8
4 Purging the Instrument Before Taking a Sample
It is advisable to carry out an initial purge of the sample loop before connecting
the instrument in order to avoid the possibility of sensor damage on start up.
Ensure all pipework is connected and leak tight
and that the head is down on the SDHmini.
Open the isolation valve slowly until there is a
small flow of air/gas at atmospheric pressure
from the pressure reduction valve. (
Fig. 9
)
Carefully open the
pressure regulator
valve (
Fig. 10
) until
a flow of 5 to 15
litres per minute
can be seen on the
flow indicator. (
Fig.
11
).
If a needle valve
is fitted, carefully
open by turning
this anti-clockwise
(
Fig. 12
) until a flow of 5 to 15 litres per minute
can be seen on the flow indicator (
Fig. 11
).
Allow the air/gas to exhaust through the sample
connection.
Switch on the
SDHmini (
Fig. 13
)
and ensure that the
display indicates that the measuring sensor is dry
(typically below -70 °C dewpoint).
If it does not, please refer to the instrument
instruction manual.
Fig. 9
Fig. 10
Fig. 12
Fig. 11
Fig. 13
