Blending tanks are containers used in the large scale manufacture of fluids such as epoxies, urethanes, silicones, and so on, as well as in the processing of resins and curatives in an economical manner. This process of mixing fluids has a history longer than the lay person would know. It was used for blending of inks and liquids. In what was quite a time consuming process, fixed quantities of the ingredient liquids were poured into a tank that was equipped with facilities for mixing. Once this process was completed, the resultant composite was mechanically mixed to attain a homogeneous product. After this, a sample of the product obtained was tested for consistency, and if found to be substandard, was subjected to another iteration of the same process. This was repeated over and over again till the desired blended liquid was created.
In tank blending can be done in two ways. The first is by means of mechanical in-tank mixers and the second by sparge mixing. If we consider the first method, meaning in-tank mixers, it essentially means that the participating fluids are agitated within the tank by means of side mounted or bottom mounted paddles till they are homogenized. This is a time consuming process, the more so when large volumes of fluids are involved. Sparge mixing if preferred for smaller volumes of liquids, and the principle in this case is that the liquid is circulated over and over again through the tank through a tube that also disperses its particles till the final homogeneous mix is obtained.
This just goes to show that both these process of in-tank blending have the same drawbacks – that they are time consuming and in each case the product obtained is erratic in quality, and depends on the quality and quantity of tests conducted, and accordingly on the judgment of an individual. Besides, the final product will also differ for different proportions of the ingredient liquids used.
Today, the blending tanks that are commercially available present a huge variety of sizes, shapes, configurations and supported presets. From about one gallon to nearly a hundred, several capacities are available. The material of the tanks is always stainless steel, but the grades can differ. So can the permissible speed at which the liquid within the tank can be safely churned. Some tanks – the larger ones usually – support speeds of 160 gallons per minute, while the smaller ones cannot withstand more than 20 gallons per minute.