Receiving failed sample results from Dyne can be stressful. It might lead to having to investigate or replace either the foam, equipment, or both which can involve a lot of time and money. Having a clear understanding of why a sample failed will help save time in figuring out how to resolve the issue. It can also save you from mistakenly replacing good foam when the equipment is to blame. Understanding common causes of foam failure will help eliminate any issues that can be dealt with before sending your samples to Dyne as well. Common reasons for foam failure include dilution, age, improper storage conditions, mixing incompatible foam, and improper sampling technique.
Dilution: Foam concentrate is designed to be mixed with water at a specific concentration prior to being applied to a fire. When water is inadvertently introduced to the foam concentrate in storage, it can create a situation where the proportioned foam will be mixed at a much lower concentration. Foams mixed at lower concentrations than designed will not perform as there will not be enough of the surfactant present. Some foams are also not designed to be premixed with water for long periods of times. If you have one of these concentrates and water has found its way into it, the chemicals may have been broken down over time and it will no longer perform as intended. For these reasons, allowing any water into a concentrate prior to a fire scenario can be a costly situation. Tanks should be sealed off from any water supplies at all times and all systems should be designed with foam concentrate isolation values. When taking a sample, water dilution might be noticeable in color, viscosity and frothiness. A field refractometer can be of useful in identifying water issues as the refractive index of water is quite a bit lower than the documented refractive index of the foam.
Aging/Improper Storage Conditions: As foam ages, the chemical ingredients can break down and the solvent in the foam can evaporate. The shelf life of a foam can be found out by contacting the manufacture. If the foam is showing low performance and is outside the shelf life, the failure might simply be caused by the normal breakdown of the foam. While this is a process that cannot be avoided, it can be accelerated by improper storage conditions. Extreme temperatures outside the recommended usage range can be harmful to the foam unless noted otherwise. One exception is if your foam is a freeze protected foam, which has a much lower freeze point for tanks in cold conditions. Try to avoid excess heat with all foams as this will accelerate the aging of the foam – most foams should not be stored above 120 degrees Fahrenheit. Chemical reactions typically happen at high temperatures where the heat will provide the necessary energy for a chemical to react and break down. If a foam is still within its shelf life but isn’t performing, looking into the storage conditions could prove beneficial as to avoid any problems with future containers of foam.
Mixing Incompatible Foam: Mixing different types or brands of foam can also lead to chemical reactions where the foam’s ingredients will break down and become less effective. Each manufacture has its own formulation of chemicals in foam to give them their desired performance. Since the exact content of the foam is considered a trade secret and is not published, it cannot be determined how exactly two foams will react. While the reaction shouldn’t be violent, it can be enough to render a surfactant useless. If an alcohol resistant foam is mixed, it might cause the polymer to drop out of solution which could create issues in a proportioner. To eliminate the unknown of this situation, NFPA 11 does not recommend that two different types of foam be mixed. If a tank is in need of topping off, the same product should be used. This is something to keep in mind if a foam is deemed to fail performance and it is known that two different foams were mixed.
The right type of foam needs to be used for the fuel it is protecting against. Standard aqueous film forming foam (AFFF), for example, will not protect against a polar solvent fire. The polar fuel will break down the foam very quickly and expose the fuel to the ignition source yet again. In this situation, an alcohol resistant AFFF should be used since it contains a polymer that protects the foam from the polar fuel.
The right product of foam should also be used with your equipment. For example, if your equipment is set up for a 1% foam but a 3% foam is put in the tank, the performance will be quite low since the foam is designed to work with three times the amount of foam than is being proportioned. A good place to start when looking at foam results is to identify the fuel the foam is protecting against and the percent the equipment is set up for. Any deviation in this may result in a failure during annual testing.
Improper Sampling: Taking a sample improperly can also lead to failed annual testing results. For bladder tanks, make sure to identify and sample the concentrate and not the bladder water. Sending in bladder water marked as a concentrate could lead to the belief that the sample is diluted as it will certainly fail the performance testing no matter the type of foam. It is always a good idea to sample more than one sample from different places in a tank to ensure the foam is performing throughout. Only a portion of the tank may fail but this will only be caught if multiple samples are taken at different areas. For example, small amounts of water may settle on the top of some tanks. If it is a small amount, only the small portion of the top may be diluted which can be removed and topped off. It is a good idea in this scenario to retest the top after the water is removed to ensure all of the diluted foam was indeed removed. Try to avoid any mineral oil layers when taking samples as well. Mineral oil is placed on the top of some foams to help avoid any solvent evaporation. This mineral oil can lower the foams performance, however, if it is mixed in the foam. Always ensure the sample was taken correctly before jumping to any conclusions on failed results.
Ensure that you are using the resources available to you at Dyne Technologies. Our staff chemists are ready to answer questions that you may have regarding your test results. Call Dyne at (800) 632-2304 for assistance with understanding your test results.