Reliable Foam Detection and Foam Control Systems that Reduce the Cost and Mess of Industrial Foam

Continuous dosing of antifoam is a costly habit—it assumes foam is always present, even when it’s not. Manual “on-demand” dosing isn’t much better, since operators often end up overdosing when pumps are left running too long. The smarter way forward is automated foam detection and control. These systems add antifoam only when foam is actually present, cutting chemical use, avoiding product loss and equipment damage, and preventing costly downtime. In most cases, the investment pays for itself quickly in both lower additive spend and reduced operational headaches.

In plants where foam is a common occurrence, antifoam chemicals are often continuously added to counteract foam generation. However, the dosage rate used does not necessarily prevent “foam-outs” or “foam-overs” caused by unexpected changes in process conditions. Plant outages and upsets can often require the manual addition of antifoam chemical over and above the quantity already being dosed.

This is not an efficient or effective approach to controlling foam, and often leads to overdosing due to the urgency of resolving the situation quickly. In these situations conditions often seesaw between excessive and insufficient use of antifoam additives, and operators find themselves frustrated with continued frequent foam-outs despite increasing usage of antifoam.

The best possible solution is to implement a foam detection and control system. Solutions range from control using a “shot and delay” pump strategy to add antifoam chemical whenever excess foam is detected or, for continuously foaming conditions, a PI control regime to continuously adjust the dosage rate of antifoam chemicals depending upon real time conditions. Adding automated foam control will go a long way to ensuring that the potential for foam-outs is mitigated before they become a problem.

Even if you choose not to automate foam control, a lower cost solution is to implement foam detection instrumentation that immediately raises awareness of a foaming event occurring. Immediate warning will allow more time to deal with the problem before it gets out of hand.

Switching to an automated foam control method which dispenses only as much antifoam as is measured by foam detection systems significantly reduces the total amount of antifoam agent used, mitigating the potential for product contamination.

Traditional, semi-autonomous foam control relies on the continuous feed of antifoam chemical into the process but the resulting level of entrained antifoam chemical can affect the quality of the end product.

Fully automated foam detection and control systems can manage foam without the need for human intervention, freeing up staff to attend to other necessities. Systems with automated antifoam control systems can even be left unattended during night shifts and weekends, potentially allowing for either reduced staffing during these periods, or re-dedication of employees to other, more critical needs.

The stopgap solution for reducing reliance on the use of antifoamer chemicals and washing stations is to reduce the process flow and agitation that creates foam. However, a lower flow inevitably means lower yields.

In the long term, the best results are produced by implementing an automated foam control solution which utilizes three probes to detect foam at various process states and can dispense antifoam chemicals as needed, early in the foam formation process.

The reason for high maintenance is that you are probably using liquid level probes. Such probes simply aren’t built to measure foam—they’re liquid instruments trying to do a foam job. Since foam is mostly air (~1% liquid), these probes are operating at the edge of what they were designed to do. When fouled, they give unreliable readings, often working only half the time at best.

Why common probe technologies struggle with foam:

• Capacitance / Admittance probes – These are designed to detect liquid level changes, not foam. Since foam is mostly air, they only respond inconsistently, and once they get coated with product they generate false positives. In practice, they may work half the time at best.
• Point-level probes – These can indicate that foam is present, but they can’t distinguish between foam and liquid. Depending on where they’re set, the warning may come too late to prevent a foam-over or vessel blockage. When fouled, they may just indicate foam all the time.
• Radar systems – Radar can sometimes pick up the top of a foam layer, but its accuracy is very sensitive to changes in foam density or liquid reflectivity. A small shift in process conditions or foam layer consistency can cause it to misread, leaving operators without reliable data.
• Microwave sensors – Microwaves usually pass through foam and lock onto the liquid below. This means they don’t actually measure foam at all, so operators may not realize a foam layer is forming until it’s too late.

The better solution is to use sensors designed specifically for foam detection. Modern foam probes can ignore product build-up and deliver consistent, accurate measurements, making them far more reliable than repurposed liquid level devices and helping prevent costly “foam-out” incidents.

Why purpose-built foam sensors are better:

• Foam-specific design – Unlike liquid probes, these sensors are engineered to detect foam’s unique composition (about 1% liquid, 99% air).
• Ignore buildup – They can automatically compensate for coating and material deposits, so readings stay accurate over time.
• Real-time tracking – They not only detect foam presence but can also measure foam thickness and growth rate, allowing better control.
• Lower maintenance – No constant cleaning or recalibration is required, cutting downtime and operator intervention.

Systematic reduction of the use of antifoam chemicals throughout the process will reduce the antifoam residual amounts in the final effluent discharge. Adopting the automatic “dose as required” system, rather than a “dose on upset” will help to reduce the amount of antifoam chemical used, leading to the overall reduction of antifoam chemicals in final effluent discharge.

This has been an effective approach for a variety of industries and applications, from vegetable processing to oil and gas production.

We have found that in wastewater treatment, foam can sometimes be controlled with water sprays which disrupt bubbles in foam, keeping them at bay. This approach does not, however, change any foaming tendency in the flowing stream as it still contains surfactants (the surface-active substances which cause foam). Monitoring the stream after or upstream of the water spray nozzles can help determine whether antifoam chemical is also necessary. Foam control systems which feature multiple inputs allow for multistage process monitoring, and can dispense antifoam chemicals only as needed.