In AI computing power clusters and high-density server cabinets, the piping space for liquid cooled circuits is often measured in millimeters - the gap between CPU cold heads and rack manifolds, the interlayer between server nodes and CDUs, leaving extremely limited channels for pipelines. Traditional straight pipes can twist and collapse in such environments with just a slight bend, which not only blocks the coolant channel, but may also cause sealing failure of the quick plug joint due to pipeline hardness during insertion and maintenance. The combination of anti twist corrugated hose and quick connector is a systematic solution for this scenario - it uses the corrugated pipe wall configuration to achieve a flexible channel that "bends without collapsing", and uses standardized quick connectors to ensure convenient maintenance of "plug and break", becoming the "one meter" flexible connection standard in high-density liquid cooling systems.
1、 Password for anti twist structure: How to achieve "bending without collapsing" of corrugated hoses
The routing of liquid cooled hoses in high-density cabinets faces two major challenges: first, the need to complete direction conversion with a very small bending radius; second, the force on the hoses cannot be transmitted to the joint sealing surface during insertion and maintenance. Although traditional PFA straight pipes have high chemical purity, they have a large bending modulus and are prone to collapse at the bending point, resulting in a "necking" and a sudden increase in flow resistance. PFA corrugated pipe fundamentally changes the mechanical response characteristics of the pipe material through the design of the corrugated structure on the pipe wall.
The wavy configuration of the corrugated pipe wall ensures that stress is no longer concentrated at a single point during bending, but is uniformly dispersed through the expansion and contraction deformation of the corrugations. The ATLC series PFA corrugated pipe has a small bending radius of only 60mm for the 3/8 inch specification and 95mm for the 1/2 inch specification. The Danfoss EHW194 EPDM liquid cooled hose also features "excellent flexibility and resistance to twisting" as its core characteristics, with a small bending radius of only 25mm for the 1/4 inch specification.
The direct value of "anti twisting" lies in ensuring the smooth flow of the coolant channel throughout the entire process. During extreme bending, the wall of a regular hose collapses, causing a sudden drop of over 50% in the flow cross-sectional area, resulting in insufficient liquid supply to the cold plate and uncontrolled chip temperature. The corrugated pipe maintains a circular inner cavity during bending by compensating for the deformation of the corrugations, resulting in minimal flow attenuation. The five layer composite corrugated pipe innovatively developed by Su Lian Co., Ltd. further enhances durability and bending performance, and can simultaneously meet the dual requirements of anti creep and medium compatibility for liquid cooling systems.
2、 System Integration: The "Synergistic Effect" of Quick Plug Connectors and Bellows
The flexibility advantage of corrugated hoses ultimately needs to be transformed into system level reliability through end quick connectors. The server liquid cooling connection system consists of two main parts: a quick connector and a connecting hose. The quick connector plays a key role in "liquid insertion and removal, no dripping".
The functional positioning of the quick plug connector is to achieve "dry disconnection" during maintenance - when the plug and socket are disconnected, the built-in double block flat valve automatically cuts off the liquid flow, and the coolant will not leak outside the system. The joint body is made of stainless steel material, and the sealing ring comes standard with EPDM, which is compatible with mainstream coolant. According to the "Technical Specification for Liquid Cooling Devices for Server and Storage Equipment Part 2: Connection System" released by the China Electronics Industry Standardization Technology Association, quick couplings should have visual, tactile or auditory feedback during the connection and disconnection process, and the supply and discharge quick couplings should be marked in blue and red respectively.
The connection process between the hose and the joint is equally critical. The connecting hose needs to be equipped with hose fittings or quick connect fittings at the pipe end according to the port type. In the matching scheme of corrugated pipe and quick plug joint, the end of the hose needs to be precision expanded or crimped to ensure the sealing reliability between the joint and the pipe body. The specification requires that the inner and outer surfaces of the connecting hose should be clean, dry, and free of defects such as damage, cracks, bubbles, shrinkage, wrinkles, and protrusions. To adapt to the OCP open computing standard, the mainstream solution in the industry adopts UQD universal quick connector, which supports one handed quick insertion, high flow transmission, and uses red green dual color coding for easy identification of media types.
3、 Application Specification: From Selection Matching to Maintenance Operations
In the actual deployment of liquid cooling systems in data centers, the reliability of the combination of "anti twist corrugated hose+quick connector" depends on the strict implementation of selection matching and operating standards.
The selection criteria include three aspects: firstly, the inner diameter of the hose should match the diameter of the quick connector to ensure that flow resistance is not increased due to diameter reduction - the standard specification connector passes helium leak detection, and the flow performance exceeds the OCP rated value by 25%; Secondly, the material of the hose needs to be compatible with the coolant. EPDM has passed compatibility verification with water ethylene glycol based coolant such as PG-25, while PFA is suitable for fluorinated liquid systems; Thirdly, the flame retardant rating is essential for data center safety, and both EHW194 and CEJN liquid cooled hoses have passed UL94 V-0 certification.
Installation and maintenance operations directly affect the long-term reliability of the system. The specification requires that the number of bends in the hose should be reduced to minimize flow resistance, and the bends should meet the small bending radius requirements of the hose. After the hose is processed, it should be rinsed internally to remove impurities, particles, and other pollutants. In the insertion and extraction operation, the quick plug connector supports one handed connection, but it is necessary to ensure that the axis of the plug and socket are aligned to avoid lateral force causing damage to the sealing ring. For the "blind insertion" scenario in high-density cabinets, CEJN's PBMC connectors can automatically align under pressure, with angular and radial deviation tolerance, and can achieve reliable connections without the need for additional alignment mechanisms.
In summary, the matching scheme of anti twist corrugated hose and liquid cooled quick plug joint perfectly meets the composite requirements of server liquid cooling system for "narrow space pipe layout, maintenance plug and break, safety redundancy and reliability" with its extremely small bending radius of corrugated structure, zero leakage plugging and unplugging of quick plug joint, and UL94 V-0 flame retardant safety guarantee. From a 25mm bending radius to helium leak testing, from red and blue dual color identification markings to blind insertion automatic alignment technology, every detail points to the same goal: to provide a reliable and flexible pathway for liquid cooling systems between the dimensions of high-density computing power cabinets, without collapsing or leaking.
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