LevelMeasurement

Inferential Level Measurement

LiquidDensity = ρ

P

h

ghP ρ=

Three Valve Manifold

HPBlockValve

Equalizing Valve

LT

Signal

HP LP

LPBlockValve

Process-High Pressure Side

Process-Low Pressure Side

3 ValveManifold

Open Tank Level Measurement

Liquid of Weight Density S

Atmospheric Pressure P atm

H

LTHP

LPIsolating Valve

Ventedto

Atmosphere

Closed Tank Level Measurement

Dry Leg System

Wet Leg

Zero Suppression

Zero Elevation

Bubblers

Effect of Temperature

Liquid of Density ρ1

Atmospheric Pressure P atm

H1

LTHP

LPIsolating Valve

Ventedto

Atmosphere

Temperature T 1

Temp. Effects in a Wet Leg

Liquid of Density ρ1H1

LTHP

LP

Isolating Valve

Isolating Valve

Pgas

ProcessTemperature T 1

Abnormalities

! Transmitter installed backwards! Over Pressure! Sensing Lines

� Blocked� Drained

For you to do.

! Read pp. 33-49! Answer Questions pp. 85-86, #15-24