The World’s
Highest-Pressure
Injection Pump
PAUL MEUTER
SULZER PUMPS
As oil exploration moves further offshore into deeper
water, the oil reservoir pressures increase far beyond
those experienced in the past. Therefore, injection
pumps used to support the oil reservoir pressure
need injection pressures far above the technology of
existing centrifugal pump designs. Sulzer Pumps has
trodden new paths – and developed the world’s
highest-pressure centrifugal injection pump.
The exploration of deepwater oil fields requires injection pumps with extremely high
pumping heads (Fig. 1). Oil companies have selected several pump
companies to develop designs to
meet their tough demands. This
gives them the opportunity to participate and review the designs
and manufacturing processes
thoroughly, to address interfaces
to the other equipment and assess
risks in an early phase. Robust, re-
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SULZER TECHNICAL REVIEW 4/2002
liable pump designs as well as
safety of the operating personnel
and production facility are of high
priority.
Based on Experienced Designs
The very high pumping head – up
to 5600 m or 580 bar – demonstrates the biggest challenge. In
order to minimize risk, the pump
selection criteria such as hydraulics, speed, head per stage,
number of stages, and design pres-
4072
1 The range chart of
type HPcp injection
pumps could be
expanded with the
development of ultrahigh-pressure injection
pumps covering a
pumping head up to
6000 m.
6000
5000
4000
Head (m)
sure should not deviate too much
from the designer’s experience
wherever possible.
Typically, the existing hydraulics
for multistage pumps, consisting
of impellers and diffusers, need a
larger shaft to transmit the high
power. This is a relatively small
design change, but nevertheless,
the altered hydraulics have to be
model-tested for validation of
their performance.
Speeds of rotation not higher than
6000 rpm are common. The generated head per stage is to be limited
to about 600 m, ensuring acceptable erosion rates for the super
duplex stainless steel and hence
achieving long operational life for
the pump parts.
The combination of number of
stages, type and size of the hydraulics, and speed determines the
rotordynamics of the pump, which
can only be analyzed after the
pump rotor has been designed. A
detailed rotordynamic analysis is
of great importance to demonstrate that the eigenfrequencies
have enough separation from the
operating frequencies and that the
damping is high enough, even
with worn internal running clearances, hence ensuring smooth running of the pumps at all operating
conditions in the field.
After the selection of the pump, a
plan has to be established addressing how the features that are beyond the manufacturers experience are handled to minimize risk.
One area of concern on all the ultra-high-pressure pump designs
are the static seals to keep the
joints of the pressure-retaining
parts tight during operation and
during hydrostatic pressure test.
Detailed finite-element calculations have to be conducted to de-
3000
2000
1000
0
0
1000
2000
Flow (m3/h)
Back-to-back design with bolted delivery cover
In-line design with bolted delivery cover
3000
4000
Installed pumps
Ultra-high-pressure
injection pumps
In-line design with Twistlock delivery cover
(Twistlock allows for a quick cartridge exchange, see STR 2/2000, p. 18)
termine the maximum stresses and
deformations. Furthermore, the
static seals are to be tested in a
test rig.
Two Different Designs
Sulzer Pumps offers two pump designs (Fig. 2):
Impellers arranged in-line for
higher flows
Impellers arranged back-toback for lower flows
The in-line design is the classical
concept used on most high-power
multistage pumps either for injection or boiler feed services. A balance drum installed after the last
stage reduces the axial hydraulic
thrust to the capacity of the double acting thrust bearing. Normally, mechanical seals seal the suction pressure to atmosphere. Pressure oil feed journal and thrust
bearings align the rotor to the
2 Two designs of
ultra-high-pressure
injection pumps are
available. With the
impellers arranged
in-line (top), the drive
power may reach up
to 34 MW. With the
impellers arranged
back-to-back (bottom),
a pumping head up to
6000 m is possible.
SULZER TECHNICAL REVIEW 4/2002
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3 Barrel casing
with bolts.
When using high
pressures, special
attention has to
be paid to the
sealing of the
delivery cover.
stationary casing. The pump
features a full pull-out cartridge,
allowing for a quick exchange of
the cartridge.
The back-to-back design balances
the thrust itself to a large extent.
Thus, a smaller thrust bearing can
be used. The center and the
throttle bushings are only subjected to half the pump pressure and
act as Lomakin type bearings. This
design is especially suited for ultra
high pressure at low flow. All
other features are the same as for
the in-line design.
Analysis of Critical Components
Components and features critical
to reliability and safety have been
identified for detailed investigation during the design process.
Here, only two parts of the many
analyzed are described.
The delivery (or discharge) cover (Fig. 3) closing the barrel casing
to atmosphere is sealed with a face
o-ring. This seal is only tight if
full metal-to-metal contact can be
maintained. To prove this, a finiteelement calculation has been performed, utilizing state-of-the-art
3D modeling techniques and analyzing tools. Figure 4 shows the
typical deformation at operating
condition presented in an exaggerated view. With this analysis it can
be proven that a positive surface
pressure at the inside of the bolting near the o-ring groove can be
maintained, thus eliminating any
possible o-ring extrusion at all operating conditions.
For safety reasons the suction
casing has to be sealed to the atmosphere for the full discharge
pressure if there is no pressure relief system installed in the suction
pipe. Only a radially arranged
sealing system is feasible by design. With rising pressure the radial extrusion gap increases. A sealing system for this purpose consists of a tough, resilient, T-shaped
ring with a pressure-actuated antiextrusion ring used in the aeronautical industry. For the first
ultra-high-pressure pump a test
rig which reproduced this radial
gap under this high pressure was
built for testing the sealing system
prior to pump manufacture. The
tests were successful and confirmed that the suction end sealing
system was fit for purpose.
Protection Against Sand Wear
4 The deflections of the bolted delivery cover connection at operating
condition has been analyzed utilizing
state-of-the-art 3D modeling and
finite-element analysis tools.
Barrel casing
Delivery cover
Nut
Bolt
Injection pumps must be capable
of handling sand, especially if
produced water is pumped. The
components forming the close running clearances have to be protected by using newly developed
HVOF coatings or wear parts with
solid tungsten carbide inserts (see
STR 1/2001, p. 22).
Highest Pressure in the World
For the BP Thunder Horse project
in the Gulf of Mexico, Sulzer
Pumps has participated in a devel-
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SULZER TECHNICAL REVIEW 4/2002
opment competition and, in 2001,
was awarded the manufacturing
and testing of the prototype injection pump with the highest pressure in the world. The pump had
to generate a head of over 5600 m,
turned at 6000 rpm and was driven through a gearbox with a
10-MW variable-frequency drive
motor. The selected pump was of
the back-to-back design and had
12 stages. The material of construction was super duplex stainless steel with high strength and
corrosion resistance.
The pump was vital to the customers’ project success. Since a
pump with such high pressure had
never been built before, a prototype pump was manufactured and
extensively tested. The hydrostatic
pressure test had to be conducted
under severe safety precautions.
The pump test assembly was set
up in a pit not accessible to the
test personnel. The pressure was
increased incrementally up to
957 bar (65% higher than the required operation pressure) and
successfully held at that pressure
for 30 min.
The predicted hydraulic performance was confirmed with the performance test conducted at full
speed at the Sulzer Pumps test
facility in Leeds (UK). The customer’s requirements including
the standards of API 610, 8th edition, could be met.
Rotordynamic tests were carried
out running the pump at full speed
and full load (Fig. 5) with two
times new running clearances simulating end-of-life condition. The
stiffness gained with close running
clearances is reduced with large
clearances, thus vibration is expected to be higher. Hardly any
change of the low vibration level
was detected between the tests
with new and worn running clearances. Vibration levels were all
within the limits set out in API 610
across the full operating range. In
addition, unbalance was added to
the coupling to check the rotor sensitivity. The measured vibration
amplitude was below the predicted value.
All test results fulfilled the customer’s requirements and demonstrated that the pump is robust
even with end-of-life running
clearances. The customer then released an order for three additional complete pump units.
This new and innovative development of ultra-high-pressure injection pumps allowed Sulzer Pumps
to extend its range of pumps in order to meet even more challenging
demands in the future.
CONTACT
Sulzer Pumps (UK) Ltd
Tony Waterfield
Manor Mill Lane
GB-Leeds LS11 8BR
Great Britain
Phone +44 (0)113-272 44 18
Fax
+44 (0)113-272 44 84
E-mail tony.waterfield@sulzer.com
5 A Thunder Horse injection pump unit mounted on a massive skid – destined for BP’s deep-water
field development in the Gulf of Mexico – is ready for a full-speed, full-load string test with all its auxiliary equipment and instrumentation in the Sulzer Pumps manufacturing facility in Leeds (UK).
SULZER TECHNICAL REVIEW 4/2002
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