Stainless Steel Coil Tube — Insulated Vibration-Damping Assembly for Refrigeration Compressors

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (Wenzhou Jixing Metal Materials Co., Ltd.)
Product Series: No. 976 — Coil Tube (盘管) Assembly
Category: Specialized Industrial Tubing Components — Thermal & Mechanical Isolation Systems

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1. Product Overview

The Stainless Steel Coil Tube Assembly is a precision-engineered component designed specifically for integration into refrigeration compressor systems. This product combines the inherent corrosion resistance and mechanical integrity of austenitic stainless steel with an integrated insulation and vibration-damping architecture, delivering a multifunctional solution for thermal management and structural isolation in demanding industrial and commercial refrigeration environments.

Unlike conventional refrigeration tubing that addresses only fluid conveyance, this coil tube assembly simultaneously resolves three critical engineering challenges: (1) thermal insulation to minimize heat gain from ambient environments, (2) vibration attenuation to reduce mechanical stress transmitted from compressor operation, and (3) long-term material durability under cyclic thermal and pressure loading. The product is manufactured by Wenzhou Jixing Metal Materials Co., Ltd., a specialized producer of high-grade stainless steel tube and pipe components based in Wenzhou, Zhejiang Province, China.

2. Material Specification & Properties

2.1 Base Material — Stainless Steel Coil Tube

The core structural element of the assembly is fabricated from austenitic stainless steel, typically conforming to the following grades:

• Grade 304 (UNS S30400): The primary material for general refrigeration applications, offering excellent corrosion resistance, weldability, and formability.
• Grade 316 (UNS S31600): Specified for environments with elevated chloride exposure or more aggressive chemical conditions.
• Grade 321 (UNS S32100): Available for applications requiring enhanced resistance to intergranular corrosion at elevated operating temperatures.

2.2 Mechanical & Physical Properties

Property	Grade 304	Grade 316
Tensile Strength (ASTM A213)	≥ 515 MPa	≥ 485 MPa
Yield Strength (0.2% Offset)	≥ 205 MPa	≥ 170 MPa
Elongation (in 5D, minimum)	≥ 35%	≥ 35%
Density	8.00 g/cm³	8.03 g/cm³
Thermal Conductivity (at 20 °C)	16.3 W/(m·K)	14.6 W/(m·K)
Operating Temperature Range	−196 °C to +870 °C	−196 °C to +870 °C
Chromium Content (min.)	18.0%	16.0%
Nickel Content (min.)	8.0%	10.0%
Molybdenum Content	—	2.0% – 3.0%

2.3 Insulation Layer

The coil tube is enveloped in a multi-layer insulation system comprising:

• Inner Barrier Layer: Closed-cell elastomeric foam (e.g., NBR — Nitrile Butadiene Rubber, or EPDM — Ethylene Propylene Diene Monomer) providing a vapor-tight seal and primary thermal resistance.
• Intermediate Insulation Layer: High-density polyurethane (PUR) or polyisocyanurate (PIR) foam with a thermal conductivity of ≤ 0.024 W/(m·K) at 0 °C, ensuring minimal heat ingress.
• Outer Protective Jacket: A UV-stabilized aluminum foil or stainless steel wrap providing mechanical protection, moisture barrier, and enhanced radiative heat reflection.

2.4 Vibration-Damping Substrate

A specialized elastomeric vibration-damping layer is integrated between the coil tube body and the mounting interface. This layer is typically composed of silicone rubber or chloroprene rubber (CR) with a Shore A hardness of 40–60, engineered to attenuate vibrational energy within the operating frequency range of 10 Hz to 2,000 Hz.

3. Technical Specifications

Parameter	Specification
Tube Outer Diameter (OD)	6.35 mm – 50.8 mm (¼" – 2")
Tube Wall Thickness	0.5 mm – 2.0 mm
Coil Inner Diameter (ID)	100 mm – 500 mm
Coil Height	50 mm – 300 mm
Number of Turns	4 – 20 turns
Insulation Thickness	10 mm – 30 mm
Thermal Conductivity (Assembly, effective)	≤ 0.035 W/(m·K) at 0 °C
Vibration Isolation Efficiency	≥ 85% at 20–50 Hz
Maximum Working Pressure	1.6 – 4.0 MPa (depending on OD and wall thickness)
Hydrostatic Test Pressure	2.0 × Working Pressure
Surface Finish (Tube)	Bright Annealed (BA) or Electropolished, Ra ≤ 0.4 μm
Operating Temperature Range (Assembly)	−40 °C to +80 °C
Refrigerant Compatibility	R-134a, R-410A, R-404A, R-407C, R-507, NH₃, CO₂
Standard Compliance	ASTM A213, EN 10216-5, GB/T 14976, ASME B31.5

4. Manufacturing Process

4.1 Tube Production

1. Coil Uncoiling & Straightening: Cold-rolled stainless steel coil is uncoiled, straightened, and cut to the required length with precision shearing.
2. Seamless or Welded Tube Forming: Tubes are produced via cold-drawing (for smaller ODs) or continuous welding (for larger ODs), followed by heat treatment to achieve the specified microstructure.
3. Pipe Bending (Coil Forming): Using a CNC-controlled pipe bending machine with mandrel support, the straight tube is formed into the precise coil geometry. Bending is performed at controlled temperatures to prevent work-hardening and cracking, maintaining wall thickness uniformity within ±10% of nominal.
4. Welding & Joining: End connections are fabricated via orbital TIG (Tungsten Inert Gas) welding, ensuring full-penetration welds with minimal heat-affected zone (HAZ) distortion. Weld seams are ground and inspected for integrity.
5. Surface Treatment: The tube undergoes pickling and passivation to remove scale and restore the chromium oxide passive layer. Optional electropolishing is applied for critical food-grade or pharmaceutical applications.

4.2 Insulation Assembly

1. Insulation Jacket Fabrication: Custom-molded insulation sleeves are manufactured to match the coil tube geometry with tight dimensional tolerances (±1 mm).
2. Application & Bonding: The insulation layers are applied to the coil tube body using high-temperature adhesive bonding, ensuring full circumferential coverage with no gaps or voids.
3. Outer Jacket Installation: The protective outer wrap is mechanically secured with stainless steel crimp bands or adhesive fasteners at regular intervals to prevent displacement during operation.

4.3 Vibration-Damping Integration

1. Damping Element Mounting: Elastomeric vibration isolators are precision-cut and bonded to the coil tube mounting flanges or brackets.
2. Bracket Assembly: Stainless steel support brackets are fabricated and welded to the coil assembly, with the damping elements positioned at calculated node points for optimal vibration isolation.

4.4 Quality Control & Testing

1. Dimensional Inspection: Coordinate Measuring Machine (CMM) verification of coil geometry, OD, wall thickness, and overall assembly dimensions.
2. Hydrostatic Pressure Testing: Each assembly is subjected to a hydrostatic pressure test at 2.0× the maximum working pressure for a minimum of 30 seconds with zero leakage tolerance.
3. Helium Leak Testing: Optional high-sensitivity helium leak detection (detection threshold: 1 × 10⁻⁹ Pa·m³/s) for critical applications.
4. Thermal Performance Verification: Heat flux measurement to confirm the effective thermal conductivity meets specified limits.
5. Vibration Frequency Response Analysis: Modal testing to validate the natural frequency and isolation efficiency of the damping system.
6. Visual & NDT Inspection: Dye penetrant testing (PT) or magnetic particle inspection (MT) of all welds and critical joints.

5. Applications

5.1 Primary Application — Refrigeration Compressors

The core application domain of this product is the refrigeration compressor industry, where it serves as a critical component in the suction and discharge line routing of reciprocating, scroll, and screw compressors. The integrated insulation prevents condensation formation and heat gain on refrigerant lines, while the vibration-damping system reduces noise transmission and mechanical fatigue on compressor mounting structures.

5.2 Extended Applications

• Industrial Process Cooling: Chilled water coil assemblies for process cooling systems in chemical, pharmaceutical, and food processing plants.
• Heat Pump Systems: Evaporator and condenser coil assemblies in commercial and industrial heat pump units.
• Air Conditioning Systems: Condenser and evaporator coil assemblies in large-capacity split and packaged air conditioning units.
• Cryogenic Applications: Insulated coil assemblies for low-temperature fluid transfer in liquefied natural gas (LNG) and cryogenic storage systems.
• Food & Beverage Processing: Sanitary-grade coil assemblies for dairy, brewery, and beverage processing where hygienic design and corrosion resistance are paramount.
• Automotive & Transportation: Compact coil assemblies for vehicle air conditioning and refrigeration units requiring vibration-resistant, lightweight thermal management.

6. Unique Selling Points

• Integrated Multifunctional Design: Unlike conventional solutions that require separate insulation wrapping and vibration mounting, this assembly integrates all three functions — fluid conveyance, thermal insulation, and vibration damping — into a single unitized component, reducing installation complexity and field labor.
• Superior Corrosion Resistance: The austenitic stainless steel construction provides exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking, ensuring service life exceeding 25 years even in aggressive environments.
• Energy Efficiency: The high-performance insulation system with effective thermal conductivity ≤ 0.035 W/(m·K) minimizes parasitic heat gain, directly contributing to improved Coefficient of Performance (COP) in refrigeration systems.
• Noise & Vibration Reduction: The integrated elastomeric damping system achieves ≥ 85% vibration isolation efficiency in the critical 20–50 Hz frequency range, significantly reducing operational noise and extending the service life of adjacent components.
• Wide Refrigerant Compatibility: Full compatibility with all major HFC, HFO, HC, and ammonia refrigerants, including next-generation low-GWP refrigerants, ensuring future-proofing as regulatory requirements evolve.
• Customizability: Wenzhou Jixing Metal Materials Co., Ltd. offers full customization of coil geometry, tube dimensions, insulation thickness, and damping specifications to meet project-specific requirements.

7. Quality Certifications & Standards Compliance

Certification / Standard	Scope
ISO 9001:2015	Quality Management System
ISO 14001:2015	Environmental Management System
ISO 45001:2018	Occupational Health & Safety Management System
CE Marking	European Conformity — Pressure Equipment Directive (PED 2014/68/EU)
ASTM A213 / A778	Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
EN 10216-5	Technical Delivery Conditions for Non-Alloy and Alloy Steel Tubes for Pressure Purposes
GB/T 14976