FLUID PRESSURE PROFESSIONAL ENGLISH IN USE FOR ENGINEERING

 

PROFESSIONAL ENGLISH IN USE FOR ENGINEERING UNIT 38. FLUID PRESSURE

 

A Gauge pressure and absolute pressure Pressure is the amount of force acting on an area. When fluids (liquids or gases) are under pressure they exert pressure on the surfaces of the tanks, pipes, etc., that hold them. Examples of pressurized fluids are compressed air inside air hoses, compressed gases such as propane in gas cylinders, and water in water mains. The SI measurement of pressure is the Pascal. One Pascal is equal to one newton per square metre (1 Pa= 1 N/m2). However, many pressure gauges (device which measure pressure) use the imperial measurement pounds per square inch (psi). Pressure can also be measured in bars. One bar is roughly equal to atmospheric pressure – that is, the pressure of the air in the atmosphere – at sea level. For example, four bars, or four bar – which can also be described as four atmospheres – is four times atmospheric pressure.   APPENDIX III UNITS OF MEASUREMENT B Hydrostatic pressure and siphonic action In liquids – most often in water – pressure and flow can be generated by hydrostatic pressure. An example is water tower which supplies drinking water to homes. See Appendix X for a description of siphonic action   APPENDIX X SIPHONIC ACTION EXERCISES 38.1 Complete the sentences using the words positive, negative and zero. 1. In a perfect vacuum, absolute pressure is ____________ and gauge pressure is ____________. 2. In a partial vacuum, absolute pressure is ____________ and gauge pressure is ____________. 38.2 Use the expressions in the box to complete the article about pressurized aircraft cabins, taken from an engineering journal. Look at A opposite to help you. at a higher pressure compressed air gauge pressure pressurized at a lower pressure exert pressure on one atmosphere outside air atmospheric pressure explode pressure differential   Ever wondered about ….. pressurized aircraft cabins? It’s a well-known fact that the cabins of commercial aircraft are (1)_________. This is an obvious requirement, given that at high altitude the air is (2)_________ than (3)_________ at ground level. If passengers were exposed to these conditions while flying at altitude, they would suffer numerous health problems. Hence the need, at high altitude, to maintain the air inside the fuselage (4)_________ than the (5)_________. But how is this achieved and controlled. 38.3 Match the two parts to make correct sentences. Look at B opposite and Appendix X to help you. 1 Header tanks are designed to a make liquid flow upwards from its surface 2 To prime means to b generate hydrostatic pressure in a building

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