Table of Contents
Advertisement
SYMPTOM
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect
while using molbloc-S to measure air flow
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect.
Flow indication appears to be incorrect in
the low end of the range.
Flow indication appears to be incorrect by
a constant offset amount.
Flow indication appears to be incorrect
and molbloc is upstream and reading high.
Flow indication appears to be incorrect
and flow rate is less than 50 sccm.
Unable
to
make
molbloc-S
measurements over full expected flow
range.
Table 25. Troubleshooting Checklist (Continued)
PROBABLE CAUSE
Reference pressure transducer(s)
(RPT) are inoperable or out of
calibration.
The gas selected is not the gas
flowing through the molbloc.
Incorrect humidity ratio is being
used.
The gas selected is the gas
flowing through the molbloc but the
molbloc has not been calibrated
for that gas.
Gas flowing through molbloc is not
pure.
The molbloc is not being used at
the
correct
pressure
pressure
dependent
type.
molbox
RFM
pressure
Reynolds numbers are outside of
limits.
Flow through molbloc is in wrong
direction.
Leak
in
pressure
molbloc to molbox RFM.
A flow adder/multiplier has been
incorrectly or inadvertently applied.
molbloc calibration has changed
due to contamination.
molbox RMF is equipped with
microrange but the option is not
on.
molbox RFM needs to be correctly
"zeroed" (tared) at the current
operating pressure.
Leak downstream of molbloc.
Flow in system is not in steady
state; too much volume between
molbloc
and
test;
pressure on molbloc.
flow
MFC or flow control valve is
connected dowsntream of molbloc-
S.
Page 151
SOLUTION
Use [P&T] to view pressure indications.
Recalibrate RPTs if necessary.
and 5.2)
Select the correct gas. (3.4.2)
Reselect Air as the test gas and make sure
the humidity ratio W is entered properly. W
should be zero for dry air and should be
calculated from ambient conditions when
measuring ambient air. 3.4.2.2.
Verify that the molbloc has calibration
coefficients for the flowing gas, have the
molbloc calibrated for the flowing gas if
necessary or accept lower accuracy flow
measurements. (1.2.4)
Check purity rating of gas used; purge
molbox/molbloc if flowing gas was just
changed. If gas is a known mix, use the
flow adder and multiplier to correct for the
mix. (3.4.4.2, 3.5.6)
Check molbloc calibration certificate for
for
its
pressure dependent calibration type and
calibration
check operating pressure. (1.2.4 and 3.4.5)
and/or
Observe pressure and Reynolds numbers
and adjust pressure/flow to be inside of
limits. (1.2.4 and 3.4.5)
Check that flow through molbloc is in
direction of arrow on molbloc.
necessary.
lines
from
Check lines for leaks and correct if
necessary. (3.4.4.3)
Check and correct if necessary. (3.5.6)
Check molbloc for contamination. Contact
your DHI Authorized Service Provider if
liquid
or
particulate
detected.
Turn on microrange option. (3.4.7)
Tare molbox RFM.
"upstream" if the upstream pressure is
constant and downstream if the downstream
pressure is constant. (3.4.4.1)
Check for and correct leak if present.
Consider using molbox RFM SYSTEM
LEAK CHECK function.
Check System)
Be sure flow is stable before reading,
reduce dead volumes, install precision
regulator.
unstable
Valve or regulator used to control flow
through
molbloc-S
upstream of the molbloc-S. When operating
an MFC with molbloc-S, the MFC must
always be upstream (3.1.2)
© 1998-2007 DH Instruments, a Fluke Company
6. TROUBLESHOOTING
(3.4.5
Switch if
contamination
is
Be sure to tare
(3.4.4.3.2, Leak
must
always
be
Advertisement
Table of Contents
