Urea Class Stainless Steel Pipe

• Overview

  Urea Class Stainless Steel Pipes are specialized stainless steel pipes designed specifically for urea production plants and other chemical processes that require high resistance to corrosion, especially in environments where urea and other aggressive chemicals are present. These pipes are modified versions of standard stainless steel grades, offering enhanced corrosion resistance and mechanical properties, making them ideal for use in urea manufacturing equipment.

• Material

  1. 316L Urea Grade (UNS S31603):

  Composition: A low-carbon variant of 316 stainless steel with increased molybdenum content (usually around 2.0-3.0%), which improves corrosion resistance.

  Key Features:

  Excellent resistance to pitting and crevice corrosion, especially in chloride-rich environments.

  Modified to handle urea production conditions, especially in high-pressure and high-temperature settings.

  Low carbon content minimizes the risk of carbide precipitation, improving resistance to intergranular corrosion.

  Applications: Urea synthesis towers, heat exchangers, piping systems exposed to urea, and ammonium carbamate.

  2. 25-22-2 Urea Grade (UNS S31050):

  Composition: A higher alloyed stainless steel containing approximately 25% chromium, 22% nickel, and 2% molybdenum.

  Key Features:

  Superior resistance to ammonium carbamate corrosion, particularly in concentrated urea solutions.

  High chromium and nickel content provide excellent resistance to both high-temperature oxidation and chloride stress corrosion cracking.

  The addition of molybdenum enhances pitting and crevice corrosion resistance, making it suitable for the harsh conditions in urea plants.

  Applications: Urea reactors, high-pressure urea strippers, and condensers.

  3. 310MoLN (UNS S31050):

  Composition: A nitrogen-enhanced stainless steel alloy containing 25% chromium, 22% nickel, and 2% molybdenum, with nitrogen for improved mechanical properties.

  Key Features:

  High resistance to corrosion in ammonium carbamate solutions, making it ideal for urea production applications.

  Nitrogen addition improves tensile strength while maintaining excellent ductility and toughness at elevated temperatures.

  Provides greater resistance to stress corrosion cracking and better performance in aggressive environments compared to traditional austenitic stainless steels.

  Applications: High-pressure urea plants, stripping sections, and critical urea process equipment.

  4. 904L (UNS N08904):

  Composition: A high alloy stainless steel with a composition of 20-23% chromium, 25% nickel, and 4.5% molybdenum.

  Key Features:

  Excellent resistance to urea and ammonium carbamate corrosion, even in high-pressure systems.

  High molybdenum and nickel content provide outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking.

  The alloy is also highly resistant to acidic environments, making it suitable for a variety of chemical applications beyond urea production.

  Applications:Urea synthesis towers, high-temperature piping, and heat exchangers.

• Features

  1. Enhanced Corrosion Resistance:

  Urea Class stainless steels are resist corrosion caused by ammonium carbamate and other chemicals commonly found in urea production. The high chromium and molybdenum content in the alloy provides strong protection against pitting and crevice corrosion, which are common in these environments.

  2. Improved Resistance to Carbamate Solutions:

  In urea plants, the presence of ammonium carbamate (a highly corrosive intermediate in urea production) can cause significant degradation in standard stainless steel. Urea Class stainless steels have been specifically designed to resist carbamate-induced corrosion, ensuring longer service life for pipes in urea synthesis reactors, strippers, and heat exchangers.

  3. High Temperature Stability:

  These pipes maintain their mechanical strength and structural integrity even under the high-temperature conditions of urea production. These alloys allow the pipes to operate efficiently at elevated temperatures without experiencing material deformation or corrosion fatigue.

  4. Enhanced Weld-ability:

  Urea Class stainless steel pipes exhibit excellent weldability, which is crucial in the construction and maintenance of urea production equipment. Their enhanced welding properties help prevent corrosion at the weld seams, a critical area that often experiences accelerated wear in corrosive environments.

• Size

  Outer Diameter:

  Urea Class Stainless Steel Pipes are manufactured in various outer diameters to suit different piping systems.

  Range:

  Seamless Pipes: 6 mm to 610 mm (¼ inch to 24 inches)

  Welded Pipes: 6 mm to 2,000 mm (¼ inch to 80 inches)

  Wall Thickness:

  Wall thickness is critical for withstanding high pressures and temperatures, particularly in urea production environments. Urea Class pipes are available in a variety of thicknesses to meet these demands.

  Range:

  Seamless Pipes: 1 mm to 50 mm (SCH 10 to SCH XXS)

  Welded Pipes: 1 mm to 70 mm (SCH 5 to SCH XXS)

  Length:

  Pipes are produced in various lengths depending on the requirements of the project, with the most common lengths being between 6 and 12 meters.

  Range:

  Standard Length: 6 meters, 12 meters

  Custom Lengths: Available upon request, including shorter lengths for specific installations or longer lengths for fewer joints and welds.

  Tolerances:

  Urea Class Stainless Steel Pipes are manufactured with strict dimensional tolerances to ensure precise fitting and performance in critical systems.

  Outer Diameter Tolerance: Typically within ±1%, ensuring uniformity and ease of installation.

  Wall Thickness Tolerance: Generally within ±10%, which ensures consistent strength and pressure handling across the pipe.

• Advantages

  1. Superior Corrosion Resistance

  Ammonium Carbamate Resistance: Urea Class stainless steel pipes are designed to resist corrosion from ammonium carbamate, a highly corrosive compound present in urea production. This enhanced corrosion resistance ensures the longevity and reliability of the pipes in harsh chemical environments.

  General Chemical Resistance: The alloy compositions, including high chromium and molybdenum content, provide excellent resistance to a wide range of chemicals, including acids and chlorides, making these pipes versatile for various industrial applications.

  2. High-Temperature Stability

  Thermal Endurance: These pipes maintain their mechanical strength and structural integrity at elevated temperatures, often exceeding 800°C. This property is crucial for high-temperature applications such as reactors and heat exchangers in urea production.

  Creep Resistance: Urea Class pipes are engineered to resist creep deformation under high-temperature conditions, ensuring they perform reliably over extended periods of operation.

  3. Enhanced Mechanical Properties

  Strength and Toughness: The special alloying elements in Urea Class pipes, such as nickel and molybdenum, provide high tensile strength and toughness. This makes them capable of withstanding high-pressure environments and mechanical stresses.

  Impact Resistance: These pipes are designed to absorb impacts and resist cracking or breaking under high-stress conditions, which is important for maintaining the integrity of critical systems.

  4. Improved Weldability

  Ease of Fabrication: Urea Class stainless steels exhibit excellent weldability, allowing for efficient fabrication and installation of piping systems. This characteristic is important for constructing and maintaining complex piping networks in urea plants and other chemical facilities.

  Weld Corrosion Resistance: Enhanced resistance to corrosion at weld seams reduces the risk of failures and leaks, ensuring the reliability of the entire piping system.

  5. Customizable Dimensions

  Flexible Sizing: These pipes are available in a wide range of sizes, wall thicknesses, and lengths to meet specific project requirements. This flexibility allows for tailored solutions in various applications, from small-diameter instrumentation pipes to large-diameter reactor tubes.

  Precision Tolerances: The pipes are manufactured to strict dimensional tolerances, ensuring consistent quality and precise fitment in complex systems.

  6. Long-Term Durability

  Extended Service Life: The combination of corrosion resistance, high-temperature stability, and mechanical strength ensures a long service life for Urea Class stainless steel pipes. This reduces maintenance needs and replacement costs over time.

  Reliability: Designed for demanding conditions, these pipes offer reliable performance and safety in critical processes, minimizing the risk of operational disruptions.

• Application

  1. Urea Production Plants:

  These pipes are specifically designed for use in urea synthesis sections, where they are used in reactors, heat exchangers, and piping systems that come into contact with aggressive chemicals. Their enhanced corrosion resistance ensures long-lasting performance and reduces the risk of leakage or failure in critical systems.

  2. Chemical and Fertilizer Industries:

  Beyond urea production, Urea Class pipes are suitable for other chemical industries that require high corrosion resistance in the presence of strong acids, ammonium compounds, and other aggressive chemicals, such as the fertilizer industry.

  3. High-Pressure Applications:

  These pipes are often used in high-pressure environments due to their ability to withstand the mechanical stresses of high-pressure operations while maintaining their corrosion resistance and mechanical properties.

• Processing

  HotForming

  Hot forming should be carried out in a temperature range of 1200-950 °C (2732-1742 ° F) after the piece has been uniformely heat treated. Final full annealing temperature is required to obtain the requested micro-structure. It will be performed at 1120 ° -1180 °C (2048 - 2156 ° F) followed by water quenching.

  
  

  ColdForming

  Due to its fully austenitic micro-structure, the alloy can be cold formed without any problem. The higher molybdenum content and cold hardening behaviour of the steel explains that it may require more powerful equipment than 304 stainless steel.

  
  

  Pickling

  The UREA must be used in the as pickled and passivized conditions. Pickling treatment may be performed with a nitro-hydrofluoric acid bath (10-20 % HN03 - 1.5-5% HF) at room temperature (few hours) or 20 minutes approx. at 60 °C (140 ° F). 10-20% H2SO4 - 1.5-5% HF pickling bath may also be used.