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Bundy tubing, structurally classified as double-walled copper-brazed steel tubing, represents the benchmark in modern thermal dynamics and high-pressure fluid applications. Originally developed to solve leakages in hydraulic brake systems, it has since become the staple element for heat exchangers, condensers, and evaporators.
An 8mm outer diameter (OD) Bundy tube is manufactured by roll-forming a high-quality, copper-coated carbon steel strip through a precise 720-degree double-wall wrap process. Under high-frequency induction heating in a controlled hydrogen reducing atmosphere, the internal and external copper layers fuse seamlessly with the steel core. This metallurgical bond results in a uniform tube with remarkable tensile strength, high burst pressure resistance, and exceptional ductility.
For refrigeration applications, the inner surface cleanliness is critical. Our manufacturing process maintains ultra-low residual carbon levels (less than 0.15 mg/dm²), preventing chemical degradation of modern eco-friendly refrigerants.
Founded in 1988 as the Xiangshan Refrigeration Accessories Factory of Zhejiang University, Ningbo Taojun Refrigeration Equipment Co., Ltd. has evolved over nearly four decades into a premier national high-tech enterprise. Situated in the manufacturing cluster of Ningbo, China, we specialize in producing Bundy tubes, copper/brass filter driers, check valves, and condenser modules.
With active R&D support featuring 15 dedicated engineers holding credentials from institutions like the University of Science and Technology of China (USTC), our factory integrates academic research with mass production systems. We maintain a strong commitment to quality control, having obtained ISO9001:2015 / GB/T19001-2016, EU RoHS, REACH, and US UL certifications.
Over the years, we have forged strategic OEM partnerships with leading global brands, including Haier, Midea, Gree, Whirlpool, and Electrolux, delivering reliable refrigeration parts to over 50 countries.
Advancing Bundy tube performance for next-generation eco-friendly refrigeration and automotive platforms.
The transition to R290, R32, and R600a requires higher operating pressures. Our development roadmap prioritizes enhanced wall-thickness consistency and refined carbon-free interior surfaces to resist high thermal loads without scaling.
We are integrating multi-layer PVF (Polyvinyl Fluoride) and electro-galvanized coatings that withstand over 1,000 hours in neutral salt spray testing. This provides reliable corrosion protection for automotive under-chassis and coastal HVAC installations.
By implementing in-line helium leak detection and high-resolution CCD visual inspection at the forming stage, we minimize critical defects to achieve a target rate below 0.05% for global OEMs.
How Ningbo Taojun ensures consistent material sourcing, production efficiency, and streamlined international logistics.
Ningbo is a key global shipping hub, offering direct sea access via Ningbo-Zhoushan Port. This proximity simplifies shipping routes and reduces transit times for customers in Europe, North America, and Southeast Asia.
By establishing long-term partnerships with domestic steel mills, we secure a stable supply of raw materials, protecting our production schedules from sudden price fluctuations. Our integrated manufacturing setup handles everything from strip rolling to copper plating and final heat treatment in-house.
1998 Original Plant
2008 MES System
2024 Plant Upgrades
From automotive fluid lines to residential heat pumps, our tubing provides structural integrity and reliable thermal transmission.
Double-walled Bundy tubing provides high vibration resistance and burst strength, making it ideal for automotive hydraulic lines and fuel routing systems.
Designed for domestic refrigerators, commercial showcase freezers, and ice makers. Features low inner surface carbon content to prevent clogging in capillary tubes.
Maintains consistent thermal transfer rates in high-efficiency heat pumps, commercial air conditioners, and chiller units using R32 or R290 refrigerants.
At Ningbo Taojun, our manufacturing processes are backed by standard industry certifications. We operate under a GB/T19001-2016 / ISO9001:2015 certification (Registration Number: 41325Q00065R0S), which covers our design, production, and quality systems.
Each production run is subject to verification through our in-house testing lab. Products are tested for tensile strength, elongation limits, and thermal shock performance.
Main Certification Document
Detailed Scope of Certification
We ensure product reliability through five stages of quality verification:
Answers to common engineering and procurement questions regarding double-walled steel tubing.
Double-walled steel Bundy tubing is formed by wrapping a single steel strip through 720 degrees, producing a two-layer wall structure. The layers are copper-brazed together, resulting in higher pressure tolerance, greater mechanical strength, and improved leak resistance compared to single-walled tubes. This makes them suitable for high-pressure HVAC systems and demanding automotive environments.
Internal carbon residue is controlled through cleaning processes before heat treatment. We use a bright annealing furnace with a hydrogen-rich atmosphere to reduce oxide layers and burn off hydrocarbons. Our standard production line maintains internal carbon residue levels below 0.15 mg/dm², minimizing the risk of reactions with HFC/HC refrigerants.
Yes, Bundy steel tubing is a common alternative to copper tubing in refrigeration applications like condensers and evaporators. Steel offers higher structural strength, lower material cost, and better resistance to physical damage. While copper has higher raw thermal conductivity, Bundy tubes can achieve comparable heat transfer efficiency when configured with external fins.
We offer several coating options based on application requirements: standard copper coating (for inner and outer surfaces), electrolytic zinc plating (galvanization), PVF (Polyvinyl Fluoride) coating, and epoxy powder spraying. Our PVF coating is designed to withstand over 1,000 hours in neutral salt spray tests, meeting automotive chassis specifications.
We conduct a range of quality checks, including mechanical properties testing (tensile strength, yield strength, elongation), workability testing (flaring, flattening, bending, expansion), non-destructive testing (in-line eddy current testing), and pressure testing (nitrogen pressure hold and burst tests up to 110 MPa).
Yes, our entire production line is certified to comply with EU RoHS (Restriction of Hazardous Substances), REACH, and WEEE directives. We use lead-free copper brazing and chromium-free surface passivation processes, ensuring compliance with global environmental standards.
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Taojun