WHY IS FOAM DETECTION IMPORTANT ?
Foam can ruin fermentation and biotechnical processes. Arising as an unavoidable consequence of the process, undetected foam build-up can lead to one or more of the following
- restricted gas flow at the liquid surface
- contamination of filter housings
- pressurisation of the vessel and loss of production.
Ultimately, uncontrolled foaming is inefficient, expensive, and liable to destroy a process.
THE PROBLEMS ASSOCIATED WITH FOAM LEVEL DETECTION
Foam can be detected. But old style foam detectors are prone to fouling by condensation, surface growth, and even the media which they ought to be monitoring. They need constant attention, cleaning and recalibration to reduce these effects, but may still give false readings and cause overdosing of antifoaming agent. The result again is damaging to production.
THERMO ELECTRON - TWENTY YEARS OF SENSOR EXPERIENCE
Now Thermo Electron have addressed these problems. Drawing on 20 years of experience in the design and manufacture of electro-chemical sensors, Thermo Electron have developed a foam detector with the accuracy and reliability that characterises all of its products.
DEVELOPED TO MEET THE DEMANDS OF INDUSTRY AND RESEARCH
The Thermo Electron foam detector is available in different versions to suit every application
- laboratory and industrial probes
- rack or wall mounted controller
- variety of probe fittings
- operates across a wide band of ionic strengths
- sensor and controller options
- adaptable for use in special applications.
The detectors truly satisfy the various demands of industry and laboratory.
TYPICAL APPLICATIONS
The foam detection technology which has been commercially developed by Thermo Electron is suitable for many industrial and research applications
- cell culture production
- cell culture biodegradation
- research fermentation
- pharmaceutical production
- brewing and distillation
- surfactant production.
Overcoming those problems associated with fouling and contamnation of the probe were crucial to the development of an accurate and reliable foam detector/controller.A new approach was required, and initiated. The problems were solved by the mounting of two electrodes on the probe ~ the first to act as a sensor, the other to act as a guard. Working together the electrodes guarantee
- maximum sensitivity to foaming
- maximum resistance to fouling.
When the ionic culture broth is whipped up into a foam it contacts first with the sensing electrode at the bottom of the probe. The resultant drop in its potential is measured by the detection circuit and dosing of antifoaming agent may be promoted. The guard electrode acts separately to give the probe its unique performance.
Insulated from the sensing electrode, and energised by an alternating potential, it protects the sensing electrode from the effects of contamination. The sensitivity to foam is at least 100 times greater than the sensitivity to any surface fouling. Thus the probe is entirely unaffected by large amounts of fouling and false positive warnings of foam are avoided. This in turn prevents over dosing with antifoaming agent. Other design features of the probe accentuate its performance
- smooth surfaces discourage the attachment of organisms
- large surface area improves accuracy
- corrosion resistant construction suitable for all conditions
- easily adapted to fit all makes of fermenter
- no drift
- no calibration required
- virtually maintenance free.
With the innovation of the probe comes new controlling electronics. The electronics contained within the detector unit are designed to fully utilise the unique features of the probe, either to generate an alarm or to form a complete control loop. The latter may be formed with an existing process control system or with the new Thermo Electron controller which optimally governs the dispensing of antifoaming agent to the broth.
The Thermo Electron controller is manufactured to the same high standards as the probe and is designed to ensure maximum foam reduction from minimum dosages.This is achieved by optimum setting of the period over which foam should be detected before antifoaming agent is added (delay time), and the period during which antifoaming agent is added (shot time). These settings establish a cycle time in which the antifoaming agent is given sufficient time to work before another dose is injected.
Thermo Electron have foam level sensors for both research and industrial processes based on the same dual electrode technology. They offer a level of reliable performance that was previously unobtainable, improving efficiency and productivity in all biotechnical processes. |
