Leak Check System - Fluke MOLBOX RFM Operation And Maintenance Manual

3.4.4.3.2

Leak Check System

PURPOSE
To leak check the external system that is connected to the molbox RFM.
PRINCIPAL
It is recommended to run the SYSTEM LEAK CHECK whenever critical physical
connections in the system attached to the molbloc are broken and reconnected.
Critical connections are ones that are between the molbloc and the DUT, which,
if they were to leak, would cause the flow through the molbloc and the DUT to
differ. Whenever a new DUT is connected to the system, it is a good idea to run
the SYSTEM LEAK CHECK.
The SYSTEM LEAK CHECK monitors changes in pressure in a closed system
defined by the user to help determine whether a leak exists in the system. One of
the ways a leak is detected is by monitoring pressure decay in the pressurized
closed system. When the test volume is large, significant leaks may exist without
being detected because the pressure decay caused by the leak is reduced.
Therefore, the SYSTEM LEAK CHECK is most effective when the volume of the
closed system is minimized.
For molbloc-L operation, the SYSTEM LEAK CHECK also measures flow through
the molbloc to help determine whether a leak is present upstream or downstream of
the molbloc. Since molbloc-S is not capable of calculating meaningful flow values
with the very small differential pressure present during this test, the SYSTEM LEAK
CHECK operates differently for molbloc-L and molbloc-S operation, as described in
the OPERATION sections immediately below.
The SYSTEM LEAK CHECK function uses molbox RFM's high precision
pressure and flow measurement capabilities to help determine whether a
leak exists in the system to which the molbloc is connected. This feature is
to assist the operator in flow measurement and calibration. The system to
which the molbloc is connected is the responsibility of the user. Failures in
the system leak check do not normally indicate defects in the molbox RFM or
molbloc itself. The molbox leak check is used to identify molbox RFM failures.
OPERATION – molbloc-L Operation
To access the system leak check press [TARE] and select <3leak check>,
<2system>. The display is:
The pressure read by the upstream RPT
1.
(left), the downstream RPT (right) and
the pressure unit of measure (middle).
This display is intended to assist the operator in setting the leak check pressure.
molbox RFM has actuated internal valves to connect the upstream and
downstream RPTs together, so they are both measuring an equal system pressure.
(see Figure 9).
347.589 kPaa 347.580
Page 49 © 1998-2007 DH Instruments, a Fluke Company
3. OPERATION