PETROCHEMICAL ENGINEERING DEPARTMENT GP313-PROCESS INSTRUMENTATION & CONTROLPREPARED BY:MOHD TAUFIK REZZA BIN MOHD FOUDZIJun 2011
Pressure MeasurementFORWARD Hydrostatic Pressure BACK PressureHOMEFIRST Type ofSLIDE Pressure MeasurementLASTSLIDE Measuring Buoyancy Instruments Applications Evaluation
PRESSUREFORWARD • Pressure units are a measure of force BACK acting over unit area.HOME • It is most commonly expressed in pounds per square inch (psi) orFIRSTSLIDE sometimes pounds per square foot (psf)LASTSLIDE in English units; or Pascals (Pa) in metric units, which is the force in Newtons per square meter (N/m²). Pressure = Force, F Exercise Area, A 2.1
HYDROSTATIC PRESSUREFORWARD BACK A B CHOMEFIRSTSLIDELASTSLIDE Which the vessels above have high pressure?
HYDROSTATIC PRESSUREFORWARD • A vertical column of fluid exerts a pressure due BACK to the column’s weight.HOME • The relationship between column height and fluid pressure at the bottom of the column isFIRSTSLIDE constant for any particular fluid (density)LASTSLIDE regardless of vessel width or shape. Exercise 2.2, 2.3 = Mass density of fluid in kilograms per cubic meter (metric) or slugs per cubic foot (British) =Weight density of fluid in Newton per cubic meter (metric) or pounds per cubic foot (British)
SPECIFIC WEIGHT TABLEFORWARD BACKHOMEFIRSTSLIDELASTSLIDE
TYPE OF PRESSURE MEASUREMENTFORWARD BACK Atmosphere PressureHOMEFIRSTSLIDE Vacuum AbsoluteLAST Pressure PressureSLIDE Gauge Pressure
PRESSURE CONVERSIONFORWARD BACKHOMEFIRSTSLIDELASTSLIDE Exercise 2.5, Extra
BUOYANCYFORWARD •Buoyancy is the upward force exerted on an object BACK immersed or floating in a liquid.HOME •The weight is less than it is in air, due to the weight of the displaced fluid. The upward force on the object causes theFIRSTSLIDE weight loss, called the buoyant force, and is given by:LASTSLIDE where B = The buoyant force in pounds y = The specific weight in pounds per cubic foot V = the volume of the displaced liquid in cubic feet.
EXERCISE 2.1FORWARD BACK The liquid in a container has a total weight of 152HOME kN, and the container has a 8.9 m² base. What is the pressure on the base?FIRSTSLIDELASTSLIDE BACK >>
EXERCISE 2.2 & 2.3FORWARD BACK What is the depth in a lake, if the pressure is 0.1HOME MPa?FIRSTSLIDE What is the pressure at the base of a water towerLAST that has 35m of head?SLIDE BACK >>
EXERCISE 2.5 & EXTRAFORWARD BACK What pressure in psi corresponds to 98.5 kPa?HOMEFIRST The atmospheric pressure is 14.5 psi. If theSLIDE absolute pressure is 2,865.6 psfa, what isLASTSLIDE the gauge pressure? What is the gauge pressure in (a) kPa, and (b) N/cm², at a distance 5.5 ft below the surface of a column of water? BACK >>
EXERCISE 2.6 & 2.7FORWARD BACK What is the buoyant force on a plastic cube with 2.5m sides, floating in water, if three-quarters ofHOME the block is submerged?FIRSTSLIDE What is the apparent weight of a 3.7m³ block ofLASTSLIDE wood totally immersed in acetone? Assume the specific weight of wood is 8.5 kN/m³. BACK >>
EXERCISE 2.8FORWARD BACK In figure below, if the area of the small piston A S is 8.2 in²,and the area of the large piston A L is 2.3 ft²,HOME what is the force FL on the large piston, if the forceFIRST FS on the small piston is 25N?SLIDELASTSLIDE BACK >>
EXERCISE 2.9 & 2.10FORWARD BACK The liquid in a manometer has a specific weight of 8.5 kN/m³. If the liquid rises 83 cm higher in the lowerHOME pressure leg, what is difference in the pressureFIRST between the higher and the lower legs?SLIDELASTSLIDE What is the liquid density in a manometer, if the difference in the liquid levels in the manometer tubes is 1.35m, and the differential pressure between the tubes is 7.85 kPa? BACK >>