Samson Media 7 5007-1, Mounting And Operating Instructions

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8-4 EB 9510 EN
Operation
The density calculation is based on the following laws of physics:
− The momentary pressure drop used for the differential pressure measurement (Δp =
p
1
– p
2
) in cryogenic tanks is the total of the individual static pressure differences which
arise due to the various heights in the tank and the measuring lines.
− The static pressure differences are proportional to the product resulting from multiplying
the column height of the medium (liquid or gas) with the momentary medium density.
− The momentary density of the medium is calculated from its boiling curve.
− The gas columns in the high-pressure and low-pressure pipes reduce the differential pres-
sure as they oppose each other
Ar, N
2
,
O
2
, CO
2
Ar, N
2
,
O
2
, CO
2
p
Gas,
ρ
Gas
p
Gas,
ρ
Gas
ρ
FL
ρ
FL
ρ
GasL
H
h
H
h
p
1
p
1
p
2
p
2
ρ
GasL
H [Length/height of tank | 2.2.1.x]
h Height of the liquid column
p [Operating pressure| 2.2.x.x]
ρ
Gas
[Gas density in tank | 2.2.x.x]
ρ
GasL
[Gas density in low-pressure
pipe | 2.2.x.x]
ρ
FL
[Liquid density| 2.2.x.x]
Outer tank
Insulated space
Low-pressure pipe (internal)
Inner tank
Low-pressure pipe (external)
Fig. 8-3: Density calculation in the tank