Tanks can be fabricated from both metal and plastic. Although both materials have their own set of advantages, poly tanks are lower-maintenance and are more durable than those made of steel, stainless steel, Hastelloy, or titanium. Poly tanks, another term for plastic tanks, have a seamless structure, and are resistant to chemicals, fuel additives, corrosion, and rust. Steel tanks can leak and fracture over time, but poly tanks have a much longer lifespan.
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Design of Poly Tanks
Unlike stainless steel tanks, plastic is much easier to mold and shape. Thus, poly tanks are much easier to install, and can be shaped to fit tank compartments of a certain size and shape. Poly tanks can vary greatly in terms of holding capacity. They can hold as little as 15 gallons to as much as 16,000 gallons. Companies who are searching for inexpensive options for storage can benefit from using poly tanks, as they cost significantly less overall than metal tanks. Poly tanks are also highly resistant to a variety of chemicals and substances, including motor oils, diesel fuels, fuel oils, hydrochloric acid, sulfuric acid, caustic soda, and sodium hypochlorite.
Applications of Poly Tanks
Because of this level of versatility, poly tanks are used in a wide range of industries and applications. Examples include tanks in irrigation and fertilization systems in the agriculture and food production industry, and storage of oils and fuels in automotive businesses. Other applications where poly tanks can be found include electroplating, parts washing, industrial manufacturing and processing, and recycling.
Types of Plastic
Poly tanks can be fabricated from many types of plastic. Some common types of plastic are as follows:
- Polyethylene (PE)
- The most popular plastic resin for fabricating storage tanks. PE is a thermoplastic that is light in weight, resistant to chemicals, and can come in several types. The first type is known as linear high density polyethylene (HDLPE). The word "linear" is used in the term for the purpose of distinguishing it from cross-linked high density polyethylene. Otherwise, the term can be used interchangeably with high density polyethylene (HDPE). HDPE is more rigid than its low-density counterpart, and is known for its superior impact resistance. Tanks made from HDPE are more reliable and are less prone to rupture and leakage of its contents. Linear low density polyethylene (LLDPE) has shorter branching in its molecular structure than low density polyethylene (LDPE), causing LLDPE to have higher tensile strength and higher resistance to rupture and impact. Finally, cross-linked high density polyethylene (XLPE). The polymer chains within XLPE are connected by heat and chemical-generated covalent bonds and subsequently elongated, making the material incredibly rigid, durable, and more chemically resistant than HDPE.
- Polypropylene (PP)
- Another highly recommended material due to its lightweight, low density, excellent strength, exceptional resistance to heat and moisture, and a melting point of 320º F (160º C). PP is also resistant to chemicals such as magnesium hydroxide, potassium carbonate, photographic solutions, oleic acid, and hydrogen sulfide. Although it has less chemical inertia than polyethylene, it is a much stronger resin.
- Polyvinyl Chloride (PVC)
- The advantageous properties of PVC include the ability to be mixed with an assortment of additives in order to improve flexibility, conductivity, insulation, and rigidity of the material. The transparency and color can also be adjusted. Despite its beneficial properties, PVC is less commonly used than PP and PE because of how much it can negatively affect human health and the environment. PVC contains toxic elements that can be released into the atmosphere or seep into the ground. Therefore, the potential hazards of PVC is important to consider when deciding on a resin from which to fabricate your poly tank.
Rotational molding, or rotomolding, is one method to manufacture poly tanks. The first step of the process involves filling a mold with the plastic material—which is ground up into powder form—and sealing the mold shut. The mold is supported on a set of arms known as spindles. Once the molds are filled, they are transferred by the molding machine to a heating chamber which melts down the powdered plastic. In the heating chamber, the mold slowly revolves around the spindles’ axes. Once the melted plastic takes the shape of the mold, it is then transferred to a cooling chamber. Within the cooling chamber, cold air and water is applied outside the mold, which helps solidify the molten plastic. Once cooled, the final product can be manually removed from the mold. Rotomolding is highly advantageous to other methods like blow molding and injection molding, due to its ability to create seamless products in one piece.