Note: Descriptions are shown in the official language in which they were submitted.
CA 02795584 2012-11-06
Specification
This invention relates to an impingement jet test rig for measurements of
erosion-
corrosion of metals under multiphase fluid flow conditions.
Erosion-corrosion refers to a mechanism resulting in an accelerated metal loss
due to the synergism of erosion and corrosion in which each process affected
by
the simultaneous action of the other. Generally, erosion-corrosion causes a
total
metal loss significantly in excess of the sum of pure corrosion and pure
erosion
processes. Erosion-corrosion has been identified as one of the primary
mechanisms resulting in structural failures in a wide variety of industrial
applications, such as oil/gas, pipeline, automotive and manufacturing
industries.
The techniques conventionally used for erosion-corrosion testing include
primarily rotating disk electrode (RDE), rotating cylinder electrode (RCE) and
impingement jet. The RDE and RCE are used for laminar and turbulent flow
study, respectively, but suffer from the inability of achieving a sufficient
mixing of
solid sands and liquid, especially at high contents of sands. Moreover, they
are
appropriate to simulate fluid flow in straight pipes only. It is difficult, if
not
impossible, to create the flow patterns representative of the actual ones
encountered at pipe bends, tee joints and uphill/downhill flows. The
impingement
jet systems used previously are incapable of controlling accurately the
content of
sands in the multiphase fluid. Moreover, it cannot separate solid from liquid
phase before the fluid goes into the pumping system, causing severe erosive
wear to pump and its accessories. They are not equipped with in-situ sensors
to
control and monitor the sand concentration in the liquid-solid fluid and the
flow
velocity, resulting in generation of misleading information regarding the
roles of
sands and fluid flow in the erosion-corrosion process of metals. Furthermore,
the
previously used impingement jet systems do not contain an independent sample
chamber and are not capable of adjusting the angle of the impinging fluid to
the
sample surface.
The inabilities of the methods previously used for erosion-corrosion testing
can
be overcome by developing an impingement jet test rig that is capable of
generating a wide variety of multiphase fluid flows that are representative of
the
actual ones encountered in the industrial applications. The test rig contains
two
individual, but interconnected loops, enabling a sufficient mixing and
complete
separation of liquid and solid phases before and after the erosion-corrosion
tests,
respectively, and thus preventing the pipes, pump and its accessories from
erosive wear in sand-containing fluid. An innovative sand concentration
controller
is installed to adjust and control conveniently and accurately the content of
solid
sands in the multiphase fluid. Moreover, the test rig is equipped infrared and
CA 02795584 2012-11-06
ultrasonic sensors to monitor the sand concentration and the fluid flow
velocity
during testing, providing accurate information for determination of the
parametric
effects on erosion-corrosion. The test rig is also equipped with an
independent
sample chamber where the testing sample can be positioned flexibly relative to
the fluid impingement, simulating the uphill and downhill pipe flows under
various
slopes.
In drawings which illustrate embodiments of the invention, Figure 1 is the
schematic diagram of the invented impingement jet test rig for measurements of
erosion-corrosion of metals, Figure 2 is the schematic diagram of the stirrer
system of the test rig, Figure 3 is the schematic diagram of the sand
concentration controller of the test rig, and Figure 4 is the schematic
diagram of
the sample chamber.
The test rig illustrated includes four essential components, i.e., a pump and
pipe
loop system, a multiphase flow recycle and solid/liquid separating system, a
sample testing chamber, and an in-situ monitoring and controlling system.
The pump and pipe loop system includes a high-pressure pump 1, pipes 2, a
driving nozzle 3 and a working nozzle 4. A high speed fluid flow is generated
by
the driving nozzle 3, and injected into the working nozzle 4. A negative
pressure
is produced in the tee joint region around the driving nozzle 3 so that the
sand-
containing fluid is suck up to enter the working nozzle 4, mixing with the
sand-
free fluid sprayed out of the driving nozzle 3 to form the multiphase fluid.
After
impingement of the multiphase fluid in the sample chamber 11, the fluid goes
to
the sand bed 5, completing one flowing cycle.
The multiphase fluid recycle and separating system is the most important and
also the most innovative part in the test rig. It includes a sand bed 5, a
filter 6, a
motor stirrer 7, a sand extraction pipe 8, a sand concentration controller 9,
and a
sand-free fluid container 10. After completing one flowing cycle, the
multiphase
fluid flows to the sand bed 5, where the solid sands are separated from the
fluid
by filter 6. The motor stirrer 7 is used to enhance the sand separation
process,
where the motor 17 exports a high speed but low torsion rotation. The rotating
torsion is increased by a gear reducer 18, and is transmitted to the stirring
blades
20 through a shaft sleeve 19. Consequently, a vortex flow is generated in sand
bed 5. The solid sands deposit and gather in the center of the sand bed 5 and
will be extracted by the sand extraction pipe 8 for another flow cycle. The
sand-
free fluid flows into the container 10, and then into pipes 2 and finally pump
1.
To measure accurately the content of solid sands in the multiphase fluid, a
sand
concentration controller 9 is wrapped around the sand extraction pipe 8. The
CA 02795584 2012-11-06
controller includes a sleeve pipe 21 with seal rings 22 at both ends. The
controller can be drawn up and down conveniently along the sand extraction
pipe
8 by a link arm 23 by adjusting the screw 24. Three states for controlling the
sand
concentration are described in Figure 3. When the sand concentration
controller
is located at the top position, as shown in Figure 3a, the two inlets for sand-
free
fluid are closed. The sand-containing fluid goes into the sand extraction pipe
8
through the bottom inlets. Thus, the maximum sand concentration flow can be
obtained. In Figure 3b, the sand concentration controller moves down and
achieves a half opening of all inlets for both sand-containing and sand-free
fluids.
With the increase of the opening for sand-free fluid inlets, the sand
concentration
of the multiphase fluid decreases. In Figure c, the inlets for sand-containing
fluid
are fully closed, and the sand concentration is reduced to zero. Apparently,
the
sand concentration in the fluid can be adjusted conveniently and accurately.
An independent sample chamber is associated with the test rig for erosion-
corrosion testing. The sample 26 in embedded in a sample holder 25, which can
rotate from 0 to 90 degree along the vertical axis, generating various
impinging
angles by multiphase fluid to the sample surface. A tubular testing sample 27
can
also be installed coaxially with the working nozzle 4 to simulate the sand
sliding
induced erosion-corrosion of metallic structure. For electrochemical corrosion
measurements, the samples 26 and 27 serve as working electrode, and a
reference electrode 23 and a counter electrode 29 are installed in the chamber
through the opening.
During erosion-corrosion testing, all flow parameters of the multiphase fluid
in the
impingement jet test rig are controlled and measured accurately. As shown in
Figure 1, the fluid flow velocity is controlled by the pump output 1 and
measured
by the ultrasonic flow meter 12. A pressure gauge 13 is installed to monitor
the
pump output pressure. The sand concentration is adjusted and controlled by the
sand concentration controller 9, and measured by the infrared back scattering
sensor 14. The impinging angle of the multiphase fluid to the sample surface
is
adjusted and controlled by rotating the sample holder 25 and measured by an
angle gauge. The operating temperature is controlled by an automatic heater 15
embedded in the sand-free fluid container 10, and measured by a thermometer.
Moreover, the gassing atmospheric condition in the fluid can be controlled
through a gas inlet 16. Furthermore, the testing sample and the associated
electrodes permit the in-situ electrochemical corrosion measurements.
