Pumping Apparatus Driver/Operator Chapter 14

Foam Proportioning Overview

• A foam proportioner is a device used to mix foam concentrate with water to create foam solution for firefighting.
• Mechanical foams need water, foam concentrate, and air to be ready for use.

Foam Concentrates and Solutions

• Foam concentrate is a concentrated liquid that, when mixed with water, generates foam.
• Foam solution is the mixture of foam concentrate and water before it is dispensed.

Foam Completion and Fuel Types

• Foam is considered a completed product once the foam solution is properly mixed and ready for discharge.
• Class B foams effectively suppress fires involving hydrocarbon fuels by forming a barrier that prevents oxygen from reaching the fuel.

Specific Gravity and Fuel Classification

• Hydrocarbon fuels like crude oil and gasoline typically have a specific gravity of around 0.6 to 0.8.
• Polar solvent fuels are known as water-miscible fuels.

Concentration and Storage

• Typical water concentration for firefighting foam concentrates ranges from 3% to 6%.
• An external pump method of proportioning foam uses a pump to force foam concentrate into the fire stream.

Proportioning Methods

• Premixing method of proportioning foam mixes foam concentrate with water prior to application.
• Induction method involves drawing foam concentrate into the water stream using a venturi effect.
• Pouring foam directly into the tank is known as the pour-in method.

Foam Storage Capacities

• Foam concentrate tank sizes on fire apparatus can range from 20 to 500 gallons.
• Foam tenders can carry up to 1,000 gallons or more for storage.
• A pail typically contains 5 gallons of foam concentrate.
• Barrels usually hold 55 gallons of foam.
• Totes can store 275 gallons or more of foam.

Foam Solution Shelf Life and Application

• Properly stored foam solution has a shelf life of 10 years or more.
• Class A foam concentrates can typically be mixed at 0.1% to 1% for fire attack and overhaul with standard fog nozzles.

Application Rate and Types of Foam

• Application rate refers to the amount of foam solution applied per unit area of the fire.
• High expansion foam is suitable for maximum penetration in confined spaces.
• The appropriate percentage range for proportioning Class A foam with air aspirating nozzles is 0.1% to 1%.

Specific Foam Recommendations

• Recommended percentage range for Class A foam when using CAFS (Compressed Air Foam Systems) is typically 0.3% to 1%.
• Properly stored synthetic foam concentrate usually has a shelf life of around 10 years.

Class B Foam Concentrations

• Typical concentration range for Class B foams when used with polar solvents is 3% to 6%.

Foam Expansion Factors

• Factors affecting foam expansion include the type of proportioner, water quality, and concentrate formulation.
• Medium expansion foam typically has a ratio range of 10:1 to 100:1.

Application Calculations and Foam Types

• Application rate calculations from nozzles depend on flow rate and nozzle size.
• Regular protein foam features a protein base, while fluoroprotein foam concentrate contains additional fluorochemical additives.

Foam Behavior and Application Techniques

• AFFF (Aqueous Film Forming Foam) or FFFP (Film Forming Fluoroprotein) applied to hydrocarbon fires displaces oxygen and cools the fuel.
• Alcohol Resistant AFFF concentrate is generally used at a concentration of 3% to 6%.

Foam Proportioning Devices

• Foam proportioning devices work on the principle of mixing foam concentrate with water to achieve desired ratios.
• High expansion foam is primarily used in confined space situations to displace air.
• An in-line foam eductor allows for continuous mixing and application of foam solution.

Eductor Specifications

• Maximum pressure allowed at the discharge side of the eductor is typically around 100 psi.
• If inlet pressure is too high at the eductor, it may reduce foam effectiveness or damage the unit.

Eductor Requirements

• Successful operation of the nozzle and eductor requires proper matching of flow rates and pressures.
• Recommended inlet pressure range for accurate blending of foam solution is 50 to 70 psi.
• Height above the foam concentrate for the eductor should not exceed 10 feet to maintain suction.

Eductor Operation

• Letting the eductor educt water for one minute allows for proper priming and mixing of foam solution.

Proportioner Disadvantages and Advantages

• Around the pump proportioners may lead to inaccurate mixing ratios, especially at low flow rates.
• Accurate foam proportioners can flow plain water and foam simultaneously for effective dispensing.

CAFS Considerations

• A significant limiting factor of using CAFS is the need for a high airflow rate, which may require a larger apparatus.
• CAFS offers tactical advantages such as faster application rates and better coverage compared to low energy systems.

Structural and Wildfire Applications

• Typical airflow rates of foam solution with CAFS in structural and wildland operations can vary but are often around 20 to 40 CFM.
• Smooth bore nozzles are utilized to deliver a solid stream of foam solution effectively.

Nozzle Functions and Application Methods

• The primary function of air aspirating foam nozzles is to create an expanded foam through aeration.
• For class B foam applications, particularly near ignitable liquid pools, specific techniques must be used to mitigate the flames.

Foam Biodegradability and Environmental Considerations

• Biodegradability of foam is usually determined through laboratory testing and environmental impact assessments.
• Studies by the U.S. Forest Service indicated that Class A foam has minimal long-term environmental effects in bodies of water.

Durable Agents and Ratios

• The standard application ratio for durable agents as extinguishing agents typically ranges from 0.3:1 to 0.5:1.
• Durable agents have a chemical composition that differs from Class A foam, offering unique benefits for structure protection.
• For structure protection, the recommended application ratio for durable agents ranges from 0.5:1 to 1:1.