Select a food-grade pump seal from the product and the cleaning regime first, because the cleaning regime fixes the line’s hygiene class and with it the seal arrangement; the design, materials and paperwork are then checked against food-contact law and hygienic-design standards. A seal is food-grade only when both halves hold: its materials are safe if trace substances reach the food, and its design can be cleaned as the line’s hygiene class requires.
Start With the Product and the Cleaning Regime
A food-grade seal selection starts from four facts about the duty:
- Food type: aqueous, acidic, alcoholic, fatty or dry.
- Temperature range: from subzero storage to pasteurization heat.
- Cleaning chemicals and frequency: the caustic, acid and sanitizers used in CIP, and how many cycles the seal sees.
- Hygiene demand: whether the line is cleaned after dismantling or cleaned and sterilized in place, and whether the product is sterile.
Dairy duty has no seal of its own: the same four facts apply.
Single, Flushed or Double Seal
The line’s EHEDG hygiene class sets the arrangement:
- Aseptic (sterile product, no micro-organism may enter): a double seal with a sterile barrier between the two seals.
- Class I (cleaned and sterilized in place without dismantling): the main seal plus a second sealing device on its atmospheric side.
- Other food duty: a plain single seal.
On a plain single seal, product that crosses the faces leaves residue on the atmosphere side. Plants handle it by inspecting and cleaning that side by hand under their HACCP programme, or by fitting a flush that carries the residue away.
For Class I, the second sealing device can be a lip seal or another mechanical seal, and the chamber between them can be flushed with a fluid acceptable for the product.
The sterile medium between the two seals of an aseptic double seal is often condensate made from food-grade steam, and the barrier fluid must itself be food-grade.
Products that crystallize at the seal do not, on their own, call for a double seal. The recognised fix is a water or steam quench on the atmospheric side of a single seal.
Hygienic Seal Design
A hygienic seal leaves nothing on the product side that cleaning fluid cannot reach. EHEDG’s seal guideline sets out the features:
- Springs and drive parts: on the non-product side.
- Corners and joints: smooth, crevice-free product-contact surfaces with no dead ends, designed corners radiused to at least 3 mm, no screws or threads in contact with product, and static joints made with an encapsulated O-ring or an edge-moulded rubber gasket.
- Position in the flow: the seal sits in the product stream, so particles do not settle on it.
- Bellows: no welded metal bellows, whose narrow, deep gaps between the plates cannot be cleaned. Rolled metal bellows are acceptable for low-viscosity products, and elastomer bellows need a smooth, pore-free surface.
- Outboard seals: acceptable only when they leave no annular dead end on the product side.
- Construction: a cartridge seal wherever one fits the pump.
Seal Materials
Every material in a food-grade seal must comply with FDA 21 CFR or the equivalent EU legislation. Beyond the law, each part must be non-toxic, non-absorbent and corrosion-resistant, and must not pass odour, colour or taint to the product.
Face Materials
Silicon carbide is the default face for food service: EHEDG’s seal guideline lists silicon carbide, aluminium oxide and stainless steel as materials with a general GRAS (generally recognized as safe) statement. A carbon-free duty runs silicon carbide against silicon carbide.
Carbon is not on that list, though sanitary seals use it. Leave carbon out of duties where its dark wear debris would show or matter in the product.
The face grade has to resist both the product and the cleaning chemicals.
Elastomers
Match the elastomer to the food and the cleaning regime, and buy it as a food-grade compound.
- EPDM: aqueous and acidic foods, hot water, steam and caustic CIP. It swells in fats and oils, the point where FKM replaces EPDM.
- FKM: fatty and oily foods, including at pasteurization temperatures.
- NBR or HNBR: products with a moderate oil content, where nitrile is the alternative to EPDM.
- Silicone: wide temperature swings, once its exposure to fats has been checked.
- FFKM or PTFE: aggressive cleaning or process chemicals.
Whatever the family, the rubber surfaces that meet product must be smooth, with no flash lines, blisters or tears.
Metal Parts
Wetted metal parts are austenitic stainless steel to AISI 316 (EN 10088-1), or an alloy with better chemical resistance: duplex or super-austenitic stainless steel, a corrosion-resistant nickel alloy, or titanium. Cast parts qualify only if their structure is fully austenitic. Sintered metal is not permitted.
Springs are stainless steel or, better, Hastelloy. Bronze grades that contain tin or lead are not acceptable for food service.
Surviving CIP and SIP
A food-grade seal must survive the line’s chemical cleaning cycle at up to about 80 °C and, on lines sterilized in place, steam.
For the elastomer, the cleaning and sterilizing temperature is the limit to check. 3-A 18-03 sorts food rubber into four temperature classes, and the highest, Class I, is rated for product or sterilization temperatures up to 149 °C; the standard’s examples list rotary seals under Class I. All four 3-A 18-03 classes are tested against cleaning and sanitizing solutions up to 82 °C.
On a line that swings between cold product and hot cleaning or steam, ceramic faces are the most exposed to thermal shock cracking.
Standards a Food-Grade Seal Must Meet
A food-grade seal must meet two kinds of standard: food-contact law on what its materials may release (FDA in the US, EU regulations in Europe) and voluntary hygienic-design standards (3-A and EHEDG).
FDA 21 CFR 177.2600
21 CFR 177.2600 governs a seal’s rubber parts intended for repeated food contact: O-rings, bellows and gaskets. The compound may contain only the polymers and additives the section lists, which include nitrile, EPDM, hydrogenated nitrile, silicone and FKM types, and the finished part must pass an extraction test for the food it will meet.
| Food type | Extraction at reflux | Total extractives, first 7 h | Total extractives, next 2 h |
|---|---|---|---|
| Aqueous | Distilled water | 20 mg/in² | 1 mg/in² |
| Fatty | n-hexane | 175 mg/in² | 4 mg/in² |
Rubber for dry food has no extraction test, only good manufacturing practice. A compound that passed in water has not been tested for fatty food.
Faces, metal and plastic parts fall outside 177.2600, and their FDA status is checked substance by substance, starting from the indirect food additive listings in 21 CFR 174–179.
EU Food-Contact Regulations
Every seal material sold in the EU falls under Regulation (EC) 1935/2004: it may not release constituents into food in quantities that endanger health or change the food’s composition, taste or smell. Regulation (EC) 2023/2006 requires good manufacturing practice at every stage of making and distributing the material.
The plastics regulation, (EU) 10/2011, covers only a seal’s plastic parts, such as PTFE, and states that it does not apply to rubber or silicones. Under (EU) 10/2011, a plastic part may release no more than 10 mg of total constituents into food simulants per dm² of food-contact surface, and it must come with a written declaration of compliance.
Rubber has no specific EU measure. A seal’s elastomers answer to the general rule of 1935/2004 and to any national provisions, and a declaration of compliance that cites 10/2011 for rubber parts cites a regulation that does not cover them.
3-A and EHEDG
3-A covers a food pump seal through two standards: 3-A 02-12, the standard for centrifugal and positive rotary pumps in dairy processing, governs the pump with its seal; 3-A 18-03 sets the material and cleaning-compatibility requirements for the seal’s rubber parts.
Since 14 January 2026, 3-A also issues an RP Mark for replacement seals, seal components and seal assemblies used in 3-A Symbol-authorized equipment, after third-party verification against the equipment standard and the 3-A General Requirements. A seal that is not from the equipment’s original maker can now be verified.
EHEDG’s mechanical seal guideline (GL 25) defines the Aseptic, Class I and Class II seal classes that set the arrangement, and the design rules under Hygienic Seal Design apply to the first two. Class II seals, cleaned after dismantling, need the same food-contact materials but less stringent design.
Documents to Ask the Supplier For
Ask for documents that name the exact compound and the regulation it meets. Five cover a food-grade seal:
- FDA letter of guaranty: FDA does not certify seals. The manufacturer certifies that the product is acceptable for its intended food-contact use, and the letter should cite 21 CFR 177.2600 and the food type.
- 3-A 18-03 rubber certification: issued by the rubber manufacturer, naming the compound, its number or grade, the part and the rubber class, backed by the testing laboratory’s results. The compound number changes whenever the formulation does, so check that the number on the certificate matches the parts you receive.
- EU declaration of compliance: required for plastic parts under (EU) 10/2011, with migration test reports for the relevant food simulants, time and temperature. Every seal material must also be traceable under 1935/2004.
- GRAS statement: for the face and metal materials; EHEDG’s seal guideline makes it the supplier’s job to hand it over on request.
- 3-A RP Mark or Symbol: checkable in 3-A’s public database of RP Mark and Symbol holders.
Send the supplier the food type, temperature range and cleaning regime with the request for a food and beverage pump seal, so the documents are issued for your duty rather than for food contact in general.