Which plant operator in the pharmaceutical industry doesn’t know the problem: a pressure transmitter
switches to fault mode or no longer delivers a valid measured value. It’s actually no big deal, a spare instru-ment is quickly installed and within minutes the new in-strument is working and production is up and running again.
But why did the instrument fail?
Damaged or cracked metal diaphragms are one of the most frequent causes of failure in pressure transmitters. The result is that isolating diaphragm liquid
(50 … 2500 µL), which serves as a transmission medium between separating diaphragm and sensor element, leaks into the process.
The fault may not even be noticed by the sensor elec-tronics since the product itself also exerts a measurable pressure on the sensor. The exact time of the damage can therefore not always be determined.
The isolating diaphragm liquids used are generally sub-ject to FDA regulations and are not harmful to health. For the plant operator, however, they represent a product quality risk. The implemented transmission oils don’t mix well with the water-based pharmaceutical products – serious contamination is sometimes the result.
The pressure transmitters with ceramic-capacitive
CERTEC® measuring cell from VEGA offer a solution for these quality and validation processes. The ceramic measuring cell works without transmission liquid and ideally satisfies all requirements of the pharmaceutical industry. The measuring cell is dry, self-monitoring and registers both damage to the diaphragm and moisture leaking into the sensor.
The diaphragm, which consists of sapphire ceramic, is
10 times harder than high-grade steel and easily defies abrasive media. The ceramic diaphragm and ceramic body are joined together with glass solder, allowing a constant product temperature up to +150 °C. The high surface quality is a guarantor of optimal cleanability and sanitation. This design is rounded out by a sophisticated seal concept. Depending on process requirements, a double seal or a hygienic form seal can be implemented.