what is dry leg and wet leg in transmeter calibration?

Answer Posted / lalit meghwal

Close tank with wet leg:
Span = ( X ) ( GL )
HW at minimum level = ( Y ) ( GL ) – ( d )( GS )
HW at maximum level = ( X + Y ) ( GL ) – ( d ) ( GS )
Where : GL = Specific gravity of tank liquid
GS = Specific gravity of tank liquid
HW = Equivalent head of water
X, Y and Z are shown in fig.


Example :
X = 300 inches
Y = 50 inches
d = 500 inches
GL = 0.8
GS = 0.9
Span = ( 300 ) ( 0.8 ) = 240 inches

HW minimum level = ( 50 ) ( 0.8 ) - ( 500 ) ( 0.9 ) = - 410 inches
HW maximum level = ( 300 + 50 ) ( 0.8 ) – ( 500 ) ( 0.9 ) = - 170 inches
Calibrated range = - 410 to –170 inches head of water.
( minus sings indicate that the higher pressure is applied to the low pressure side of the transmitter )

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