Pressure tubing is a type of industrial tubing designed to carry fluids, air, or other gases under higher-than-normal atmospheric pressure. It comes in a variety of sizes and types, and is made out of plastics compounds, such as nylon or rubber, as well as metals such as copper, tin, and stainless steel. Many plastic-based pressure tubing materials are also reinforced with a form of weaved sheath embedded in the tubing material itself, and usually made out of reinforced fiber cord or steel wire. This increases the ability of the tubing to resist high pressure failures, and, at the same time, it reduces the flexibility of the tubing somewhat depending on how the sheathing is weaved and what it is composed of.
The strength of pressure tubing over standard tubing can be substantial. High pressure steel tubing and tubing fittings, for example, can typically withstand pressures of 150,000 pounds per square inch, or psi (10,342 bar). The pressure rating by contrast for normal steel tubing is in the range of 10,000 – 25,000 psi (689-1,724 bar). One of the highest-rated plastic pressure tubing products is molecularly-oriented polyvinyl chloride (PVC-O), which has a pressure rating between 4,000-7,000 psi (276-483 bar). PVC-O is stronger than standard PVC tubing because the molecules of plastic are oriented in a radial direction around the pipe during the heating and manufacturing process.
Specific capabilities of pressure tubing, whether stainless steel, medium pressure tubing, and so on, determine the applications. Among the most common uses are those of transporting caustic chemicals and wastewater, high or low temperature fluids for heating and cooling purposes, or compressed and toxic gases. Pressure tubing is also widely employed in industries where low pressure environments are necessary for the pumping out of atmosphere from a vacuum chamber. In that case, the tubing and fittings must durably resist leaks for the long term from the constant weight of atmospheric pressure against its exterior, which is 14.696 psi (1,013.25 millibars) at sea level.
The largest commercial demand for pressure tubing is in chemical and petroleum processing, with high pressure steel tubing being the standard in use. High pressure plastic tubing is most commonly used in consumer and agricultural water delivery. Other uses include food delivery, geothermal energy systems, and as compressed air lines for a range of power tools and industrial equipment. Polyvinyl chloride is the most widely used plastic tubing worldwide, making it the third most commonly manufactured plastic. This is due to the fact that it is easy to work with, generally corrosion resistant, durable, and inexpensive.