1 Project Background and Technical Requirements
The Afipka Refinery Hydrocracking Complex is a critical component of Russia’s modernized refining infrastructure, designed to process high-sulfur crude oil and produce clean fuels meeting Euro V standards. The project involves extreme operating conditions, including high temperature (up to 550°C), high pressure (up to 20 MPa), and highly corrosive media (sulfur and hydrogen-containing), demanding exceptional reliability, sealing integrity, and durability from piping systems and connectors.
2 Core Material Advantages Analysis
2.1 SMLS (Seamless Pipes) and ERW (Electric Resistance Welded Pipes)
| Type | Advantages | Application Scenarios |
|---|---|---|
| SMLS Seamless Pipes | No weld weaknesses, uniform mechanical properties, resistant to high pressure/high temperature/corrosion, suitable for harsh media (e.g., hydrogen, hydrogen sulfide) | Inlet/outlet of hydrogenation reactors, high-pressure heat exchanger pipelines |
| ERW Welded Pipes | High dimensional accuracy (±0.5%), cost-effective, suitable for medium-low pressure systems (e.g., cooling water, utility pipelines) | Auxiliary system pipelines, low-pressure transmission lines |
Key Performance Comparison:
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SMLS Pipes: Pressure-bearing capacity ≥25 MPa, impact toughness ≥100 J (-46°C), compliant with API 5L/5CT standards.
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ERW Pipes: Weld strength ≥95% of base material, outer diameter tolerance ±0.5 mm, compliant with ASTM A53/A135 standards.
2.2 BW (Butt Weld) Fittings and Forged Fittings
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Structural Integrity: Forging process eliminates pores and inclusion defects, increasing fatigue life by over 50% compared to castings.
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Sealing Design: Precisely machined bevels (e.g., 37.5°±1°) ensure zero-defect full penetration welds, verified through 100% RT/UT testing.
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Material Adaptability: Use of ASTM A105/A182 F316 (for high-temperature sulfur corrosion environments) and A350 LF2 (for low-temperature conditions).
2.3 Forged Flanges (D15-DN1050)
| Type | Advantages |
|---|---|
| WN/RF Flanges | Optimized neck length-to-diameter ratio disperses stress; sealing surface Ra ≤ 3.2 μm ensures even gasket compression. |
| SO/BL Flanges | Back reinforcement design improves deformation resistance by 30%; suitable for high-vibration areas (e.g., pump inlets/outlets). |
Standard Compliance:
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Pressure Rating: Class 150~2500 (ASME B16.5/B16.47)
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Material Certification: NACE MR0175 (resistant to hydrogen sulfide stress corrosion).
2.4 Bolts, Nuts, and Gaskets
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High-Temperature Bolts: ASTM A193 B7/B16, preload loss rate <10% (after 1000 hours at 550°C).
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Locking Nuts: ASTM A194 2H/4H, with locking thread structure, torque retention rate ≥90% in vibrating environments.
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Metal Gaskets: Flexible graphite + 316L spiral wound gaskets (for environments with pH ≤ 12); serrated gaskets (for high-pressure flange connections).
3 Project-Specific Advantages
3.1 Corrosion Resistance
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Use of duplex steel 2205 (S31803) fittings for acidic media pipelines, pitting resistance equivalent number (PREN) ≥35.
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Tungsten carbide (WC-Co) coating on flange sealing surfaces, hardness ≥70 HRC, extending erosion-corrosion service life by 3 times.
3.2 Modular Construction Adaptability
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ERW pipes cut to precise lengths (±1 mm tolerance), improving prefabricated module对接 efficiency by 40%.
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Mechanically drilled bolt holes (H7 tolerance) for flanges enable blind assembly, reducing on-site adjustment time.
3.3 Lifecycle Cost Efficiency
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SMLS pipe wall thickness reduced by 10% (based on ASME B31.3 calculations), lowering material costs by 15%.
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Maintenance cycle for forged components extended to 15 years (compared to 8 years for castings), reducing downtime losses.
4 Quality Control and Compliance
| Item | Standard | Testing Method |
|---|---|---|
| Material Traceability | EN 10204 3.1 | Spectral analysis + mechanical property test blocks |
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Weld Inspection | ASME Sec V | Automated UT + Phased Array |
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Hardness Testing | ISO 6506 | 10-point grid measurement on flange sealing surfaces |
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Gasket Sealing Performance | EN 13555 | Thermal cycling tests from room temperature to 550°C |
5 Conclusion
In the Afipka Refinery Hydrocracking Project, the combination of SMLS/ERW pipes, BW fittings, forged flanges, and connectors provides:
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Safety: Passes hydrogen-induced cracking (HIC) tests per NACE TM0284 standards.
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Economy: Reduces installation costs by 20% (due to reduced welding rework and gasket replacements).
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Longevity: Designed for a 30-year service life without mid-term replacements.
This configuration has become a benchmark solution for high-sulfur crude oil processing projects in Russia, suitable for energy facility construction under extreme operating conditions.
