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between water and sludge. The concentration of hy-
drogen in the sludge is less compared with water, less
neutrons are scattered therefore reduces the intensity
of recorded neutron signal. With proper calibration, the
arrangement of vapour, organic water and hydrocar-
bon can be exactly determined. Hence the quantity of
hydrocarbon left in the tank can calculated accurately.

2.5 Application in Tank Floor Gap
Determination

Storage tank is traditionally standing on the founda-
tion which is designed properly as it is made by the
soil or grout concrete. There is some tiny gaps left in
between the tank floor with the top surface of founda-
tion. The condition of surface soil or grout foundation
such as a gap size under the floor of storage tank is
almost impossible to access except the whole tank is
removed. Initially, the formation of floor and foundation
of storage tank is consists of very small gap and it is
almost consistent through out the floor and foundation
area. However, during loading and unloading of crude
oil to and from the storage tank, there will left some
permanent effect on the foundation surface cause by
fatigue load. By time, some areas will suffer more load
and other area will compensates the load. This phe-
nomenon will effect some floor presses the foundation

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