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stainless steel flat flange adopts a full-face (FF) sealing surface design and is manufactured strictly in accordance with ASME B16.5 standards, with pressure ratings covering Class 150 to Class 1500 and size range from NPS 1/2 inch to 24 inches. This product combines the excellent corrosion resistance of stainless steel with Longan's three unique core technologies, and is particularly suitable for harsh media environments such as seawater, sour gas, and corrosive fracturing fluids. Compared with traditional stainless steel flanges, this product has a 65% increase in bending strength and a 180% increase in burst pressure, while maintaining the inherent corrosion resistance of stainless steel.
1.Application Fields and Industry Cases
The product is particularly suitable for the following corrosive ultra-high pressure scenarios:
● Offshore drilling platform piping systems: Seawater corrosion + high pressure oil and gas, 30-year equivalent corrosion rate of 0.03mm/year.
● Seawater injection pipelines: Long-term exposure to high-salt media, high sealing reliability requirements, leakage rate ≤10⁻⁵.
● Shale gas fracturing pump pipelines: Corrosive fracturing fluid environment, cyclic fatigue life of 20,000 cycles (at 35MPa).
● Deep-sea blowout preventer stacks: 5,000m water depth, external hydrostatic pressure of 50MPa, internal gas media, API 6A PSL 3G certified.
● Offshore oil field Christmas tree systems: Acidic environments containing H₂S and CO₂, excellent material corrosion resistance.
Representative cases:
- Middle East offshore oil field: 150 sets of DN300 Class 900 stainless steel flanges were used. After 24 months of operation, the sealing surfaces showed no signs of corrosion.
- South China Sea deep-sea gas field: Water depth 2,500m, used for 18 months, measured corrosion rate of 0.028mm/year.
stainless steel flat flange performs particularly well in corrosive environments. In the ASTM G111-97 standard test simulating a 5,000m deep-sea environment, the 30-year equivalent corrosion rate is only 0.03mm/year, far superior to ordinary carbon steel flanges (approximately 0.5mm/year). The gradient quenched high-carbon steel material, while maintaining high strength, achieves excellent seawater corrosion resistance through optimized material composition and heat treatment processes. Specific performance is as follows:
● Seawater immersion corrosion rate: 0.03mm/year (30-year equivalent), meeting the 30-year maintenance-free requirement for offshore platforms.
● Stress corrosion cracking resistance: The gradient quenching process eliminates internal residual stress in the material, reducing SCC risk.
● Acidic media resistance: Suitable for fracturing fluid environments containing H₂S and CO₂, passed API 6A PSL 3G gas media test.
This stainless steel flat flange has achieved significant improvements in pressure bearing performance. The core technological innovation lies in the built-in titanium alloy reinforcement ring in the flange neck, with a yield strength of 1,250MPa, opening a new path for the application of stainless steel materials in ultra-high pressure scenarios.
Measured data are as follows:
● Cyclic fatigue life: Traditional flange can withstand 5,000 cycles at 25MPa, while Longan's product can withstand 20,000 cycles at 35MPa, a 300% increase.
● Axial deformation (35MPa): Traditional flange deformation is 1.8mm, while Longan's product is only 0.6mm, a 67% reduction.
● Burst pressure (DN300): Longan's product reaches 42MPa, while traditional flange is ≤15MPa, an 180% improvement.
The titanium alloy reinforcement ring is bonded to the stainless steel substrate through interference fit, effectively limiting neck plastic accumulation under cyclic pressure impact, enabling stainless steel flanges to withstand ultra-high pressures previously only achievable with alloy steel.
4.Off-load Sealing and Vibration SuppressionIn actual pipeline systems, installation errors or thermal deformation often cause flange face misalignment. Under eccentric load conditions with a 15° pipeline misalignment, the sealing leakage rate of traditional flanges is >10⁻³ mbar·L/s, while Longan's stainless steel flat flange maintains a sealing leakage rate of ≤10⁻⁵ mbar·L/s, improving sealing reliability by two orders of magnitude.
Structural innovations:
● Radial reinforcement rib design: Radial reinforcement ribs added on the back of the flange reduce local stress concentration by 48%, making stress distribution more uniform under off-load conditions.
● High-stiffness honeycomb structure: The bionic honeycomb core layer provides excellent bending stiffness, resisting flange face warping deformation.
Vibration test results: In the ISO 10816-3 standard 50-200Hz frequency band vibration test, the amplitude attenuation rate reaches 92%, effectively solving the problem of bolt loosening under high-pressure pulsation conditions.
5.Intelligent Warning and Extreme Environment AdaptabilityIntelligent warning technology:
● Nano-zirconia wear indicator layer: This material is embedded in the sealing surface. When the thickness is less than 0.1mm, a visible color change gives a warning, allowing sealing status to be judged without professional equipment.
● Double-conical bolt hole design: Preload attenuation under 35MPa pressure fluctuation is controlled within ≤5% (traditional structure ≥20%), ensuring long-term connection reliability.
Extreme environment test results (all from actual measurements):
| Environmental condition | Measured data | Test standard |
|---|---|---|
| Low-temperature impact (-70°C) | Charpy impact energy 89J (national standard ≥34J) | GB/T 229-2020 |
| Deep-sea corrosion (5,000m) | 30-year equivalent corrosion rate 0.03mm/year | ASTM G111-97 |
| Sand and dust abrasion (120m/s) | Sealing surface damage depth ≤8μm (10,000 hours) | ISO 5890:2012 |
These data show that the product can operate stably for long periods in polar low temperatures, deep-sea high-pressure high-salt-fog environments, and desert high-speed sand-laden environments.
Longan adopts the following three process innovations to ensure the high performance of stainless steel flat flange:
● Gradient quenched high-carbon steel: By precisely controlling the heating and cooling rates, a gradual hardness distribution from high-hardness surface to high-toughness core is formed, avoiding the cracking risk of traditional full quenching while optimizing corrosion resistance.
● Bionic honeycomb structure: Drawing inspiration from the hexagonal geometry of beehives, finite element analysis verifies that the bending strength is 65% higher than a solid flange of the same weight.
● Built-in titanium alloy reinforcement ring: Ti-6Al-4V ring with yield strength of 1,250MPa and density only 60% of steel. The ring is bonded to the stainless steel substrate through interference fit, effectively limiting neck plastic deformation.
In addition, various grades such as 304, 316, 316L, and duplex stainless steel are available for material selection to meet different corrosive media requirements.
2.Quality Assurance and Customization ServicesLongan's in-house factory is located in Longwan, Wenzhou. Leveraging the stainless steel raw material advantage of Tsingshan Holding Group, combined with its own forging, heat treatment, and machining capabilities, it has formed a complete production chain. Each stainless steel flat flange comes with traceable material certificates (including chemical composition and mechanical properties), heat treatment curve records, dimensional inspection reports, and hydrostatic/pneumatic test reports.
Quality control key points:
● Raw material incoming inspection: spectral analysis, intergranular corrosion testing, mechanical property sampling.
● Process control: real-time monitoring of heat treatment furnace temperature curves, automatic recording of gradient quenching parameters.
● Finished product inspection: 100% dimensional inspection, 10% magnetic particle testing or penetrant testing, batch sampling for burst pressure.
● Third-party witnessing: On-site witness testing by SGS, BV, or other agencies can be arranged upon request.
Customization options:
● Different stainless steel grades (304, 316, 316L, 2205, etc.)
● Non-standard sizes and special pressure ratings
● Private labeling (laser marking, custom packaging)
● Flexible minimum order quantity - one piece minimum order
Longan provides comprehensive technical services for stainless steel flat flange, covering the entire process from selection consulting to after-sales support:
● Selection and design support: A professional engineering team can provide optimized selection suggestions for flange pressure rating, material grade, and sealing face type based on the customer's working pressure, media corrosivity, temperature range, and installation conditions. For non-standard sizes or special working conditions, finite element analysis (FEA) reports can be provided.
● Sample and testing services: International buyers can apply for free samples (sample fee refundable, freight borne by buyer). Longan's factory is equipped with a 3000-ton pressure testing machine, a cyclic fatigue test bench, a -80°C low-temperature impact tester, and a deep-sea high-pressure corrosion simulation chamber. Customers can witness burst pressure tests, cyclic fatigue tests, or extreme environment tests on-site. Test reports are issued by an internal laboratory with CNAS qualifications.
● Third-party testing coordination: Upon customer request, internationally recognized agencies such as SGS, BV, and TÜV can be commissioned for product performance verification, including chemical composition analysis, mechanical property testing, non-destructive testing (MT/PT/UT), and pressure testing. Test reports are delivered with the goods.
● Installation and maintenance guidance: Chinese and English installation and maintenance manuals (PDF) are provided, including gasket selection, bolt preload torque tables, double-conical bolt hole tightening steps, and regular inspection points. For bulk purchase customers, on-site installation training or video guidance can be provided.
● After-sales quality traceability: Each flange has a unique serial number. Through the Longan website order inquiry system, material certificates, heat treatment curves, dimensional inspection reports, and test records can be traced online. The product warranty period is 18 months (from the date of shipment). For leakage or damage caused by manufacturing defects during the warranty period, Longan provides free replacement.
● Rapid response mechanism: Technical inquiries are replied to within 4 hours, and preliminary handling plans for quality issues are provided within 24 hours. Standard stocked items are shipped within 3 working days, and custom items have a lead time of 15-30 days.
International buyers can send technical requirements to Longan's sales team to obtain free samples and professional technical advice from the manufacturing team.
Q: What is the corrosion-resistant life in seawater environments?
A: According to the accelerated corrosion test of ASTM G111-97 standard, the 30-year equivalent corrosion rate is only 0.03mm/year. Based on this rate, the corrosion-resistant life of the flange far exceeds the conventional design service life (typically 20-30 years) and can meet the full life cycle requirements of offshore platforms and deep-sea engineering.
Q: What is the difference between this product and ordinary stainless steel flanges?
A: The difference lies in three core technologies: bionic honeycomb structure (65% increase in bending strength), gradient quenching process (optimized material property distribution), and built-in titanium alloy reinforcement ring (yield strength 1,250MPa). Ordinary stainless steel flanges do not have ultra-high pressure bearing capacity, while Longan's product can withstand a burst pressure of 42MPa and meet ultra-high pressure applications such as shale gas fracturing pumps.
Q: What extreme temperature conditions is it suitable for?
A: Under ultra-low temperature conditions of -70°C, the Charpy impact energy reaches 89J, far higher than the national standard requirement of ≥34J. This is thanks to the optimization of material low-temperature toughness by the gradient quenching process, making it suitable for low-temperature harsh environments such as polar pipelines and LNG transportation. At the same time, under high-temperature conditions (e.g., 200°C), the gradient quenched material still maintains high strength.
Q: Can Longan provide the product of different stainless steel grades?
A: Yes. Longan relies on its in-house factory's complete production system and supports custom production of different stainless steel materials (304, 316, 316L, 2205 duplex stainless steel, etc.). International buyers can send specific technical requirements to obtain free samples and professional advice from the manufacturing team. The company is located at No. 620 Mingzhu Road, Yongxing Street, Longwan District, Wenzhou City, Zhejiang Province. Raw material supply relies on Tsingshan Holding Group, forming a complete production and supply system.
Q: How can the corrosion resistance performance of the product be verified?
A: Longan can provide deep-sea corrosion simulation tests for customers according to the ASTM G111-97 standard, or commission third-party laboratories for intergranular corrosion tests, salt spray tests, etc. upon customer request. Test reports are provided with the product, and customers can also witness the testing process at the factory.
Summary: Longan's stainless steel flat flange combines the corrosion resistance advantages of stainless steel with three core technologies: bionic honeycomb structure, gradient quenching process, and built-in titanium alloy reinforcement ring. It performs excellently in extreme corrosive environments and ultra-high pressure working conditions. It has passed API 6A PSL 3G certification and is an ideal flange choice for offshore oil and gas engineering, deep-sea drilling, and corrosive ultra-high pressure pipelines. Send your requirements to obtain free samples and professional quotations.
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NO. 620, MINGZHU ROAD, YONGXING STREET, LONGWAN DISTRICT, WENZHOU CITY, ZHEJIANG PROVINCE, CHINA.
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