HYDROLOGICAL SERVICES PTY LTD
_______________________________________________________________________________________
Constant Flow Regulator
3 4 metersH
2
O
MAX
Constant
Supply Pressure
Set at
2 to 3 times
The head being
MIN
P
R
ES
S
U
R
E
Sherlock Pressure
Sensing Unit
MAX
Measured Head
MIN
Automatically
Regulated pressure
Maintained at
3 to 4 metres of
Water above head
“Falling “ Situation
The “falling” situation is of course the reverse of the rising situation except that there is now
excess pressure in the system. If we were to suddenly lift up the orifice in Fig. 4, the pressure
would drop to the new head, seen by the sudden rush of bubbles.
Accordingly, even the lowest bubble rate will suffice for falling conditions.
In practice, it may take some time to the pressure to “bleed” away”, but this is usually less than
the response time of the sensing unit.
Field Requirement of Gas Purge Systems
The principle requirements of gas purge are-
1.
a fine metering valve and sight feed for accurately setting the bubble rate.
2.
Constant regulator to maintain a constant bubble rate with changes of head.
3.
Pressure connections and valves for connecting the tubing to the river and the
instrument.
With the overall provision that the unit must be “leak proof”, otherwise the true head will not be
recorded.
The configuration most widely used is illustrated in Fig.6
Fig. 6 - Diagramatic view of field gas purge, single line without purge facilities.
Gas Purge Compressor
Issue 7:
16/12/03
© Copyright
HS55 110-018
