Calibration and initialization of Wet leg impulse tube Rosemount 3051CD series LT

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Calibration and Initialization of Impulse tube type Level Transmitter Rosemount 3051CD:

here it should be noted that this is method for wet type (not dry legs),i.e. impulse tubes filled with liquids

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Initial setting and calibration for water tank (here specific gravity =1)

Initial setting:

Take tap to tap measurement, for example if tap to tap measurement is 600mm then put

LRV=negative of tap to tap reading= -600mmWC    {negative value because after filling water on LP side the reading will be a negative value}

Put URV=0mmWC

Calibration of LT

here we are doing only zero checking; fill the impulse tube with water on both sides the transmitter reading should show zero reading i.e. -600mmWCor 0% level then the transmitter is O.K.

Initialization and calibration of tank having liquid of specific gravity other than water and impulse tube filled with liquid like that of glycol:

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Initial setting:

take tap to tap measurement for e.g. if tap to tap measurement is 600mm and we are filling with glycol of 0.86 s.g. then

LRV=negative of tap to tap reading *s.g. of liquid inside impulse tube

=-600*0.86

=-516mmWC

and URV because of liquid inside vessel of s.g. 0.92is

URV=  LRV+ level(height) to be measured*s.g. of liquid inside vessel

= -516+(0.92*600)

=-516+552

=36 mm WC

Calibration (Zero checking):

fill the impulse line with glycol on both LP and HP side then the transmitter should show LRV=-516mmWC and 0% level

CROSS CHECKING OF  THE LRV AND URV IF THE TANK IS FILLED WITH WATER INSTEAD OF OTHER SPECIFIC GRAVITY

LRV= -600*1= -600mmWC

URV=LRV+HEIGHT OF LIQUID *SPECIFIC GRAVITY

= -600+(600*1)

= -600+600

= 0 mmWC

NOW NOTE THAT THIS IS THE SAME LRV & URV AS DERIVED ABOVE FOR WATER

N.B.  Calibration and initialization of DP type level follows a simple rule

LRV= level and property of liquid in impulse tube acting on LP side of LT

URV=LRV+level and property of liquid inside vessel acting on HP or

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