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  • Materials
  • 2 мин чтения

EPDM or PTFE: which seat survives your CIP

Most seat failures on a sanitary line are not wear. They are the wrong elastomer meeting a cleaning regime nobody described when the valve was bought.

What actually kills a seat

A seat rarely dies of the product. It dies of what cleans the product away.

A daily caustic clean at 80 °C, a weekly acid pass, a steam sterilisation before a run: each of those is a different chemistry and a different temperature, and a seat is chosen against the worst of them rather than the average. An EPDM seat that handles milk perfectly will craze in months under a regime that finishes with steam at 140 °C, and the fault will be filed as wear.

So the first question is never "what runs through it". It is "what cleans it, how hot, and how often".

Where EPDM wins

EPDM is the default for a reason. It takes hot caustic and hot water without complaint, it stays elastic through thousands of cycles, and it is the cheapest thing on the shelf that does both.

Its ceiling is roughly 140 °C in steam and it will not tolerate fats and oils for long. A line running cream, a line running vegetable oil, or a line with a mineral-oil lubricant that can migrate to the seat — those are the ones where an EPDM seat swells, loses its seal geometry and starts weeping past.

Where PTFE wins

PTFE is chemically almost indifferent. It takes solvents, fats, acids and steam, and it is the answer where EPDM's chemistry runs out.

What it is not is elastic. A PTFE seat does not recover the way an elastomer does, so it relies on the geometry holding it rather than on its own spring. That makes it less forgiving of thermal cycling and of over-torqued assembly, and it is why a PTFE-seated valve that is opened and closed hundreds of times a day wears differently from one that sits open for a shift.

On a line that swings between hot and cold repeatedly, a PTFE seat backed by a spring energiser buys back some of what the plain material gives up.

What to write on the enquiry

Seven lines are enough to get a seat specified correctly rather than guessed: size and connection standard, body material, what runs through it, the cleaning chemistry and its temperature, how often that clean happens, the sterilisation step if there is one, and the cycle count per day.

A quotation against those comes back priced. A quotation against "DN50 butterfly, EPDM" comes back as a question, and the seat that eventually ships is the one that was cheapest to assume.

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