Edible Oil Refinery
Process Overview
Edible Oil Refinery — Process Overview
An edible oil refinery turns crude vegetable oil (soybean, sunflower, palm, rice bran, mustard and others) into refined cooking oil. Gums are removed with water or acid, free fatty acids are neutralised with caustic to form soapstock (in chemical refining), colour bodies are adsorbed on bleaching earth under vacuum, and odours and remaining fatty acids are stripped with steam in the deodoriser at 230–260 °C under deep vacuum. A thermic fluid heater supplies the deodoriser.
For milk and dairy see Dairy Processing; for brewery and beverages see Beverage & Brewery; for biodiesel see Biofuels.
Key Sealing Challenges
- Vacuum suction: bleachers and deodorisers run under vacuum; air drawn past the seal oxidises the oil and causes rancidity.
- Abrasive slurry: bleaching earth wears soft faces and needs a hard SiC pair with a pressurised barrier.
- High temperature: deodorised oil and thermic fluid exceed elastomer limits; metal bellows seals with graphite are used.
- Food contact: elastomers and barrier fluids must be food-grade.
What mechanical seal is used on deodoriser pumps in edible oil refineries?
Deodorised oil pumps typically use a metal bellows seal with flexible graphite secondary seals and SiC vs. carbon faces, because the oil is at 230–260 °C. Since the pump draws from deep vacuum, an API Plan 32 cool oil flush or a double seal with a barrier keeps air out, preventing oxidation of the refined oil.
Root-Cause Failure Analysis — Field Example
Symptom: Refined oil shows rising peroxide value; deodorised oil pump seal faces are dry and the chamber is under vacuum.
├── Incorrect Response: "Replace the seal with the same type."
├── Diagnostic Evidence Required:
│ ├── Is the seal chamber under vacuum, drawing air across the faces into the oil?
│ ├── Is a flush or barrier fitted, and is its pressure above seal-chamber pressure?
│ └── Check the elastomer or graphite secondary seals for heat damage.
└── Engineered Solution:
├── Metal bellows seal with graphite secondary seals for 230–260 °C.
├── API Plan 32 cool refined-oil flush, or a double seal with a food-grade barrier.
└── Verify seal-chamber pressure under all operating conditions.
Frequently Asked Questions
Why is a double seal used on bleaching earth slurry pumps?
The slurry is abrasive and the bleacher runs under vacuum. A pressurised double seal with a food-grade barrier oil keeps the faces clean and stops air entering the oil.
Which faces suit soapstock?
Soapstock is alkaline, so sintered SiC vs sintered SiC is used. Reaction-bonded SiC contains free silicon that alkalis attack.
Related: Dairy Processing · Beverage & Brewery · Biofuels · Refinery.
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Pump Duty & Mechanical Seal Selection Matrix
Typical values for selection guidance only. Final selection is made against the customer duty sheet.
| Pump duty | Fluid | Typical temp. | Typical pressure (bar) | Seal arrangement | Faces / elastomer | API piping plan |
|---|---|---|---|---|---|---|
| Crude Oil Feed Pump | Crude vegetable oil | 40–90 °C | 3–6 bar | Balanced multi-spring cartridge | SiC vs carbon / FKM (food-grade) | API Plan 11 |
| Soapstock Pump | Alkaline soapstock, viscous | 60–90 °C | 2–4 bar | Balanced multi-spring cartridge | Sintered SiC vs sintered SiC / FFKM | API Plan 11 + Plan 62 hot-water quench |
| Bleaching Slurry Pump | Oil with bleaching earth, abrasive, under vacuum | 90–110 °C | Suction under vacuum | Double cartridge, back-to-back (pressurised) | SiC vs SiC / FKM (food-grade) | API Plan 53A with food-grade barrier oil (≥ 1.4 bar above seal chamber) to stop air ingress |
| Bleached Oil / Filter Feed Pump | Bleached oil | 90–110 °C | 3–6 bar | Balanced multi-spring cartridge | SiC vs carbon / FKM (food-grade) | API Plan 11 |
| Deodorised Oil Pump | Hot refined oil from deodoriser, deep vacuum suction | 230–260 °C | Suction under deep vacuum — confirm per pump | Metal bellows seal | SiC vs carbon / flexible graphite | API Plan 32 (cool oil flush) or double seal with barrier, to stop air ingress and oil oxidation |
| Fatty Acid Distillate (FFA) Pump | Fatty acid distillate | 50–70 °C | 2–4 bar | Balanced multi-spring cartridge | SiC vs carbon / FKM | API Plan 11 |
| Refined Oil Transfer / Filling Pump | Refined oil | 30–50 °C | 2–5 bar | Balanced multi-spring cartridge | SiC vs carbon / FKM (food-grade) | API Plan 11 |
| Thermic Fluid Pump | Thermal oil | 250–300 °C | 3–6 bar | Metal bellows seal | SiC vs carbon / flexible graphite | Cooled seal chamber per pump design + Plan 62 steam or nitrogen quench |
Reviewed by Gipfel Engineering’s technical team.
Technical Information Disclaimer
The information on this page, including process descriptions, flow diagrams, operating ranges, seal arrangements, materials and piping plans, is general technical guidance for information only. Values shown are typical industry ranges, not guaranteed ratings or specifications of any Gipfel Engineering product. Each application differs. Seal selection, material compatibility, installation and operation must be verified by qualified personnel against the specific equipment data sheet, process conditions, applicable codes and the pump manufacturer’s instructions. A binding recommendation is given only in a written quotation or technical offer from Gipfel Engineering.
References to standards (such as API 682, ISO 21049, ISO 3069, FDA 21 CFR 177.2600 and NACE MR0175 / ISO 15156) describe common industry practice. They do not mean that any product is certified, qualified or approved to that standard unless this is confirmed in writing for a specific order. Third-party company and product names, including “equivalent to” references, are used for identification only and remain the trademarks of their owners. No affiliation, endorsement or OEM approval is implied.
Compliance with safety, hazardous-area, environmental and statutory requirements at the user’s site remains the responsibility of the plant owner or operator. To the extent permitted by law, Gipfel Engineering accepts no liability for loss or damage arising from reliance on this general information without a confirmed written recommendation. Content may change without notice.