Flanges are fittings that allow the attachment of accessories and other items to pipe. They can also increase the strength of pipe. Flanges are a disc-like fitting that create a tight seal by pressing two surfaces together with bolts, clamps, edges, or a compressive force. Most flanges, however, use bolts to join the two surfaces together. PVC flanges are available with slip or threaded ends. Because of the strength required of flanges.

A chemical tank-vessel is of necessity designed for a specific chemical, as all chemicals have variable corrosion potentials there are no, one size fits all. The chemical and application parameters should design tank-vessel, the following is a "tip of the iceberg" view of what goes into defining a Chemical storage tank.