Cracking Furnace Coil Tube (Coiltube) — High-Temperature Alloy Seamless Pipe for Pyrolysis Service

Product Overview

The Cracking Furnace Coil Tube (Coiltube) is a critical component manufactured by Wenzhou Jixing Metal Materials Co., Ltd., engineered specifically for use in steam cracking furnaces within the petrochemical and olefins production industry. These coils operate under extreme thermal and mechanical conditions, where they serve as the primary heat-exchange conduit for the pyrolysis of hydrocarbon feedstocks (e.g., naphtha, ethane, propane) into valuable monomers such as ethylene and propylene.

Unlike conventional straight pipe segments, coil tubes are cold-bent into precise helical or U-shaped geometries, enabling efficient heat transfer within the radiant zone of the cracking furnace. The product addresses longstanding challenges identified in the localization of high-performance furnace tubes — including premature oxidation, scale spallation, creep deformation, and thermal fatigue cracking — through advanced material selection, optimized manufacturing processes, and rigorous quality control protocols.

Material & Properties

Cracking furnace coil tubes are fabricated from specialized high-temperature austenitic stainless steels and nickel-based superalloys, each selected to meet the demanding requirements of sustained high-temperature service. The primary material grades include:

Key metallurgical properties of these materials include high tensile strength at elevated temperatures, excellent thermal stability, resistance to sulfur-induced hot corrosion, and controlled grain growth under prolonged thermal exposure. The materials are supplied in the solution-annealed condition (Annealed & Pickled, A&P) to ensure optimal microstructural homogeneity and mechanical performance.

Specifications

Parameter Specification
Product Name Cracking Furnace Coil Tube (Coiltube)
Product Code 1615
Material Grades HR3C, Alloy 617, HP-Nb, Alloy 60, 310S, Custom Alloys
Outer Diameter (OD) 45 mm – 114 mm (1.77 in – 4.49 in)
Wall Thickness (WT) 2.0 mm – 10.0 mm (0.079 in – 0.394 in)
Coil Bend Radius 1.5 m – 3.0 m (5.9 ft – 9.8 ft), customizable
Coil Length Up to 120 m (394 ft) per continuous coil
Applicable Standards ASTM A213/A213M, ASTM A336/A336M, ASME B36.19M, EN 10216-5, GB/T 14976
Surface Condition Pickled & Passivated (P&P), or Polished
Maximum Service Temperature Up to 1200°C (2192°F), depending on grade
Operating Pressure Up to 25 bar (363 psi) design pressure
Heat Treatment Solution Annealed at 1050°C – 1150°C, water or air quenched
Delivery Form Cold-bent coils, hot-bent coils, or straight lengths

Manufacturing Process

The production of high-quality cracking furnace coil tubes involves a multi-stage manufacturing sequence designed to ensure metallurgical integrity, dimensional accuracy, and long-term service reliability:

  1. Raw Material Preparation — High-purity nickel, chromium, and iron alloys are melted via Vacuum Arc Remelting (VAR) or Electro-Slag Remelting (ESR) to achieve homogeneous chemistry and eliminate inclusions. Billets are forged and rolled into seamless tube blanks.
  2. Piercing & Hot Rolling — Billets are heated to 1150°C – 1250°C and pierced through a mandrel die to form hollow tube blanks, followed by hot rolling to achieve near-final dimensions.
  3. Cold Drawing & Cold Sizing — Tubes undergo cold drawing and cold sizing operations to achieve precise outer diameter and wall thickness tolerances (typically ±0.05 mm for OD, ±0.05 mm for WT).
  4. Solution Annealing — Tubes are solution annealed at 1050°C – 1150°C followed by rapid quenching to dissolve carbides and restore full austenitic microstructure, ensuring maximum corrosion and creep resistance.
  5. Pickling & Passivation — The tube surface is chemically cleaned via acid pickling (HNO₃/HF blend) to remove oxide scale, followed by passivation to form a protective chromium oxide film.
  6. Cold Bending / Coiling — Tubes are cold-bent into helical or U-shaped coil geometries using CNC-controlled bending machines. The bending process is carefully controlled to avoid localized thinning, micro-cracking, or residual stress concentrations. Post-bend stress relief may be applied when required.
  7. Non-Destructive Testing (NDT) — All coils undergo 100% ultrasonic testing (UT) for wall thickness verification, eddy current testing (ECT) for surface and near-surface defect detection, and hydrostatic pressure testing per ASTM A213 requirements.
  8. Final Inspection & Packaging — Coils are inspected for dimensional accuracy, surface finish, and material certification traceability before protective packaging and shipment.

Applications

Cracking furnace coil tubes are indispensable components in the following industrial applications:

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system aligned with international standards, ensuring that every coil tube lot meets the stringent requirements of global petrochemical and energy sector specifications:

Unique Selling Points

Wenzhou Jixing Metal Materials Co., Ltd. addresses the critical challenges identified in the localization of cracking furnace coil tubes — including premature failure, excessive scale buildup, and limited domestic supply of high-performance alloys — through the following differentiators:

Technical Notes

Operators and procurement engineers are advised to consult with the manufacturer regarding specific material grade selection based on furnace operating parameters, including peak metal temperature (PMT), carbon deposition rate, sulfur content in feedstock, and expected campaign duration. Proper installation practices — including maintaining adequate tube-to-tube spacing, ensuring uniform heat flux distribution, and monitoring tube skin temperature (TST) and tube metal temperature (TMT) — are critical to maximizing coil tube service life and preventing premature degradation.