Hydrocarbon Processing - December 2021 - 75

Valves, Pumps and
Turbomachinery
S. ZARDYNEZHAD, Turbotech Consulting Corp.,
Calgary, Alberta, Canada
Mitigation actions to prevent vibration during
factory tests of SAGD boiler feedwater pumps
The most vital information on the condition
of boiler feedwater (BFW) pumps
is vibration. The vibration data will determine
the mechanical condition of the
pump and is an index for acceptance or
rejection of the pump during shop performance
tests or mechanical running tests at
the factory or in the field. This information
is also very useful in predictive or preventive
maintenance and reliability programs.
This article reviews practical engineering
mitigation actions to minimize the risk
of vibration of BFW pumps during factory
performance or mechanical running tests.
Introduction. BFW pumps are the most
critical pumps in many industries, such
as power, mining, steam-assisted gravity
drainage (SAGD), refining, chemical
and petrochemical production, and
gas processing. The reliability of BFW
pumps has a significant impact on production.
FIG. 1 shows a typical steam generation
process in an SAGD plant. The
BFW pumps are used to increase the hot
water pressure before entering the oncethrough
steam generators (OTSG).
Vibration monitoring of high-pressure
BFW pumps is similar to other types of
high-speed turbomachinery that employ
fluid film bearings. American Petroleum
Institute (API) Standard 6701
covers the
details of permanent vibration monitoring
systems for critical rotating equipment.
High-pressure and high-temperature
BFW pumps used in SAGD and
many other industries will often be supplied
with vibration monitoring systems
in accordance with API 670.
The vibration monitoring elements
that are normally used for high-pressure
FIG. 1. Typical steam generation process in a SAGD plant.
TABLE 1. Vibration monitoring for high-pressure and high-temperature BFW pumps1
Measurement
Journal bearing
Description
Two proximity probes X-Y (45°)
for each journal bearing
Thrust bearing
Shaft speed/
phase reference
Two proximity probes located
at NDE side of thrust bearing
A key phasor transducer to be
installed in each independent
shaft (non-mechanically
coupled); normally a driver
shaft to support the driver in
uncoupled running condition
Casing vibration
Bearing housing
For machines that are extremely
compliant, or as per client
specification or vendor's standard
As per client specification
and high-temperature BFW pumps are
summarized in TABLE 1.
Vibration consists of four main elements:
amplitude, frequency, phase and
direction. These elements are the minimum
information required to diagnose
any vibration from a machine. Vibration
measurements of the BFW pump are
normally taken by the shaft displacement
probes. In addition, API 610 (Clause
Role
Observing relative motion
between bearing and shaft
Observing axial position
of the shaft within thrust
bearing clearance
To provide a once-perrevolution
reference signal
for determining vibration
phase and shaft rotation
speed
Shutdown
Shutdown
6.9.3) requires vibration of the bearing
housing to be measured in three planes:
vertical, horizontal and axial.2
Vibration amplitude in each direction
is measured in in./sec or mm/sec (peak).
Vibration amplitude is an index of the severity
of the problem, and the frequency
[in cycles per minute (cpm) or Hz (cycles
per sec)] indicates what is causing
the vibration. Basically, the frequency of
Hydrocarbon Processing | DECEMBER 2021 75
Signal
Alarm and
shutdown
Alarm and
shutdown
Hydrocarbon Processing - December 2021

Table of Contents for the Digital Edition of Hydrocarbon Processing - December 2021
