Vent valve instead of vent hole: With this option, the model PG43SA-S hygienic diaphragm pressure gauge is even suitable for pharmaceutical cleaning from the outside with particularly aggressive agents. The closed valve seals the inside of the pressure gauge in accordance with IP68 ingress protection. In this way, it prevents the penetration of cleaning media.
In the pharmaceutical industry, protecting active ingredients and medicines from contamination is a top priority. Therefore, thorough cleaning of the equipment after each batch is indispensable. However, its effectiveness depends critically on the concentration of the substances used and the level of the temperatures.
Cleaning: Caustic soda and nitric acid
In various cases, the equipment not only undergoes cleaning on the process side (CIP, SIP), but also cleaning from the outside. This also applies to a pharmaceutical company that uses the WIKA model PG43SA-S for pressure monitoring in mobile tanks. Here, the cleaning process is carried out from the outside at high temperatures and with chemicals that have a significantly higher concentration. The media include, for example, 30 % caustic soda and 60 % nitric acid – both in diluted form. With these substances, the measuring instrument is cleaned from all sides in a cleaning system using nozzles.
During such an operation, chemicals can enter the case of the pressure gauge through the vent hole. The materials of the measuring instrument can withstand the typical cleaning agent concentrations and temperatures. However, extremely aggressive substances, as in the application described, and/or very high temperatures attack the inside of the pressure gauge over time. The consequence: The measuring instrument must be replaced.
Pressure measurement with open valve
WIKA therefore addressed the question: How can the service life of the PG43SA-S be extended, even when cleaned from the outside under extreme conditions? The answer: by using a version with a vent valve. The closed valve (IP68) seals off the inside of the instrument from cleaning substances. However, during its actual function, pressure monitoring, it must be open. Otherwise, correct measurement of the gauge pressure is impossible. This is because internal pressure builds up in a closed case, which leads to a falsified measurement result.
The new vent valve is clearly visible and mounted on top of the case for easy access. It can be opened or closed without tools via a wing nut. The direction of rotation, as well as open and closed positions, are clearly marked on the case. The nut and the valve seal are in hygienic design. A safety ring prevents the valve from being unscrewed.
Sterilisation in an autoclave
Before each external cleaning, the vent valve is closed. The pressure gauge then has an ingress protection of IP68. If the cleaning process is followed by sterilisation in an autoclave, the valve must be opened again. As a result of the saturated steam conditions that occur there, internal pressure would otherwise also build up – with negative consequences for the measuring instrument.
The model PG43SA-S diaphragm pressure gauge has been specifically designed for a wide variety of sanitary applications. The new variant with vent valve and IP68 ingress protection has further extended the range of applications for the pressure gauge.
Further information on the model PG43SA-S hygienic pressure gauge and other models of the PG43SA series can be found on the WIKA website. If you have any questions on pressure gauges with the IP68 ingress protection option, your contact will gladly help you.