Stainless Steel Coil Tube for Ethylene Cracker Feed Preheater Service

Product Overview

The Stainless Steel Coil Tube (盘管 / Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product specifically designed for high-temperature, high-pressure process environments within ethylene cracking furnaces. Coil tubes serve as critical heat-exchange elements in feed preheater sections, where they transfer thermal energy from combustion gases to process feedstocks prior to the cracking reaction. These tubes are continuously wound into helical or serpentine configurations to maximize heat transfer surface area within compact furnace geometries.

Based on extensive engineering analysis of corrosion and leakage failure modes in ethylene cracker feed preheater coil tube sections (乙烯裂解炉原料预热盘管段), this product line incorporates advanced metallurgical design principles to mitigate the primary degradation mechanisms observed in service, including creep rupture, internal corrosion, external oxidation, scaling, and thermal fatigue cracking. The coil tubes are engineered to withstand the aggressive chemical environment of hydrocarbon feed preheating, where temperatures typically range from 250°C to 650°C with exposure to hydrogen, hydrogen sulfide, and carbon-containing species.

Material & Properties

Material Grades

The coil tubes are fabricated from a range of austenitic and austenitic-ferritic stainless steel grades selected for superior resistance to the combined mechanical and chemical demands of ethylene cracker preheater service:

Key Mechanical Properties

Corrosion Resistance Characteristics

Specifications

Parameter Specification
Outer Diameter (OD) Φ19.05 mm, Φ22.23 mm, Φ25.40 mm, Φ28.58 mm, Φ31.75 mm, Φ38.10 mm, Φ44.45 mm, Φ50.80 mm (custom sizes available)
Wall Thickness 1.5 mm – 6.0 mm (tolerance ±10% or ±0.1 mm, whichever is greater)
Coil Inner Diameter (ID) 300 mm – 1,200 mm (configurable per furnace design)
Tube Length per Coil 15 m – 120 m (continuous length, no butt welds within coil)
Bend Radius ≥ 3D (minimum bend radius to prevent wall thinning and cracking)
Operating Temperature Up to 650°C continuous; peak transient up to 750°C
Operating Pressure Up to 6.0 MPa (design pressure per ASME Section VIII)
Surface Finish Pickled and passivated; Ra ≤ 0.8 μm (inner surface, optional)
End Condition Plain ends, beveled ends, or pre-fitted with expansion joints per customer drawing
Applicable Standards ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 14976
Heat Treatment Solution annealed at 1050–1150°C followed by rapid water quench; stress-relieved per ASME code
Coil Configuration Helical coil, serpentine coil, or U-tube arrangement per furnace layout requirements

Manufacturing Process

1. Raw Material Selection and Inspection

High-purity stainless steel ingots or continuously cast slabs are procured from certified steel mills. Incoming materials undergo rigorous verification including chemical composition analysis (spectrometry), mechanical property testing, and ultrasonic flaw detection to ensure conformance with the specified grade requirements. Traceability is maintained through heat number tracking from mill certificate through final product delivery.

2. Hot Rolling / Seamless Tube Production

Coil tubes are produced via the seamless tube manufacturing route to eliminate the risk of weld-related failure at high temperature. The process involves:

3. Cold Working (Optional)

For tight dimensional tolerances, the tubes may undergo cold drawing or cold rolling to achieve final OD and wall thickness within ±5% tolerance. Cold working improves surface finish and mechanical properties but requires subsequent stress relief.

4. Solution Annealing

Finished tubes are solution annealed at 1,050–1,150°C in a protective atmosphere (endothermic gas or vacuum) to dissolve carbides and restore full austenitic microstructure. Rapid quenching in water or forced air follows to prevent sensitization. This step is critical for ensuring corrosion resistance and ductility.

5. Coil Bending / Forming

The straight tubes are cold-bent into the required coil geometry using precision bending machines equipped with internal mandrels to prevent ovality and wall thinning. Key process controls include:

6. Surface Treatment

Coil tubes undergo acid pickling and passivation to remove mill scale, oxide films, and surface contaminants. The pickling process utilizes a mixed acid solution (nitric acid + hydrofluoric acid) followed by passivation with dilute nitric acid to restore the chromium oxide passive film. Optional electropolishing may be applied for critical internal surface applications.

7. Quality Inspection and Testing

Comprehensive inspection protocols are applied at every stage:

Applications

Primary Application: Ethylene Cracker Feed Preheater

The primary application of these coil tubes is in the feed preheater section of ethylene cracking furnaces (乙烯裂解炉原料预热段), where they serve as the heat exchange medium between furnace combustion gases and the hydrocarbon feedstock (ethane, naphtha, or LPG). The coil tubes absorb radiant and convective heat from furnace flue gases, raising the feedstock temperature to the cracking inlet temperature (typically 800–900°C at the coil outlet). This product is engineered with specific attention to the failure mechanisms identified in corrosion and leakage analysis of preheater coil tube sections, including:

Secondary Applications

Quality Certifications

Product Certifications

Testing and Inspection Standards