Foam Fire Suppression Systems: Features and Operating Principles

Fire safety is a critical aspect of the operation of various facilities, from residential buildings to airports. Foam fire suppression systems remain one of the most effective methods for combating fires. These systems can quickly and efficiently localize and extinguish a fire. What types of foam systems exist, and how do they work? Read on to find out.

What Are Foam Fire Suppression Systems?

Foam fire suppression systems are specialized systems designed to extinguish fires using water-foam mixtures. The core principle of this method involves isolating the flames and creating an oxygen-deprived environment.

Foam systems can operate in two modes: manual or automatic. This versatility enhances the speed of response to a fire outbreak. Additionally, the installation method is variable: foam systems can be mobile (portable units or specialized vehicles) or stationary. The type of system is selected based on the facility and the class of potential fire.

Foam systems are most effective in extinguishing Class B fires, which involve flammable liquids such as oil, solvents, and similar substances. Unlike water, foam does not mix with the liquid; instead, it forms a protective barrier on the surface, preventing the evaporation of flammable vapors and further ignition.

How Do Foam Fire Suppression Systems Work?

The operating principle of foam systems is based on mixing water with a foam concentrate, followed by aerating this mixture with air to create foam. The resulting foam is delivered to the fire source through a network of pipelines and specialized foam generators or nozzles.

The suppression process begins with fire detection. In automatic systems, sensors trigger pump stations, which supply water and foam concentrate to a mixer. The mixture is then directed to generators, where it combines with air to produce foam of the desired expansion ratio.

Foam acts through several mechanisms simultaneously:

• Isolating oxygen: It blocks oxygen access to the fire.
• Cooling surfaces: It reduces the temperature of the burning area.
• Preventing re-ignition: It forms a protective film that inhibits further combustion.

This multifaceted approach makes foam a versatile tool for fire protection.

How Is a Foam Fire Suppression System Structured?

A typical foam suppression system consists of the following key components:

• Water source
• Foam concentrate
• Pump station
• Mixing device
• Foam generators or nozzles
• Control system

All these components must work in sync to ensure rapid and reliable foam delivery.

Water can be sourced from a centralized water supply, reservoirs, or pump stations. The foam concentrate is stored in separate containers and mixed with water at a ratio of 3% or 6% using an injector or mixing pump.

As mentioned, foam systems can be manual or automatic. In automatic systems, additional equipment such as sensors, controllers, and programmable logic devices enables autonomous activation, which is particularly crucial for high-risk facilities.

Classification of Foam Fire Suppression Systems

Foam systems are classified based on several criteria:

By foam expansion ratio:

• Low-expansion foam (up to 20x): Suitable for open areas, flows well, and covers large surfaces.
• Medium-expansion foam (20–200x): Used indoors, with better insulating properties.
• High-expansion foam (over 200x): Creates voluminous coverage, ideal for sealed spaces.

By delivery method:

• Stationary systems
• Mobile systems

By purpose:

• Volumetric suppression: Fills entire spaces with foam.
• Surface suppression: Applies foam to surfaces.
• Localized suppression: Protects specific equipment or areas.

By type of foam generator:

• Fan-based
• Injector-based
• Compressor-based

What Types of Foam Concentrates Exist?

Foam concentrates are chemical substances mixed with water to produce foam. They include:

• Protein-based: Create heat-resistant, stable foam but are less effective against some modern flammable substances.
• Synthetic: Form foam quickly, perform well at low temperatures, but have a shorter duration.
• Universal: Suitable for low-, medium-, and high-expansion foam suppression.

The choice of foam concentrate depends on the facility type, fuel, and storage conditions.

Features of Foam Fire Suppression Systems

The primary feature of these systems is their ability to create stable foam that not only extinguishes flames but also remains on the surface, preventing re-ignition.

Another advantage is the adaptability of foam expansion to specific conditions: high-expansion foam for enclosed spaces and low-expansion foam for open areas. Additionally, systems can operate autonomously if sufficient resources are available.

Advantages of Foam Fire Suppression Systems

• Effective for flammable liquids (Class B fires).
• Prevents re-ignition.
• Suitable for indoor and outdoor use.
• Rapid fire localization.
• Fully automatable.
• Supports volumetric and surface suppression.
• Compatible with stationary and mobile systems.
• Integrates with other fire suppression systems.

However, it’s worth noting certain limitations of foam suppression systems. A complicating factor is the need for separate storage of foam concentrate. After use, foam residues require cleaning and removal. Most importantly, foam systems should not be used to extinguish fires involving energized electrical equipment, as this poses significant risks.