From pressure cookers in the family kitchen to big industrial autoclaves used for medical and pharmaceutical sterilisation – airtight pressure tanks have to be monitored very closely. For its steam sterilisers, Belimed Sauter AG relies on pressure transmitters from Baumer Bourdon-Haenni that guarantee high precision and excellent stability even under constantly changing temperature conditions.
Andrea Finkel
The Swiss based Belimed Sauter AG was originally established as a blacksmith’s shop by Josef Sauter in 1923. In 1976, the company launched the development and production of sterilisers, decontamination and disinfection systems and today, this technology venture employs more than 200 people. Its sterilisation and disinfection units for hospitals, laboratories, research institutes and the pharmaceutical and biotech industries are sold worldwide and account for 90 % of the firm’s total turnover. Since 1999, Sauter has been part of the Belimed Group offering instruments and services for the worldwide infection control market.
As a manufacturer of steam sterilisers for the hygienic sector, Belimed Sauter sets great store by the quality of the components used in its instruments. The Swiss based Baumer Bourdon-Haenni AG is a trusted supplier that delivers pressure monitoring devices for Belimed Sauter’s autoclave production. On the laboratory and pharmaceutical line in particular, the majority of pressure transmitters installed to control the system and record the sterilisation process are Baumer products. Several hundred devices with clamp process connections in the ED 701 series were sold to Belimed Sauter in the course of the last year. Furthermore, the company has integrated another set of ED 701 transmitters with special aseptic process connections into autoclaves manufactured for Sanofi Aventis. To meet the high hygienic standards, the Frankfurt based pharmaceutical company uses measuring devices with Neumo BioConnect aseptic connections for all its sterilisers. In addition to pressure transmitters with clamp or aseptic connections that are installed mainly in pharmaceutical systems, Baumer also manufactures measuring devices with screw threads for use in laboratory sterilisers.
Functionality
The ED 701 is a piezo-resistive pressure transmitter with a stainless steel dia-phragm for industrial and hygienic applications. The broad range of process and electrical connections, a 4…20 mA current loop and several voltage output signal versions make these transmitters suitable for a great variety of applications. The line’s most distinctive features are its very high accuracy over a wide temperature range, excellent repeatability, long-time stability and response times as short as 5 ms.
The pressure transmitter is based on a silicon sensor designed for high precision across the largest possible temperature range. Its downstream digital compensation reduces signal drift. The piezo-resistive silicon sensor is anodic bonded on a very stable glass base that is attached to a stainless steel structure. This arrangement guarantees excellent thermal insulation. The sensor is isolated from the process pressure by a stainless steel dia-phragm and a specially treated filling liquid. The electronics are located inside the hermetically sealed transmitter housing, making the ED 701 exceptionally resistant to humidity, shock and vibration. Depending on the electrical connection, the degree of protection varies from IP 65 to IP 67. The heart of the electronics is a microcontroller that compensates any drift effects on the sensor signal due to temperature changes. These effects can thus be eliminated with a short response time over a wide temperature range.
The ED 701 is available with many different pressure and electrical connections. All electrical connections can be easily replaced and provide access to the auto zero adjustment. The hygienic design of the ED 701 series is ideal for applications in the food and beverage industry as well as in pharmaceuticals and biotechnology. All media-contacting parts are made of 316L/1.4435 stainless steel and all materials, including the white oil used as standard filling liquid, comply with FDA standards. If required, Baumer can deliver the relevant certificates of conformity. Depending on its Atex approval, the ED 701 can be used in potentially explosive atmospheres such as gases, vapours and dust. In addition, the device has Lloyd’s Register approval and is therefore suitable for marine, offshore and industrial applications.
Pressure monitoring in pharmaceutical sterilisers
To monitor the pressure in autoclaves for the pharmaceutical market, Belimed Sauter uses the ISO 2852 clamp process connection with an external diameter of 50.5 mm, a nominal diameter DN 33.7 or DN 38 and a pipe according to ISO 2037 as a standard feature. The electrical connection is an IP 65 plug according to DIN 43650. An accuracy of 0.2 % FS is ensured for high medium temperatures up to 200 °C. The absolute pressure range is 0 to 4 bar and the filling liquid is white oil. The pressure transmitter is scaled for medium temperatures of 80 °C. To meet its exceptionally high hygienic demands, pharmaceutical manufacturer Sanofi Aventis was provided with a special version of the ED 701 equipped with the Neumo BioConnect aseptic pressure connection, a V-type flange with a nominal diameter of 48.3 mm and an external diameter of 100 mm. Since there are no standards for this proprietary product, it can only be manufactured in consultation with Neumo Germany. The connection is sealed with an O-ring protected by a little jut that prevents it from being crushed when the flange is being screwed together.
Two 0 to 4 bar pressure transmitters are used for each steam steriliser. A further unit with an absolute pressure range of 0 to 6 bar is integrated in the steam pipe.
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