3Leak Check - Fluke MOLBOX RFM Operation And Maintenance Manual

molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL
The purge time can be edited. Pressing [ENTER] causes molbox RFM to set
its internal valving to the purge configuration (see Figure 14) and go to the
PURGE display:
molbox RFM remains in the purge condition until the purge time countdown
elapses. It then automatically returns to normal operation. When the countdown
elapses operation returns to the run screen from which PURGE was accessed.
To interrupt the PURGE function, press [ESCAPE].
3.4.4.3
To access the molbox LEAK CHECK and SYSTEM LEAK CHECK functions
which use molbox RFM's pressure and flow measurement capabilities to check
molbox RFM and/or the system to which it is connected for leaks.
molbox RFM is used both as a tool to accurately measure unknown flow values
and as a calibration standard to calibrate other devices by comparison. Leaks
within the molbox RFM pneumatic circuit can cause erroneous flow measurements.
Leaks in the external flow circuit can cause the flow through the molbloc to be
different from the flow at another point in the system so that, even with an
accurate measurement and steady state flow, the molbox RFM indication is not
an accurate indication of flow at the other point in the system.
To obtain valid measurement results, it is important that leaks in molbox RFM
and/or the external flow system be identified and eliminated to the extent
possible.
measurement capabilities to help identify leaks with INTERNAL and EXTERNAL
LEAK TESTING functions.
Press [TARE] and select <3leak check> to access the LEAK CHECK functions.
Then select <1molbox> or <2system>.
<1molbox> is designed to leak check the internal molbox RFM pneumatic circuit.
<2system> is designed to leak check the system to which the molbloc/molbox
is connected.
© 1998-2007 DH Instruments, a Fluke Company
1. The current pressure read by the upstream
(left) and downstream (right) RPTs in the
current pressure unit of measure.
2. <PURGING> to indicate that this is a PURGE
display.
3. Countdown of purge time remaining in
seconds.
The appropriate purge time setting is dependent on the flow rate and the
volumes upstream and downstream of the molbloc. Typically, 15 to 30
seconds is adequate. The time needed increases as flow rates go down and
volumes go up.
When using the PURGE function, remember that the molbox RFM absolute
RPTs are exposed to the pressure. Do not apply pressure greater than 600
kPa absolute (87 psia).
<3Leak Check>
PURPOSE
PRINCIPAL
molbox RFM uses its precision on-board pressure and flow
OPERATION
Page 46
202.347 kPaa 202.311
PURGING 15 sec