|Tech Talk – Pressure Terminology
Pressure – the continuous physical force exerted on or against an object by something in contact with it – often dictates what tubing or hose style and material should be used in an application. Some uses call for reinforced hose to handle pressure, while others can be satisfied with unreinforced tubing in a strong and durable material.
Typically, hoses are tested at ambient temperatures (68°F-70° F) in a controlled environment to the point of bursting – that determines their burst pressure. Working pressure is calculated using a safety factor related to the burst pressure (usually a ratio of 3:1, 4:1 or 5:1 for tubing and hose available from NewAge Industries). This means that it is generally considered safe to use the tubing/hose up to the given working pressure at room or ambient temperature; working pressures can increase or decrease with changes in temperature. Field testing should be performed to find the actual values for an application.
On to the definitions…
Absolute pressure – A quantity of pressure with respect to total vacuum; equal to the sum of a pressure gauge reading plus atmospheric pressure (14.69 psia at sea level)
Bar – A metric unit of pressure, often called an atmosphere; equal to 14.5 pounds per square inch (psi)
Burst pressure – The pressure point at which a tube or hose will suddenly and violently rupture (the video to the right shows testing to determine the burst point of welded TPE tubing)
Compressed gas – A gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 70°F or an absolute pressure exceeding 104 psi at 130°F, regardless of the pressure at 70°F
Pressure drop – The difference in pressure between any two points of a component or system
PSI (more commonly: psi) – Pounds per square inch; a typical method of measuring and expressing working and burst pressure
PSIA (more commonly: psia) – Pounds per square inch absolute; used to make clear that the pressure is relative to a vacuum rather than the ambient atmospheric pressure
Working pressure – The maximum recommended pressure at ambient temperature for continuous operation
When you have questions about pressures and your tubing choices, contact us at 800-506-2934, 215-526-2300 or email@example.com. Engineers are on staff to assist with your application specifics.
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