™/S, MOLBLOC TERMINAL OPERATION AND MAINTENANCE MANUAL
© 1995 - 2010 Fluke Corporation, DH Instruments Division
Page 28
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.
Caution
Operating at pressures other than those of the molbloc-L pressure
dependent calibration type (see Section 1.2.5.1.2) or molbloc-S calibration
type may result in out of tolerance flow measurements. Refer to the
molbloc Calibration Report to determine its calibration type.
2.3.5
Vacuum Supply (molbloc-S only)
In some cases molbloc-S is operated with a vacuum downstream of the molbloc to reduce
the back pressure so that critical flow can be reached at a lower upstream pressure (see
Section 3.1.5).
There is no lower limit to the pressure that may safely be applied to RPTs.
If you are using DHI supplied downstream vacuum connect kit and vacuum pump:
Install the kit and pump following the supplied instruction sheet or manual. Carefully follow
the pump manufacturer’s recommendations for pump operation.
If you are NOT using DHI supplied downstream vacuum connect kit and vacuum pump:
Carefully evaluate vacuum pump specifications to be sure that the vacuum source available
has the pumping speed necessary to safely handle the planned flows and to maintain low
enough pressure at planned flow rates.
Be sure to provide facilities to avoid flowing into the pump when the pump is not ON as this
will cause pressure to build up on the pump and may damage it. Normally, a shut-off valve
should be included between the pump and the molbloc-S.
It is preferable to install a check valve with very low cracking pressure between the molbloc
and the vacuum shut-off valve.
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.
Caution
Operating at pressures other than those of the molbloc-S calibration type
may result in out of tolerance flow measurements (see Section 1.2.5.2.2).
Refer to the molbloc Calibration Report to determine its calibration type.
2.3.6
Communications Connections
If is being interfaced to a computer, connect an RS232 cable to COM1
or an IEEE-488 cable (cables not supplied) to the IEEE-488 interface. Configure
the interface (see Section 3.6.6).