Power Plant and Industrial Piping 3LPE Coating Line DN219-1220 mm
Overview
Plant piping and power station piping are fabricated in a shop and delivered as spools, and that single difference drives most of the design. A spool may be a straight length, or it may carry a flange, an elbow or a tee, which means the conveyor has to accommodate an end that is larger than the pipe and the coating has to stop at a controlled distance from that end. The diameter band itself is wide but not extreme, roughly 8 to 48 inch, while the wall thickness band is much wider than on a pipeline, and heating a 40 mm wall takes a very different time from heating an 8 mm wall of the same diameter. The line therefore computes heating from the measured wall thickness rather than from a diameter table. The third constraint is the building. Prefabrication shops are organised around a crane and a bay, so the coating line is laid out to the available length and clear height instead of asking the customer to rebuild. The result is a compact line that holds several specifications side by side and reports a spool rather than a metre, which matches how the shop is actually paid.
Key Configuration
Blast chamber with two 75 kW wheels, with the chamber shortened rather than the wheels repositioned, so that spool work of 3 to 12 m stays inside the blast zone. Induction heater in the 500 to 750 kW band with liquid-cooled power unit, closed-loop surface temperature measurement and a heating table entered by wall thickness. Twin extruders at 1,200 kg/h with a dedicated adhesive head and a 1000 mm T-die, screw and barrel in 38CrMoAlA nitrided 0.4 to 0.7 mm above HV 740. Gun array with redundant positions and cartridge recovery. Roller conveyor with flange relief and adjustable mask position. Water spray cooling with recycle, plus an air pre-cooling zone ahead of the spray for heavy wall spools. Well-known brand PLC with a recipe library by diameter and wall thickness band, producing a spool record rather than only a batch record.
Process Flow
A spool is received from the fabrication bay with its weld and its end preparation already complete, so it is inspected and measured rather than aligned. Wall thickness is taken at several points and the heating recipe is selected from the measured value, not from the nominal schedule. The spool is loaded onto a roller conveyor with clearance for flanges and fittings, and the uncoated length is set by a mechanical mask rather than by operator judgement. External shot blasting to Sa 2.5 or better follows, and the blast chamber is sized for spool work so that a shorter length does not leave the wheels throwing past the work. The pipe is purged and the ends are masked. Induction heating brings the surface to the coating window with the coil set back from any flange, temperature is measured on the pipe, and epoxy powder, adhesive and polyethylene follow. Cooling is by water spray with a recycle tank, with air pre-cooling ahead of the spray when the wall is thick. Cutback is cut to the drawing dimension, the coating is holiday tested and thickness gauged, and the spool is released with a record that travels with it to erection.
Applications
Power station main steam and reheat piping; circulating water and cooling water piping; boiler feed and condensate lines; industrial utility piping in chemical, steel and cement plants; plant air and instrument air headers; process piping spools in refineries and petrochemical units; prefabricated pipe racks and manifolds. The buyer is almost always a fabrication shop whose output feeds an erection schedule, and a missed spool stops a crane. We therefore quote the machine with spare capacity at the mask and cutback stations rather than only at the coating station, because those two stations are the ones that hold up a schedule.
| Item |
Specification |
| Model / Type |
3LPE Coating Line for power plant and industrial process piping spools |
| Pipe Diameter Range |
DN219-1220 mm (8 to 48 inch) |
| Typical Specification |
external three-layer polyethylene on prefabricated spools, not only on line pipe |
| Pipe Spool Length |
3-12 m, including spools with flanges or fittings at one end |
| Pipe Wall Thickness |
6 to 40 mm |
| Coating Capacity |
up to 500 m²/h at nominal wall thickness |
| Surface Preparation |
shot blasting to Sa 2.5 or better, ISO 8501-1 |
| Wall Thickness Handling |
heating time computed from measured wall thickness, not from diameter alone |
| Heating |
intermediate frequency induction, 500 kW to 750 kW class |
| Extruder |
with dedicated adhesive head and 1000 mm T-die |
| Spray Guns |
16 guns with four redundant positions and cartridge recovery |
| Powder Recovery |
95 percent or above with automatic filter cleaning |
| Cooling |
water spray with recycle, air pre-cooling ahead of the spray for thick wall pipe |
| Conveyor |
roller conveyor with flange clearance so a spool end can pass without fouling |
| Tolerance Control |
coating thickness and cutback measured and recorded per spool |
| PLC and HMI |
Well-known brand, recipe per diameter and wall thickness band, batch records for QA review |
| Operators per Shift |
4 |
| Dust Extraction |
three-stage, sized for continuous shop duty |
| Warranty |
12 months machine, 24 months drive train |
| Certification |
ISO 9001, Shandong First-Set Technical Equipment award |
Main Equipment List and specification
| No. |
Name |
Specification |
| A. Surface Cleaning Equipment |
| 1 |
Steel pipe conveyor |
Adjustable speed and angle, pipe uploading and unloading controlled by PLC |
| 2 |
Shot blasting machine |
|
| 3 |
Cyclone dust collector |
High efficient downwind cyclone dust removal |
| 4 |
Impulse cartridge dust collector |
|
| 5 |
Centrifugal fan |
|
| 6 |
PLC control system |
Automatic control of the line |
| B. Coating Equipment |
| 1 |
Spiral pipe conveyor |
Adjustable speed and angle |
| 2 |
Induction heating machine |
|
| 3 |
Powder spraying device |
Spraying thickness 80-800μm |
| 4 |
Automatic feeder&dryer |
|
| 5 |
SJ-PE Extruder |
|
| 6 |
SJ-AD Extruder |
|
| 7 |
Adhesive extruder die mould |
High quality die steel |
| 8 |
PE sheet extruder die mold |
High quality die stee |
| 9 |
Adhesive/PE sheet coating device |
Pressing roller with silicon coating and internal cooling |
| 10 |
Environmental Protection Ventilation equipment |
|
| 11 |
Cooling Spray equipment |
|
| C.Platform Equipment |
| 1 |
Steel pipe platform |
High quality |
| D.Groove Equipment |
| 1 |
PE Beveling Machine |
Steel brush disk, |
| 2 |
Hydraulic Lifting and Turning Machinery |
For lifting and turning the pipe |
| 3 |
Hydraulic Equipment |
|
A power plant or process plant consumes coated pipe as spools, not as line pipe, and a spool can carry a flange or a fitting on one end, which changes how it can be conveyed and how the uncoated length is controlled.
Plant piping often mixes wall thickness far more widely than a pipeline does, so heating has to be computed from the measured wall thickness rather than from diameter alone.
The coating work sits inside a prefabrication shop with a fixed crane and a fixed bay length, so the line is designed to fit the building rather than the other way round.
Because spools flow to erection on a schedule, the value of the line is measured in spool turnaround time, not in metres per hour.
Thermal service piping and utility piping are on the same contract but not on the same specification, so the line is set up to hold several recipes side by side.
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: DN219-1220 mm (8 to 48 inch)
2. Processing capacity: ≥250m2/h
3. Cleaning level: ≥Sa2.5
4. Materials for production: epoxy powder, adhesive, polyethylene
Standards Compliance
External three-layer coating follows ISO 21809-1, with GB/T 23257 for Chinese domestic plants. Where the plant is exported or built to a European specification, DIN 30670 is commonly named. Surface condition is prepared to ISO 8501-1. Because plant piping is frequently mixed specification, we quote coating thickness ranges against each service rather than a single figure, and the recipe library keeps them separate so the wrong one cannot be selected by accident.
Service & Support
Site supervision by 2 engineers over 15 to 25 days, timed to the shop's own commissioning rather than to a production milestone. Training focuses on the heating table by wall thickness and on mask control, since those two settings account for most of the variation between spools. English-language documentation includes layout, foundation, electrical, PID and manuals. Critical spares by air within 72 hours, with induction coil and mask parts held as stock items because a damaged mask stops the shop. Machine warranty 12 months, drive train 24 months.
Why Choose Qingdao Huashida
We build coating lines for pipeline mills and equipment for our own pipeline companies, and a large share of that work is thick wall and heavy section rather than thin line pipe. Our anti-corrosion equipment has been recognised on the Shandong Province First-Set Technical Equipment list, and our internal and external coating range covers the same diameters a prefabrication shop works in. That matters because heating a heavy wall spool efficiently is a different problem from heating line pipe of the same diameter.
---FAQ---
Q: Can the line coat spools that already carry a flange?
A: Yes. The conveyor is built with flange relief and the uncoated length is controlled by a mechanical mask, so the coating stops at the drawing dimension without an operator judgement call.
Q: How is heating controlled when wall thickness varies?
A: Wall thickness is measured at several points on the spool and the heating recipe is selected from that measurement. Diameter alone is not used, because it does not determine heat input on heavy wall pipe.
Q: Will the line fit our existing prefabrication bay?
A: The layout is quoted against your building, and in most cases it is the blast chamber and the cooling tunnel that set the length requirement. We ask for bay length and clear height before quoting.
Q: What is the typical coating thickness for plant piping?
A: Three-layer systems on plant piping usually run 2.5 to 3.7 mm total, but the figure is set by the service and the project specification, and we keep separate recipes where several specifications share a line.
Q: Does the line handle both thermal service and utility piping?
A: Yes, as separate recipes. Thermal service pipe and utility pipe can sit on different specifications, and the recipe library keeps them apart so the wrong one cannot be selected.
Q: How is a spool identified in the records?
A: Each spool carries its own release record with blast grade, coating thickness, cutback dimension and holiday test result, which is what the shop needs to hand the spool to erection.
Q: What is the operating crew?
A: Four operators per shift for this diameter range, including one on the mask and cutback stations.
Q: How long is installation and commissioning?
A: Installation and commissioning normally run 15 to 25 days, and it is scheduled to finish before the shop needs to release coated spools rather than before a fixed project date.
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