ger4606_6-4-2010
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GE Energy
Wireless Connecting RodTemperature Measurementsfor Reciprocating Compressor
MonitoringGER-4606 (06/10)
Author:
Brian Howard, P.E.
Sr. Technologist
Reciprocating Compressor Condition MonitoringGE Energy
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IntroductionUndetected bearing failures result in long outages and extensive
repairs for reciprocating machinery. In slow speed reciprocating
compressors and engines, main bearing temperature monitoring
has proven to be valuable in assessing bearing condition1,2.
Monitoring of the moving bearings at either end of the connecting
rod has proven to be more difficult. As the crankpin bearing often
shares design features with the main bearing, temperature
measurements on this bearing would have the same benefits as
it does on the main bearings. On the other end of the connecting
rod, industry experience in operating reciprocating compressors
has shown how important loads and reversal can be in determining
the crosshead pin bushing condition3,4,5. The ability to correlate
these loads with temperature results in improved ability todetermine crosshead pin bushing condition.
Wireless Connecting Rod Temperature Measurementsfor Reciprocating Compressor Monitoring
Eutectic devices have provided one method for indicating bearing
temperature. In recent years a radar-based wireless temperature
system has come to the market that enables end-users to make
connecting rod bearing temperature measurements on-line. This
application note provides background on the radar measurement,
legacy discrete measurement technology, detail on the installation
arrangements and describes how to interface it with GEs Bently
Nevada* 3500 Series Monitoring Systems and System 1* Condition
Monitoring Software (referred to as 3500/S1 hereafter).
GE Energy | GER-4606 (06/10) 1
Crankpin Bearing
Connecting Rod
Crosshead Pin Bushing
Figure 1. Reciprocating Compressor Assembly.
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Eutectic-Style Connecting RodBearing Temperature Installation
ArrangementsThe relative motion between the connecting rod and compressor
frame presents a special challenge to those trying to make a
temperature measurement on the main connecting rod bearing
and crosshead pin bushing. One technique that has been used for
decades involves installing a device assembled with a eutectic
alloy weld that melts at a pre-determined temperature6.
When the local temperature reaches the melting point of the
fusible alloy used to weld the actuator rod to the spring retainer
end, the inner spring forces the actuator rod out through the
detector body (See Figure 2 and Figure 3 for installation details).
GE Energy | GER-4606 (06/10) 2
Fusible Alloy Weld
Spring Retainer End
Detector Body
Pressure Switch
Actuator RodActuator Rod Sleeve
Inner Compression Spring
Outer Compression Spring
Figure 2. Eutectic-Type Wireless Switch Arrangement. Re-drawn from (6).
Detector Body
Actuator Rod
Actuator Rod
Figure 3. Crankpin Eutectic Switch Installation.
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The extension of the actuator rod allows contact with a pressure
switch. The contact with the pressure switch opens the line to
atmosphere, releasing air pressure in the sensing line. The drop in
pressure causes a pressure switch connected to this line to change
state. This switch, in turn, provides an alarm for the operators.
Integration to Reciprocating Compressor
Condition Monitoring System
The 3500/62 Process Variable monitor, combined with an
external power supply, can be used to detect a change in state
of the pressure switch as shown in Figure 4. Although this method
involves more cost than using the discrete input of a PLC or DCS,
it has the advantage of driving data collection directly on the
3500 rack when an alarm condition is reached. This high-resolution
alarm event dataset includes the static and dynamic data from the
compressor and is very useful when trying to understand what led
to a change in machine condition. In particular, when the condition
monitoring system includes crosshead pin bushing temperature
and cylinder pressure data, the effects of overload and/or lack
of reversal can be effectively assessed.
GE Energy | GER-4606 (06/10) 3
Figure 4. 3500/62 Process Variable Monitor Field Wiring (Internal Terminations Shown, External Terminations Similar).
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Wireless Connecting Rod BearingTemperature Installation
ArrangementsRadar-based wireless temperature sensors have gained
acceptance in application to low speed reciprocating compressors.
These systems enable trending of moving bearing temperature,
rather than the discrete values provided by the eutectic systems.
The concept for radar-based sensors grew out of technology
used for tagging automobiles as they pass through automated
toll collecting systems7. Initial testing of these toll identification
systems revealed an appreciable sensitivity to temperature. While
this made reading the tags difficult, it turned out that the system
could be used to estimate temperature.
Unlike traditional wireless radio frequency systems, which require
power to transmit a signal, radar-based systems induce a signal in
the moving component. This has the advantage of not requiring
power for the moving component.
The measurement process begins when the stationary antenna
outputs an interrogation pulse. When this pulse reaches the
antenna wires, the electromagnetic energy excites elastic surface
waves that radiate out from the transducer on the sensing element
substrate. The acoustic waves travel from the transducer to each
of the reflectors mounted on the substrate. When the waves
reach a reflector, an electromagnetic pulse is generated that is
then picked up by the stationary antenna.
The speed of the surface acoustic wave propagation through
the substrate is much lower than the speed of light. The resultingdelay between the interrogation pulse and pulse response from
the moving sensors allows the signal processing equipment to
separate out the valid sensor responses from electromagnetic
echoes within the compressor frame7. The signal processing
equipment then evaluates the shape and spacing interval of
the pulse response from the sensing element to determine the
temperature of the probe tip.
Figure 6 shows the typical packaging layout and radar signal path.
The assembly on the left mounts in either the crank pin bearing
or crosshead pin/crosshead pin bushing. The stationary antennamounts to the compressor frame. The air gap between the moving
and stationary elements can be as large as 50 mm (1.97 in) 7.
Figure 7 shows the mechanical installation of the wireless
temperature sensor.
GE Energy | GER-4606 (06/10) 4
Wireless Temperature Sensor Stationary Antenna
Pulse Response From Sensor
Interrogation Pulse From Antenna
Figure 6. Radar-Based System Arrangement. Redrawn from (7).
Antenna Wires
Transducer
Reflector 1
Reflector n
Absorber
Piezoelectric Substrate
Figure 5. Radar Sensing Element. Re-drawn from (7).
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Integration to Reciprocating Compressor
Condition Monitoring System
The radar-based systems provide a continuous signal, available
for trending and analysis. Kongsbergs Sentry system has gained
acceptance in reciprocating compressor application in the
downstream/petrochemical segments and will be used as an
example of integration to 3500/S1.
The Sentry system has the ability to output a 4-20mA signal
that can be accepted by the 3500/62 process variable monitor.
Figure 8 shows a field-wiring diagram for the Sentry system
connected to a 3500/62 monitor. Figure 9 shows a sample of
one of the channel configuration options. Table 1 outlines initial
alarm and filter settings for the monitor.
GE Energy | GER-4606 (06/10) 5
Figure 7. Wireless Temperature Sensors Installation on Connecting Rod.
Figure 8. 3500/62 Process Variable Monitor Field Wiring (External Terminations Shown, Internal Terminations Similar).
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Within System 1 software, the points should be mapped to therespective throws as shown in Figure 10. No associations are
required for these points.
Software alarms can be set, if desired. In the case that the Cylinder
Trim RulePak has been installed, the result of the crosshead pin
condition rule can be combined with the temperature measurement
to drive an alert specific to crosshead pin wear as shown in
Figure 11.
System 1 Display client plot sessions should include a plot
group with a trend of degrees of reversal, combined rod load
tension/compression, crankpin bearing temperature and
crosshead bushing temperature. Figure 12 shows a sample
of this plot arrangement.
GE Energy | GER-4606 (06/10) 6
Crankshaft
Stg 1 X-Head Temp B
Stg 1 X-Head Temp A
Throw 1 Diagnostics - Hydrogen
Stg 1 Xhead Accel
Cylinder 1 (Stage 1)
Throw 1 (Stage 1)
Figure 10. Radar-Based Temperature Mapping.
Figure 11. Sample Rule Combining Pin Load and Radar-Based WirelessTemperature.
Figure 9. 3500/62 Process Variable Configuration Screen.
Table 1. Initial Monitor Alarm and Filter Settings.
Filtering Not Applicable
Alarm / Danger - In the absence of
OEM recommendations or engineering
data, these are the recommended*initial alarm and danger set points.
Alarm: 200F (82C)
Danger: 220F (93C)
*These should be adjusted based on actual operating conditions
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ConclusionThe wireless measurement systems provide critical information
about the health of the connecting rod bearings. Combining this
measurement with other condition monitoring parameters
provides helpful insight into machine condition.
GE Energy | GER-4606 (06/10) 7
Stage 1 Rod ReversalRecip. Comp. From 17MAY2008 17:40:00 To 29MAY2008 17:40:00 Historical
17:4017MAY2008
17:4021MAY2008
17:4025MAY2008
17:40
TIME : 12 Hours /div
AMPLITUDE:
0
50
100
150
26MA Y2 00 8 18 :3 6:3 4 17 9 deg 3 00 rpm Stage 1 Pk. Rod Load (C)Recip. Comp. From 17MAY2008 17:40:00 To 29MAY2008 17:40:00 HistoricalStage 1 Pk. Rod Load (T)Recip. Comp. From 17MAY2008 17:40:00 To 29MAY2008 17:40:00 Historical
17:4017MAY2008
17:4021MAY2008
17:4025MAY2008
17:40
TIME : 12 Hours /div
AMPLITUDE:
0
50
100
150
26MAY2008 18:19:54 110966 lbf 300 rpm
26MAY2008 18:29:29 117973 lbf 300 rpm
Stage 1 Crank Pin Temp
Recip. Comp. From 17MAY2008 17:40:00 To 29MAY2008 17:40:00 Historical
17:4017MAY2008
17:4021MAY2008
17:4025MAY2008
17:40
TIME : 12 Hours /div
AMPLITUDE:
50
100
150
200
26MAY2008 18:36:32 147 deg F NA Stg 1 X-Head Pin Temp ARecip. Comp. From 17MAY2008 17:40:00 To 29MAY2008 17:40:00 HistoricalStg 1 X-Head Pin Temp BRecip. Comp. From 17MAY2008 17:40:00 To 29MAY2008 17:40:00 Historical
17:4017MAY2008
17:4021MAY2008
17:4025MAY2008
17:40
TIME : 12 Hours /div
AMPLITUDE:
50
100
150
200
26MAY2008 22:00:08 148 deg F NA
26MAY2008 21:26:17 146 deg F NA
29MAY2008
10
38
66
93
10degF/div
AMPLITUDE:
5.6
degF/div
10deg/div
29MAY2008 29MAY2008
29MAY2008
10
38
66
93
AMPLITUDE:
5.6
degF/div
10degF/div
0
220
440
660
10klbf/div
AMPLITUDE:
44kN/div
Figure 12. Radar-Based Temperature Plot Group Layout.
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Bibliography[1] Leon-Gomez, Steve and Smalley, Anthony. Main Bearing
Temperature Monitoring. Report No. TR 97-7. Gas Machinery
Research Council, 1997
[2] General Electric. Protecting and Managing API-618
Reciprocating Compressors. Document Number 178896,
Revision NC.
[3] Davis, Greg. Using PV Curves to Diagnose A Recip Valve
Problem. Orbit, pp48-54, First Quarter, 2004.
[4] Diab, Sary and Howard, Brian. Reciprocating Compressor
Management Systems Provide Solid Return on Investment.
Proceedings of the ROTATE 2004 Conference.
[5] Howard, Brian and John Kitchens. On-line Acceleration and
Cylinder Pressure (PV) Measurements for Reciprocating
Compressor Diagnostics. Proceedings of the Gas Machinery
Conference, 2007.
[6] Munroe, William O. Temperature Detecting Actuator For
Bearings. Amot Controls Corporation, assignee. Patent
3,401,666. 1968.
[7] Gemdjian, Ed and Cornelius, Larry. Safety And Prevention Of
Costly Undetected, Developing Failures In Crank And Crosshead
Bearings Of Gas And Process Compressors. Proceedings of theGas Machinery Conference, 2007.
GE Energy | GER-4606 (06/10) 8
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GE Energy
Optimization and Control
1631 Bently Parkway South
Minden, NV 89423
+1 775.782.3611
www.ge-energy.com/oc
*Bently Nevada and System 1 are trademarks of the General Electric Company.
2010, General Electric Company.
All rights reserved. GER-4606 (06/10)