Fitting Inconel 718

I. Energy and Electric Power Industry

• Nuclear power system
  • Application scenario: The coolant pipeline of nuclear reactor and the connecting pipe of steam generator should be resistant to high temperature and high pressure (such as 300℃ and 15MPa) and the corrosion of boric acid-containing water.
  • Material selection: 316L stainless steel pipe fittings (chloride ion stress corrosion resistance) and Inconel 600 alloy pipe fittings (radiation resistance and high temperature oxidation resistance).
  • Key requirements: the pipe fittings shall be certified by ASME BPVC, and the welds shall be 100% nondestructive testing (RT/UT).
• Thermal power and new energy
  • Supercritical unit: The main steam pipeline (temperature 580℃+, pressure 25MPa+) uses Super304H stainless steel pipe fittings, which is resistant to high temperature creep and steam oxidation.
  • Photovoltaic/photothermal power generation: The high-temperature pipeline (350~500℃) of molten salt energy storage system adopts 310S stainless steel pipe fittings to resist molten salt crystallization corrosion.

II. Petroleum, Chemical Industry and Coal Chemical Industry

• Oil refining and petrochemical plant
  • Hydrocracking unit: 2507 dual-phase stainless steel pipe fittings is used for high-pressure hydrogen pipeline (400℃, 10MPa) to resist hydrogen embrittlement and HS corrosion; The feed pipe of ethylene cracking furnace adopts HK40 alloy pipe fittings, which can resist coking at 850℃.
  • Acid gas treatment: Hastelloy C-276 pipe fittings are used for the inlet and outlet pipelines of desulfurization tower, which can resist the combined corrosion of wet HS+Co+Cl (pitting potential > ＞600mV).
• Chemical pipeline system
  • Concentrated acid transportation: 904L stainless steel pipe fittings (high Mo content) is selected for 98% sulfuric acid pipeline to prevent intergranular corrosion; Monel alloy pipe fittings are used in hydrofluoric acid alkylation unit, which is resistant to fluoride corrosion.
  • Gasifier for coal chemical industry: The synthesis gas pipeline (300~450℃, including HS) adopts duplex stainless steel 2205 pipe fittings, giving consideration to strength and corrosion resistance.

III. Ocean Engineering and Shipbuilding Industry

• Deep-sea oil and gas development
  • Submarine pipeline system: Super duplex stainless steel 2507 pipe fittings are used for oil pipelines with water depth exceeding 1000 meters to resist stress corrosion of seawater chloride ions (rupture time > 10000 hours @400mV).
  • isers for offshore platforms: 6Mo stainless steel (N08367) pipe fittings are adopted, which are resistant to seawater erosion and microbial corrosion, and can replace traditional titanium alloys to reduce costs.
• Ship power system
  • Diesel engine exhaust pipe: 310S stainless steel pipe fittings (resistant to 1000℃ high temperature exhaust gas) is used, and the surface is aluminized to enhance oxidation resistance; 316L stainless steel pipe fittings for seawater cooling system is lined with anti-corrosion coating to resist biological fouling.

IV. Aerospace and High-end Manufacturing

• Aircraft engine
  • Fuel pipeline: Inconel 718 alloy pipe fittings are used in high temperature area (300~500℃), which is resistant to fuel erosion and oxidation; The hydraulic system uses 17-4PH precipitation hardening stainless steel pipe fittings with strength σ b > 1300 MPa and resistance to hydraulic oil corrosion.
• Space propulsion system
  • Rocket fuel delivery pipe: titanium alloy (TC4) pipe fitting for liquid oxygen/kerosene engine, which is resistant to-183℃ low temperature and oxidant corrosion; Haynes 282 alloy pipe fittings for high temperature gas pipelines are resistant to gas erosion at 1200℃.

V. Environmental Protection and Waste Disposal

• Garbage incineration power generation
  • Flue gas purification system: waste heat boiler pipeline (800℃) uses 310S stainless steel pipe fittings, which is resistant to chloride high temperature corrosion; 253MA stainless steel pipe fittings is used for the inlet and outlet pipelines of the desulfurization and denitrification (SCR) reactor, which is resistant to NOx and NH corrosion.
• Sewage treatment and seawater desalination
  • Reverse osmosis (RO) membrane pipeline: 904L stainless steel pipe fittings for seawater desalination, which is resistant to high concentration of Cl (> 20,000 ppm) and osmotic pressure impact; Titanium alloy pipe fittings for electrolytic water treatment are resistant to electrochemical corrosion of electrolyte.

VI. Medical Care and Food Medicine

• Medical equipment
  • High-temperature sterilization equipment: 316L stainless steel pipe fittings is used for the steam pipeline of the autoclave, and the inner wall is electropolished (roughness Ra < 0.8μ m), which meets the GMP aseptic requirements.
  • Connecting pipe of pharmaceutical reaction kettle: 316L stainless steel sanitary pipe fittings (quick-assembly connection) are adopted, which are resistant to corrosion of acid-base liquid medicine and CIP/SIP cleaning (saturated steam at 134℃).
• food processing
  • High-temperature sterilization line for dairy products: UHT ultra-high temperature sterilization pipeline (135℃) uses 316L stainless steel pipe fittings, and the surface is passivated to prevent protein deposition corrosion; The CO pipeline of beer brewing equipment is made of 304 stainless steel pipe fittings, which is resistant to organic acid corrosion.

VII. Machinery and Semiconductor Industry

• High end machinery and equipment
  • Connecting pipe of high-temperature high-pressure pump: 2507 duplex stainless steel is used for inlet and outlet pipe fittings of chemical process pump, which is resistant to medium erosion (flow rate > 10m/s) and cavitation damage; 15-5PH stainless steel pipe fittings is used for the hydraulic pipeline of injection molding machine, which can resist the aging corrosion of high-pressure oil.
• Semiconductor manufacturing
  • Wafer cleaning equipment: PVDF-lined 316L stainless steel composite pipe fitting for hydrofluoric acid (HF) etching liquid conveying pipeline, which is resistant to strong corrosion and does not pollute the medium; The N-pipe of high temperature diffusion furnace is electropolished with 316L stainless steel, and the impurity content is controlled to be less than ＜1ppm.

Typical materials and application characteristics of high alloy stainless steel pipe fittings

Key technical points of application scenario

• Temperature and pressure resistance design: pipe fittings shall conform to ASME B31.3 (chemical engineering) /B31.1 (power) standards, and allowable stress shall be calculated at high temperature (for example, allowable stress of 310S at 700℃ > ＞20MPa).
• Anti-corrosion technology: For Cl environment, pipe fittings need to be treated by solid solution (such as water quenching of 2205 dual-phase steel at 1050℃) to improve pitting corrosion resistance (PREN value > 40); The inner wall can be protected by electrochemical polishing or PVD coaTiNg (such as tin).
• Connection and sealing: Butt-welded pipe+spiral wound gaskets shall be used for high-pressure scenes (> ＞10MPa), and socket welding or sleeve connection shall be used for low-temperature or corrosive scenes to avoid crevice corrosion.