Stainless Steel Coil Tube for Ammonia Synthesis Plant LPG Heater Systems

Product Overview

The Stainless Steel Coil Tube (also known as Coiltube or U-tube Heat Exchanger Coil) is a precision-engineered heat transfer component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for use in liquefied petroleum gas (LPG) heater systems within ammonia synthesis plants, where it serves as the critical heat exchange element in preheating and process heating applications.

In ammonia synthesis processes, the efficient conversion of feedstock requires precise thermal management. The coil tube assembly functions as the core heating element within shell-and-coil heat exchangers, facilitating the transfer of thermal energy from a process fluid or combustion gas to the working medium. The replacement and upgrade of these coils is essential for maintaining operational efficiency, safety, and compliance with environmental regulations in nitrogen-based chemical production facilities.

Wenzhou Jixing Metal Materials Co., Ltd specializes in the design, fabrication, and supply of high-performance stainless steel coil tubes tailored to the demanding thermal and chemical environments encountered in ammonia synthesis and related petrochemical processes.

Material & Properties

The coil tube is fabricated from high-grade austenitic stainless steel alloys, selected based on the specific service conditions including operating temperature, pressure, and the chemical composition of the process fluids. The following materials are commonly specified:

Mechanical Properties (Typical for SAE 316L)

Specifications

Parameter Specification
Product Designation Stainless Steel Coil Tube (Coiltube) — Model No. JX-CT-1425
Material Grade SAE 304 / 304L / 316 / 316L / 321 (as per customer specification)
Outer Diameter (OD) 19 mm – 76 mm (customizable)
Wall Thickness 1.5 mm – 5.0 mm (customizable)
Coil Inner Diameter (ID) 300 mm – 1,500 mm (as per heat exchanger design)
Coil Height / Length 500 mm – 3,000 mm (customizable)
Operating Temperature −196°C to 870°C
Operating Pressure Up to 30 MPa (4,350 psi)
Surface Finish 2B / BA (Bright Annealed) / No. 4 / Mirror (as required)
End Connections Flanged (ASME B16.5) / Butt Weld / Threaded
Applicable Standards ASTM A213 / A269 / A312, ASME B31.3, EN 10216-5
Heat Treatment Solution Annealing (1010–1150°C followed by rapid quench)
Minimum Order Quantity 10 sets
Custom Fabrication Available — full engineering support for non-standard designs

Manufacturing Process

The fabrication of stainless steel coil tubes for ammonia synthesis plant LPG heaters follows a rigorous, multi-stage manufacturing process designed to ensure dimensional accuracy, mechanical integrity, and corrosion resistance:

  1. Material Selection & Verification — Raw stainless steel seamless tubes are procured from certified mills with full material traceability. Incoming inspection includes spectroscopic analysis (PMI), mechanical testing, and chemical composition verification in accordance with ASTM A213/A269 specifications.
  2. Cutting & Preparation — Tubes are precisely cut to the required length using cold sawing or plasma cutting methods, followed by end preparation including chamfering and deburring to facilitate welding operations.
  3. Bending & Coiling — The straight tube segments are formed into the required coil geometry using hydraulic cold-bending machines or induction heating hot-bending equipment. The bending process is controlled to maintain wall thickness uniformity and prevent ovalization, with a minimum bend radius of 5D (where D is the tube outer diameter) for cold bending and 3D for hot bending.
  4. Welding — U-bends and end connections are fabricated using Gas Tungsten Arc Welding (GTAW) or Shielded Metal Arc Welding (SMAW) with appropriate filler metals (e.g., ER308L, ER316L, or ER321) matched to the base material. Welding procedures are qualified per ASME Section IX.
  5. Post-Weld Heat Treatment (PWHT) — Solution annealing is performed to relieve residual stresses introduced during welding and forming. The coil is heated to 1,010–1,150°C and rapidly quenched to restore full austenitic microstructure and maximize corrosion resistance.
  6. Pickling & Passivation — The annealed coil undergoes acid pickling (nitric/hydrofluoric acid blend) to remove surface scale and oxide deposits, followed by passivation to form a protective chromium oxide layer. This ensures a clean, corrosion-resistant surface finish.
  7. Quality Inspection & Testing — Final inspection includes dimensional verification (OD, wall thickness, coil geometry), hydrostatic pressure testing (1.5× working pressure), radiographic testing (RT) or ultrasonic testing (UT) of welds, and visual examination in accordance with ASME B31.3 and applicable customer specifications.
  8. Packaging & Delivery — Completed coil tubes are protected with anti-corrosion wrapping, crated or loaded onto specialized transport frames to prevent mechanical damage during shipment.

Applications

The stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd is specifically engineered for the following industrial applications:

Technical Context: Ammonia Synthesis LPG Heater Coil Replacement

In ammonia synthesis plants, the LPG heater coil is a critical component that preheats the process gas to the temperature required for catalytic conversion (typically 380–500°C). Over time, these coils degrade due to thermal cycling, corrosion from residual sulfur compounds, and mechanical fatigue. The replacement of these coils with high-grade stainless steel coil tubes ensures restored thermal efficiency, extended service life, and compliance with safety standards governing high-pressure ammonia production systems. The learning and application of best practices in coil replacement — including proper material selection, installation procedures, and commissioning protocols — is essential for minimizing downtime and ensuring long-term operational reliability.

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications to ensure product reliability and compliance with international standards:

Unique Selling Points

Technical Data Reference

For detailed engineering calculations, thermal performance data, and compatibility assessments specific to ammonia synthesis plant LPG heater applications, Wenzhou Jixing Metal Materials Co., Ltd provides:

For further technical inquiries, product specifications, or custom quotation requests, please contact Wenzhou Jixing Metal Materials Co., Ltd directly. All products are subject to written order confirmation and applicable quality assurance protocols.