316L Seamless Stainless Steel Coil Tube for Amine Regeneration Tower Reboilers
Product Overview
This precision-engineered 316L seamless stainless steel coil tube is purpose-designed for use in amine regeneration tower reboilers within natural gas processing facilities. These coil tubes serve as critical heat exchange elements responsible for regenerating spent amine solvents—specifically monoethanolamine (MEA) and diethanolamine (DEA)—by stripping absorbed acid gases (CO₂ and H₂S) under controlled thermal conditions ranging from 120 °C to 150 °C (248–302 °F).
Operating in one of the most corrosive environments encountered in petrochemical processing, these coil tubes must withstand aggressive amine solution chemistry, elevated temperatures, and continuous acid gas loading cycles. Wenzhou Jixing Metal Materials Co., Ltd. delivers coil tubes engineered to maximize service life, minimize unplanned shutdowns, and ensure consistent regeneration efficiency throughout the asset lifecycle.
Material & Properties
The coil tube is manufactured from AISI 316L / UNS S31603 seamless stainless steel, selected specifically for its superior resistance to chloride pitting, stress corrosion cracking, and attack by amine degradation products such as heat-stable salts (HSS), organic acids, and sulfide compounds.
Key Material Characteristics
- Molybdenum Content: 2.0–3.0% Mo provides enhanced resistance to localized corrosion in chloride-containing amine solutions
- Low Carbon Grade: Carbon ≤ 0.03% minimizes intergranular corrosion risk during prolonged exposure to elevated temperatures and eliminates sensitization concerns
- Chromium Content: 16.5–18.5% Cr ensures a robust passive oxide layer in oxidizing and mildly reducing environments
- Nickel Content: 10.0–14.5% Ni stabilizes the austenitic microstructure and improves ductility for coil forming operations
- Maximum Service Temperature: Suitable for continuous operation up to 150 °C (302 °F) with significant design margin to standard 316L limits of ~870 °C in air
- Weldability: Excellent weldability with minimal risk of sensitization in the heat-affected zone
Corrosion Resistance Considerations
In amine regeneration service, the primary corrosion threat arises not from the parent amine itself but from degradation products accumulated over extended operation. These include heat-stable salts (ammonium sulfate, ammonium carbonate), thiodiglycolic acid (TDGA), and various organic sulfides. The 316L alloy's molybdenum enrichment provides a critical margin of protection against these aggressive species, particularly when chloride concentrations from feedwater carryover or process contamination are present.
Specifications
| Parameter | Specification |
|---|---|
| Material Grade | AISI 316L / UNS S31603 (ASTM A213 TP316L) |
| Tube Type | Seamless Coil Tube (spiral wound or helical coil configuration) |
| Outer Diameter (OD) | 12.7 mm – 38.1 mm (½" – 1½") — customizable per design requirement |
| Wall Thickness | 1.65 mm – 4.57 mm (0.065" – 0.180") — selected based on pressure and corrosion allowance |
| Coil Diameter (CD) | 150 mm – 1,200 mm (5.9" – 47.2") — tailored to reboiler vessel geometry |
| Coil Length | Custom — typically 5 m – 50 m (16.4' – 164') per coil assembly |
| Operating Temperature | 120 °C – 150 °C (248 °F – 302 °F) |
| Operating Pressure | Up to 2.5 MPa (363 psi) — design pressure per ASME VIII Div. 1 |
| Surface Finish | Mill finish or polished (Ra ≤ 0.8 µm / 32 µin) upon request |
| End Preparation | Plain ends, beveled ends (75° or 37.5°), or U-bend formed per specification |
| Corrosion Allowance | 0.5 mm – 1.0 mm (0.020" – 0.040") recommended for amine degradation environments |
| Applicable Standards | ASTM A213, ASTM A778, ASME B31.3, EN 10216-5, GB/T 14976 |
Manufacturing Process
Wenzhou Jixing Metal Materials Co., Ltd. employs a rigorous multi-stage manufacturing process to ensure coil tubes meet the exacting demands of amine regeneration service:
- Hot-Rolled Billet Selection: Certified 316L seamless billets sourced from reputable mills with full chemical and mechanical traceability documentation.
- Piercing & Seamless Tube Milling: Billets are pierced and drawn through rotary or plug mills to produce seamless tube blanks with uniform wall thickness and minimal internal inclusions.
- Pipe Milling & Cold Drawing: Tubes are cold-drawn through precision dies to achieve exact OD, wall thickness, and dimensional tolerances per ASTM A213 specifications.
- Solution Annealing: Tubes are solution-annealed at 1040–1100 °C (1904–2012 °F) followed by rapid water quench to restore full corrosion resistance and eliminate cold-work stresses.
- Coil Forming / Bending: Annealed tubes are cold-coiled or helically formed using CNC-controlled bending equipment to achieve the precise coil diameter and pitch specified by the reboiler design. Forming is performed in the solution-annealed condition to prevent work-hardening-induced sensitization.
- Post-Forming Stress Relief (if required): For applications where forming introduces residual stresses that could compromise corrosion performance, a controlled stress-relief anneal is performed.
- End Forming & Inspection: Tube ends are machined, beveled, or U-bent as specified. Each coil undergoes 100% visual inspection and dimensional verification.
- Non-Destructive Testing: All tubes are subject to eddy-current testing and/or ultrasonic testing to detect internal and external defects. Helium leak testing may be applied for critical pressure boundaries.
- Surface Cleaning & Passivation: Final acid pickling and passivation treatment ensures a clean, corrosion-resistant surface free of scale, carbon residue, and free iron contamination.
Applications
This coil tube product is specifically engineered for the following natural gas processing applications:
- MEA (Monoethanolamine) Regeneration Reboilers: Providing heat input to regenerate 15–30 wt% MEA solutions, stripping dissolved CO₂ and H₂S from natural gas streams.
- DEA (Diethanolamine) Regeneration Reboilers: Suitable for selective H₂S removal service where DEA solutions are employed at 120–150 °C.
- MDEA (Methyldiethanolamine) Regeneration Service: Compatible with MDEA systems where lower regeneration temperatures are utilized.
- Lean Amine Reboilers: Heating lean amine to pre-regeneration temperature prior to contact with rich amine in the regenerator column.
- Sour Water Amine Reboilers: Regeneration of amine solutions used in sour water treatment where higher chloride and sulfide concentrations are present.
Unique Selling Points
- Optimized for Amine Degradation Environments: 316L material selection specifically addresses the aggressive chemistry of amine degradation products including heat-stable salts, TDGA, and organic sulfides—providing significantly longer service life than standard 304L or 316L in non-degraded service.
- Seamless Construction: Eliminates the weld seam vulnerability inherent in welded coil tubes, removing a potential initiation site for stress corrosion cracking in chloride-containing amine solutions.
- Full Traceability: Each coil tube shipment includes mill test certificates (MTCs) conforming to EN 10204 3.1, with full chemical analysis and mechanical test data from heat-to-heat traceability.
- Custom Coil Geometry: CNC-controlled forming enables precise coil diameters, pitches, and lengths tailored to specific reboiler vessel designs, maximizing heat transfer surface area within constrained vessel dimensions.
- Low-Carbon Grade Advantage: The 316L "L" designation (C ≤ 0.03%) eliminates intergranular corrosion risk during prolonged exposure to amine service temperatures, a critical advantage over standard 316 in regeneration environments.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification programs to assure compliance with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality assurance processes
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- ASME "S" Stamp — Authorization for seamless tube production per ASME Boiler and Pressure Vessel Code
- API Monogram — American Petroleum Institute certification for materials used in oil and gas processing equipment
- EN 10204 3.1 MTC — Third-party inspection and testing reports available upon request
- Product Standards Compliance: ASTM A213/A213M, ASTM A778, ASME B31.3, EN 10216-5, GB/T 14976
Technical Advisory Note
While 316L seamless coil tubes provide excellent performance in standard amine regeneration service, operators should monitor amine solution quality through regular laboratory analysis of heat-stable salt (HSS) concentration, organic acid content, and amine degradation byproducts. If HSS levels exceed 2 wt% or if chloride contamination from feedwater or process carryover is significant, Wenzhou Jixing Metal Materials Co., Ltd. can advise on enhanced alloy alternatives (e.g., Alloy 625, Alloy C-276, or duplex 2205) to further extend asset life and reduce maintenance intervals.