Stainless Steel Coil Tube for Tubular Furnace Overheated Steam Systems

1. Product Overview

The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product designed specifically for high-temperature and high-pressure process applications, particularly within Tubular Furnace Overheated Steam Systems used in petrochemical refining, naphtha cracking, and ethylene production facilities. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube is fabricated from austenitic stainless steel grades and formed into continuous helical coils to maximize heat transfer surface area within compact furnace configurations.

Coil tubes serve as critical heat exchange elements in tubular furnaces where process fluids—such as saturated steam, naphtha, or hydrocarbon mixtures—are superheated to extreme temperatures. The product is engineered to withstand thermal cycling, cyclic oxidation, and mechanical stresses associated with continuous industrial operation at elevated temperatures ranging from 400°C to over 900°C.

2. Material & Properties

2.1 Material Grades

Coil tubes are typically manufactured from the following austenitic stainless steel grades, selected based on operating temperature, corrosive environment, and mechanical requirements:

2.2 Key Mechanical Properties (Typical for SAE 310 at Room Temperature)

2.3 Corrosion & Oxidation Resistance

The high chromium content (≥ 24-25%) in grades such as SAE 310 forms a robust, self-healing chromium oxide (Cr₂O₃) protective layer on the tube surface, providing outstanding resistance to:

3. Specifications

Parameter Specification / Range
Outer Diameter (OD) 19.05 mm – 101.60 mm (¾" – 4")
Wall Thickness (WT) 1.20 mm – 6.35 mm (0.047" – 0.250")
Coil Inner Diameter (CID) 600 mm – 3,000 mm (depending on furnace design)
Coil Length (per spool) Up to 500 meters (continuous helical coil)
Manufacturing Standard ASTM A213 / ASTM A269 / ASME SA-213 / EN 10216-5
Welding Standard ASME B31.3 / ISO 15614 / EN ISO 6947
Heat Treatment Solution Annealed + Water Quenched (SA Condition)
Surface Finish Pickled and Passivated (P&P); Ra ≤ 0.8 μm available on request
End Condition Plain Ends / Beveled Ends / Flanged Ends
Applicable Pressure Rating Up to 40 MPa (5,800 psi) at design temperature
Applicable Temperature Range Cryogenic (−196°C) to 1,150°C (depending on grade)
Minimum Bend Radius 3D (three times the outer diameter)
Coil Pitch 50 mm – 150 mm (adjustable per furnace design)
Coil Turns Multiple continuous turns (single-piece coil, no intermediate welds)
Packaging Wooden crate / Steel frame with moisture-proof wrapping

4. Manufacturing Process

The production of stainless steel coil tubes for tubular furnace applications involves a multi-stage precision manufacturing process designed to ensure metallurgical integrity, dimensional accuracy, and long-term operational reliability:

  1. Raw Material Selection & Inspection: High-purity austenitic stainless steel seamless tubes are procured from certified mills, with incoming inspection including chemical composition analysis (OES), mechanical testing, and visual examination per ASTM A213.
  2. Hydrostatic Testing: Each tube undergoes hydrostatic pressure testing at 1.5 times the design pressure to verify weld integrity and freedom from internal defects.
  3. Coil Forming (Roll-Bending): Straight tubes are fed through a precision roll-bending machine with hydraulic control systems to form continuous helical coils. The bending process is carefully controlled to prevent wall thinning, ovality distortion, or work hardening beyond acceptable limits. Computerized CNC systems ensure consistent coil pitch and diameter throughout the entire length.
  4. Intermediate Heat Treatment (Optional): For thicker wall tubes or applications requiring enhanced formability, intermediate annealing may be performed during the coiling process to relieve residual stresses and restore ductility.
  5. Welding (if applicable): Where coil lengths require joining, automated orbital GTAW (Gas Tungsten Arc Welding) or TIG welding is employed with inert gas shielding to maintain the metallurgical integrity of the austenitic microstructure. Weld procedures are qualified per ASME Section IX.
  6. Post-Forming Heat Treatment: The completed coil is subjected to solution annealing (typically at 1050-1100°C for SAE 310) followed by rapid water quenching to dissolve carbide precipitates, restore full austenitic structure, and maximize corrosion resistance.
  7. Pickling & Passivation: Surface oxides formed during heat treatment are removed through acid pickling (nitric/hydrofluoric acid blend), followed by passivation treatment to establish a uniform, protective chromium oxide film on the surface.
  8. Final Inspection & Testing: Completed coil tubes undergo comprehensive quality assurance including dimensional verification (OD, WT, coil diameter, pitch), visual inspection (VT), ultrasonic testing (UT) for internal defects, and eddy current testing (ET) for surface and near-surface discontinuities.

5. Applications

Stainless steel coil tubes are indispensable components in a wide range of high-temperature industrial processes:

6. Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications to ensure product conformity and international acceptance:

Unique Selling Points: The coil tube product line from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through several key advantages: (1) Single-piece continuous coil construction eliminating intermediate welds that represent potential failure points in high-temperature service; (2) Advanced metallurgical control with solution-annealed microstructures ensuring maximum resistance to cyclic oxidation and thermal fatigue—the primary failure mechanisms identified in tubular furnace overheated steam coil damage analyses; (3) Customized coil geometry tailored to specific furnace designs and thermal load requirements; (4) Comprehensive traceability from raw material mill certificate through final shipment documentation; and (5) Proven field performance in demanding petrochemical and refining applications worldwide.

7. Engineering Notes on Damage Prevention

Based on technical analysis of overheated steam low-temperature coil tube failures in tubular furnaces, the following engineering considerations are integral to the product design philosophy:

This technical specification reflects industry best practices and applicable international standards for the design, manufacture, and application of stainless steel coil tubes in high-temperature tubular furnace systems. For specific project requirements, Wenzhou Jixing Metal Materials Co., Ltd. offers full engineering support, including material selection guidance, thermal analysis, and application-specific design optimization.