| Quantity: | |
|---|---|
Product Description
Performance requirements of water pipes connected to thermostats
In automobile cooling system, thermostat, as the core temperature control element, realizes the accurate management of engine temperature by adjusting the coolant circulation path (large cycle/small cycle). The water pipe connected with the thermostat directly participates in the dynamic heat exchange process, and must meet the following key performance requirements:
1. High temperature tolerance and thermal stability
Working temperature range: it is required to withstand severe temperature fluctuation from -40℃ (cold start) to 130℃ (extreme working condition), and the instantaneous peak value can reach 150℃ (turbocharged vehicle).
Material selection:
Base material: ethylene propylene diene monomer (EPDM) or fluororubber (FKM) is preferred, which has low glass transition temperature (Tg) (EPDM is -60℃) and excellent softening resistance at high temperature.
Reinforcement layer: built-in polyester fiber or aramid woven layer to prevent pipe diameter deformation caused by thermal expansion.
Thermal aging performance: Tested by ISO 1817 standard, after 168 hours at 150℃, the tensile strength attenuation rate is ≤20% and the volume expansion rate is ≤5%.
2. High pressure sealing and anti-pulsation ability
Pressure adaptability: keep the seal under the system pressure of 1.5~3.0 bar, and the bursting pressure is ≥8 bar (conventional system) or ≥12 bar (high-voltage hybrid/pure electric platform).
Anti-pulsation design:
The thickness of the pipe wall is ≥3.5mm, and a multi-layer composite structure (inner rubber layer+reinforcing layer+outer protective layer) is adopted to inhibit the expansion of the pipe caused by the pumping pressure pulsation of coolant.
The joint between the metal joint and the rubber pipe is molded and vulcanized to eliminate the risk of interlayer peeling.
3. Dynamic seal and interface reliability
Sealing form:
Clamp connection: use constant tension spring clamps (such as Norma or Tridon series), and the tightening torque is 2.5~4.5 N·m to ensure that the sealing surface is continuously pressed at high temperature.
Quick plug connector: equipped with double O-rings (made of HNBR or FKM), pre-coated with silicone grease to reduce the friction coefficient, and the plug-in force is ≤ 50 N.
Anti-vibration fatigue: passed the vibration test of SAE J1632 (frequency 10~200 Hz, acceleration 30 g), and there was no leakage or crack for 500 hours.
4. Chemical corrosion resistance and medium compatibility
Coolant compatibility: Resistant to ethylene glycol-based and propylene glycol-based coolants and additives (silicate, nitrate). The inner wall adopts low permeability formula to prevent plasticizer from precipitating and polluting the coolant.
Environmental resistance:
Ozone aging resistance: Under the condition of ozone concentration of 50 pphm, there is no surface crack for 500 hours (ASTM D1149).
Oil resistance: hardness changes ≤10 IRHD(ISO 1818) when exposed to engine oil.
5. Flow resistance optimization and thermal response efficiency
Inner wall smoothness: surface roughness Ra≤6.3 μm, reducing pressure drop loss caused by turbulence (δ P ≤ 0.2 bar/m).
Heat conduction design:
Small circulation pipeline (when thermostat is closed) adopts thin-walled structure (wall thickness is 2.0~2.5mm) to accelerate cold start and warm-up.
The large circulation pipeline (when the thermostat is fully open) is matched with the elbow with large curvature radius to reduce the flow resistance and improve the heat dissipation efficiency.
6. Mechanical stress resistance and durability
Bending fatigue life: after passing through ISO 6803 pulse test (pressure 0.3~1.5 bar, frequency 1 Hz), there is no leakage for ≥ 5 million cycles.
Spatial adaptability: The pipeline direction should avoid high-temperature components (such as exhaust manifold), and the minimum bending radius should be ≥4 times the pipe diameter to avoid bending stress concentration.
7. Compatibility of intelligent diagnosis (new energy vehicles)
Conductivity adaptation: some models of water pipes integrate conductive layers (such as carbon fiber doped rubber), which are linked with leakage detection circuits to monitor leakage in real time.
Thermal management coordination: the pipeline layout should be compatible with the PID control logic of the electronic thermostat to ensure that the flow change matches the millisecond response of the temperature signal.
Failure mode and maintenance specification
Typical faults: cracking of pipe body, loosening of joint and peeling of inner layer lead to leakage of coolant, which leads to overheating of engine or failure of warm air.
Maintenance period: It is recommended to check the pipeline hardness (measured by Shore A hardness tester, attenuation > 15% needs to be replaced) and clamp torque every 60,000 kilometers.
Replacement standard: it must be replaced if there is a deep crack ≥2mm on the surface, local expansion rate > 10% or it has been used for more than 8 years (whichever comes first).
summary
The water pipe connected to the thermostat is the physical carrier of the temperature control logic of the cooling system, and its performance directly affects the thermal efficiency, emission level and reliability of the engine. With the evolution of intelligent thermal management technology, such pipelines are upgrading from passive pressure-bearing components to key execution units of active thermal control systems, and innovative technologies such as flow sensing and self-repairing coating will be integrated in the future to further strengthen their strategic position in vehicle energy management.
Name1
Name2
Name3
Name4
