Dealing with Foam in Flumes and Weirs

Foam can be a serious headache in your flow measurement operations. It creates errors in your numbers and often invokes overhead in the need for additional maintenance. It can be caused by many factors, and dealing with it is important. Learn how foam affects flow meters, what causes it and how you can deal with foam in flumes and weirs when it happens.

Types of Foam

There are two major types of foam: chemical and biological. Chemical foams are fluffy and white, and when you touch them, they collapse. Biological foams are off-white or brownish in color and can be sticky, slimy, and dull. They are usually the result of fat, oil, and grease in your system or are due to the presence of hydrocarbons. In industrial systems like bakeries, biological foams are sometimes caused by proteins and starches.

Why Foam in Flumes and Weirs Is a Problem

Foam in flumes and weirs is a major problem because it makes it impossible to accurately measure flow, especially with an ultrasonic flow meter where foam impedes the sound pulses. Moving to a submerged probe or bubbler can be a partial solution, but the only ideal solution is to get rid of the foam entirely.

You can also modify your flume or weir to minimize the impact of the foam while you work to eliminate the issue. You can use a stilling well that allows the flow to cover the inlet, but this can create maintenance issues and can cause clogging in sanitary flows. Freezing and lag are also an issue.

Another modification is using underflow baffles that extend from above the surface to the floor of the device. They stop foam upstream and quiet the flow after the baffle. These baffles are present in many standard weir boxes but are not usually used with flumes as flumes are exceptionally sensitive to variance in inflow conditions.

Eliminating Foam in Your System

The steps for eliminating foam in your system depend largely on the type of foam you have. If you’re experiencing chemical foams, you will likely use a defoaming or anti-foaming agent. These agents can typically reduce or even eliminate your problem. Defoaming agents are fed into the system where the foam is generated with the intent of knocking foam out and eliminating it after its creation. Anti-foaming agents, on the other hand, are fed in before the foam occurs to keep it from forming at all.

If you’re already experiencing foam, your first step will be to use a defoaming agent to eliminate the existing problem, followed by an anti-foaming agent in the future to keep it from returning. If you don’t have foam but are concerned about it, simply use anti-foaming agents.

Biological foams, on the other hand, do not respond well to these products. For biological foam issues, you may need to modify your flume or weir or take action to eliminate the biological agents causing the problem.

Contact Tracom for Foam Control

If you’re experiencing foam problems in your open channel flow measurement system, the right flume or weir can help. Tracom carries a wide range of fiberglass flume and weir products for many applications. Check out our full product list and get in touch with us for more advice or to place an order today.

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