In-line Seal Pressure Sensors – a Good Choice for Hygienic Applications

Related Vendors

EagleBurgmann Germany GmbH & Co. KG

Glatt Ingenieurtechnik GmbH

Anton Paar GmbH

WIKA Alexander Wiegand SE & Co. KG

Sanitary Standards

Pressure measuring instruments with diaphragm seals are supplied in a range of diameters to suit all standard pipe sizes. They are available with weld stubs for direct orbital welding, and also with a variety of clamp, flange and screw connections to match systems such as the DIN 11864 aseptic standard, DIN 11851 (as used in the dairy industry), Variline from GEA Tuchenhagen, and Neumo’s BioControl range. Careful matching between the internal diameter of the diaphragm and that of the neighbouring pipe eliminates even small variations in diameter that can create flow restrictions or contamination traps.

Advantages of the standardized approach through in-line housings include lower costs for spares stockholding, less chance of error during plant construction, and flexibility during design and operation: a pressure gauge can easily be replaced by a trans-mitter, or a temperature sensor added, with the minimum of disturbance to the process.

The surface finish of standard Wika in-line diaphragm seals easily meets the minimum hygienic quality requirement of Ra<0.8 µm, and even higher specifications — electropolish and cleanability tests — can be supplied on request. The instruments are therefore suitable for the most demanding requirements in both Europe and the USA.

For instance, they not only meet the standards laid down by the European Hygienic Equipment Design Group (EHEDG) for the food industry, but even form part of the EHEDG test equipment operated by TU Munich’s Faculty for Machine and Apparatus Studies in Weihenstephan. All Wika in-line diaphragm seals with hygienic fittings are also independently certified as meeting standard 74–03 from 3-A Sanitary Standards, which governs the design of instrumentation for hygienic applications in the US market, and can be supplied with the 3-A logo.

Conclusion

In-line diaphragm pressure gauges have a lot of advantages compared to conventional pressure transmitters or diaphragm gauges: The in-line setup is well suited for continuous processes and cleaning in place techniques. Its crevice free designs without kinks or sharp bends reduces the risk of sediments or deposits in the pipework. Complying to recent hygiene standards, in-line diaphragm pressure gauges can be a good choice for clean and hygienic processes in spite of their slightly more elaborate construction.

* The author is product manager Diaphragm Seals, WIKA Alexander Wiegand, Klingenberg/Germany.

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