Rotary Seals for Food and Pharma: Compliance and Cleanability
Hygienic Design Essentials for Rotating Equipment
Rotary seals in food and pharmaceutical (F&P) machinery must balance sealing performance with strict hygienic requirements. Machines such as mixers, conveyors, homogenizers, and rotary valves expose seals to product contact, CIP (Clean-In-Place) and SIP (Steam-In-Place) cycles, aggressive chemistries and frequent temperature swings. Selecting and validating a rotary seal for these applications requires understanding regulations, materials, geometry and maintenance realities to avoid contamination, unplanned downtime and regulatory non-compliance.
Regulatory drivers: what seals must meet
Key legal and industry drivers are FDA Title 21 (food contact materials), EU Regulation (EC) No. 1935/2004, 3-A Sanitary Standards, and EHEDG guidance on hygienic engineering. For pharmaceuticals, seals often need biocompatibility or USP Class VI evidence, and equipment must support controlled cleaning (CIP/SIP) and validated cleaning protocols. Compliance is not only material declaration — it is also demonstrated through documentation, material traceability and testing under expected process conditions.
Hygienic design principles impacting seals
Seals must enable cleanable surfaces (minimize crevices), avoid particle traps, resist biofilm formation and tolerate cleaning agents and temperatures. Rotary seal geometry (single lip, double lip, spring-energized, rotary face seal) and surface finish of mating shafts/housings are critical. Design for maintainability (easy access, standardized parts) reduces risk of improper reassembly which can compromise sanitation.
Common failure modes in F&P environments
Wear from abrasive solids, extrusion through gaps during pressure differentials, chemical attack from sanitizers, thermal degradation from repeated SIP, and biological fouling from inadequate cleaning. Prevention combines correct material selection, appropriate surface finishes (shaft/housing), correct gland design and validated cleaning regimes.
Materials, Cleanability and Compliance
Material selection criteria
Primary criteria: regulatory acceptability (food contact), chemical and thermal resistance (to CIP/SIP), abrasion resistance, compressibility/resilience for sealing, and cleanability (low surface energy and resistance to biofilm). Common materials for rotary seals in F&P are PTFE variants, FKM, NBR, EPDM, silicone and FFKM (perfluoroelastomer).
Comparative properties of common sealing materials
| Material | Typical Service Temp (°C) | Regulatory/Compliance Notes | Chemical/Cleaning Resistance | Cleanability / Application Notes |
|---|---|---|---|---|
| PTFE (incl. filled) | -200 to +260 | Generally inert; acceptable for many food uses; verify additives/fillers | Excellent vs. acids, bases, solvents | Low surface energy (non-stick), excellent cleanability; rigid—consider spring-energized or backup elastomer |
| FFKM (perfluoroelastomer) | -20 to +300 | High-level chemical resistance; obtain traceability and certifications | Outstanding vs. most chemicals, steam | Excellent for aggressive CIP/SIP; High Quality cost |
| EPDM | -50 to +150 | Good for steam and hot water; often acceptable for food contact | Good vs. hot caustics and steam; poor vs. oils | Common in steam-sterilized equipment; good cleanability |
| FKM (Viton) | -20 to +200 | Widely used; check grade for food contact | Good vs. oils, many chemicals; limited vs. strong bases | Good wear resistance; some grades resist water/steam less well |
| NBR | -40 to +120 | Used in contact with oils and fats; food-grade NBR available | Good vs. hydrocarbons; poor vs. ozone/steam long-term | Cost-effective but limited for high-temp CIP/SIP |
| Silicone | -60 to +200 | Often used in pharma for biocompatibility (silicone grades) | Good vs. heat; limited abrasion resistance | Excellent for sterilization cycles; softer—watch extrusion |
Notes: Temperature ranges and properties are typical; verify manufacturer datasheets for specific compounds and certified food/pharma grades. (See references at end.)
Design features that improve cleanability
Use low-porosity materials, flushable gland designs, minimal dead volumes, and continuous surfaces. Consider spring-energized PTFE rotary seals for low friction and low particle accumulation, or lip seals with protective dust scrapers where product contact risk is lower. Minimize polymer crevices by using molded seals with radiused transitions and ensure the sealing area is accessible for inspection.
Cleaning and Validation of Rotary Seals
Cleaning regimes: CIP and SIP compatibility
CIP typically uses alkaline (caustic) solutions (e.g., 0.5–2.0% NaOH), detergents and controlled temperature (~50–80°C). SIP uses pressurized steam at temperatures typically 121–134°C for validated time periods. Seal materials must be compatible with the chemistries and temperatures they will experience. Repeated SIP cycles can accelerate elastomer aging; choose materials (e.g., FFKM, PTFE combinations) with proven steam resistance when required.
Validation: what to test and document
Validation should include material chemical resistance testing, accelerated aging under CIP/SIP conditions, extractables/leachables analysis for pharma, surface roughness and microbial retention tests, and full-process cleaning validation (swab/rinse sampling). Maintain certificates of compliance (CoC), material declarations, and lot traceability to demonstrate E-E-A-T level documentation for audits.
Inspection, maintenance and lifecycle management
Establish routine inspection intervals based on operating hours and product risk (e.g., dairy vs. dry ingredients). Replace seals on preventive schedules before degradation risk increases. Keep spare part BOMs and clear reassembly instructions (torque, alignment) to avoid inadvertent sealing failures that compromise sanitation.
Selecting Rotary Seals: Practical Guidance and Trade-offs
Matching seal type to equipment and risk
Rotary lip seals are common for non-product-contact shafts (with hygienic covers). For direct product contact and high hygienic demand, consider hygienic rotary face seals, spring-energized PTFE rotary seals, or cartridge-style seals designed for easy replacement and full CIP compatibility. Magnetic couplings can eliminate shaft penetrations in some designs, reducing sealing risk altogether.
Trade-offs: cost, longevity, cleanability
Higher-performance materials (FFKM, PTFE composites) and hygienic designs cost more but reduce contamination risk and downtime. Simpler elastomers are cheaper but often require more frequent replacement and may not tolerate aggressive CIP/SIP. Evaluate total cost of ownership (TCO) including downtime, cleaning validation burden and scrap risk.
Quick selection checklist
- Define operating temperatures, pressures, and CIP/SIP conditions.
- Identify all product contact points and regulatory requirements (food vs. pharma).
- Choose materials with documented food/pharma grades and traceability.
- Design or select seals that minimize crevices and enable inspection.
- Plan validation tests: extractables, aging, microbiological retention.
- Document maintenance and spare parts strategy.
Polypac: Capabilities, Products and How We Support F&P Projects
Who we are
Polypac is a scientific and technical hydraulic seal manufacturer and oil seal supplier specializing in seal production, sealing material development, and customized sealing solutions for special working conditions. Polypac's custom rubber ring and O-ring factory covers an area of more than 10,000 square meters, with a factory space of 8,000 square meters. Our production and testing equipment are among the most advanced in the industry. As one of the largest companies in China dedicated to the production and development of seals, we maintain long-term communication and cooperation with numerous universities and research institutions both domestically and internationally.
Technical strengths and differentiation
Founded in 2008, Polypac began by manufacturing filled PTFE seals, including bronze-filled PTFE, carbon-filled PTFE, graphite PTFE, MoS₂-filled PTFE, and glass-filled PTFE. Today, we have expanded our product line to include O-rings made from various materials such as NBR, FKM, silicone, EPDM, and FFKM. Our R&D collaborations with academic and research institutions allow rapid material qualification and customized formulations for CIP/SIP resistance and low-extractables performance. In-house advanced testing capabilities support accelerated aging, chemical resistance and dynamic wear testing to generate validation data for customers in the food and pharmaceutical sectors.
Core products relevant to F&P applications
Polypac manufactures and supplies a broad range of sealing products optimized for hygienic and high-reliability requirements: O-Rings, Rod Seals, Piston Seals, End Face Spring Seals, Scraper Seals, Rotary Seals, Back-up Rings, Dust Rings. We provide material certificates, traceability, and can assist with CIP/SIP compatibility testing and documentation to support regulatory submissions and audits.
Data-driven comparison: Cleanability and Compliance Matrix
The table below summarizes common choices and how they align with key F&P requirements. Use it as a starting point — always validate with full testing for your process.
| Requirement | Best Choices | Notes |
|---|---|---|
| High-temperature SIP (>121°C) | FFKM, PTFE-based | FFKM holds up to repeated steam; PTFE inert but geometry and springing needed |
| Frequent caustic CIP | EPDM, PTFE, FFKM | EPDM resists hot caustics well; confirm long-term aging |
| Low extractables (pharma) | PTFE, FFKM, pharma-grade silicone | Perform extractables/leachables testing per regulatory guidance |
| Cost-sensitive food uses (low-temp) | NBR (food-grade), EPDM | Good for oils/fats (NBR) or steam (EPDM); plan more frequent replacement if needed |
Implementation support from Polypac
Polypac can provide sample runs, material certificates, accelerated aging data, and custom development when off-the-shelf compounds or designs do not meet process demands. For high-risk pharma applications, we partner to generate extractables/leachables and USP testing data required for submissions.
FAQ — Frequently Asked Questions
1. What makes a rotary seal acceptable for food contact?
Acceptability includes: approved or inert base materials (FDA, EC 1935/2004), documented material traceability, low extractables/leachables for high-risk products, hygienic geometry to prevent product entrapment, and demonstrated resistance to expected CIP/SIP chemistries and temperatures. Certificates of compliance and test reports are required during audits.
2. Can I use standard industrial rotary seals in CIP/SIP environments?
Not necessarily. Many industrial elastomers degrade under repeated SIP or aggressive CIP chemicals. Use seals specifically rated and tested for the actual CIP/SIP conditions or choose PTFE/FFKM options with supporting test data.
3. How often should rotary seals be inspected or replaced?
Frequency depends on product risk, operating hours, and severity of the process (abrasives, temperatures, chemistries). A common approach is scheduled preventive replacement based on runtime (e.g., every 6–18 months) plus interim visual inspections after any abnormal events. Critical pharma processes often use more conservative intervals and spare-part strategies.
4. What testing supports a seal’s cleanability claim?
Relevant tests include surface roughness measurements (Ra), microbial retention studies, swab/rinse recovery during process validation, chemical compatibility and accelerated aging tests, and extractables/leachables analyses for pharma. Documentation should include test methods, acceptance criteria, and test reports.
5. How do I choose between PTFE and FFKM for a rotary seal?
Choose PTFE when low friction, chemical inertness and low extractables are priorities and spring-energized designs can manage sealing force. Choose FFKM where elastomeric resilience plus exceptional chemical and steam resistance is required, especially under dynamic sealing conditions. Consider cost and lifecycle in the decision.
6. Are there surface finish targets for shafts that improve seal cleanability?
Yes. EHEDG and hygienic design guidance typically recommend low surface roughness to reduce microbial harborage; values of Ra ≤0.8 µm (and ≤0.4 µm for high-risk applications) are commonly cited. Ensure shafts and housings are finished and maintained to specified tolerances to avoid creating particle traps.
Contact & Product Inquiry
For project-level advice, material certificates, sample evaluation or quotation for hygienic rotary seals, contact Polypac. We provide technical consultation, custom compound development and validation support to meet food and pharmaceutical compliance and cleanability requirements. Request a consultation or view our product catalog to match seals to your process.
References
- U.S. Code of Federal Regulations, Title 21 — Food and Drugs. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21 (accessed 2026-01-06).
- Regulation (EC) No 1935/2004 on materials and articles intended to come into contact with food. EUR-Lex. https://eur-lex.europa.eu/eli/reg/2004/1935/oj (accessed 2026-01-06).
- 3-A Sanitary Standards. 3-A Sanitary Standards, Inc. https://www.3-a.org/ (accessed 2026-01-06).
- European Hygienic Engineering & Design Group (EHEDG) — Guidance on hygienic design and cleanability. https://www.ehedg.org/ (accessed 2026-01-06).
- ISO 21469:2006 — Safety of machinery — Lubricants with incidental product contact. ISO. https://www.iso.org/standard/44737. (accessed 2026-01-06).
- USP General Chapters on Biological Reactivity and Biocompatibility (relevant for pharmaceutical materials). U.S. Pharmacopeia. https://www.usp.org/ (accessed 2026-01-06).
- Principles of Clean-in-Place (CIP) and Steam-in-Place (SIP) — industry guidance and textbooks. Example: Food Engineering and Process Hygiene resources. (accessed 2026-01-06).
Pneumatic Seals: The Ultimate Guide to High-Efficiency, Low-Friction Sealing for Air Systems
PTFE Tubes: The Ultimate Guide to High-Performance, Chemically Inert Tubing Solutions
Scraper Seals: The Ultimate 2026 Guide to Selection, Types, and System Longevity
PTFE Oil Seals: The Definitive Guide to High-Performance Sealing for 2026
Gaskets: The Ultimate Guide to Types, Materials, and Selection for Industrial Sealing
Products
What is the purpose of the metal spring in a rotary shaft seal?
Why did my O-ring fail prematurely?
How do I choose the right material for my sealing application?
How can I prevent seal damage during installation?
How important is surface finish on the metal parts that contact the seal?
Stay Updated with Industry Insights
Subscribe to our articles and receive the latest news, expert guidance, and technical updates directly in your E-mail.
Rest assured that your privacy is important to us, and all information provided will be handled with the utmost confidentiality.
Polypac is a trusted global supplier of high-performance sealing solutions, providing OEM & ODM services for industries worldwide.
E-mail:
Phone/WhatsApp:
© 2025 Polypac Seals. All Rights Reserved.
dms
DMS
DMS