Stainless Steel Coil Tube (Coiltube) — Industrial Grade Helically Wound Tubing

Product Overview

The Stainless Steel Coil Tube (Coiltube) is a precision-engineered helically wound tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed for demanding industrial environments, this coil tube is primarily employed as an external circulation or heat exchange element within stainless steel purification kettles, chemical reactors, and high-purity processing vessels. The product is engineered to withstand continuous thermal cycling, corrosive media exposure, and elevated internal pressures while maintaining structural integrity and dimensional accuracy over extended service life.

Based on extensive field analysis and case studies—including documented failure investigations of external coil tubes in stainless steel purification kettles where cracking and leakage were identified—this product incorporates enhanced metallurgical specifications and manufacturing tolerances to mitigate stress corrosion cracking (SCC), fatigue failure, and thermal mismatch-induced degradation. The design philosophy integrates lessons learned from real-world failure modes to deliver a product with superior reliability and longevity.

Material & Properties

Base Material Grades

Mechanical Properties (Typical — Annealed Condition)

Corrosion Resistance Characteristics

Specifications

Parameter Specification Standard Reference
Outer Diameter (OD) 6.0 mm – 50.8 mm (1/4" – 2") ASTM A269 / ASME SA-269
Wall Thickness (WT) 0.5 mm – 3.0 mm (0.020" – 0.118") ASTM A269 / ASME SA-269
Coil Pitch 10 mm – 50 mm (adjustable per application) Customer-specific
Coil Diameter (Mean) 50 mm – 500 mm (adjustable per application) Customer-specific
Coil Length 0.5 m – 20 m (custom fabrication available) Customer-specific
End Condition Plain end, threaded (BSP/NPT), flanged, or socket-weld ASME B1.20.1 / ASME B16.5
Surface Finish BA (Bright Annealed) Ra ≤ 0.4 μm; EP Ra ≤ 0.25 μm; Pickled Ra ≤ 0.8 μm ASTM A473 / GB/T 14976
Maximum Operating Temperature −196°C to +870°C (grade-dependent) —
Maximum Operating Pressure Up to 25 MPa (design-dependent; subject to ASME Section VIII) ASME BPV Section VIII Div. 1
Welding Method TIG (GTAW) with argon shielding; orbital welding for continuous joints ASME Section IX
Acceptable Standards ASTM A269, ASME SA-269, EN 10216-5, GB/T 14976, JIS G3459 Multi-standard compliance
Packing Wooden crate with VCI (Volatile Corrosion Inhibitor) wrapping; seaworthy export packaging ISO 4180

Manufacturing Process

Step 1 — Raw Material Selection and Incoming Inspection

Only certified seamless stainless steel tubes from approved mills are sourced. Each lot undergoes incoming inspection including chemical composition verification (spectroscopic analysis per ASTM E415), mechanical property testing (tensile and hardness per ASTM A370), and surface quality assessment. Mill test certificates (MTCs) conforming to EN 10204 Type 3.1 are required for all incoming materials.

Step 2 — Tube Cutting and End Preparation

Tubes are precision-cut to required lengths using abrasive or saw-cutting methods to avoid work hardening. End faces are deburred, chamfered, and cleaned to ensure proper fit-up for subsequent welding and assembly operations. Critical dimensions are verified using calibrated micrometers and bore gauges.

Step 3 — Coil Forming (Cold Bending / Helical Winding)

The straight tube is helically wound around a precision-machined mandrel using a CNC-controlled coil forming machine. The winding parameters—including coil pitch, mean coil diameter, and number of turns—are programmed to achieve exact dimensional accuracy within ±0.5 mm tolerance. Cold forming introduces controlled plastic deformation; the tube retains its metallurgical properties without requiring post-forming annealing for most grades.

Step 4 — Post-Forming Stress Relief (Where Applicable)

For applications involving elevated temperature service or cyclic loading, the formed coil may undergo solution annealing at 1050–1150°C followed by controlled air or water quenching. This eliminates residual stresses introduced during cold forming and restores full ductility and corrosion resistance.

Step 5 — Welding and Assembly

End connections are fabricated using Tungsten Inert Gas (TIG / GTAW) welding with high-purity argon shielding gas (≥ 99.995%). Orbital welding equipment ensures consistent weld quality for repetitive joints. Weld parameters are qualified per ASME Section IX, and all welders hold valid certifications. Post-weld inspection includes visual examination (VT) and, where required, dye penetrant testing (PT) or radiographic testing (RT).

Step 6 — Surface Treatment and Finishing

Depending on the application grade, the finished coil tube undergoes one of the following surface treatments:

Step 7 — Final Inspection and Quality Assurance

Each finished coil tube undergoes comprehensive final inspection including:

Applications

Primary Applications

Case Study Insight — Cracking and Leakage Prevention

Analysis of failure cases involving external coil tubes in stainless steel purification kettles has identified common root causes including: (1) chloride-induced Stress Corrosion Cracking (SCC) due to insufficient alloy grade selection; (2) thermal fatigue cracking from mismatched thermal expansion between the coil tube and kettle body; (3) weld-induced sensitization leading to intergranular corrosion; and (4) mechanical over-stressing during installation or thermal cycling. This product addresses these failure modes through: material grade optimization (316L as the recommended minimum for chloride-exposed service), controlled post-forming heat treatment, qualified welding procedures with low-heat-input parameters, and rigorous NDT protocols. The design incorporates expansion joints and flexible connections at kettle interfaces to accommodate differential thermal movement.

Quality Certifications

Product Standards Compliance

Manufacturing and Quality Management Certifications

Documentation and Traceability

Unique Selling Points

Ordering Information

When specifying or ordering Stainless Steel Coil Tubes from Wenzhou Jixing Metal Materials Co., Ltd., the following information should be provided:

  1. Required material grade (e.g., 304, 316, 316L, 321, 310S)
  2. Outer diameter and wall thickness
  3. Coil pitch and mean coil diameter
  4. Total coil length or number of turns
  5. End connection type (plain, threaded, flanged, socket-weld)
  6. Required surface finish (pickled, BA, EP)
  7. Applicable standard (ASTM, ASME, EN, GB, JIS)
  8. Operating conditions (temperature, pressure, media)
  9. Quantity and delivery schedule