We all experience foam every day. Foam forms when squeezing a bath sponge, shaking a can of soda, or whipping a cup of coffee.
Foam also arises in many industrial processes. It can be produced biologically—due to anaerobic digestion or brewing—during wastewater cleanup, while cleaning and preparing starchy vegetables, or even when drilling oil and gas. In these applications, the formation of foam can pose a real problem.
Foam buildup is an unstable mixture, a two-phase medium of gas and liquid. A typical foam structure consists of gas pockets trapped in a network of liquid films.
Industrial foam looks like a simple formation of bubbles, but the reality is that foam is a complex and unstable material.
A foam structure consists of a two-phase medium of gas and liquid. Gas pockets become trapped within the liquid film. Foam that is non-destructive will eventually dissipate. The bubbles in a bubble bath, for example, lose their structure after just a short time. Why? Liquid always flows from top to bottom. The foam at the top collapses as the film becomes too thin to support the weight of the bubbles. This process limits the height that a foam column can attain.
This is not true of industrial foam, which can persist for hours or even days and continue to form upward rising columns. Industrial foam has high surface tension caused by mixing, stirring, or sparging. This type of mechanical agitation is common in many industrial manufacturing processes. In addition, in some processes, foam stabilizing agents are added to the process. These stabilizers include soaps, detergents, and/or proteins. These agents reduce drainage, allowing the column to continue growing.
Foam buildup can cause production delays, damage machinery, and reduce yields, which is why engineers have worked for years to find ways to mitigate foam formation.
Foam that does not dissolve—and, in some cases, continues to grow—is a real problem. These bubbles can occupy a lot of space, limiting the volume available for manufacturing a product. Foam coats everything it touches. In dirty water applications, the solids in the water are also in the foam. As the foam bubbles burst and drain, these solids are often left on the surfaces the foam touched, creating, in some cases, a thick, sticky mess that takes a great deal of effort to clean off. This coating can also clog pipes and valves and interfere with monitoring instrumentation, creating maintenance needs that can lead to long production delays.
Foam buildup must be carefully monitored to prevent problems. But monitoring foam is a full-time job and doing so manually comes with mixed results. The “eye test” is fallible. It is easy to miss the existence of foam and even easier to add the wrong amount of antifoam additives, which can potentially result in even worse foam conditions.
Most manufacturers have moved to measurement tools to help them control foam. Three of the most common instrument types utilized for foam measurement are:
Radar: Radar systems are typically mounted looking down at the surface of the liquid to be measured. Designed to measure level, there are two radar technology types – through air and guided wave. A microwave pulse is directed at the liquid. When it reaches the liquid, a proportion of the emitted signal is reflected back to the instrument. Water is a strong reflector, so an aqueous foam layer can reflect back a signal strong enough for a radar system to “lock on to”. However, radar systems can be easily fooled if the foam layer becomes lighter or denser, or its surface becomes more uneven. For very consistent applications, radar can work reasonably well although foam problems are rarely consistent!
Capacitance: Capacitance probes have been successful in detecting the presence of foam in some cases and have been used widely across industries. These probes work by detecting the dielectric properties of the foam as it builds up. However, capacitance probes overall are not an ideal solution for foam detection. Designed to measure 100% liquid, adjusting them to detect foam (1% liquid) means that when set, they are operating at the very end of their measurement capabilities. Furthermore, they cannot distinguish between foam and liquid and give a false positive if they become coated with material – fouling essentially renders capacitance probes useless.
Ultrasonic: In a similar way to radar systems, ultrasonic sensors emit a soundwave that is used to detect foam. Sound is reflected from the foam layer back to the sensor where it is used to give an indication of distance from the sensor and therefore foam height. Ultrasonic sensors can be highly unreliable when measuring foam. A foam layer can cause the transmitted signal to become scattered and lost and as the foam layer becomes lighter, the sensor can lock onto the signal being returned from the liquid layer below, ignoring the foam altogether.
The probes listed above are often used, but none offer an ideal solution for controlling foam.
Here is why Hycontrol’s SureSense foam control technology is better than the rest.
Hycontrol has developed a versatile range of foam detection and control systems to meet the challenges of foam in all industries. The technology behind these systems originated directly from foam control research, meaning that these highly specialized devices were designed specifically for foam control applications. They are not simply modified liquid level sensors—these are tools that have been created specifically for this challenging task.
To be reliable in use, Hycontrol probes use IMA technology, a patented method of ignoring coating and fouling on their active surfaces so they remain reliable, even when heavily soiled. Hycontrol SureSense and SmartFoam instrumentation uses probes that are based on this enhanced conductivity measurement technology.
The SmartFoam probe is a single point switch that provides an output when foam is detected. The SureSense system is a fully featured foam detection and control unit. It can be used as a standalone or in conjunction with a supervisory control system to automatically add defoamer chemicals on demand as foam is detected.
A typical SureSense system comprises of a sensor and a controller connected via special cables. The probe is installed in the process with its tip above the liquid level. When foam reaches the probe, the controller begins dosing chemicals using a configured strategy until the foam level subsides. Hycontrol SmartFoam and SureSense instruments:
- Generate significant cost savings by reducing antifoam use and protecting equipment
- Reduce downtime and labor costs
- Increase productivity and quality of product
Hycontrol’s foam detection technology is the best available solution for controlling foam and preventing major foam disasters. Contact South Fork Instruments today to learn how we can help you prevent foam and maintain production efficiency.
