Sample Flow Alarms - Michell Instruments Condumax II User Manual

Condumax II User's Manual
• To increase the speed of response of the measurement of the main
process gas it is highly recommended that a fast bypass loop is installed
into the gas sampling system. The recommended fl ow through the bypass
loop should be typically 3 to 4 times that of the hydrocarbon channel.
Therefore, typically, the bypass gas fl ow should be set to approximately 3
to 4 Nl/min (0.18 to 0.24 Nm
• If a water dew-point channel is fi tted, the gas fl ow through its sensor
should be set at approximately 3 Nl/min (0.18 Nm
2.8

Sample Flow Alarms

An alarm state will be indicated on the Error Message line at the bottom of the
display. Refer to Section 4.6 for further details.
After the correct fl ow of sample gas is set, the alarm states will be indicated when the
gas fl ow has fallen below that required to make effective measurements.
The fl ow switches fi tted are adjusted during factory test to activate the alarm when
the fl ow falls below approximately 20 to 10% of the normal recommended sample fl ow
setting (see Section 2.7). During the factory setting procedure the gas pressure that is
applied represents the most common application analysis conditions for hydrocarbon
(27 barg (391 psig)) and water (68 barg (986 psig)) dew-point sensors.
The operation of these variable area fl ow switches are infl uenced by pressure. For
increased pressure the fl ow alarm activation point will be at a higher fl ow rate and
conversely, for reduced pressure, the activation point will be at a lower rate. These
devices exhibit a hysteresis that may require a fl ow of greater than 100% of the
recommended fl ow setting for a brief period in order to clear the alarm condition.
NOTE: If the Condumax II main unit is going to be operating with signifi cantly
different analysis pressures to those used during factory testing, then fi ne
re-adjustment of the fl ow switches may be benefi cial to suit the application
conditions. If this is the case contact Michell Instruments (www.michell.
com) for guidance as to how adjustments can be made on site.
Michell Instruments
/hr) (6.3 to 8.5 scfh).
3
The fl ow switches are supplied to alert the user to either
severely reduced or discontinuation of sample gas fl ow
through the system.
INSTALLATION
/hr) (6.3 scfh).
3
MAIN
19