Abstract
The proper concentration of foam concentrate in water solution is a key factor in the effectiveness of fire-fighting foams produced using all currently used foam systems. The standard method for measuring the concentration of foaming agent, used to control the operation of the foam systems, is conductivity method. In this study, the applicability of the refractive index of the solution and the conductivity method was tested. The research found that the conductivity method can be used to determine the actual concentrations of all types of foaming agents in the solutions made from tap water, or water of similar electrical conductivity, of approx. 0.5 ÷ 0.8 mS/cm. Conductivity meter must be equipped with temperature compensation system. Measurement uncertainty is estimated to be ± 0.1 vol. % under optimal conditions for this method. In the case of water with high electrical conductivity, also refractometric method gives good results. In the case of solutions made with tap water and foaming agents working concentrations of 3% and more acceptable uncertainty in the measurements provides portable digital refractometer without temperature stabilization. In other cases, obtaining sufficient accuracy requires sample temperature stabilization during the test.
Highlights
Foams are the primary agent of fighting the fire of hydrocarbon and polar liquids
The research found that the conductivity method can be used to determine the actual concentrations of all types of foaming agents in the solutions made from tap water, or water of similar electrical conductivity, of approx. 0.5 ÷ 0.8 mS/cm
Conductivity meter must be equipped with temperature compensation system
Summary
Foams are the primary agent of fighting the fire of hydrocarbon and polar liquids. They are used in the fire department operations, in both fixed fire extinguishing systems and portable and mobile extinguishers. Admission to the an accurate reading off the concentration is the steepness of the calibration line This condition is fulfilled in the case of tap water or a similar water with low conductivity and a P, FP-foaming agents, and some S type. In the case of industrial water or surface water and the use of AFFF and AFFF AR, a small slope of the calibration line makes it difficult to read true concentration with sufficient accuracy Another problem is the significant influence of temperature on the electrical conductivity of the solutions. The condition for the practical application of these instrumental methods is the thermostatting or compensation of the influence of temperature on a given parameter This is due to the high temperature effect on the results of measurements of electrical conductivity, refractive index or solution viscosity. In this study two of the most commonly used methods for determining the actual foam concentrate concentration in a solution were analyzed - the conductometric method and the method of measuring the refractive index
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