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SECTION 1
1.1 Introduction:
The HCG 8370 Series Hydrostatic tank Contents Gauge, ECON figure 8370, has long been
considered as one of the most reliable forms of tank gauging equipment available. The
instrument will indicate continuously the liquid contents of any shape of storage tank, and
display the data at considerable distance from the tank. The HCG 8370 Series can be supplied
with either an internal or external tank mounting transmitter plus a comprehensive range of
bulkhead plates or fittings, which allow the passage of capillary through oil and watertight
compartments in marine applications. In addition a special isolating maintenance valve assembly
is available for external transmitters.
Indicators have been designed to provide clear, easy to read data in one size, 160 mm diameter.
Dials are graduated in units to meet user’s requirements and are often marked with redial lines
to denote critical levels at various specific gravity’s.
The power required to operate the HCG 8370 Series hydrostatic tank contents gauge is derived
from the pressure exerted by the head of liquid within the tank (hydrostatic pressure). This
pressure is sensed by a stainless steel diaphragm set into the face of the transmitter and
conveyed by a length of capillary to a diaphragm within the indicator.
Deflection of the diaphragm within the indicator actuates a precision mechanism, which rotates a
pointer over a calibrated scale. The transmitting diaphragm, capillary and indicator diaphragm
together form a sealed system, prior to being charged with oxygen, is thoroughly examined for
leaks.
Not attempt should be made to disconnect the capillary from the instrument, except for mounting
if necessary.
1.2 Description & Operation
A flexible metallic diaphragm contained in the transmitter is so arranged that its internal volume
is connected, by capillary tubing, to a diaphragm within the indicator. The total volume contained
by these two diaphragms and the capillary tubing is charged with an gas and sealed. When the
transmitter is connected or installed in the tank the transmitting diaphragm is exposed to the
pressure exerted by the head of liquid above the transmitter‘s datum. This pressure adjusts the
position of the diaphragm and causes an equal pressure to be imparted to the gas within the
system, such pressure being conveyed by the capillary tubing to the indicator. With the increase
in pressure this diaphragm distends and causes a precision mechanism to rotate the pointer
over the calibrated scale.
1.3 Filling & Emptying the Tank:
The following points should be borne in mind when filling and emptying the tank.
1. The tank must be kept fully vented to atmosphere.
2. Overload must be kept within the limits stated when the instrument was ordered.
3 The temperature of the liquid must not be widely divergent from that specified.
(The gauge is fully compensated for all normal ambient temperature changes)
