How2Day: Pitot Tube Specifications

Pressure measurement Riou/Polka Dot/Getty Images
Pitot tubes are air and liquid flow speed indicators, named after their inventor, Henri Pitot, a French hydraulic engineer, in 1732. Pitot created this instrument during a field assignment to measure the velocity of water flow in the Seine River. During the past 278 years, pitot tubes have been used in many applications, most commonly in aircraft and boats.

Early pitot tubes consisted of a short straight tube with a short angled bend at one end and a measurement device attached. The angled end of the tube was placed directly in the path of moving fluids or air flow, where the mouth of the bent end became the intake valve for the liquid or air. This allowed the measurement device to register the pressure and accurately calculate the speed for the inflowing liquid or air. Engineers have modified this design over the years. Today, pitot tubes consist of a short, straight insertion tube, ranging from 6 inches to 2 feet, with a vertical measurement gauge attached at the center point. Tube width varies depending on the application. Many pitot tubes are engineered for 150 PSI, or pounds of force per square inch.

Dynamic sensor information on air and liquid pressure is crucial for the safe handling of boats and, especially, aircraft. It provides pilots pertinent information about the air or liquid pressure at the speed and altitude they are traveling. Engines are prone to stall when pressure drops too low, and structural damage can occur when pressure is too high. Maintaining a safe pressure during any accelerated movement is not necessary to protect passengers from harm.

Pitot tubes should be checked and cleaned regularly. Trapped debris and build-up can cause blockage in the tubes, affecting the accuracy of the pressure reading. Extreme temperatures can also cause the tubes to shrink or expand and change in shape, which also alters the force and weight of the air or liquid intake, leading to inaccurate readings.

How2Day