Hydrocarbon Processing - December 2022 - 65

Valves, Pumps and Turbomachinery
ing temperature is within 40°C (104°F)
of the operating temperature and the
pump has experienced a heat soak at that
temperature for a minimum of 2 hr. FIG. 2
shows the same pump casing's thermal
signature; however, the thermal signature
now clearly indicates that there is a uniform
temperature distribution across the
entire casing (top to bottom).
Typical warm-up system design. A
typical warm-up system piping and instrumentation
diagram (P&ID) for the subject
design-which is a double-suction, radially
split between bearing, top-top nozzle
configuration-is shown in FIG. 3. As
shown in this case, there are three warmup
lines, each entering the pump bottom
casing drains. A multi-stage orifice is also
utilized to effectively break down the high
pressure and provide the required warmup
flowrate to satisfy warm-up criteria.
CASE STUDY: PUMP FAILURE
Three process areas are classified as
hot service applications at one Saudi Aramco
Red Sea refinery. Each process area
utilizes a 3 × 50% pump configuration
with an API BB2 radially split between
bearing design. The pumps are driven by
an induction motor and utilize an API
Plan 54 mechanical seal support system.
The hot service applications are outlined
in TABLE 1, which detatils service, process
temperature and operating philosophy.
Observed failures. Multiple failures
were observed with these pumps during
the first 3 mos of commissioning.
The main failure modes observed were
related to mechanical seal failures and
galling of internal running clearances, as
outlined below:
1. The process fluid solidified,
leading to a compromised
hydraulic balance line and a
subsequent loss of axial thrust
balance. This condition also overpressured
the sealing chamber,
resulting in contamination of
the API Plan 54 seal support
system. Subsequently, the entire
central barrier skid system
supplying the main process
pumps was contaminated.
2. The pump was started with a
blinded warm-up line without
meeting the previously specified
criteria, resulting in the seizure
FIG. 2. Thermal signature showing a uniform
temperature distribution.
FIG. 4. View of the seized rotor at the balance
line/sleeve.
TABLE 1. Hot service applications at a Saudi Aramco refi nery
Process description
Vacuum residue pumps
Atmospheric residue pumps
HVU LCR pumps
Process temperature, °C (°F)
362 (684)
357 (675)
306 (583)
of the rotor at the balance line/
sleeve location (FIG. 4).
The investigation team performed a thorough
assessment to analyze the pump
failure modes and provide recommendations
to improve reliability and prevent
reoccurrence. The primary findings of
the investigation were related to warm-up
system deficiencies, as outlined below:
* All hot service pumps have no
thermal insulation, which can
affect both the warm-up rate
and the effectiveness of the
overall warm-up process.
* Improper warm-up line restriction
orifice sizing resulted in
compromised warm-up conditions.
* A lack of a proper warm-up of
the standby pump was due to a
normally closed discharge valve
that was motor operated. The
normal location for the warmup
line take-off is between the
discharge valve and the check valve.
* There was no permissive
to start controls to prevent
startup of the pump without
proper thermocouple
temperature readings.
* Generic warm-up procedures did
not meet the required warm-up
procedure that was recommended
by the pump vendor and also
specified on the P&ID. Often with
new installations, the P&IDs are
developed prior to awarding the
pump designer. This can lead to
discrepancies in what is represented
on the P&ID and the actual
requirements of the pump designer.
Key takeaways and best practices.
Hot pump applications require special
considerations in terms of design and
operation. It is important to understand
the recommended warm-up procedures
for a particular pump design to ensure
a reliable startup and operation of the
pump. The following outlines some of
the considerations and best practices for
hot pump applications:
* Pump casing thermocouples
should be used to ensure uniform
warm-up of the pump and to
verify that all criteria have been
satisfied for a successful startup.
This temperature instrumentation
can also be used to configure
FIG. 3. View of typical warm-up system
flowlines and restriction orifices.
Operating philosophy
Two running + one spare
(3 × 50%)
Hydrocarbon Processing | DECEMBER 2022 65
Hydrocarbon Processing - December 2022

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