This paper refers to a detailed study conducted in March 2017 by SUMICO Technologies to evaluate the mechanical performance and condition of critical reciprocating engines, compressors and associated pipelines using state-of-the-art technologies at a natural gas booster station in Mari Gas Field (Sindh, Pakistan). Results of the study revealed various hidden areas requiring attention to increase efficiency, reduce operational costs and increase reliability of the plant. This paper describes the technologies used, performance parameters analyzed,some interesting findings and the benefits gained through the study. Prepared by Abdul Basit Bashir (SUMICO Technologies) https://www.linkedin.com/in/abdulbasitb/

1. Background
The gas compressor station is run by seven identical
compressor sets (GE Ajax model DPC-2804) connected in
parallel to boost natural gas for fertilizer production. As the
station is critical for manufacturing process’ reliability, it is
essential to regularly monitor compressor’s health to get early
warning of any developing faults and avoid catastrophic
failures. It is not commercially feasible to repeatedly shutdown
and disassemble compressor sets and their auxiliaries to
inspect their internal conditions. Condition Monitoring
activities were therefore in place, however they only involved
vibration analysis and infrared thermography techniques. As
the mechanical behaviour of reciprocating machinery is more
complex than rotating machinery, additional analysis
techniques were recommended for their better health
evaluation.
Advanced performance and condition
analysis of reciprocating engines,
compressors and gas pipelines
March 2017
Executive Summary
This paper refers to a detailed study conducted in March 2017
by SUMICO Technologies to evaluate the mechanical
performance and condition of critical reciprocating engines,
compressors and associated pipelines using state-of-the-art
technologies at a natural gas booster station in Mari Gas Field
(Sindh, Pakistan).
Results of the study revealed various hidden areas requiring
attention to increase efficiency, reduce operational costs and
increase reliability of the plant. This paper describes the
technologies used, performance parameters analysed,
some interesting findings and the benefits gained through the
study.
Advanced Machinery Analysis Solutions
by SUMICO Technologies

2. Study overview
SUMICO’s engineers collected data from each of the seven
compressor sets and adjacent pipelines while they were
operational using Windrock™PA6320and EmersonCSI2140
analyzers. The data types collected included dynamic
pressures, vibration, ultrasound, spark voltage and
temperatures, each measured simultaneously with the
dynamic crankshaft position data.
The technologies provided by SUMICO, allowed recording
faster than 50,000 data points per second from each sensor
point. In that way, every performance parameter’s dynamic
behaviour could be thoroughly studied with reference to the
compressor’s dynamic crankshaft position.
3D computer models were also designed by SUMICO’s
engineers for all compressor sets and the measured vibration
data was input to analyse ODS (Operational Deflection Shape)
of the discharge pipelines which had been subject to high
vibrations.
ODS (Operational Deflection Shape) computer model
SUMICO’s engineers then analysed the recorded data using
specialized computer software through various types of charts;
PV (Pressure-Volume) curves, ultrasonic waveforms, spark
traces, vibration FFT spectra and vibration waveforms, to name
a few.
Analysis examples
1. Identified piston ring leakage
Image 1A shows ultrasound data measured initially from the
four cylinders of engine no. 1. The pattern revealed that in
cylinder no. 2 (red) there were momentary high levels of
ultrasound (highlighted by black circle), occurring every time
the crankshaft had rotated 45° after passing cylinder’s TDC
(Top Dead Centre) which are symptoms of gas leakage through
piston rings. Furthermore, the P-V (Pressure vs. Volume) curve
(image2A)ofcylinder no.2 showed ahighrate ofpressure drop
after achieving the peak firing pressure. After analysis of the
data, SUMICO’s engineers recommended to inspect the piston
rings.
Image 1A – Ultrasonic patterns of engine cylinders (initial)
When the engine cylinder was later opened by plant
maintenance team, piston rings of cylinder no. 2 were found to
be broken (image 1B).
Image 1B – Broken piston ring from engine #1,cylinder #2
After the piston rings were repaired, data retaken showed
significant improvements (image 1C).
Image 1C– Ultrasonic patterns of engine cylinders (after repair)
Leaving such an abnormality undetected could have continued
to waste fuel through the leakage. Moreover, the fault could
have further worsened over time and if any debris from broken
ring interacted with internal moving parts, it could have
ultimately caused catastrophic failure of the engine and
unscheduled downtime which would be very costly.

3. 2. Identified abnormal spark plug timings
P-V curves (Cylinder Pressure vs. Volume) of engine no. 1
showed that cylinder no. 3 and 4 were experiencing improper
ignition and low PFP (peak firing pressure) values. The 1St
derivative of Pressure-Time curves of cylinder no. 3 showed
inconsistent firing from cycle to cycle (image 2B). It was
therefore recommended to replace spark plugs.
Image 2A – P-Vcurves (Cylinder pressure vs. Volume) before repair
Image 2B – P-T (Cylinder Pressure vs. Crankshaft angle) and dP/dT
(1st derivative) curves of multiple cycles overlapped for comparison
After spark plugs were changed, the behaviour of cylinder
pressures improved significantly (image 2C) which resulted in
great improvement in engine performance and efficiency.
Image 2C– P-V curves (Cylinder pressure vs. Volume) after repair
3. Identified damaged crankshaft bearings
Analysis of vibration data in crankshaft angle domain showed
abnormal patterns of crankshaft bearing no. 2 on compressor
set 1 with a transient appearing once per revolution.
Image 3B – Main bearings vibration vs crankshaft angle
When the bearing was later disassembled for inspection, it
was found to be damaged at the inner race (Image 3C). The
data retaken after repair showed significant improvement in
the vibration waveforms and spectra (Image 3D).
Image 3C – Eroded inner race of compressor set #1, crankshaft
main bearing #2
Image 3D – Main bearings vibration vs crankshaft angle
4. Compression efficiency evaluation
The collected data also allowed performance evaluation of
everycompressorcylinder individually through P-V(Pressure vs.
Volume) curves. As the example shows in image 4A, the
measured PV curve was compared with an ideal performance
curve(dashed)accordingtothe cylinder’sdimensions. Thearea
of difference was highlighted by shaded area to easily visualize
the energy losses within every cylinder individually.
Image 4A – Pressure-Volume curve of compressor cylinder
5. Identified locations requiring additional piping supports
Some pipe sections had been experiencing excessive vibration
but the causes were unknown before the study was conducted.
Taking compressor set 1 as an example, by collecting vibration
at the discharge pipeline and analysis through frequency
domain (spectrum) it was found that vibration was highest at
20 Hz (image 5A) which was 3X compressor running speed
when operating at 400 rpm.
Image 5A – Compressor #1 discharge piping vibration spectrum
Inconsistent pressure rise from cycle to
cycle during ignition period
Ignition
period
Dominant vibration at 1200 rpm
(20 Hz) = (3 X crankshaft speed)
Measured PV curve
Ideal PV curve

4. `
CORPORATE HEAD OFFICE
185/J-1, M.A. Johar Town,
Lahore, Pakistan
KARACHI
E-24, Block-A, Railway Society,
Gulshan-e-jamal, Karachi, Pakistan
ISLAMABAD
No. 307, Main Margala Road, F-11/3
Islamabad, Pakistan
Tel: +92 42 35315541 Tel: +92 21 34682766 Tel: +92 51 2225472
Fax: +92 42 35315540 Fax: +92 21 34688265 Fax: +92 51 2225151
Email: info@sumico.com.pk Email: info@sumico.com.pk Email: info@sumico.com.pk
www.sumico.com.pk
The Advanced Machinery Analysis division of SUMICO Technologies is the leading provider in Pakistan of critical machine health
analysis including gas turbines, steam turbines, reciprocating enginesand reciprocating compressors using in house state-of-the-
art technologies and a strong team of internationally trained engineers.
SUMICO has personnel certified in Reciprocating Compressors and Engines Analysis
from Windrock Inc. Knoxville, TN, USA. In addition, there are ISO-18436-2 certified
vibration analysts up to Category III certified by Mobius Institute, Australia who can
be deployed anytime to your plant for analysing health of your critical machinery.
Advanced Machinery Analysis Solutions
Image 5B – Compressor #1 discharge piping pressure curve
Vibration bump test conducted on the pipeline showed that
no natural frequencies existed near 20 Hz which confirmed
that the issue was not related to structural resonance. By
further analysis through ODS (image 5C) and the
compressor’s discharge pressure data plotted against
compressor’s crankshaft angle (image 5B), it became clear
that the 20 Hz vibration was mainly caused by compressor’s
pressure pulsation and the back and forth gas flow occurring
betweenNRV (Non-Return Valve) downstream of compressor
set #1 and the main discharge header.
Image 5C – ODS (Operational Deflection Shape) of existing piping
system
Image 5D –Piping modifications recommended
Based on the analysis, it was recommended to add
additional piping support and change location of the existing
NRV as shown in image 5D so that it can prevent any reverse
flow of gases from the main discharge header towards the
compressor. The test results together with the
recommendations acted as evidences to help plant teams
justify the modification actions required.
Findings summarized
Along with the few examples described in detail, a number of
beneficial findings were made through the study:
 Enginecylinders withearlycombustion, latecombustion
and peak firing pressure instabilities were identified
 Cylinder valve leakages and lash issues were identified
 Engine and compressor efficiency benchmarks were
established for future comparison
 Compressor skid and piping vibrations were compared
against API 618 standards and benchmarks were
established for future comparison
 Engine cylinders with poor performance were identified
and engine balancing requirements were determined
accordingly
 Requirements for modifying piping supports were
determined to reduce vibration significantly
 Engine spark plugs which were causing improper
ignition were identified
 Identified bearing faults of compressor crankshafts,
cooler fans, lubrication oil pumps and hydraulic pumps
 Identified gear mesh problems of lubrication oil pumps
Conclusion
The findings helped identify key areas to reduce operational
costs and increase reliability of the plant. As shown through
examples, the study not only helpedincrease plant efficiency
and performance by identifying poor performance areas, but
also helped identify faults which could have further
progressed ifleftundetected,leadingtocatastrophic failures
and unplanned downtimes. For equipment with normal
performance, the result reports provided by SUMICO would
be useful for future comparison in case of performance
deviations and would also help in any future fault
investigation for the plant engineers.
Piping section with
excessive vibration
Existing NRV
location
New NRV
location
suggested
New NRV location
suggested
Location suggested for
additional pipe support
To main
discharge
header
Updated09.06.2017