PC-JUN09-PGS12.OK:PC-JUN09-PGS12.OK.qxd 01/06/2009 14:22 Page S12
Focus Food processing & packaging
Milking transmitter flexibility
Pressure monitoring on the heat exchangers at the Nestlé
Product Technology Centre in Switzerland is now carried
out by Baumer pressure transmitters. Andrew Sim,
UK managing director, explains their role, and outlines why
these transmitters suit applications in the food industry
T
he Nestlé research and develop- isolation. A stainless steel diaphragm
ment centre in Konolfingen, and a specially processed filling liquid
Switzerland, develops milk- isolate the sensor from the process
The differential pressure at the
based constitutional food prod- medium.
heat exchangers is measured
ucts and the respective production using the ED701 transmitter
processes. The main focus is on infant Humidity resistance
food and special diet nutrition and The electronics are located within the long-term stability. The hygienic
health care products. hermetically sealed transmitter hous- design means the series is suitable for
For hygienic reasons, all measuring ing, which helps the ED 701 resist food and beverage applications, and
devices in the new testing facilities humidity, shock and vibration. all materials, including the white oil
have to be equipped with an aseptic used as standard filling liquid, are
screw connection according to DIN compliant with the FDA standards.
11864-1. Pressure transmitters from In this particular heat exchanger
Baumer’s ED701 series were already application, the pressure transmitters
being used in various other applica- were constructed with an accuracy of
tions at the Product Technology Centre 0.4% FS and a compensated tempera-
(PTC) including homogenisers, mills ture range of -10 to 125°C (on the cool-
and filling equipment. As Nestlé was ing water side) respectively, and a high
satisfied with the operation of these medium temperature of 300°C maxi-
devices, they were also chosen for the mum (on the heating side). The mea-
pressure measurement at the new suring range of the gauge pressure
facility’s heat exchangers. Depending covers 0 to 20 bar.
on the processes to be tested, up to six
heat exchangers are used for heating Making the connection
and/or cooling the products, with Depending on the choice of the electri- The CombiConnect Since a new process connection was
temperatures reaching up to 150°C. cal connection, the protection classes
system provides a
also required for the new milk tube,
vary from IP65 to IP67. A micro-con-
series of hygienic,
the Nestlé PTC and Baumer co-oper-
Differential pressure troller compensates any drift effects on
replaceable,
ated on the development of a special
At high temperatures, the products the sensor signal due to temperature
process
adapter for the ED701. Whereas
precipitate protein, which then sedi- changes. Therefore, these effects can
connections
Baumer delivered the connection for
ments on the heat exchanger’s metal be eliminated over a range of tempera- the pressure-receiving side, the match-
plates. If there is too much sediment tures, with a short response time. ing part on the product side was con-
on the exchanging face, the differential The ED 701 is available with a vari- structed by Nestlé.
pressure between the product and ety of pressure and electrical connec- Ernst Strahm, measurement technol-
medium side rises and the heat tions, a 4…20 mA current loop and ogist at the Nestlé PTC in Konolfingen,
exchangers have to be cleaned. In this various voltage output signals. It offers A selection of said: “For the milk tube fitting, Baumer
application, the PTC developers are a short response time (max. 5 ms) and Nestlé products offered us the CombiConnect adapter,
testing the recipes and manufacturing which we found most suitable thanks
processes with different kinds of to its flush-mounted O-ring.” The
liquid products, ranging from milk to CombiConnect system provides a series
dessert crème. Among other results, of hygienic, replaceable process con-
the tests show the possible range of nections made of acid-proof stainless
process temperatures between steel, which fulfil the FDA and EHEDG
medium and product, as well as how criteria. The connectors can be used
long production can run before a heat with FlexBar and ED701 pressure trans-
exchanger needs to be cleaned. mitters, as well as the CombiTemp tem-
The differential pressure is mea- perature measuring device.
sured by the ED701, a piezo-resistive A further challenge in this applica-
pressure transmitter with a stainless tion was the small pipe with a diame-
steel diaphragm. It is based on a sili- ter of only 10mm, making it difficult to
con sensor designed for precise mea- clean. The problem was solved by
surement within a wide temperature choosing a high flow rate and a pres-
range. Its downstream digital compen- sure transmitter with a small volume
sation reduces the signal drift. The compared to that of the tube.
piezo-resistive silicon sensor is anodi-
cally bonded to a stable glass base
Baumer
attached to a stainless steel construc-
T: 01793 783839 Enter 234
tion, which guarantees a good thermal
www.baumerprocess.com
S12 JUNE 2009 Process & Control
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