PUMPS
INDUSTRY CHALLENGES
SULZER
OEMs are an excellent source of engineering expertise.
OPTIMIZING PUMP
RELIABILITY AND
PERFORMANCE
The offshore industry faces two main
challenges: maximizing production within
the limits of the reservoir, and minimizing
operational costs while maintaining the
safety of the platform. Pumps form one
of the main groups of equipment that
influence the outcome of both challenges
and they require expert knowledge
to ensure continued reliability and
performance.
Murray Wilson, Sulzer UK argues that in
each case, industry engineering expertise
and commercial innovation are required
to deliver these goals. Furthermore, the
capital expenditure to improve reliability
is most often far outweighed by the costs
incurred by an unexpected failure and the
subsequent costs of lost production. By
taking a proactive approach and involving
an expert maintenance provider, platform
operators can deliver significant benefits to
the business in the long term.
IMPROVING PERFORMANCE
In the years following commissioning, the
actual duty requirements of production
pumps are likely to change - production
rates may start to decline after the initial
plateau period or the connection of
additional wells may mean that potential
production is being limited by the
processing trains which were designed for
lower volumes.
As equipment is pushed to operate
significantly outside of its original design
envelope, this can often cause operating
problems which impact reliability and
ultimately affect platform production. This
also results in increased maintenance costs
as operators and equipment specialists are
required to overhaul plant more frequently.
Ultimately, the goal is to improve reliability
and efficiency while reducing downtime
and energy consumption, at the same
time as satisfying API, ATEX, and many
other engineering standards. However,
this seemingly impossible task can be
achieved through the implementation
of preventative maintenance techniques
and the adoption of the latest engineering
designs for pumps.
Water injection pumps, seawater lift
pumps, crude oil offloading pumps and fire
suppression systems all require individual
designs to deliver the best efficiency and
productivity. At the same time, they also
need specialist maintenance routines that
will prolong reliability and effectiveness.
PROACTIVE MAINTENANCE
A proactive maintenance regime is crucial
to identifying potential issues before they
develop into problems. However, this
requires knowledgeable and experienced
personnel to carry out the in-situ platform
maintenance and these skills take time to
perfect. The time required for this process
can be greatly reduced by instigating a
training program prepared by experts in
equipment maintenance, who can pass on
their collective knowledge in a structured
and efficient manner.
In terms of through-life maintenance cost,
preventative action is almost always less
costly than corrective action, and adopting
a carefully managed, proactive regime
is crucial to identifying potential issues
before they develop into problems. Two of
the most prominent symptoms that occur
prior to failure in mechanical and electrical
equipment are increasing vibration and
rising operational temperature.
Regular trending and analysis of radial and
axial vibration signatures and thermographic
/ visual inspections of bearings, coils and
electrical connections can prove invaluable.
The latest developments in operational
monitoring can be applied to existing assets
and then used to determine the optimal
point at which planned maintenance should
be conducted.
UNDERSTANDING
CAVITATION
Most commonly seen on the pump
impeller, cavitation is caused by a pressure
difference, either on the pump body or
the impeller. A sudden pressure drop in
the fluid causes the liquid to flash to vapor
when the local pressure falls below the
saturation pressure for the fluid being
pumped. Any vapor bubbles formed by the
pressure drop are swept along the impeller
vanes by the flow of the fluid. When the
bubbles enter a region where the local
pressure is greater than saturation pressure,
the vapor bubbles abruptly collapse,
creating a shockwave that, over time, can
cause significant damage to the impeller
vanes or pump housing.
In most cases it is better to prevent
cavitation rather than trying to reduce the
effects on the pumping equipment. This
is normally achieved by one of the three
actions:
• Increase the suction head
• Lower the fluid temperature
• Decrease the Net Positive Suction Head
Required (NPSHR)
For situations where cavitation is
unavoidable, or the pumping system suffers
from internal recirculation or excessive
turbulence, it may be necessary to review
the pump design or minimize the potential
for damage using a bespoke coating
system.
For more information on Sulzer,
visit www.sulzer.com
Issue 35 PECM
165