Plastic tubing is used to transfer air, liquids, or solids, in a variety of industrial, agricultural, medical, aircraft, mining, and laboratory applications, and in the food and beverage industries. Plastic tubing is characterized by a hollow center, and comes in a variety of types such as flex, thin wall, and hollow bar. Tubing application ability is affected by variables such as pressure, pump speed, and substance being transferred. Temperature capability, chemical resistance, and bend radius (flexibility) also affect performance. Tubing wall material can have optical clarity properties to help monitor air or material flow, or to provide ultraviolet (UV) resistance. Extrusion or cast construction methods are used to form plastic tubing. Plastic tubing is measured in the U.S. version and the metric system, and varies in length, from one inch to hundreds of feet. When selecting plastic tubing, there are several characteristics to consider, such as outer and inner diameter, shape, wall thickness, and material type.
Plastic tubing is sized according to outer diameter (OD) and inner diameter (ID). OD refers to the exterior dimension of a round tube, from outside edge to outside edge. ID refers to the interior dimension of a round tube, from interior wall to interior wall.
Although most plastic tubing comes in a round shape, plastic hollow bar tubing can come in a variety of shapes including square, rectangular, and round. Plastic hollow bar tubing is commonly used for machining parts when a rigid material and shape is needed for specific application.
Plastic tubing is sized by its wall thickness. The formula used to calculate wall thickness is OD minus ID, divided by two ([OD-ID]/2). For example, tubing with an OD of 0.5” and an ID of 0.37” would have a wall thickness of 0.065”.
Plastic tubing is commonly made with material types such as polyurethane, nylon, polyimide, and polytetrafluoroethylene (PTFE). Plastic tubing materials offer strength, and have a range of flexibility levels, mechanical and weight properties, and chemical, solvent, abrasion, cracking, corrosion, heat, ultraviolet (UV), gamma, and environmental resistances. Some material types and their formulations can be medical or food-grade, and can conform to standards such as Food and Drug Administration (FDA), United States Department of Agriculture (USDA), National Sanitation Foundation (NSF), Federal Aviation Administration (FAA), or International Organization for Standardization (ISO) for specific application. Polyurethane is commonly used in industrial fluid transfer. Polyimide material can be used in electronics. Beverage and laboratory tubing can be made from flexible polyvinyl chloride (PVC). Plastic tubing must be tested and monitored by the purchaser to ensure it is safe and appropriate for its intended application.