Name two common types of foam proportioning devices used in transfer stations?

• A. Mechanical meters and centrifugal mixers
• B. Venturi meters and static mixers
• C. In-line/induction proportioners and eductor-type proportioners
• D. Gravity-fed drip systems

Answer: (C)

Foam proportioning devices are used to mix AFFF concentrate with water to create the foam solution at a controlled dilution. The two common types you’ll see at transfer stations are inline/induction proportioners and eductor-type proportioners.

Inline/induction proportioners sit in the water line and draw concentrate into the flowing water using suction generated by the water flow or a small pump. This setup provides a stable, adjustable mix across a range of flow rates and pressures, and it’s easy to integrate into existing piping for reliable, consistent foam production.

Eductor-type proportioners operate on a venturi principle: as water passes through a narrow throat, it creates suction that pulls concentrate through a suction line into the stream, mixing at the desired ratio. They’re simple, portable, and versatile for feeding foam at multiple points or in temporary configurations.

Why the other options aren’t the best fit here: those items either describe flow measurement or general mixing approaches that don’t specifically control the concentrate-to-water ratio, or they rely on gravity without providing the precise, adjustable proportioning needed for reliable AFFF operation.