FAQs

FAQs

WHY IS FOAM TESTING REQUIRED?

Quality foams exhibit excellent storage characteristics.

For example, most AFFF manufacturers offer at least a 10 year life for products stored in original and unopened containers.

  • However a foam's performance can be compromised by:
  • Dilution
  • Contamination
  • Extremes of temperature

For these reasons NFPA11, BS5306, UKOOA/HSE recommend that:
"Foam concentrates and produced foams should be tested on at least an annual basis."

WHAT IS A PRODUCED FOAM TEST REPORT?

The purpose of a Produced Foam Test Report is to determine the suitability and accuracy of a foam system's proportioning / induction equipment.

Each Produced Foam Test Report shows the calculated % Induction measured using the sample provided.

This result is compared against Foam Standards NFPA 11 and BS 5306.

HOW IS A PRODUCED FOAM TEST DONE?

This is a method for calculating the actual premix concentration of a produced foam and is used to test the accuracy of the proportioning equipment used.

  • To do this test you need samples of:
  • Produced Foams
  • Foam Concentrate Used
  • Induction Water Used

Note − it is important to use the actual induction water used (the refractive index of sea water, for example, is highly variable!).

Test Procedure
Using a refractometer, the Refractive Index (RI) of the produced foam is compared with the Refractive Index of known foam solutions.

It is advisable to make known foam solutions (using the Foam Concentrate) which are above and below the Produced Foam Concentration.

For example, if testing a 3% Produced Foam sample take the Refractive Index of:

  • Sea Water
  • 2,3,4 and 5% Foam Concentrate/Water Solutions

A Refractive Index vs. Concentration Curve is then drawn using the RI of the known Foam Solutions.

The % Foam solution is the Vertical Axis and the RI is the Horizontal Axis.Using the RI of the Produced Foam Sample, plot the point at which it meets the pre−calculated curve (using the known foam solutions).

Read off on the Vertical Axis the % concentration to water of the Produced Foam relating to the Produced Foams RI.

WHAT SAMPLES ARE REQUIRED OF PRODUCED FOAM?

  • Provide at least:
  • 1 Litre of Foam Concentrate
  • 1 Litre of Induction water
  • 0.5 Litre of Produced Foam
  • Samples should ideally be provided in clean tightly sealed polythene bottles and be labelled with the following information:
  • Type of Foam Concentrate/Produced Foam e.g. 3% AFFF-LF
  • Name of Company
  • Date of Sample Taken
  • Sample Source

HOW DO I TAKE A SAMPLE OF PRODUCED FOAM?

Produced or Expanded Foam samples should represent as closely as possible the foam reaching the designated discharge area. Collecting samples from nozzles, monitors and overhead sprinklers. Collect sample from point of impact in the discharge area. Collecting samples from Foam Pourers. Insert sample container into the edge of produced foam stream and take sample.

  • Practical Points
  • Before taking a sample, activate the foam system long enough to remove standing columns of water (which otherwise would contribute to a dilute produced foam sample).
  • Sample when the system is in equilibrium.

WHAT IS IN FOAM CONCENTRATE TEST REPORT?

The purpose of a Foam Concentrate Test Report is to evaluate if the sample tested is in satisfactory condition and most importantly is within the manufacturer's specification. Each Foam Concentrate Test Report offers analysis of 11 key features:

  • Appearance
  • Specific Gravity
  • pH
  • Viscosity
  • Surface Tension
  • Freeze Point
  • Expansion
  • 25% Drainage
  • Sediment
  • Fire Extinquishment Properties
  • Burnback Performance

WHAT IS THE DEFINITION OF APPEARANCE?

Samples are visually examined for visible sediment, concentrate colour and whether homogeneous

  • Visible sediment indicates contamination (possibly due to poor storage conditions).
  • Colour change, when compared to the manufacturer's specification, could indicate contamination by a different foam type or concentrate degradation.
  • Non homogeneous liquid suggests a serious failure.

WHAT IS THE DEFINITION OF SPECIFIC GRAVITY?

Change in Specific Gravity, when compared to the manufacturer's specification, indicates whether a foam concentrate has been diluted or in temperate climates concentrated due to losses caused by evaporation.

WHAT IS THE DEFINITION OF PH?

Change in pH when compared to the manufacturer's specification can be caused by one or all of the following:

  • Product degradation
  • Product contamination
  • Biological decomposition

WHAT IS THE DEFINITION OF VISCOSITY?

Reduced viscosity, when compared to the manufacturer's specification, can be a sign of dilution and/or degradation.
Excessively high viscosity can effect induction strength and performance.

WHAT IS THE DEFINITION OF SURFACE TENSION?

Surface Tension indicates how well the foam will "spread" across the surface of a fire.
Surface Tension is measured using a Torsion Balance measure.
Change in Surface Tension, when compared to the manufacturer's specification, can effect performance.

WHAT IS THE DEFINITION OF FREEZE POINT?

Foam concentrates are placed in a freezer and the temperature taken at transition point between crystal and homogeneous liquid phase.

Changes in Freeze Point, when compared to the manufacturer's specification, can indicate dilution or contamination of Foam Concentrate.

WHAT IS THE DEFINITION OF EXPANSION?

Expansion is the ratio of foam produced to the volume of solution used to generate that foam, ie Expansion = Volume of Foam / Volume of Foam Solution.

Expansion is related not only to the Foam concentrate but to temperature, water quality, foam making equipment and test procedure.

For these reasons, the temperature of the Foam Concentrate water, air and Foam Solution is recorded.

Similarly, standard Foam making equipment and collection procedure should always be used in order to compare results obtained.

Change in Expansion, when compared to the manufacturer's specification, can effect performance.

WHAT IS THE DEFINITION OF 25% DRAINAGE?

Drainage Time is the speed at which water drains from a foam and is therefore a critical measure of a Foam's stability.

Foam Test laboratories measure the 25% Drainage Time (sometimes referred to as Quarter Drainage). This is the time taken for 25% of the water content to drain from a foam.

Change in 25% drainage, when compared to the manufacturer's specification, can effect performance.

WHAT IS THE DEFINITION OF SEDIMENT?

  • Sediment is tested using a Centrifuge tube "spin". Sediment can arise from:
  • Degradation
  • Contamination
  • Mixture of incompatible foams

Typically Protein based foams should not exhibit greater then 0.5% sediment and AFFF's less than 0.1%.

WHAT IS THE DEFINITION OF FIRE EXTINQUISHMENT PROPERTIES?

Fire Extinguishment properties are tested by igniting a quantity of fuel (heptane or alcohol) in a test pan and applying a quantity of foam after a set time. If the fire is not extinguished within a set time, the foam has failed.

WHAT IS THE DEFINITION OF BURNBACK PERFORMANCE?

Burnback performance is measured using a rectangular test pan filled with a quantity of heptane. This pan is divided − 90% of the surface has foam applied to it and the remaining 10% surface is ignited. After a set time, the divider is removed and the progress of the fire's spread is measured and timed. The foam has passed if the flames have not progressed to a set percentage of the surface area after a set time.

WHAT SAMPLES ARE REQUIRED OF FOAM CONCENTRATE?

  • Provide at least:
  • 1 Litre of Foam Concentrate
    Samples should ideally be provided in clean tightly sealed polythene bottles and be labelled with the following information:
  • Type of Foam Concentrate/Produced Foam e.g. 3% AFFF-LF
  • Name of Company
  • Date of Sample Taken
  • Sample Source

HOW DO I TAKE A SAMPLE OF FOAM CONCENTRATE?

The Foam Concentrate sample should be representative of the stored product.
The three recognised sample procedures most frequently used are:

Single Sample
Circulate the stored product to obtain a single homogeneous sample.

Two Samples
Take a sample from the top and bottom of the stored product and composite the samples into a single unit.

Three Samples
Take a top, middle and bottom sample and composite into a single unit. NB − It is important that sludge, sediment, rust, scale etc is removed before collection of the bottom sample. To do this draw off at least 5-10 Litres of product before taking a sample.