PowerPoint Presentation

Measurement of Pressure and Vacuum IntroductionMeasurement of Pressure and Vacuum is extremely important in Process Industries.Pressure can be defined as amount of force acting normal per unit surface area.

Units of PressureNewton per square meter ( N/m2) Pascal Atm or barPounds per square inch (psi)Torr ( 1 torr = 1 mm Hg)Head units - in mm of mercury or water or any other liquid used.

2Relationship between various units of pressure measurement

Pressure Scales

Gauge Scale

Lowest point of measurement is atmospheric pressureZero pressure correspond to 1 atm (normal atmospheric pressure)Absolute Scale

This scale has absolute zero pressure as lowest (zero point)Instrument measuring pressure absolute scale units balances unknown pressure against vacuum.Conversion between absolute pressure and gauge pressure isAtmospheric pressure = Gauge pressure + Atmospheric pressure. Vacuum Scale

Vacuum scale is below atmospheric pressure. Gauge scale and vacuum scale uses atmospheric pressure as reference.Vacuum = - ( gauge pressure) 4Hydrostatic EquationAir pressure is due to force exerted by weight of all air lying above the height.Consequently the pressure of air decreases w.r.t height.

Piezometer

U-tube Manometer

Micromanometer

U-tube differential Manometer

U-tube differential Manometer for measuring pressure in a pipe

Inverted U tube differential Manometer