Screw pumps, often known as progressive cavity pumps or single screw pumps, are positive displacement pumps used for transferring viscous or abrasive fluids in various industrial and commercial applications. The design of these pumps involves a helical rotor (the single screw) turning within a double helix stator, creating a series of sealed cavities that move the fluid axially along the screw's length. The operation of a screw pump involves the rotation of the helical rotor within the stator. As the rotor turns, it pushes the fluid through the cavities formed between the screw and the stator. This pushing action results in a smooth, non-pulsating flow of the fluid, making screw pumps suitable for handling shear-sensitive or delicate liquids.

Pall rings are a type of random packing used in chemical processing and various gas and liquid treatment applications. These rings are typically made of materials like metals, plastics, or ceramics and are characterized by their cylindrical shape with several internal and external structural features. The key design elements of pall rings include a series of internal and external structural elements—inner crossbars or struts and outer cylindrical walls—that provide a high surface area within a relatively small volume. This configuration ensures efficient contact between gas or liquid and the packing material, facilitating processes like gas absorption, distillation, and chemical reactions.