Interface Measurement - Honeywell 854 ATG Series Instruction Manual

3.4.4 Interface measurement

Interface 3 (I3) is used as product / water interface measurement (with interface 2 (I2) another interface can
be measured). The set point S3 has to be set to such a value that half of the displacer volume is immersed in
the water and the other half of the displacer volume is immersed in the product.
That can be calculated as follows (refer to figure 3.9 and to Appendix B for detailed displacer information):
S3 = DW - (½ DV x ρ
product
where:
S3 : set point I3 measurement [g]
DW : displacer weight [g]
DV : displacer volume [cm
ρ : density of the product [g/cm
product
: density of water [g/cm
ρ
water
Example:
Displacer #0815.343
Displacer weight (DW)
Displacer volume (DV)
Volume lower conical part
Height lower conical part
Density product
S3 = 223 - (52.5 x 0.9 + 52.5 x 1) = 123.25 [g]
A level offset must be given as the displacer is now immersed for half of the volume in water. On product
level the displacer is immersed less. The difference between both immersion depths must be given in item L3
Example:
1) Immersion depth on product level surface:
displaced volume
volume in cylindrical part
immersion of cylindrical part
immersion depth on product
2) Separation line product / water :
water volume in cylindrical part : ½DV - 3.2 = 52.5 - 3.2 = 49.3 cm
water height in cylindrical part
separation line product / water : 31 + 6 = 37 mm (from lower end of displacer)
Hence, level offset L3 becomes
Item Name Description
W2= Protection level 2
S3= Set point I3
L3= Level offset I3
EX Exit
Instruction manual 854 ATG
+ ½ DV x ρ ) [g]
water
3
]
3
]
3
]
: ø45 mm
: 223 g
3
: 105 cm
3
: 3.2 cm
: 6 mm
3
: 0.9 g/cm
: (DW - S1)/ρ
product
: 16.67 - 3.2 = 13.47 cm
2
: 13.47/πr = 13.47/(π x 2.25
: 8.5 + 6 = 14.5 mm
2
: 49.3/πr = 49.3/(π x 2.25
: 37 - 14.5 = 22.5 [mm]
Enter protection level 2 password
Standard floating point format; units: grams.
Set point for the product / water interface measurement.
Format according to item LD.
Level offset between interface 1 immersion depth (where the gauge is
calibrated) and the product / water interface immersion depth.
Exit protection level
Figure 3.9 Calculation of set point
3
= 15/0.9 = 16.67 cm
3
2
) = 0.85 cm = 8.5 mm
3
2
) = 3.1 cm = 31 mm
Commissioning
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