3. INSTALLATION
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© 2007 DH Instruments, a Fluke Company
molstics provide a quick means to connect to the gas supply output of the GFS. This is
followed by a 2 micron (0.5 micron for low flow) filter to protect the downstream components.
Then, an adjustable regulator sets and regulates optimum molbloc upstream pressure and
protects the molbox transducers against accidental overpressure. The regulator range(s)
supports all standard molbloc operating pressure ranges. A bellows shut-off valve, just
before the molbloc, allows the gas supply to be shut-off for configuration changes and/or
system leak checking. Special cradles support the molbloc(s). A connection and pads are
provided downstream of the molbloc for mounting the MFC (mass flow controller), and/or
another device under test.
There are low, mid and high flow versions of molstic. Only the single channel, low and mid-
flow molstics are used with the GFS-2102 system. Low flow molstics use a unique, very high
stability pressure regulator and minimize dead volumes. They are required for effective use
of 2E2 and lower molblocs and can be used up to the 1E3 molbloc size. The mid flow
molstics cover the ranges of all the molblocs from as low 2E2 up to the 3E4, and the low end
ranges of molbloc-S.
If an appropriate molstic for the DUT is unavailable, then at a minimum an individual non-
venting regulator and shutoff valve upstream of the DUT are required. If the DUT is a
molbloc 1E3-L or below an LNI or equivalent regulator is recommended. If the DUT is larger
than a 1E3-L then an appropriate standard non-venting regulator is recommended.
For an upstream molbloc, the recommended flow path is GFS, (heat exchanger when
appropriate), regulator, shutoff valve, upstream molbloc, flow controller, and optionally a
downstream molbloc.
For a downstream DUT, the recommended flow path is GFS, (heat exchanger when
appropriate), regulator, shutoff valve, optional upstream molbloc, flow controller, and a
downstream molbloc.
While the optional molblocs are not required, they help the flow controllers to operate more
efficiently and can serve as a check standard. Both an upstream and downstream molbloc
can be calibrated at the same time against the GFS.
3.3.16
CONNECT GAS CONVEYANCE LOOP
Connect the gas conveyance loop by connecting the quick-connect fittings at each end. If
the flow path outside of the enclosure is prepared, then install the loop by first connecting the
downstream side at the enclosure sidewall column quick-connector, then connecting the
reference gas cylinder assembly quick-connector. Attempting to connect in the opposite
order will cause gas to flow out of the cylinder into the enclosure until the downstream
connection is made. Be careful not to disturb the position of the reference gas cylinder while
making the connection. Use the loop alignment tool to align the connections and ensure the
loop is parallel from end to end.
After connecting the gas conveyance loop, check again that a stable mass indication can be
viewed in GFS Tools software before starting to flow. This indicates that the balance,
cylinder and AMH are still in correct position.