predictive maintenance:
Periodic monitoring of the machinerys actual operating conditions is
mandatory for predictive maintenance
The on-board machinery supervisory systems currently installed in most
process plants is inadequate to provide complete knowledge of
compressor behaviour
Monitoring readings without the interpretation of a compressor specialist are
not very useful - unless an on-board Real Diagnostic System is provided
Portable diagnostics are much less intrusive than on-board systems, in
fact the number of on-board sensors is reduced
Portable diagnostics create a fruitful link with the machine designer,
which leads to machinery modernization (proactive maintenance)
Customer benefits include:
Substantial elimination of failures
Increased machine availability and reduced
downtime
Reduced maintenance costs
Optimization of spare parts usage
Energy savings
g What it is
Typical areas measured
Portable diagnostics kit
Diagnostic and maintenance services
for reciprocating compressors have
proven their value to customers. Our
knowledge, experience and scientific
approach are key to defining specific
services that provide maximum
economic advantages.
Machine and plant control guidance is
provided through the use of dedicated
transducers that monitor the efficiency
and natural wear of machine
components. Our diagnostic activities
employ sophisticated instrumentation
and information control systems. As a
compressor manufacturer, we have the
expertise and in-depth knowledge of
design calculations to define needed
modifications without impairing safety
margins.
Thermodynamic and Mechanical
Parameters
Even with regular monitoring of key
parameters, it is often necessary to
check thermodynamic and mechanical
behaviour using portable
instrumentation. Based on obtained
results, the ability of the compressor
to continue to operate until its next
scheduled shutdown can be assessed.
Thermodynamic and mechanical
performance is checked by
specialized technicians using
dedicated instrumentation and
calculations to determine the target
operating parameters to be achieved
at the site.
These measurements allow an
assessment of:
Pressure drops
Filter condition
Valve and cylinder operation
Valve lifter operation
Functioning of onboard
instrumentation and equipment
Sealing of piston rings
Gas leakage from stuffing box
Loosening of valves
Gas leakage from seals
Cooling
Pressure pulsations
Electrical Parameters
A typical application is to measure
electrical parameters including voltage,
absorbed current, Cos
and power.
These checks are performed with a
power grid analyzer connected
directly to the low voltage engine, or
to the secondary transformer for high
voltage engines.
These measurements allow an
assessment of:
Electrical feed
Electrical engine cooling
Absorbed power
Monitoring the Vibrations of the
Compressor Casing and Components
Measurement and analysis of the
vibration of reciprocating compressors
is necessary in order to detect
operating conditions that may rapidly
become abnormal, and to keep track
of the condition of mechanical
components (for example, loosening of
pipe brackets). Many failures show
their development through variations
in a machines vibration signature.
Our experts measure vibrations
using transducers connected to the
portable diagnostic kit that operates
as a spectrum analyzer. These
piezoelectric transducers can be
installed with magnetic or fixed
supports on:
Crankcases
Cylinders
Dampers
Valve covers
Piping
Other components
The vibration measurements allow an
assessment of:
Balance problems
Alignment problems
Loosening of components (flywheel,
tie rod, rod cross head, etc.)
Correct connection of the
compressor to the electric drive
Assessment of the condition of the
foundation
Assessment of piping supports
Correct operation and closing of the
valves
Assessment of the clearances and
wear of components subject to
sliding and rolling
Condition of supports and bearings
Excessive pressure pulsations
Transducer signals are sent to a
spectrum analyser for processing,
and the following performance data
are supplied:
Overall displacement, velocity or
acceleration
Frequency spectrum
Pick values for key frequencies:
synchronous frequency or other
important critical frequencies
Other parameters and/or dedicated
processing
Data is collected for each
measurement point and for all
Cartesian directions.
Compressor Indicated Cycles
Even with regular monitoring of key
parameters, it is often necessary
to verify the actual P-V cycles using
portable instrumentation (Figure 1).
Based on results achieved during
diagnostic testings, an assessment of
whether the machine can continue to
operate until its next scheduled
shutdown can be made.
The analysis of the indicated cycle
allows our diagnostic specialists to
prepare a detailed report on the
condition of the compressor to
optimizing its use, evaluating the
wear state, and to scheduling
maintenance more effectively.
Measurements are carried out by
experts with dedicated
instrumentation, and use
mathematical/statistical models to
determine the ideal operating
parameters for the site. What it is
Specifically, pressure transducers are
connected to the cylinders
compression chamber and the
acquired data is synchronized with
the shaft rotation to supply pressure
trends during a complete rotation.
Data includes:
Suction and delivery pressure for
each phase and effect
Cylinder pressure for each effect
Actual rotating speed of the
machine
These measurements allow an
assessment of:
Excessive gas leakage from piston
rings and stuffing box
Delayed breakaway of valve
shutters from their seat and
counterseat due to excess lubricant
or the presence of impurities in
the gas
Gas discharged to suction and
delivery valves
Valve lifter operation
Gas leakage from seals
Excessive pressure drops
Condition of filters
Pressure pulsations
Absorbed power
Cooling system functionality
Thermography
Thermography employs infrared
technology, which is based on the fact
that all objects emit electromagnetic
energy as radiation at temperatures
above absolute zero. The higher the
temperature, the more electromagnetic
energy is emitted. The electromagnetic
spectrum is a continuum of all
electromagnetic waves across their
frequency and wavelength, and
includes various frequency ranges of
radiated energy, including Gamma
rays, X-rays, ultraviolet, visible,
infrared and radio. Infrared emissions
cover the spectrum of 0.7 micron to
100 microns and are invisible without
special instrumentation. The intensity
of the infrared radiation from an
object is a function of its surface
temperature so that instruments that
are able to measure this intensity can
be used to determine the surface
temperature of bodies. Three types of
instruments can be used to measure
thermal emission radiation:
Infrared thermometers or spot
radiometers which are designed to
provide the actual surface
temperature at a single, relatively
small point on a machine or
surface
Anomalus cycle
(Possible discharge valves problems)
Cycle measured after discharge replacement
Discharge valve problems
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30
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Stroke (mm)
Indicated cycle
Analytical cycle
Indicated cycle
Analytical cycle
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60
50
40
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Pr
essur
e (bara)
Stroke (mm)
Indicated cycle
Analytical cycle
Indicated cycle
Analytical cycle What it is
How it works
In addition to the tools and
instrumentation already illustrated we
are able to provide:
Specialized technicians using
dedicated instrumentation to
perform on-site measurements for
a wide variety of machine types
and/or operating conditions
A diagnostic team at our Florence
GE Oil & Gas headquarters analyzes
the data to assess the condition of
the machine
Detailed reports on the status of
the machine, operational
irregularities, and
recommendations for corrective
action to improve performance or
repairs
Periodic reports based on the type
of maintenance activity (periodic,
scheduled, on condition, etc.), that
analyze the trends of the most
significant or critical parameters
Customer support via phone or
e-mail from experts at our Florence
facility
Line scanners which provide a
single-dimensional scan or line of
comparative radiation
Thermal infrared imagers (see
Figure 2) which, unlike other
infrared techniques, can scan the
infrared emissions from wide areas
of a machine or process equipment
in a very short time. The imaging
systems function much like a video
camera. The user can view the
thermal emission profile of a broad
area by simply looking through the
instrument optics
The data collected by the infrared
Imager can be downloaded to a
portable PC, transformed into digital
data and processed into video images
called thermograms.
Some functional deviations that can
be detected by thermography are:
high energy loss at cylinder valves
due to valve plugging
cylinder valve back flow
high gas leakage at piston rings
and piston rod packing
defective operation of capacity
control devices
ineffective cylinder cooling
abnormal crank mechanism friction
heat generation
Figure 2: Thermal infrared i