304TP / 316TP Seamless Stainless Steel Coil Tubes for Economizers and Low-Pressure Heaters in Thermal Power Plants

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 130) manufactures high-performance seamless stainless steel coil tubes specifically engineered for economizer sections and low-pressure feedwater heaters in coal-fired thermal power generation facilities. These coil tubes are designed to operate reliably in feedwater environments with temperatures ranging from 150°C to 300°C (302°F–572°F), where strict oxygen content control and resistance to Flow Accelerated Corrosion (FAC) are critical to maintaining long-term integrity and system efficiency.

Coil tubes offer superior flexibility and compact installation geometry compared to straight tube assemblies, making them ideal for space-constrained economizer banks and LP heater tube bundles. The seamless construction eliminates weld seams that could serve as initiation sites for corrosion under aggressive feedwater conditions, providing an uninterrupted corrosion-resistant barrier throughout the tube's length.

Material and Properties

Grade 304TP (UNS S30403 / EN 1.4301)

Grade 316TP (UNS S31603 / EN 1.4401)

Anti-FAC Design Considerations

Flow Accelerated Corrosion (FAC) is a major degradation mechanism in thermal power plant feedwater systems, particularly at temperatures above 150°C (302°F) where high-velocity water flow at bends, reducers, and tube entries accelerates oxide layer removal. The "TP" (Tube Plant) designation ensures these grades meet the tighter impurity specifications required for power plant tube applications, including:

Specifications

Parameter Specification Standard Reference
Outer Diameter Φ19.05 mm (0.75 in) to Φ60.3 mm (2.375 in) ASTM A213 / EN 10216-5
Wall Thickness 0.8 mm (0.031 in) to 4.0 mm (0.157 in) ASTM A213 / EN 10216-5
Coil Inner Diameter 300 mm (11.8 in) to 1,500 mm (59.1 in) Per customer requirement
Coil Length 5 m (16.4 ft) to 50 m (164 ft) per coil Per customer requirement
Material Grades 304TP (UNS S30403) / 316TP (UNS S31603) ASTM A213 TP304/TP316
Manufacturing Method Pillared-rod hot extrusion + cold drawing ASTM A213 / EN 10216-5
Surface Finish 2B cold-rolled / Bright annealed / Pickled & passivated ASTM A240
Operating Temperature 150°C – 300°C (302°F – 572°F) Application-specific
Feedwater Oxygen Content ≤0.002 mg/L (ppb) dissolved O₂ IEA Power Plant Practice
Maximum Feedwater Velocity ≤3.0 m/s (9.8 ft/s) EPRI FAC Guidelines
Tolerance on OD ±0.05 mm (±0.002 in) EN 10216-5
Tolerance on Wall Thickness ±10% of nominal ASTM A213
Coil Bend Radius ≥5× tube OD (minimum) Per design specification
End Condition Plain cut / Beveled / Threaded (on request) Per customer requirement

Manufacturing Process

  1. Raw Material Selection: Vacuum Induction Melting (VIM) or VIM + Electro-Slag Remelting (ESR) of 304TP/316TP steel ingots with certified chemical composition meeting ASTM A213 TP304/TP316 specifications. Pillared rod billets are produced to minimize internal porosity and segregation.
  2. Hot Extrusion: Pillared rod billets are heated to 1,050–1,200°C (1,922°F–2,192°F) and extruded through precision dies to produce seamless tube blanks with controlled wall thickness and outer diameter.
  3. Heat Treatment: Solution annealing at 1,010–1,120°C (1,850°F–2,048°F) followed by controlled cooling to achieve a fully austenitic, carbide-free microstructure with optimal corrosion resistance.
  4. Cold Drawing: Tubes are cold-drawn through calibrated dies and mandrels to achieve precise dimensional tolerances (±0.05 mm on OD) and improved mechanical properties while maintaining the austenitic grain structure.
  5. Pickling and Passivation: Tubes are acid-pickled (nitric/hydrofluoric acid blend) to remove mill scale and oxidation, followed by passivation to establish a uniform, protective chromium oxide surface layer.
  6. Coil Forming: Straight tubes are precision-coiled on CNC-controlled forming equipment with controlled bend radii (≥5× OD) to avoid wall thinning, ovality, or residual stress concentrations that could accelerate FAC.
  7. Final Inspection: Each coil undergoes 100% ultrasonic testing (UT) for internal defects, eddy current testing (ECT) for surface/subsurface discontinuities, and hydrostatic pressure testing per ASTM A213 requirements.

Applications

Primary Application: Thermal Power Generation

Secondary Applications

Quality Certifications and Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and standards compliance:

Unique Selling Points

1. TP-Grade Chemistry for FAC Resistance: Our 304TP and 316TP seamless tubes are produced to tighter impurity specifications than standard 304/316 grades, with reduced carbon, nitrogen, sulfur, and phosphorus content. This minimizes carbide precipitation and sensitization, directly addressing Flow Accelerated Corrosion concerns in high-temperature feedwater systems.

2. Seamless Construction — Zero Weld Weak Points: Unlike welded coil tube alternatives, our seamless tubes provide a homogeneous material structure throughout the entire tube length, eliminating weld seams that serve as preferential FAC initiation sites under high-velocity feedwater flow.

3. Precision Coiling with Controlled Residual Stress: CNC-controlled coiling equipment ensures uniform bend radii and minimal residual stress, reducing the risk of stress-corrosion cracking and FAC at coil bends.

4. Full Traceability and Documentation: Every coil is accompanied by complete mill test certificates with heat-number traceability, chemical composition analysis, mechanical property data, and non-destructive testing reports, ensuring full compliance with power plant procurement requirements.

5. Application-Specific Engineering Support: Our technical team provides FAC risk assessment support, material selection guidance (304TP vs. 316TP), and coil geometry optimization for specific economizer and LP heater designs, drawing on deep expertise in thermal power plant applications.

Ordering Information

Wenzhou Jixing Metal Materials Co., Ltd. offers flexible ordering options including: