Bubbler method level calculation – Liquid level calculation (Transmitter Installed with single Bubble tube)
Examples of standard calculations for measuring liquid levels in an open tank with a single Bubble tube Transmitter Installation are provided in this section.
It is important to keep in mind that the upper-range values (URV) and lower-range values (LRV) relate to the highest and minimum measurements that are intended, respectively. The Calibrated Span is equal to the URV minus the LRV. The output at LRV greater than 0% represents the value of the suppression.
Abbreviations
The following acronyms are utilized in this directive.
LRV = Lower-range value (a measurement that’s output is 4 mA).
URV = Upper-range value (a measurement with a 20 mA output).
SG = A liquid’s specific gravity (relative density). Water has a specific gravity of 1.00 in both traditional and SI systems.
HW= Equivalent Headlevel pressure of Water
Formulas for Converting Specific Gravity for All Liquids
Specific gravity = Density [lb/ft3 ] / 62.4
Specific gravity = Density [kg/m3] / 1.00
Liquid Level Calculations (Transmitter installed with single Bubble Tube)
SGL = Specific gravity of Tank Liquid
H = Height of the bubble tube immersed inside the process liquid
H1 = Tank level need to be measured.(head between LRV and URV)
H2 = Head level below minimum level (suppression)
Calibrated Range of the transmitter = LRV to URV
where: SGL = Specific gravity of tank process liquid
HW= Equivalent Headlevel pressure of Water
Span value of the transmitter = H1*SGL
Equivalent Head level pressure of Water(HW) at Lower range value
HW at LRV = H1*SGL = Suppression
Equivalent Head level pressure of Water(HW) at Higher range value
Hw at URV = (H1 +H2)*SGL
Example calculation- Transmitter installed with single Bubble Tube for level measurement
The transmitter installed in open tank with following parameters
Height level measured between LRV and URV is
H1= 2000mm,
Head level distance below minimum level(LRV) (suppression)
H2 = 200mm,
The process liquid’s specific gravity is
SGL = 0.8
Find the calibration range of the transmitter?
Span value calculation
Span value = H1*SGL
Span = (2000)*(0.8)
Span value of the transmitter = 1600 mmH2O
LRV calculation (4mA)
HW at LRV = H1*SGL
Hw at LRV = (200)*(0.8)
Hw at LRV= 160 mmH2O = Suppression
URV calculation (20mA)
Hw at URV = (H1 +H2)*SGL
Hw at URV = (2000 + 200) (0.8)
Hw at URV = 1760 mmH2O
Calibration Range of the transmitter = 160 to 1760 mmH2O
