CIP Temperature Monitoring in a Food Plant: Proving Every Wash

In food production, a clean-in-place (CIP) cycle that ran is not the same as a cycle that cleaned. The difference is temperature at the hardest-to-heat points of the circuit — and those are rarely where the only sensor sits. This anonymized case shows how a mid-size food plant closed the gap between running CIP and proving it.

The situation

A producer of sauces and ready meals cleans its cooking vessels, pipework and filling line with a central CIP skid: caustic and acid circuits at specified temperatures, with the return temperature at the skid logged for the HACCP file. The quality team knew the weak point in this arrangement — the skid's return sensor proves the wash solution left and came back hot, but says little about dead legs, the far end of the filling line, or a partially fouled spray ball cooling one vessel's circuit.

The challenge

An external audit raised exactly this: temperature evidence existed for the skid, not for the circuit. Adding measurement points meant sensors that survive daily caustic/acid exposure and steam, fit sanitary clamp connections without creating crevices, respond fast enough to track a wash profile (a slow sensor can average away a short cold excursion), and feed the plant's existing recorder/PLC inputs — in washdown areas where electronics live hard lives.

The solution

Fast-response Pt100 sensors in sanitary (clamp) housings were installed at the identified cold spots: the far end of the longest circuit, a known dead leg, and the return of the vessel with the questionable spray coverage. Thin-film elements in short, polished stems give the fast thermal response; each point has a head-mounted 4–20 mA transmitter at the sensor, so the long runs back to the panel carry a robust current signal rather than a raw RTD resistance through a washdown environment. The PLC program now records each circuit point's profile and alarms any cycle whose coldest point does not hold the specified temperature for the specified time.

The result

At the follow-up audit, the plant presented per-cycle temperature records for the circuit's cold spots, not just the skid — the finding was closed. Internally, the data earned its keep within weeks: one vessel's profile showed a persistent cool tail traced to a worn spray ball, found from the temperature record before it became a hygiene failure. CIP is now validated by evidence, and exceptions are flagged the same shift, not at the next audit.

The lesson generalizes beyond food: if a process must be proven, measure it at the point where it is most likely to fail, not where it is easiest to install a sensor.

Products used: Platinum Resistance Sensors · Temperature Transmitter Modules

Industry: Food & beverage production

Related products: Platinum Resistance Sensors · Temperature Transmitter Modules