Yokogawa application note.
Ceramic lined magnetic flowmeters have seen increased use in biotechnology industries in recent years, the characteristics of the liner making it highly desirable in sanitary applications. Ceramic liners can tolerate higher temperatures and pressures than most other liner materials; other liners can also release plasticisers and drying agents into the product in a process referred to as leaching. Ceramic liners are much less likely to contaminate the process by leaching. One particular concern when using ceramic liners is thermal shock and the damage that can be done when inferior designs are subjected to large, rapid swings in temperature.
Application
Yeast is used in industrial processes such as the production of antibiotics, penicillin and other medicines, as well as in the fermentation of beer and alcoholic beverages. If the lines are not properly sterile, yeast fungus can infect the process and ruin the batch. Cleaning and sterilisation between batches is an absolute necessity and is often accomplished through the use of hot water or steam.
CIP (clean in place) and SIP (sterilise in place) applications can subject meters to drastic temperature fluctuations in short periods of time, which can lead to a variety of failures in meters with inferior design and materials of construction. Electrode seals can fail due to differing expansion rates of the liner and electrodes and inferior liner materials can crack and fail causing leakage and loss of measurement.
Solution
Yokogawa’s ceramic liner can offer customers superior resistance to thermal shock and thus failures that occur due to liner cracking. Yokogawa’s extremely pure (99,9%) Al2O3 liner material increases the host meter’s resistance to thermal shock considerably. Another major advantage of the Admag ceramic design is the electrode construction, all sizes utilise a platinum-alumina cermet electrode. The electrode is a mixture of platinum and alumina powders sintered into the liner during the manufacturing process, resulting in an electrode that is an integral part of the liner. This method of construction has several major advantages over solid electrode designs: the primary benefit is the elimination of two potential leak paths and, since the electrodes are an integral part of the liner, there is no seal to fail as with meters using solid electrodes.
Another advantage of the construction is that the electrode and the liner have the same thermal expansion rates. Differing expansion rates can lead to improper sealing around the electrode and, over time, can contribute to stress cracks at the electrode/liner seal. Both can lead to premature failure of the meter due to leakage.
A major biotechnology manufacturer recently conducted a yearlong test to evaluate the effects of thermal shock from CIP cleaning on magnetic meters with ceramic liners. Yokogawa’s Admag AXF series completed the test with no problems, while other meters showed blistering and cracking. Some even had to be withdrawn before the tests were completed.
Summary
Yokogawa’s use of cermet electrodes and 99,9% pure Al2O3 liner material allows the Admag to provide reliable service where other devices may fail due to leakage around the electrode or thermal cracking of the liner. This offers longer service life with less down time, reduced maintenance and lower overall operating cost.
For more information contact Johan van der Westhuizen, Yokogawa SA, +27 (0)11 831 6300, [email protected], www.yokogawa.com/za
| Tel: | +27 11 831 6300 |
| Fax: | +27 11 86 411 8144 |
| Email: | [email protected] |
| www: | www.yokogawa.com/za |
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