Oval Delta Flowpet FLX B Series, Инструкция по эксплуатации, Страница: 12 / 40

D-555-3-E
5.6 Prevention of Excessive Flowrate
To ensure long meter life, transient flowrates should
be held below 1.6 times the meter's maximum
rating. Shown below are typical examples in
steam measurement where excessive flow is often
encountered:
Examples where meter's maximum rating is
exceeded on a momentarily basis
In steam measurement, when P1> P2, quickly
opening the valve will result in a fluid flow at a rate
dependent on the line resistance (mainly valve
port position in "A" or meter resistance in "B").
The resultant rate of incoming flow is the sum of
downstream pipeline volume and consumption, but
P1
P2
FLOW
P1 P2
FLOW
VALVE
METER
GAGE
GAGE
"B"
"A"
DOWNSTREAM
VALVE
METER
UPSTREAM
VALVE
VALVE IN BYPASS LINE
FLOW
Fig.5.5
Fig.5.6
if pressure differential across the valve is great, the fluid velocity will easily reach the sonic speed, momentarily
well in excess of meter's maximum rating. (Such phenomenon is often experienced at system startup or in
batch operation.)
5.7 Prevention of Slug Flow
This meter can measure both gases and liquids, but slug flows (where gases exist in the process liquid) will
produce a loss of meter accuracy.
5.8 Partially Filled Pipe
When making a liquid measurement, ensure that the piping remains full of the process liquid. Installation in
locations where it is difficult to keep the piping filled with the process liquid, or where bubbles tend to collect
should be avoided.
5.9 Bypass Line
For maintenance and servicing purposes, it is a good
practice to provide a bypass line. Valves upstream
and downstream of the meter should be of a design
which will not disturb fluid flow pattern, such as ball
valves (full bore type), in this arrangement (see Fig.
5.6).
For general considerations to be observed, refer
to JIS Z 8766, "Flowrate Measurement Methods
with Vortex Shedding Flowmeters".