When considering chemical tank design, it is vital to consider the chemical you’re storing first. That tells the manufacturer what material to use, what types of fittings and accessories are needed, and whether or not the tank needs an antioxidant layer or other special considerations. It is equally important to have an upfront understanding of what processing temperatures are needed for the chemical, because that, too, helps the manufacturer design the best tank for your chemical storage application.
How Chemical Temperature Affects Polyethylene
Cross-linked polyethylene (XLPE) chemical storage tanks expand and contract for many different reasons, with one cause being temperature fluctuations. The tanks are designed with the chemical and the way the chemical is stored (including the temperature at which it is stored) and filled in mind.
The weight, maximum temperature (the hottest the chemical will be in the tank), and ambient temperature (the resting temperature) of the chemical dictate the thickness of the tank. If these things are not taken into consideration and a chemical of a greater weight or hotter temperature is stored in a tank not designed for those metrics, the tank can expand until it exceeds allowable hoop stress and can result in tank failure. Not all chemical storage tanks are made equal because not all chemicals are equal in their properties.
Why Chemical Temperature Can Vary
Some chemicals must be stored at specific elevated temperatures because of their chemical properties. Once a chemical like sodium hydroxide falls below a certain temperature, it will crystallize or freeze. Others, like alums, ferrics and polymers, are often delivered hot and later cool down to their ambient temperature.
In certain mixing tank situations, a higher concentrated chemical can be delivered in bulk when a lower concentration is what is actually eventually needed. This means that the highly concentrated chemical must be diluted. If it is a chemical like sodium hydroxide, dilution causes a chemical reaction that can be exothermic in nature, causing elevated temperatures within the tank. These are all reasons why a tank designed to meet the custom needs of your chemical and application is essential.
The Benefits of a Custom Tank
It is possible to buy a standard tank that meets general ASTM specifications, prepped for a maximum of 73 degrees. By using a tank that merely meeting ASTM standards, a chemical temperature above 73.4 downgrades the maximum allowable hoop stress, resulting in a compromised tank. A custom tank, however, is designed with the chemical and the chemical’s temperature in mind, so the material and thickness of that material is correct for the application. A thicker tank is needed based on the chemical’s specific gravity, and in most cases chemicals with higher ambient temperatures will require XLPE rather than linear polyethylene. XLPE has a 20-40 degree higher tolerance over HDPE by ASTM standards.
Consult An Expert Above 100F
Poly Processing’s XLPE tanks are designed for 100°F chemical storage, but can withstand even higher temperatures. We design our tanks with your chemical and chemical application in mind.