Here is an interesting case study regarding reciprocating compressors of a major US refinery. Check out this case study to know, how condition monitoring reduced the need for “just in case” inspections, lengthy outages, and improved machine reliability.

1. GE Energy
Oil & Gas – Petroleum Refining
Customer Success Story
Bently Nevada* Asset Condition Monitoring
Using PV Curves to Diagnose a Recip Valve Problem
The single most important measurement for condition monitoring of
reciprocating compressors is cylinder pressure. Armed with accurate
cylinder pressure at each point in the piston’s stroke, a Pressure-Volume
(PV) curve can be constructed, which provides indispensable information
on the machine’s health.
Problem
Three reciprocating compressors provide compressed hydrogen for the catalytic cracker in
a major US refinery. In order for the unit to run at full output, all three compressors must run
simultaneously. The loss of one machine results in a 20% loss in plant production.
Solution
A 3500 Series monitoring system provides alarms on high vibration and transmits all
parameters to System 1* Condition Monitoring and Diagnostics Software for storage and
display. Parameters monitored include cylinder pressure (displayed as pressure vs. volume, System 1* Software
or PV), cylinder valve temperature, main bearing temperature, suction and discharge
temperatures, frame velocity, crosshead acceleration, piston rod vibration, and rod position.
Important parameters derived from these measurements include rod load (compression
and tension), degrees of reversal, peak cylinder pressure, discharge pressure, minimum
cylinder pressure, suction pressure, and compression ratio.
Payback
An increase in vibration in the crosshead vibration on the low-purity, third-stage cylinder 3500 Series
triggered an alarm in the 3500 monitor which alerted the plant’s rotating equipment Monitoring System
engineering group. Through cylinder pressure information provided online by System 1,
engineering was able to assess the stresses that the malfunction induced upon the recipro-
cating compressor and, based upon these stresses, decide when to shut down the machine
so that further damage did not occur. This resulted in a shorter outage, lower maintenance
cost, and the prevention of a major failure. As a 20% reduction in production results from
having one machine down for maintenance, a large part of the savings can be attributed to
the decrease in unscheduled maintenance downtime.
Benefits
• Reduced need for “just in case” inspections through accurate, real time machinery
information that shows actual mechanical stresses and conditions.
• S
horter, more efficient outages by knowing what needs attention and what doesn’t
along with what parts and skills are needed.
• Improved machinery reliability through the ability to correlate process conditions
with mechanical conditions and make necessary operating adjustments to prolong
asset life. As seen in
Learn more by reading the
feature-length case study
article in ORBIT magazine
Vol. 24, No. 1, 2004 at
© 2008 General Electric Company, all rights reserved. www.orbit-magazine.com
* Trademarks of Bently Nevada, LLC, a wholly owned
subsidiary of the General Electric Company. www.ge-energy.com/ocsuccess
GEA17072 (08/08)