Crimp connections are widely adopted in thin-walled stainless steel piping systems due to their reliable sealing, efficient installation, and corrosion resistance. However, their applicability is constrained by four core factors: pipe material, conveyed medium, pressure and temperature conditions, and application scenarios. The following details both “suitable applications” and “inappropriate scenarios,” while clearly defining key limitations:
I. Core Application Scope
Crimp connections are designed for thin-walled, highly ductile metal pipes and must meet the fundamental requirements of “low/medium pressure, ambient/moderate temperature, and clean media.” Specific applicable scenarios are as follows:
1. Applicable Pipe Materials
Crimp connections rely on plastic deformation of the pipe to achieve sealing (by compressing the pipe and fitting with a die to form a tight interlock). Therefore, they are only suitable for thin-walled metal pipes with sufficient ductility. Common types include:
Stainless Steel Tubing: The most prevalent application, such as austenitic stainless steels like 304, 316L, and 304L (compliant with GB/T 19228 “Stainless Steel Compression Fittings” and GB/T 12771 “Welded Stainless Steel Tubes for Fluid Conveyance”). Pipe diameters typically range from DN15 to DN100 (special reinforced fittings are required for large diameters above DN100).
Copper and Copper Alloy Pipes: Such as pure copper pipes (T2) and brass fittings (H62), suitable for water supply and heating systems (compliant with GB/T 18033 “Seamless Copper Water Pipes and Copper Gas Pipes”), particularly ideal for scenarios demanding high hygiene standards (e.g., medical, food processing).
Other Special Pipes: Certain thin-walled aluminum alloy pipes (requiring specialized anti-corrosion treatment) and plastic-lined stainless steel pipes (compression-fitted outer metal layer with inner plastic lining for corrosion resistance). However, these are less commonly used and must strictly adhere to their specific product standards.
Inappropriate Materials: Cast iron pipes (high brittleness, incapable of plastic deformation), seamless steel pipes (excessively thick walls preventing effective crimping engagement), plastic pipes (e.g., PPR, PE, requiring heat fusion/electrofusion connections; crimping provides no seal).
2. Suitable Conveyed Media
The seal in press-fit connections relies on rubber gaskets (e.g., EPDM, NBR). The conveyed medium must be compatible with the gasket material and free from strong corrosion or large solid particles. Commonly suitable media include:
Civil Fluids:
Drinking Water (Tap Water, Direct-Drinking Water): Gaskets must meet “food-grade” standards (e.g., GB 4806.11) to prevent harmful substance leaching.
Hot water / heating water: Temperature ≤95°C (requires high-temperature resistant EPDM seals; standard NBR seals only withstand ≤80°C).
Air conditioning water: Chilled water (0-20°C), cooling water (20-40°C), free of corrosive additives.
Gas: Natural gas, liquefied petroleum gas (LPG) (requires dedicated gas-grade fittings, oil-resistant NBR seals, and must pass gas tightness testing per GB 50028 “Code for Design of Urban Gas Supply Systems”), limited to indoor branch pipes or low-pressure networks (≤0.4MPa).
Industrial Auxiliary Fluids:
Clean compressed air (oil-free, impurity-free, pressure ≤1.0MPa).
Mildly corrosive fluids (e.g., circulating water with pH 6-8; requires 316L stainless steel tubing to prevent corrosion).
Unsuitable media:
Strongly corrosive fluids (strong acids, strong alkalis, organic solvents; corrode tubing or swell seals).
Fluids containing solid particles/impurities (e.g., sewage, slurry; particles wear seal surfaces causing leakage).
High-temperature steam (temperature > 100°C; steam accelerates seal aging, and high pressure may damage the crimped interlocking structure).
3. Suitable Application Scenarios
Based on the above conditions, press-fit connections are primarily used in low-pressure, ambient-temperature scenarios demanding high installation efficiency and sealing performance. Common fields include:
Building Sector:
- Water supply piping in residential/commercial buildings (indoor branch pipes, vertical risers in common areas).
- Low-temperature hot water radiant floor heating systems (branch pipe connections).
- Central air-conditioning water systems (fan coil unit branch pipes, condensate drain lines).
Public Utilities & Facilities:
Clean water supply piping in hospitals and food processing plants (sanitary-grade stainless steel to prevent secondary contamination).
Indoor gas piping in urban areas (branch lines from building pressure regulators to user appliances/water heaters).
Solar water heating systems (cold water makeup, hot water delivery ≤85°C).
Industrial Support:
Clean compressed air piping in electronics manufacturing (oil-free, contaminant-free).
Purified water delivery pipelines in pharmaceutical plants (sanitary press fittings compliant with GMP standards).
Non-applicable scenarios:
Deep buried pipelines (burial depth > 1.5m; soil pressure may compress press fittings causing deformation and leakage; use “special reinforced press fittings for buried applications” or switch to welding).
Pipes subject to frequent vibration (e.g., pump outlets, air compressor outlets; vibration loosens crimped joints; flexible connectors required for cushioning).
High-pressure industrial main pipelines (e.g., chemical plant process lines with pressure > 2.5MPa; welding or flange connections required).
Outdoor exposed pipelines in extreme cold/heat regions (e.g., northern outdoor pipes below -30°C; sealing rings prone to brittleness).
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