Seals for food and pharma: certifications and material selection

In food processing and pharmaceutical production it is not enough for a seal to survive the medium, the temperature, the pressure and the motion. It also needs a document proving it may touch the food or the drug. Standard industrial NBR carries no food-contact certification by default — and this is where the most expensive mistakes are made: a black O-ring from the maintenance cabinet installed in a dairy line means contamination risk, stopped production and an audit finding. This guide sums up which certifications you actually need and when to choose VMQ silicone, EPDM, PTFE or FFKM.

Which certifications you actually need

When buying, you will meet several levels of paperwork. FDA is the US food-contact standard and EC 1935/2004 is its European counterpart — for the EU market it is the baseline. USP Class VI covers pharmaceutical biocompatibility, 3-A Sanitary Standards cover dairy equipment and BfR is the German food-contact recommendation. Drinking water has its own schemes: WRAS (United Kingdom), KTW and DVGW (Germany) and NSF 61. One important distinction: for some materials the certification is a property of every ordinary compound, for others only specially certified compounds exist. FKM and EPDM have FDA compounds available on request — the specific compound is certified, not the material as such. When ordering, always ask for a declaration of conformity for the specific compound, not just the material name.

VMQ silicone — the first choice for food contact

Silicone rubber VMQ is the default starting point for food-grade applications and carries the broadest certification portfolio: FDA, USP Class VI, BfR, EC 1935/2004 and 3-A. It works from -60 °C to +200 °C continuously, short-term up to 230 °C, comes in hardnesses from 30 to 80 Shore A, and besides the standard compound a white one is common — dairies use white VMQ precisely for visual detection of fragments in the product. VMQ is biocompatible, handles most foods, water and dilute acids, and leaves no off-taste in foodstuffs during dry storage of bulk ingredients. It has two weaknesses: poor mechanical strength, so it does not belong in dynamic seals, and it cannot take high-pressure steam, concentrated acids, alkalis, hydrocarbon oils or fuels. Price comes out at roughly 3.5 times NBR.

EPDM — water, steam and CIP

EPDM is the workhorse for water and steam: -40 °C to +130 °C continuous, 150 °C short-term, hardnesses 40 to 90 Shore A. For drinking water it is the only sensible choice — it carries WRAS, KTW, DVGW and NSF 61 approvals, and FDA and USP Class VI certified compounds exist on top. The cure system is the key detail: standard sulfur-cured EPDM is for ordinary duty, but for steam, CIP and pharma ask for a peroxide-cured compound — it survives repeated steam cycles and resists NaOH as well as diluted HNO₃, the usual sanitation chemistry. EPDM also handles acidic fruit juices — citric and acetic acid do it no harm, unlike NBR. But beware: EPDM cannot take mineral oils, fuels or most hydrocarbon oils at all — an oily joint is a death sentence for it. At around 1.2 times the price of NBR it is the cheapest certified route.

When it has to take more: PTFE and FFKM

PTFE (Teflon) resists virtually all chemicals and solvents, works from -200 °C to +260 °C, short-term 300 °C, and carries FDA, USP Class VI and NSF. It is not an elastomer though — it is a rigid polymer with zero elastic memory, so it belongs in static joints, or serves as a back-up ring or a spring-energized seal. Price is around 8 times NBR. FFKM perfluoroelastomer is the most resistant elastomer on the market: -20 °C to +260 °C continuous, short-term up to 325 °C, with FDA and USP Class VI certification. It survives sterilisation processes under extreme conditions and has the longest lifetime of all elastomers. It costs 20 to 50 times as much as FKM though — deploy it only at critical points where a seal change means stopping the whole line.

What about FKM?

FKM (Viton) has FDA-certified compounds and earns its place in food processing where higher temperature meets aromatic media — typically flavourings, oils and fats at temperatures EPDM cannot handle; FKM works continuously up to +200 °C. For acidic juices, FKM at 75 Shore A is the alternative for strong acids where EPDM is not enough. The fundamental limitation: FKM cannot take hot water and steam, so it is unsuitable for steam-sanitised CIP. Price is around 5 times NBR.

CIP and SIP: what to ask about sanitation

Clean-in-Place means the seal regularly sees lye (NaOH), diluted nitric acid and, during steam sterilisation (SIP), temperatures of 120 °C and above. The first choice is peroxide-cured EPDM at 70 Shore A; for extremely demanding sterile processes the backup is FFKM at 75 Shore A. Sulfur-cured EPDM and standard VMQ are not enough for repeated steam cycles — high-pressure steam demonstrably harms silicone. At an audit, expect to document the compound, not the material: EPDM written on the order is not enough — for pharma, ask for a peroxide-cured compound with USP Class VI.

The decision procedure in practice

The procedure is the same as for any seal — medium, temperature, pressure, motion — just with a certification filter up front. Milk and dairy products up to 100 °C: VMQ 70 Shore A in a white compound, backed by peroxide-cured EPDM 70. Dry bulk ingredients: VMQ 70, backed by EPDM 70 with excellent ozone and UV resistance in dry storage. Acidic juices: EPDM 70, for strong acids FKM 75. Pharma and sterile processes: peroxide-cured EPDM 70 with USP Class VI, backed by VMQ 70, which is biocompatible and safe for pure water. CIP and SIP with steam above 120 °C: peroxide-cured EPDM 70, for extremes FFKM 75.

Frequently asked questions

Is food-grade silicone without paperwork enough?

No. The certification belongs to a specific compound and the supplier must be able to prove it with a declaration of conformity — referencing EC 1935/2004 for the EU, or a USP Class VI protocol for pharma. If the document does not exist, the seal is not certified as far as an audit is concerned, no matter how white it is.

Which material for drinking water?

EPDM with WRAS, KTW, DVGW or NSF 61 approval, depending on the market the equipment ships to. VMQ is safe for pure water too, but it is EPDM that has the drinking-water schemes covered.

You can pick the exact size and a certified compound yourself: our configurator has food processing and pharma as dedicated applications and proposes a material together with the hardness, the chemical compatibility chart verifies the medium against the material, the size converter helps identify inch dimensions, and for a failed seal try the failure analysis. If things are still unclear after that — say with non-standard sanitation chemistry — write to Filip.