Sihe Steel
Sihe Steel
In high-temperature, high-pressure (HTHP) deep-well operations, structural and material performance boundaries are pushed to their physical limits. S31603 (commonly known as 316L or UNS S31603) is a low-carbon, molybdenum-bearing austenitic stainless steel engineered to excel in aggressively corrosive environments. Crucial to its application in subsurface control strings and chemical injection capillaries is its composition balance: chromium (16-18%), nickel (10-14%), and molybdenum (2-3%), paired with a carbon ceiling of 0.030% max.
This restriction in carbon content eliminates sensitization—the precipitation of chromium carbides along grain boundaries when subjected to hot thermal zones during welding or heat treating. By maintaining an uncompromised grain matrix, S31603 downhole capillary string tubing completely prevents Intergranular Corrosion (IGC). The 2-3% Molybdenum content specifically enhances resistance to localized pitting and crevice corrosion under high concentrations of chloride ions, which are prevalent in deep subterranean reservoir fluids.
Through advanced bright annealing at temperatures exceeding 1050°C and instant inline gas quenching, we lock in a fully recrystallized, single-phase austenitic structure. This minimizes magnetic permeability and maximizes ductility, making the tube robust enough to undergo high strain during downhole deployment and retrieval operations without structural failure.
Modern oil and gas extraction has moved from simple land operations into deeper reservoirs, subsea environments, and high-temperature geothermal formations. Subsurface flowassurance challenges—such as the formation of inorganic scales, hydrates, asphaltenes, and paraffin waxes—can restrict production or damage downhole infrastructure. S31603 stainless steel capillary strings act as the physical link for continuous injection of custom chemical treatments (corrosion inhibitors, biocides, scale inhibitors, and solvents) directly down the wellbore to the perforation zone.
Continuous transmission of scale inhibitors and demulsifiers into deep oil horizons to prevent hydrocarbon pathway blockage. Essential for sustaining long-term well productivity.
High-reliability hydraulic conduit lines operating downhole safety valves (DHSV) and packers, securing immediate well shutdown capability under unexpected surface pressure drops.
Housing high-accuracy fiber optic monitoring lines inside protective capillary tubes to transmit continuous temperature, acoustics, and pressure readings from deep reservoirs.
Additionally, downhole capillary string tubing serves as hydraulic control lines for Subsurface Safety Valves (SSSVs). These hydraulic systems require continuous pressure up to 15,000 PSI to hold subsurface valves open. Any wall thickness variation, metallurgical defect, or micro-cracking in the control string could lead to complete well control loss. Liaocheng Sihe's S31603 capillary tubes undergo 100% pneumatic, air tightness, and structural testing to guarantee system reliability in offshore subsea fields.
Liaocheng Sihe Stainless Steel Material LTD manufactures coiled tubing and capillary strings under strict international standards including ASTM A269, ASTM A312, ASTM A789, ASME SB358, JIS G3459, and EN 10216-5. Custom sizes outside the standard scope can be formulated to match specific deepwell and subsea umbilical engineering plans.
| Outer Diameter (OD) Range | Wall Thickness (WT) Range | Maximum Continuous Length | Standard Equivalents | Key Testing Regimes |
|---|---|---|---|---|
| 0.125 inch (3.175 mm) to 1.00 inch (25.4 mm) | 0.020 inch (0.50 mm) to 0.165 inch (4.19 mm) | Up to 32,800 feet (10,000 meters) | 316L, UNS S31603, 1.4404, SUS316L | Flaring, Flattening, Hardness 100%, Tensile, Hydrostatic & Air Tightness |
| Custom Capillary Sizes (1.0 mm to 10.0 mm) | 0.20 mm to 2.0 mm | On-demand customization | ASTM A269, GB/T 14976 | Pneumatic Leak Testing, Eddy Current Verification |
| Duplex & Nickel Alloy Alternatives | Custom sizes match severe service parameters | Up to 25,000 feet (7,620 meters) | Duplex 2205, Super Duplex 2507, Alloy 825/625 | NACE MR0175 Compliance, Positive Material Identification (PMI) |
Our factory features 6 cold-drawing and cold-rolling lines, backed by bright annealing technology. This process allows us to perform online softening of the stainless steel tubing under a dry protective hydrogen atmosphere, yielding an internally and externally clean surface, free of oxidation scale. This ultra-clean inner surface prevents turbulence and clogging of chemical inhibitors at high velocities.
As global energy exploration shifts to deeper waters where offshore conditions require reliable safety standards, using the correct corrosion-resistant material for coiled umbilical tubing is vital for reliable operations. Over the past ten years, Liaocheng Sihe has expanded its international footprint. Today, our products are exported to over 30 countries and regions worldwide, including the United States, Germany, Spain, South America, Southeast Asia, the Middle East, and Eastern Europe. Approximately 80% of our high-end coiled tubing products are exported, supporting offshore drilling programs in the Gulf of Mexico, North Sea, Persian Gulf, and Caspian Sea.
Supporting operators in the Gulf of Mexico with high-grade, continuous chemical injection strings, ensuring compliance with local safety standards.
Supplying Germany and Spain's heat exchanger, automotive, and industrial engineering facilities with high-precision polished capillary lines.
Providing high-resistance downhole capillary lines for high-temperature sour oil reservoirs containing high levels of hydrogen sulfide.
Delivering long-length, splice-free coiled tubing for deepsea umbilical configurations, ensuring continuous hydraulic control line integration.
Every coil of stainless steel capillary tubing and control line manufactured by Liaocheng Sihe is backed by a complete quality verification process. View our certified standards and test documentation below:
Our manufacturing infrastructure supports custom forming, treating, and finishing services to meet specific project demands:
We fabricate stainless steel coils in various materials (304, 316L, 2205) and custom diameters (6.35mm to 19.05mm) to meet specific offshore performance requirements.
Precision spiral forming, structural bending, and custom heat exchanger configurations engineered for high thermal transfer efficiency.
High-speed laser cutting, mechanical deburring, and computer-controlled tube straightening to guarantee dimensional accuracy and smooth end connections.
Mechanical polishing, electrochemical passivation, and ultrasonic cleaning stages ensure contamination-free inner diameters (ID) and corrosion-resistant outer surfaces.
Precision flanging, expanding, and swaging services to support seamless integration into automotive exhaust systems, process pipelines, and downhole instruments.
Continuous development of customized alloy components and tube dimensional ranges designed for extreme deep-well environments.
Our high-precision S31603 stainless steel capillary tubing and coiled strings are used across critical global industries:
High-thermal conductivity S31603 coils facilitate heat transfer in refining, chemical production, and power generation systems.
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Continuous, leak-free coiled tubing loops ensure refrigerant containment under high system operating pressures.
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Unmatched resistance to aggressive process chemicals, organic acids, and chloride-induced pitting at high process temperatures.
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Sanitary-grade internal surfaces eliminate bacterial build-up and withstand clean-in-place (CIP) chemicals.
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High-purity capillary lines designed for analytical instruments, sampling lines, and sterile transfer systems.
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Instrument tubes and steam trace heating lines engineered to withstand elevated operating pressures and steam temperatures.
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Downhole capillary lines, chemical injection networks, and control lines deployed in challenging land and offshore wells.
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Precision hydraulic tubes, high-pressure fuel lines, and structural elements designed for extreme vibration environments.
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High-precision capillary tubing engineered for analytical systems, defense components, and marine operations.
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2205 stainless steel is a duplex stainless steel containing austenitic and ferritic structures, offering exceptional stress corrosion resistance.
High-precision stainless steel coiled tubing available in multiple wall thicknesses and specifications to support subsea completion setups.
There are specialized factories in China manufacturing 310S heat resistant stainless steel coiled tubing for high-temperature furnace designs.
As global energy transitions toward sustainable systems, hydrogen transport and ultra-deep reservoir development are defining next-generation infrastructure design. Under hydrogen storage and distribution setups, ordinary stainless steels can suffer from Hydrogen Embrittlement, where microscopic hydrogen atoms diffuse into the crystal lattice, leading to premature cracking under mechanical stress.
Liaocheng Sihe is active in developing next-generation alloy configurations, including Duplex 2205 (UNS S31803 / S32205), Super Duplex 2507 (UNS S32750), Incoloy 825 (UNS N08825), and Inconel 625 (UNS N06625). These advanced grades feature balanced nickel and chromium contents to maintain microstructure stability. This helps resist stress cracking under high temperatures and pressures, as well as in sour gas environments with high hydrogen and hydrogen sulfide levels.
Our technological development focuses on creating continuous, splice-free capillary strings with lengths exceeding 15,000 meters. This supports deepwater umbilical applications, helping operators minimize downhole connections and simplify logistics.
