Gas Supply And Flowpath Connections - Fluke MOLBOX RFM Operation And Maintenance Manual

For the electrical/data connection, use the molbox to molbloc electrical/data connection cable
(P/N 102096). Connect the cable to the molbloc and then to molbox RFM rear panel
connector labeled "molbloc".
Avoid making molbloc electrical connections to molblocs while molbox RFM is plugged in.
Damage to the molbloc EEPROM may result (see Section 5.5.5)
2.3.4

GAS SUPPLY AND FLOWPATH CONNECTIONS

Connect a gas supply to the molbloc. Gas supply requirements are:
•
The gas supply must be clean and dry (especially free from oil and particulates) to avoid
contaminating the molbloc.
•
For correct measurements, the gas must be of the same species as that selected by the
molbox RFM GAS function (see Section 3.4.2). Gas purity affects the measurement
uncertainty of flow measurements as molbox RFM uses the thermodynamic properties
of the flowing gas in its flow calculations. Generally, gases with purity of 99.9 % or
better are used for molbloc measurements. Except when using ambient air with
molbloc-S, the test gas should be free of any humidity (dew point less than – 40 °C).
•
If the molbloc is connected upstream of the DUT, the supply pressure must be regulated
and stable within the limits of the molbloc-L pressure dependent calibration type (see
Section 1.2.4.1.2) or molbloc-S calibration type (see section 1.2.4.2.2). If the molbloc is
connected downstream of the DUT, use regulators and valves to make sure that the
pressure that is delivered to the molbloc will be within the limits of the molbloc calibration type.
•
Care should also be taken to make sure that the pressure and flow supplied to the
molbloc are always low enough to avoid over pressuring the molbox RFM RPTs (see
Sections 1.2.2, 3.1.6). If a DUT upstream of the molbloc is operated at high pressure, a
pressure reducing regulator should be connected between the DUT and the molbloc to
ensure that even momentary high pressure spikes do not reach the molbox RPTs.
The gas supplied to the molbloc should be clean and dry. Contamination of the molbloc
flow passage with liquids, particulates or any other matter will alter the molbloc
calibration and can lead to out of tolerance flow measurements.
NEVER connect a pressure source to the molbloc that is greater than the overpressure
limit of your molbox RFM. molbox RFM overpressure limit is 660 kPa absolute/560 kPa
gauge (95 psia/80 psig). Overpressure can damage the molbox RFM internal RPTs (see
Section 1.2.2, 3.1.6).
If you are using a DHI molstic: Install the molbloc into the molstic and connect a gas
supply following the molstic instruction sheet or manual. The flow through the molbloc must
be in the direction of the arrow engraved on the molbloc.
If you are NOT using a DHI molstic: Connect a gas supply to the molbloc according to the
molbloc instruction sheet and the pressure limits of the molbloc calibration type. A valve
should be installed between the pressure supply and the molbloc to allow flow to the molbloc
to be interrupted. The flow through the molbloc must be in the direction of the arrow
engraved on the molbloc.
Adaptor kits are available from DHI to make connections from the molbloc or molstic fittings
to other common connector types. Ask you DHI Sales Representative about your specific
adaptor requirements.
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2. INSTALLATION