Technical Analysis: Application of 317LMN Stainless Steel in Palm Oil Fractionation II Units
创建于06.11
Technical Analysis: Application of 317LMN Stainless Steel in Palm Oil Fractionation II Units
Abstract
This paper examines the strategic implementation of 317LMN (UNS S31726) austenitic stainless steel in palm oil fractionation II units. Through comparative analysis with conventional 304L/316L alloys, we demonstrate how 317LMN’s superior corrosion resistance and mechanical properties resolve chronic equipment failures while delivering 34% lower lifecycle costs. Data from field deployments confirm 8–10-year service intervals without corrosion-related downtime.
1,Critical Function of Fractionation II Units in Palm Oil Production
Fractionation II constitutes the core refining stage where crude palm oil (CPO) undergoes thermal separation into distinct triglyceride fractions:
- Input:
CPO with 3–5% FFA (free fatty acids), 0.1–0.3% chloride contaminants
- Process:
Multi-stage crystallization at 50–55°C → Heating to 220–260°C → Vacuum distillation
- Output:
- Olein (24°C melting point): Liquid frying oils
- Stearin (44°C+ melting point): Solid fats for cosmetics/confectionery
Operational Significance:
- Determines final product functionality (melting profile, oxidative stability)
- Processes 95% of global palm oil output (2024: 78 million tonnes)
- Energy intensity: 85–110 kWh/tonne, making equipment reliability critical
2. Process-Specific Challenges for Construction Materials
2.1. Corrosion Mechanisms in Fractionation II
Threat Source | Impact on Materials | Critical Zones |
Free Fatty Acids | Uniform thinning (0.5–2 mm/year) | Evaporators, reboilers |
Chlorides (50–500 ppm) | Pitting/crevice corrosion | Condenser tubes, weld joints |
Thermal Cycling | Stress corrosion cracking (SCC) | Flange connections, pump volutes |
2.2. Key Material Requirements:
- Temperature Resistance: Sustained 260°C + thermal shocks
- Corrosion Resistance: PREN ≥ 30 for Cl⁻ > 200 ppm environments
- Mechanical Integrity: Yield strength > 200 MPa at 260°C
3. Limitations of 304L/316L in Service
3.1. Documented Failure Modes:
- 304L (PREN=19):
- Severe pitting in condensers (Cl⁻ > 100 ppm)
- SCC cracks in flange necks after 12–18 months
- 316L (PREN=26):
- Organic acid corrosion > 0.8 mm/year at 220°C
- Weld decay requiring post-weld heat treatment
3.2. Operational Costs of Conventional Alloys:
Failure Mode | Downtime Frequency | Cost Impact (Per Incident) |
Heat exchanger leaks | Every 2–3 years | $120k (repair) + $400k (production loss) |
Pump replacement | Annually | $65k (part) + $200k (cleanup) |
Product contamination | -- | $2M+ (recall/penalties) |
4. 317LMN: Performance Advantages & Economic Rationale
4.1. Material Science Superiority:
- Enhanced PREN (≥36): Mo (4.5%) + N (0.15%) synergy
- Critical Pitting Temperature: 55°C vs. 25°C for 316L
- SCC Threshold: 90°C in 25% NaCl vs. 60°C for 316L
4.2. Field Performance Data (Malaysian Plant, 2021–2024):
Parameter | 316L | 317LMN | Improvement |
Corrosion rate | 0.45 mm/year | 0.03 mm/year | 15X |
Maintenance interval | 3 years | 8+ years | 167% |
Total cost/10-years | $3.2M | $1.8M | 44% savings |
5. Metallurgical Profile of 317LMN
5.1. Composition (ASTM A312):
Element | Range (wt%) | Function |
Cr | 18.0–20.0 | Passive film stability |
Ni | 13.5–17.5 | Austenite phase retention |
Mo | 4.0–5.0 | Chloride resistance |
N | 0.10–0.20 | Strength boost, pit healing |
5.2. Mechanical Properties at 260°C:
Property | 317LMN | 316L | Advantage |
Yield Strength | 248 MPa | 172 MPa | +44% |
Creep Resistance | 120 MPa | 85 MPa | +41% |
Elongation | 42% | 35% | +20% |
6. Kherlyn’s Integrated Supply Solution for 317LMN Systems
6.1. End-to-End Quality Control:
- Raw Material Stage:
- VOD refining (Vacuum Oxygen Decarburization) achieving:
- O ≤ 30 ppm | S ≤ 0.003% | N=0.15±0.02%
- ASTM A1063-compliant slab ultrasonic testing
- Manufacturing Process:
- PQF® (Premium Quality Forging) for seamless pipes (OD 12–24")
- Solution annealing: 1120°C ±10°C, WQ < 60 sec
- Electrolytic polishing (Ra ≤ 0.8 μm)
6.2. Third-Party Verified Compliance:
- ITP (Inspection Test Plan):
- Stage 1: PMI (Positive Material Identification) – Full spectrometer check
- Stage 2: ASTM A262 Practice E – Intergranular corrosion test
- Stage 3: Hydrotest at 1.5X design pressure
- Certifications:
- ASME B31.3 Process Piping
- PED 2014/68/EU Annex I
- Halal/Kosher material compliance
6.3. Prefabricated Piping Package Advantages:
Component | Kherlyn’s Solution | Industry Standard |
Pipes | OD tolerance ±0.2%, WT +15%/-10% | ±0.5%, WT ±12.5% |
Fittings | CNC-machined from forged blanks | Cast/pressed |
Flanges | RT (Radiographic Testing) on all welds | Spot RT |
Delivery Cycle | 12 weeks (ex-works) | 18–24 weeks |
Conclusion
The adoption of 317LMN stainless steel in palm oil fractionation II units resolves the fundamental conflict between corrosion resistance and high-temperature strength. Kherlyn’s vertically integrated supply model—combining precision metallurgy, digital traceability, and third-party validated quality—reduces lifecycle costs by 34% while eliminating food contamination risks. As global palm oil capacity expands toward 95 million tonnes by 2028, 317LMN represents the new benchmark for sustainable refining infrastructure.
Contact
Leave your information and we will contact you.