Metal hoses can indeed become brittle and prone to breakage at low temperatures due to cold brittleness. This phenomenon is closely related to the material properties and microstructural changes under low-temperature conditions. The toughness of metallic materials decreases significantly at low temperatures. When the temperature drops below the material's brittle transition temperature, the intermolecular gaps in the metal decrease, and internal stress increases, making it more susceptible to brittle fracture under external impact. For metal hoses, this characteristic is particularly pronounced when transporting cryogenic fluids or in extremely cold environments. Without effective preventative measures, this can lead to safety accidents such as pipe rupture and media leakage.
The primary measure to prevent low-temperature brittle fracture of metal hoses is scientific material selection. Materials with excellent low-temperature resistance, such as stainless steel and austenitic steel, are preferred. Among them, 316 stainless steel, due to the addition of molybdenum, exhibits better low-temperature corrosion resistance and impact resistance, making it especially suitable for extreme low-temperature environments. For further performance enhancement, PTFE-lined metal hoses offer dual protection: PTFE maintains flexibility even at -200°C and exhibits excellent chemical stability, resisting both low-temperature embrittlement and chemical corrosion, making them suitable for harsh conditions such as chemical and liquefied gas applications.
Insulation design is crucial for mitigating the effects of low temperatures. Wrapping the hose with polyurethane foam, rubber-plastic insulation, or fiberglass effectively slows heat transfer from the cryogenic fluid to the metal hose, preventing a sudden drop in pipe wall temperature. For pipelines transporting ultra-low temperature media such as liquid nitrogen (-196°C) and liquefied natural gas (-162°C), a double-layer insulation structure is recommended, with an outer protective shell to enhance impact resistance. In extreme conditions, electric heating technology can be introduced, using electric heating strips installed on the pipe wall to maintain temperature balance and prevent material embrittlement.
Proper pipe support and protection can significantly reduce mechanical stress damage to the metal hose. In low-temperature environments, the brittleness of metal materials increases. Hoses require brackets, support rings, and other devices to distribute external forces and prevent localized overload. Simultaneously, adding a protective sleeve or spiral spring to the outer layer of the hose can isolate it from external impacts and friction, reducing surface damage caused by collisions. For pipelines exposed outdoors for extended periods, the integrity of the insulation layer must be checked regularly, and any detached or damaged areas should be repaired promptly to ensure continued effective insulation.
Precise installation procedures are equally important in preventing low-temperature brittle fracture. During installation, avoid excessive bending or twisting of the hose, ensuring the bending radius meets design requirements to prevent corrugated pipe deformation or damage to the braided mesh layer. Joint connections must strictly adhere to operating procedures; direct hammering during installation is strictly prohibited to prevent thread damage or seal failure. Furthermore, sufficient displacement space should be allowed during installation to accommodate deformation caused by equipment thermal expansion and contraction or vibration, preventing pipe rupture due to restraint stress.
Regular inspection and maintenance are the last line of defense for ensuring the safe operation of metal hoses at low temperatures. Hardness testing, toughness assessment, and surface crack detection can promptly identify signs of material aging or damage. Periodic inspections of the insulation layer ensure its thickness and integrity meet standards. In extremely cold conditions, media flow rate and pressure must be adjusted to prevent the hose from being under prolonged overload, thus extending its service life.
The risk of brittle fracture of metal hoses in low-temperature environments can be effectively reduced through comprehensive measures such as optimized material selection, enhanced insulation, support and protection, standardized processes, and regular maintenance. Meticulous management at every stage, from material selection to installation and maintenance, is crucial for ensuring the safe and stable operation of the pipeline system.
