FuelsManager Defense
302 Administrator Manual
This correction is only applied to float gauges. It does not apply to non-contact
measurement devices.
Corrected height = measured height + Δh
(b)Thermal correction. This is necessary to account for the thermal expansion of
the tank or stilling well and the gauge wire. For a float gauge this will be carried out
in addition to the buoyancy correction.
The correction is:
Where:
Note! When a float gauge is used
H is the value after the buoyancy
correction has been carried out.
The use of as the coefficient of thermal expansion of the tank or stilling well
depends upon the mounting of the gauge. When the gauge is mounted on the
tank, or on the well but this is not rigidly fixed to the tank base, the coefficient of
the tank is used. The well coefficient is only used when the gauge is mounted on
the well and this is rigidly fixed to the tank bottom. In this case movement of the
gauge, relative to the bottom of the tank, is governed by stilling well expansion and
contraction.
Typical values of thermal expansion coefficients are:
The corrected level (HC) is given by:
p
1
density of liquid at the time of
calibration
p density of liquid at the time of
gauging
Δh
2
correction to gauge readout for thermal expansion
α
w
= coefficient of thermal expansion of gauge wire /°C
α
m
= coefficient of thermal expansion of gauge mounting
(tank or well) /°C
TV = average vapor temperature°C
TL = average liquid texnperature°C
HT = total height of mounting (tank or well) in mm
H = depth of liquid in mm
Δh
2
αw 15 TV–()HT H–()α
m
15 TV–()HT H–()– α
m
15 TL–()H–=
Aluminium 0.000023 /°C
Mild steel 0.000011 /°C
Stainless steel 0.000017 /°C
HC H ΔH
1
ΔH
2
++=
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