Foshan Xinliheng Stainless Steel Co., Ltd.（佛山市鑫利恒不锈钢有限公司）
Comprehensive Analysis of Stainless Steel Pipe Fittings
1. Definition and Core Functions
Stainless steel pipe fittings are key components used to connect, bend, branch, or change the flow direction of stainless steel pipelines. Their main functions include:
- Enabling flexible assembly of pipeline systems to adapt to complex installation scenarios
- Ensuring the tightness of pipeline joints to prevent medium leakage
- Adjusting fluid flow rate, pressure, or direction to meet process requirements
- Protecting the pipeline system and reducing the impact of vibration, corrosion, and other factors on the overall structure
2. Main Types and Classifications
(1) Classification by Connection Method
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Type
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Characteristics
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Application Scenarios
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Threaded Fittings
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No welding required, easy installation, detachable
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Low-pressure pipelines (≤1.6MPa), domestic water supply, small industrial equipment
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Flanged Fittings
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High connection strength, good tightness, easy maintenance
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High-pressure pipelines (≥4.0MPa), chemical equipment, large storage tanks
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Welded Fittings
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Compact structure, strong corrosion resistance, no leakage risk
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Stainless steel pipeline systems, food and pharmaceutical industries, high-temperature fluid transportation
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Press-Fit Fittings
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Cold connection technology, efficient construction, environmentally friendly and pollution-free
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Building water supply, underfloor heating systems, gas pipelines
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(2) Classification by Function
- Connection type: Coupling, Reducer, Tee, Cross
- Direction-changing type: 90° Elbow, 45° Elbow, Return Bend
- Sealing type: Cap, Plug, Union
- Control type: Valve fittings (e.g., globe valve joints, ball valve connection ends)
3. Core Material Properties
- Corrosion Resistance: Contains elements such as chromium (Cr ≥ 10.5%) and nickel (Ni), forming a passive film that can withstand acid, alkali, salt spray, and other environments. Suitable for chemical industry and marine engineering.
- High-Temperature Stability: Models such as 304 and 316L maintain mechanical properties within the range of -270℃ to 800℃, and can be used in high-temperature steam pipelines.
- Strength and Toughness: Tensile strength ≥ 515MPa, elongation ≥ 40%, strong impact resistance, and not easily damaged by vibration or pressure fluctuations.
- Hygiene: Smooth surface (Ra ≤ 0.8μm), no rust or precipitates, complying with food-grade (FDA) and pharmaceutical-grade (GMP) standards.
4. Common Application Fields
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Industry
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Typical Applications
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Recommended Materials
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Food and Beverage
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Beer brewing pipelines, dairy product transportation systems
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304, 316L
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Petroleum and Chemical
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Crude oil transportation, acid-base solvent pipelines
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316, 317L
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Construction and Building Materials
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Water supply and drainage pipelines, fire-fighting systems, curtain wall supports
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304, 201 (economical type)
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Medical Equipment
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Operating room water supply, medical solution transportation pipelines
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316L (ultra-low carbon)
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Marine Engineering
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Ship ballast water systems, offshore platform pipelines
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316L, 2205 duplex stainless steel
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5. Standards and Specifications
- International Standards:
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- ASTM A403: American standard for stainless steel pipe fittings (covering welded and threaded types)
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- DIN 11850: German standard for food-grade stainless steel pipe fittings
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- JIS B2311: Japanese industrial standard for stainless steel pipe fittings
- Chinese Standards:
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- GB/T 12459: Steel Butt-Welded Seamless Pipe Fittings
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- GB/T 13401: Steel Plate Butt-Welded Pipe Fittings
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- CJ/T 192: Stainless Steel Press-Fit Pipe Fittings (for construction use)
6. Installation and Maintenance Points
- Before Installation:
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- Check for scratches and rust on the fitting surface; the sealing surface must be free of impurities.
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- Confirm that the fitting specifications match the outer diameter and wall thickness of the pipeline (e.g., DN25 corresponds to φ32mm pipeline).
- During Installation:
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- Use Tungsten Inert Gas (TIG) welding to avoid oxidation in the heat-affected zone.
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- For threaded connections, apply food-grade sealant (e.g., polytetrafluoroethylene (PTFE) tape) and avoid over-tightening to prevent thread damage.
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- For press-fit connections, ensure the pressing depth meets the standard (usually 1.2~1.5mm).
- Maintenance:
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- Regularly clean the surface with neutral detergent to remove dirt and salt deposits.
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- For long-term unused pipelines, fill them with inert gas (e.g., nitrogen) to prevent internal rust.
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- Inspect flange gaskets and threaded joints every 1~2 years, and replace aging components in a timely manner.
