Ametek 3050-OLV

PN 305200901, Rev YT
Since the ow control is a closed loop method of control, troubleshooting and
isolating the Proportional Solenoid Valve (PSV) versus the Flow Meter can be
slightly dicult. First, focus on the control of the PSV. This proportional valve is
ever neither completely closed nor completely open. During normal operation,
its duty cycle range is approximately 45–50 % (or, 45–50 % open). To check the
PSV duty cycle, observe the Flow Duty parameter on the Monitor tab.
As the Reference and Sample Period timers count down during their corre-
sponding cycles, you can observe the ow duty number changing in order to
maintain the 50 SCCM ow rate, regardless of the path or leg the gas is owing
through. If you notice that during the Sample Countdown period, the ow
seems to be controlled, but during the Reference period the ow seems to
drift out of tolerance, then you have isolated the ow problem to the Refer-
ence path or leg. Try removing the Reference Dryer and installing a jumper
or bypass in its place (1/8-inch tubing). There could be some obstruction in
the Dryer (internal). As a result, even when the PSV valve is at its maximum
duty cycle, a higher pressure dierential will be needed to overcome the ow
obstruction. This will cause the electronic feedback loop ow control to fail.
If after removing the Dryer the ow problem persists and you cannot deter-
mine if it is in either the Sample or Reference legs, the next step will be to re-
place the Flow Meter. Contact AMETEK to purchase a Flow Meter replacement
kit (PN 305449901S). If the new Flow Meter still does not x the problem, the
last step will be to replace the PSV valve (PN 230510001).
In summary, ow problems could be caused by one or more of the following
factors:
• Inlet pressure, Outlet pressure, or both.
• Partially or fully plugged capillary or manifold.
• Bad PSV valve, Flow Meter, or both.
• Software problem. Software problems on ow are not common, but
should be considered and checked. AMETEK will have you check software
parameters if needed.
4-16 | 3050-OLV Moisture Analyzer