Stainless Steel Coil Tube for Cartridge Fitting Applications — Two-Step Tightening Installation System

Product Overview

The Stainless Steel Coil Tube (Product No. 220) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing solution designed specifically for installation and maintenance applications involving cartridge (compression) fittings. This product forms the backbone of fluid transport and pneumatic systems where reliable, leak-free connections are critical.

Unlike conventional pipe connection methods that rely on welding or threaded joints, the coil tube system employs a two-step tightening protocol — pre-tightening followed by final tightening — to achieve a gas-tight and liquid-tight seal. This method ensures consistent clamping force distribution across the ferrule-to-tube interface, significantly reducing the risk of field failures caused by improper installation.

Unique Selling Points

• Two-Step Tightening Protocol: A standardized installation sequence (insert → hand-tighten → wrench 1.25 turns) eliminates guesswork and ensures repeatable joint integrity across all operators.
• Coil-Formed for On-Site Flexibility: Delivered in coil configuration for easy field cutting, bending, and routing without additional forming operations.
• Zero-Weld Construction: Eliminates heat-affected zones, preserves metallurgical integrity, and allows for post-installation repositioning.
• Damage-Controlled Tolerances: Tight manufacturing controls on ovality, surface finish, and dimensional accuracy directly address the three primary causes of leakage in cartridge-fitting systems.

Material & Properties

The coil tube is manufactured from high-grade austenitic stainless steel, offering an optimal balance of corrosion resistance, formability, and mechanical strength required for compression-fitting applications.

• Base Material: SUS304 / AISI 304 (1.4301) — the industry standard for general-purpose fluid handling
• Alternative Grades Available: SUS316 / AISI 316 (1.4401) for elevated corrosion resistance in chemical and marine environments
• Surface Condition: Bright annealed (BA) or pickled & passivated finish; free of scale, burrs, and machining marks
• Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and mild chemical environments
• Formability: High ductility permits cold bending to radii as small as 3× the outer diameter without cracking
• Temperature Range: Continuous service from −196 °C (−321 °F) to +450 °C (+842 °F)
• Mechanical Properties: Tensile strength ≥ 520 MPa (75 ksi); elongation ≥ 40%

Specifications

Parameter	Specification	Standard / Reference
Product Name	Stainless Steel Coil Tube	—
Product Code	220	Internal Catalog
Material Grade	SUS304 / SUS316	ASTM A269 / ASTM A554
Tube Type	Seamless (cold-drawn)	ASTM A213
Outer Diameter Range	3.18 mm (1/8") to 22.23 mm (7/8")	ASME B36.19M
Wall Thickness Range	0.50 mm (0.020") to 3.00 mm (0.118")	ASME B36.19M
Coil Length (Standard)	10 m (32.8 ft) / 20 m (65.6 ft) / 50 m (164 ft)	Custom lengths available
Coil Inner Diameter	150 mm (5.9") to 300 mm (11.8")	—
Ovality Tolerance	≤ 0.5% of OD	ASTM A554
Surface Roughness (Ra)	≤ 0.8 μm (32 μin)	ISO 1302
Dimensional Tolerance (OD)	±0.05 mm (±0.002")	ASTM A554
Dimensional Tolerance (WT)	±5% of nominal	ASTM A554
Recommended Bending Radius	≥ 3× OD (cold); ≥ 2× OD (with mandrel)	—
Operating Pressure	Up to 10 MPa (1,450 psi) — grade dependent	ASME B31.3
Installation Method	Cartridge (compression) fitting — two-step tightening	ISO 8434-1 / ISO 16028

Manufacturing Process

The production of this coil tube follows a rigorously controlled multi-stage process to ensure dimensional accuracy and surface integrity:

1. Material Selection & Incoming Inspection: Cold-rolled stainless steel strip is sourced from certified mills with full mill test certificates (MTC). Incoming material undergoes spectrographic verification and surface inspection.
2. Forming & Welding (or Seamless Drawing): Seamless tubes are produced via hot-rolling followed by cold-drawing through precision dies, eliminating weld seams entirely. Alternatively, welded tubes are produced with high-frequency induction welding and subsequent cold drawing to homogenize the weld zone.
3. Cold Drawing & Sizing: Tubes are drawn through calibrated tungsten-carbide dies to achieve precise OD and wall thickness tolerances. Multiple passes ensure uniform microstructure and dimensional consistency.
4. Pipe Milling & Deburring: End faces are milled square, and internal/external burrs are removed to prevent ferrule damage during insertion.
5. Pickling & Passivation: Tubes are subjected to acid pickling (HNO₃/HF blend) to remove surface contaminants, followed by passivation to establish a protective chromium oxide layer.
6. Surface Inspection: Every coil undergoes automated optical or dye-penetrant inspection to detect scratches, dents, or surface defects that could compromise seal integrity.
7. Ovality & Dimensional Verification: Coordinate measuring machines (CMM) or laser micrometers verify OD, wall thickness, and ovality against specification limits.
8. Coiling & Packaging: Tubes are wound onto protective steel or wooden cores, wrapped in VCI (volatile corrosion inhibitor) film, and secured with strapping for shipment.

Installation & Connection Procedure

The cartridge fitting system employed with this coil tube utilizes a two-step tightening method to ensure reliable, leak-free connections:

1. Tube Preparation: Cut the tube square (90°) using a dedicated tube cutter. Deburr the cut end thoroughly. Inspect for scratches, ovality, or dimensional deviation — these are the primary causes of leakage.
2. Insertion: Insert the prepared tube end fully into the fitting body until it seats against the internal stop. The tube must be inserted to the full bottom of the fitting body.
3. Hand-Tightening (Pre-Tightening): Turn the nut by hand until it contacts the fitting body. This step seats the ferrule against the tube without inducing deformation.
4. Final Tightening: Using the appropriate wrench, rotate the nut an additional 1.25 turns (1¼ turns) past the hand-tight position. This controlled angular rotation deforms the ferrule radially inward, creating a uniform metal-to-metal seal.

Critical Note: Over-tightening beyond 1.25 turns can crush or displace the ferrule, causing internal leakage. Under-tightening fails to achieve sufficient clamping force. The 1.25-turn specification is validated through pressure testing and must be followed precisely.

Key Failure Mode Prevention

• Scratches: Any surface scratch on the tube OD at the seal zone can act as a stress concentrator and leak path. Handle with gloves; avoid dragging on abrasive surfaces.
• Ovality: Excessive ovality (>0.5% of OD) results in uneven ferrule compression. Inspect all tubes before cutting; reject any visibly deformed sections.
• Dimensional Deviation: Tubes with OD or wall thickness outside specification will not engage the ferrule geometry correctly. Verify with calibrated gauges.

Applications

This stainless steel coil tube is engineered for demanding industrial and commercial applications where reliable, maintainable fluid connections are essential:

• Hydraulic Systems: High-pressure hydraulic circuits in manufacturing equipment, mobile machinery, and automation systems
• Pneumatic Systems: Instrument air lines, compressed air distribution networks, and pneumatic actuator connections
• Food & Beverage Processing: CIP (Clean-in-Place) systems, dairy processing lines, and sanitary fluid transfer (SUS316 grade)
• Pharmaceutical & Biotech: Process piping for clean steam, pure water, and chemical transfer in GMP-regulated environments
• Semiconductor Manufacturing: Ultra-pure gas and chemical delivery systems requiring zero-contamination connections
• Oil & Gas: Instrumentation lines, control valve connections, and sampling systems
• Power Generation: Cooling water circuits, steam sampling, and turbine control systems
• Commercial Refrigeration: Ammonia and refrigerant piping in industrial cold storage facilities
• Water Treatment: Chlorination systems, dosing lines, and process water distribution

Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product reliability and regulatory compliance:

• ISO 9001:2015 — Quality Management System certification
• ISO 14001 — Environmental Management System
• ASTM A269 / A554 — Seamless and welded stainless steel tubing standards
• ASME B36.19M — Welded and seamless wrought stainless steel pipe dimensions
• ISO 8434-1 — Hydraulic fluid power — tube fittings (cartridge type)
• ISO 16028 — Fluid power — tube and tube fittings (cartridge type)
• EN 10217 — European standard for cold-drawn seamless steel tubes
• GB/T 14976 — Chinese national standard for seamless stainless steel tubes
• Mill Test Certificate (MTC) — Provided with every shipment per EN 10204 Type 3.1
• Material Traceability: Full heat-lot traceability from raw material to finished product

Technical Support & Ordering Information

Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including:

• Selection guidance for tube OD/wall thickness based on system pressure and fluid type
• Installation training for cartridge fitting two-step tightening procedures
• Custom coil lengths, cutting to length, and pre-formed bends upon request
• Ferrule and fitting compatibility verification for cross-brand installations
• Pressure test validation protocols and leak-testing recommendations