Huashida

We build coating lines for our own coating plant group as well as for customers, so the difference between a PE and a PP cooling schedule is something we work with in production rather than only in the design office. Our three-layer anti-corrosion line holds a Shandong Province First-Set Technical Equipment award, and we hold 58 invention patents and 38 software copyrights. For a plant converting from PE to PP, we will quote a structure switch kit rather than a new line, and we will say plainly if your existing conveyor and blast chamber are already adequate for the larger pipe sizes.

---FAQ---

Q: When should we choose 3LPP instead of 3LPE?

A: When the design temperature of the line exceeds the polyethylene service ceiling. If your operating temperature stays below that figure, PE is the more economical and more widely available choice, and we will tell you so rather than upselling.

Q: Can the same line produce both 3LPE and 3LPP?

A: Yes. The conveyor, blast chamber, heating and handling sections are shared. What changes is the extruder profile, the die, the cooling schedule and the recipe file, which is why we quote a structure switch kit for plants that need both.

Q: Why is the cooling section staged?

A: Polypropylene shrinks on a different curve from polyethylene. A single water drench cools the outside faster than the inside, and the resulting stress shows up as distortion or loss of bond. Staging the water spray holds the gradient within the limit the material tolerates.

Q: How tight is the heating tolerance?

A: Tighter than for polyethylene. The window is narrower, so we measure wall temperature rather than relying on coil power alone, and the PLC holds the recipe within that band.

Q: What surface preparation is required?

A: Sa 2.5 minimum and we recommend Sa 3 for PP systems. Anchor profile matters more than on PE because the primer and adhesive have to carry load across a wider temperature range.

Q: What pipe size range does the line cover?

A: DN219 mm to DN1720 mm, which is 8 inch to 68 inch, with a clear height of 8 m in the workshop.

Q: What are the main running costs?

A: Polypropylene granules, epoxy powder and abrasive consumption. Abrasive is usually the largest controllable item, and our blast head geometry is set to reduce collision between thrown and returning shot, which is where most abrasive is wasted.

Q: What is the delivery time?

A: Generally 60 to 90 days from deposit and approval of drawings, with installation and commissioning adding 15 to 30 days on site.