™/S, MOLBLOC TERMINAL OPERATION AND MAINTENANCE MANUAL
© 1995 - 2010 Fluke Corporation, DH Instruments Division
Page 70
OPERATION
Select
[TARE]
,
<5BPR>
. The display is:
1.
The current pressure read by the upstream (left) and
downstream (right) RPTs without taking into account
the current tare value. These are untared readings in
the current pressure unit of measure.
2.
The current BPR (ratio of downstream to upstream
absolute pressure).
259.312 kPa
↓
99.5769
BPR 0.38
Press
[ENTER]
or
[ESCAPE]
to exit the BPR function and return to the previous
RUN screen and BPR mode.
3.4.5
[P&T] (Pressure and Temperature)
PURPOSE
To provide continuous display of the pressures measured by , the Reynolds
number of the flow through the molbloc, the temperature of the molbloc and other pressure
measurement information depending on whether the is used with molbloc-L or
molbloc-S.
PRINCIPLE
continuously measures pressures and molbloc temperature and uses these
measurements to calculate flow.
The pressure at the molbloc upstream and downstream ports is read by two absolute
Reference Pressure Transducers (RPTs). In molbloc-L operation, the flow is calculated from
the differential pressure across the molbloc. The differential pressure is calculated as the
difference between the two, tared (see Section 3.4.4.1.1), absolute RPTs (upstream -
downstream) and is displayed in the molbloc-L mode pressure screen.
In molbloc-S mode, the flow is calculated from the molbloc-S upstream pressure. The
upstream pressure may be read by either one or both of the RPTs, depending on which BPR
mode is in use (see Section 3.6.9). When the is in a valve state called BPR OFF,
the molbloc-S downstream pressure is not measured and both RPTs are used to measure
the molbloc-S upstream pressure. Their readings are averaged to reduce the uncertainty of
the molbloc-S upstream pressure measurement. An indicator is used next to the “downstream”
RPT value to show whether the RPT is currently measuring the molbloc downstream or
upstream pressure. Whenever the molbloc-S downstream pressure is measured, the BPR is
calculated and shown in the P&T pressure screen. When both RPTs measure the upstream
pressure (BPR OFF mode), the indicated pressure for both RPTs is adjusted to equal the
average of the two using the dynamic tare and BPR is no longer displayed.
Since the displays and operation of the P&T pressure screen are different for molbloc-L and
molbloc-S, they are described separately in Sections 3.4.5.1 and 3.4.5.2.
For temperature measurement, two Platinum Resistance Thermometers (PRTs) are embedded
in each molbloc. These are connected to the by the to molbloc cable.
The ohmic measurement system reads the resistance of the PRTs and calculates
molbloc temperature.
continuously calculates the Reynolds number of the flow through the molbloc.
The ’s current pressure and temperature readings as well as the Reynolds number
of the current flow can be displayed using the P&T function.
