Yamatake Corporation Operation of the Transmitter
ST3000 Smart Transmitter Series 900 Electronic Differential Pressure/Pressure Transmitter 5-57
Set range calculation Ex. STE/STR Type
Calculate the set range using these procedure:
The following symbols are used to express density and distance.
It is assumed that the density is fixed during liquid level measurement.
: Specific gravity of liquid in tank
: Specific gravity of sealed liquid
l : Distance between 100% liquid level and 0% liquid level (measurement range)
h : Distance between 0% liquid level and lower flange of tank
d : Distance between upper flange of tank and lower flange of tank
Figure 5-15 Closed Tank (Wet Leg)
Differential pressure at 0% liquid level (Pressure on high-pressure side - Pressure on
low-pressure side) = d - h = LRV
Differential pressure at 100% liquid level (Pressure on high-pressure side - Pressure
on low-pressure side) = d - (l+h) = URV
Therefore, set the range as follows:
Low limit (LRV): d - h, High limit (URV): d - (l+h)
Example of calculation:
l = 1500 mm, h = 250 mm, d = 2000 mm, = 0.9, = 0.935
If the above conditions are assumed, the following results are obtained:
Differential pressure at 0% liquid level = (2000 x 0.935) - (250 x 0.9) = 1645 mmH
2
O
= 16.13 kPa
Differential pressure at 100% liquid level = (2000 x 0.935) + (1500 x 250) x 0.9 = 295
mmH
2
O = 2.893 kPa
Therefore, set the range as follows:
Low limit (LRV): 16.13 kPa{1645 mmH
2
O}, High limit (URV): 2.893 kPa {295
mmH
2
O}
ρ
ρ
0
h
ρ
ρ
0
d
100% liquid level
Closed tank
0% liquid level
ρ
0
ρ
ρ
0
ρ
ρ
0
ρρ
0
ρ
ρρ
0
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