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Chapter 3 Operation Series 830/840/860 Instruction Manual
3-6 IM-83/84/86-H
Valve Purge Function
Electromagnetic valves are driven with either 15 or 30 volts de-
pending on the range and pressure. In general, units below 10 slpm
have the 15 volt valve. When the purge function occurs, electro-
magnetic valves are driven fully open regardless of the set point
input. Furthermore, the purge function will override any valve-off
function. This option is not available on motor-operated rotary
valves. Motor-operated valves are purged by setting the command
signal to full scale. There is no equivalent monitor function.
The Model 860 allows valve monitoring and the purge function to
be utilized in either analog or digital (RS-485) mode. If both hard-
ware and software control options are used simultaneously on an
860, conflicts may occur that can produce undesired results.
For +15 Volt Valve Controllers: The valve purge function is acti-
vated when the Valve Test Point/Purge connection is connected to
ground. The maximum valve voltage is indicated in the “comments”
field of the calibration certificate. (Units with ranges below 10
slpm)
For +30 Volt Valve Controllers: The valve purge function is acti-
vated when the Valve Test Point/Purge connection is connected to
+15 VDC. The maximum valve voltage is indicated in the “com-
ments” field of the calibration certificate.
A Sierra controller intended as a replacement for another manufac-
turer’s controller may have Pin D and other pins disconnected. Some
options may not be available.
Purging Non-Reactive Gases:
Purge the transducer with clean, dry nitrogen for a minimum of two hours.
Purging Reactive Gases:
One of the following methods may be used:
• Cycle purge. This is done by alternately evacuating and purg-
ing the transducer for two to four hours with clean, dry nitro-
gen.
• Purge the transducer with clean, dry nitrogen for eight to
twenty-four hours.
• Evacuate the transducer for eight to twenty-four hours.
When toxic or corrosive gases are used, purge unit thoroughly with
inert dry gas before disconnecting from the gas line. If a transducer
used with a toxic or corrosive gas is returned to the factory, a Ma-
Caution!
Do not use the man-
ual purge function
when RS-485 is ac-
tive.
Caution!
Always fully neutralize any
toxic gas trapped inside the
transducer before removing
from the gas line.