Measuring and testing – Volume or rate of flow – Using differential pressure
Reexamination Certificate
1999-09-13
2001-11-06
Oen, William (Department: 2855)
Measuring and testing
Volume or rate of flow
Using differential pressure
Reexamination Certificate
active
06311568
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the process measurement and control industry. The measurement and control industry employs process variable transmitters to remotely monitor process variables associated with fluids such as slurries, liquids, vapors, gasses, chemicals, pulp, petroleum, pharmaceuticals, food and other food processing plants. Process variables include pressure, temperature, flow, level, turbidity, density, concentration, chemical composition and other properties.
FIG. 1
is an exploded view of a prior art process flow device
50
for measuring process variables, such as differential pressure and flow. As shown in
FIG. 1
, flow plate
52
is clamped between flanges
54
,
56
in a flow path to produce a differential pressure across a constriction for measuring flow rate of fluids through a pipe
58
. Differential pressure across the flow constriction is measured at pressure taps
60
,
62
. As illustrated in
FIGS. 1-2
, pressure taps
60
,
62
are separate from flow plate
52
clamped between pipe flanges
54
,
56
so that seams separate pressure taps
60
,
62
from flow plate
52
. Pipe
58
conveys process fluid at a high pressure. Such pressure is a combination of the differential pressure developed in response to the constriction and the static pressure within the pipe which can be 1000 psi or more. The high pressure can cause fluid and pressure to leak from seams between the flow plate
52
and pressure taps
60
,
62
. Vibration and other motion of the flow pipe can loosen the connection between the flow plate
52
and pressure taps
60
,
62
contributing to fluid and pressure leakage at the seams.
Within device
50
, flow rate is calculated based upon differential pressure across a flow constriction, pipe diameter and constriction profile. Pressure loss and leakage at seams changes the measured differential pressure across the flow constriction and the pressure loss or change is not attributable to flow rate. The non-attributable pressure loss at the seams degrades flow calculations. Additionally, device
50
requires significant field installation time due to the necessity of joining all the couplings together and performing leak checking upon the couplings. Moreover, whenever maintenance is required for device
50
, significant disassembly/reassembly time is usually required which increases undesirable downtime. Thus, it is desirable to provide a process fluid flow measurement device with increased accuracy and reduced field installation time, downtime, and cost.
SUMMARY
Embodiments of the invention relate to a flow plate having a seamless interface between first and second pressure taps and flow interrupter to reduce non-attributable pressure loss at seams between first and second pressure taps and the flow interrupter. Reduced non-attributable pressure loss improves measurement accuracy, while the seamless interface reduces field installation time.
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Oen William
Rosemount Inc.
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