Cooling Hose Supplier – EPDM Available, ISO 9001 Certified
1. Product Definition and Application Scope
The UL94 V-0 liquid cooling hose is a specialized flexible thermal management tube designed for liquid circulation in high-power electronic and energy storage systems. The "UL94 V-0" designation refers to the flame retardancy classification under the UL94 standard for flammability of plastic materials. A V-0 rating represents the highest level of flame resistance in the vertical burning test, requiring that the material self-extinguishes within 10 seconds after removal of the test flame and does not produce flaming drips that could ignite cotton indicators.
This product category serves as the fluid conduit in liquid cooling circuits, transporting coolants between heat-generating components and heat rejection systems. Key application areas include battery thermal management in electric vehicles and stationary energy storage systems, cooling of power electronics and inverters, thermal regulation in data center server racks, and liquid cooling of high-power charging cables for electric vehicles.
The flexible construction allows routing through confined spaces with tight clearances, reducing the number of connection points required and simplifying system assembly. The UL94 V-0 flame retardancy provides critical fire safety protection, particularly in high-energy environments where electrical faults or thermal events could potentially ignite surrounding materials.
2. Material Composition and Structural Design
Inner Tube Layer: The fluid barrier is typically manufactured from peroxide-cured EPDM rubber or cross-linked polyethylene. Peroxide-cured EPDM is preferred for its excellent resistance to glycol-based coolants, low extractable content that prevents coolant contamination, and wide temperature capability. The inner tube surface is extruded to a smooth finish that minimizes flow resistance and reduces the risk of particle entrapment that could affect system performance.
Reinforcement Layer: To provide pressure containment and structural integrity, the hose incorporates a reinforcement structure. Common constructions include high-tensile synthetic fiber braid, such as polyester or aramid, applied as a single or multiple-layer braid. For applications requiring greater pressure capacity or resistance to collapse under vacuum or suction conditions, a steel wire helix may be incorporated between braid layers. The reinforcement preserves dimensional stability under pressure while maintaining the flexibility required for installation in compact equipment spaces.
Outer Cover: The exterior layer is formulated from flame-retardant rubber compounds or thermoplastic materials that achieve the UL94 V-0 classification. The cover provides resistance to ozone, weathering, and mechanical abrasion while serving as the primary fire barrier. The V-0 rated compound contains flame retardant additives that act in both the gas and condensed phases to inhibit combustion and promote self-extinguishing behavior.
Bonding and Adhesion: The layers are bonded through vulcanization or lamination processes to prevent delamination under flexing or pressure cycling. Adhesion strength is verified through peel testing as part of quality control.
3. Performance Specifications
Temperature Capability: UL94 V-0 liquid cooling hoses are engineered for reliable operation across a broad temperature range. Standard products are rated for continuous service from -40°C to +125°C, with some designs capable of withstanding short-term excursions up to +150°C. This wide operational envelope accommodates both cold-climate installations and the elevated temperatures encountered in high-power electronics cooling circuits.
Pressure Ratings: The working pressure is determined by the reinforcement construction and hose diameter. For typical battery and power electronics cooling applications, working pressures range from 1.4 MPa to 2.4 MPa (approximately 200 to 350 psi). Burst pressure is typically four times the working pressure, providing a substantial safety margin against pressure surges. The reinforcement design ensures the hose maintains pressure integrity throughout its service life.
Bend Radius: Flexibility is a key performance attribute. High-quality UL94 V-0 liquid cooling hoses achieve a minimum bend radius equal to the hose outside diameter, enabling installation in tight spaces without compromising flow performance. This 1:1 bend radius capability simplifies routing through battery modules, cabinet interiors, and equipment enclosures.
Coolant Compatibility: The inner tube material demonstrates resistance to water-glycol coolant mixtures, the standard heat transfer fluid in liquid cooling systems. Key compatibility parameters include resistance to swelling or degradation, low metal ion leach rates to maintain coolant purity, and minimal permeation to prevent fluid loss over the system life.
Electrical Properties: For use in electrical systems, the hose may be required to provide insulation resistance. EPDM and other suitable materials exhibit high dielectric strength, reducing the risk of leakage current through the coolant circuit.
4. UL94 V-0 Flame Test and Certification
The UL94 vertical burning test is conducted on material samples of specified dimensions. The test procedure involves applying a controlled flame to a vertically suspended sample for 10 seconds, then removing the flame and measuring the self-extinguishing time and observing any dripping behavior. A V-0 classification requires all three of the following criteria: each individual specimen extinguishes within 10 seconds after removal of the test flame; the total flaming combustion time for five specimens does not exceed 50 seconds; and no specimen produces flaming drips that ignite cotton placed beneath the test apparatus.
For liquid cooling hoses, the UL94 V-0 rating is typically achieved through the cover material formulation. The flame-retardant cover compound contains halogenated or phosphorus-based additives that interrupt the combustion process. The certification is performed by UL or other recognized testing laboratories, and the manufacturer maintains the UL Yellow Card or equivalent documentation as evidence of compliance.
In addition to the material-level UL94 rating, complete hose assemblies may be evaluated under end-use standards such as UL 4303 (Standard for Safety for Hoses and Tubing in Liquid Cooling Systems). This assembly-level testing verifies that the hose maintains pressure integrity and flame resistance under the combined conditions of temperature, pressure, and coolant exposure encountered in service.
5. Application Areas and Installation Practice
Electric Vehicle Battery Cooling: In electric vehicle battery packs, liquid cooling hoses connect the battery modules to the cooling manifold and chiller circuit. The hoses must accommodate vehicle vibration and thermal expansion while maintaining leak-free connections over the vehicle service life. The flexible construction enables routing between modules in the limited space available within the battery enclosure. The UL94 V-0 flame retardancy contributes to overall battery pack fire safety.
Stationary Energy Storage Systems: In containerized or cabinet-based battery storage systems, the hoses connect battery racks to the cooling distribution system. The installation may involve longer hose runs with multiple connection points. The flexibility and bend radius capability facilitate efficient routing within cabinet layouts.
Data Center Liquid Cooling: In server racks employing liquid cooling, the hoses distribute coolant to individual servers or to cold plates mounted on processors and memory modules. The compact server enclosures require hoses with tight bend radii and reliable long-term performance.
Charging Pile Cable Cooling: In high-power DC fast charging cables, liquid cooling hoses are integrated into the cable assembly to enable sustained high-current operation while maintaining cable temperatures within safe limits.
6. Quality Assurance and Testing
Production Testing: Each production batch of UL94 V-0 liquid cooling hoses undergoes hydrostatic proof testing to verify pressure integrity. Test pressure is typically 1.5 times the rated working pressure, and the hose is held at pressure for a specified duration without leakage.
Flame Test Verification: Periodic flame testing is performed on material samples to verify continued compliance with the UL94 V-0 classification. The test results are documented for quality records and for submission to certifying bodies.
Coolant Compatibility Testing: The hose is evaluated for chemical resistance to the specified coolant at the maximum operating temperature. Performance parameters include dimensional stability, tensile strength retention, and weight change.
7. Selection Criteria
When selecting a UL94 V-0 liquid cooling hose for a thermal management application, the following criteria should be assessed:
Operating Temperature Range: Verify that the hose rating covers both the minimum and maximum temperatures expected in service.
Working Pressure: Confirm that the working pressure rating meets system requirements, including allowance for pressure surges.
Bend Radius: Evaluate the minimum bend radius relative to installation clearances and routing constraints.
Coolant Compatibility: Verify that the inner tube material is compatible with the specific coolant formulation used in the system.
Fire Safety Requirements: Confirm that the UL94 V-0 rating meets the regulatory and project-specific fire safety standards.
