GEMeasurement & Control
Valve Temperature Measurement for Reciprocating CompressorsGER-4491C (01/15)
Author:
Brian Howard, P.E.Sr. Technologist Reciprocating Compressor Condition Monitoring GE Measurement & Control
IntroductionReciprocating compressor users frequently report that valve
failures rank among the leading causes of unplanned outages
[1,2]. They apply a number of technologies to assess the condition
of the valve to better manage their compressors. One technique
that has been around for years—perhaps decades—is valve or
valve cover temperature [3,4].
Properly understood and applied, this measurement provides
valuable insight into reciprocating compressor cylinder valve
health. This article reviews the successes and limitations of
this measurement and discusses the three primary methods of
monitoring valve temperature, comparing the advantages and
disadvantages of each.
Measurement ApplicationThe reciprocating compressor valve is, in principle, a check valve.
Figure 1 shows a cross-sectional schematic of a valve (the figure
does not show valves springs and other internals).
The valve operates on differential pressure. For a suction valve,
when the pressure inside the cylinder falls below the suction
manifold pressure, the valve opens and gas flows into the cylinder.
The bottom illustration in Figure 1 shows how the sealing elements
seal against the guard when the valve is open. When the pressure
inside the cylinder rises above the suction manifold pressure the
valve closes, as shown in the top illustration.
Discharge valves in a reciprocating compressor cylinder open
when the cylinder pressure exceeds the discharge manifold
pressure and close when the cylinder pressure falls below
discharge manifold pressure.
When reciprocating compressor valves fail, they can no longer
provide effective sealing. This allows small quantities of gas to
escape the valve. In the case of the suction valve, compressed gas
escapes into the suction manifold and in the case of the discharge
valve, compressed gas escapes back into the cylinder. In both
cases, the leak introduces the same gas back into the compression
process where it is heated again. The re-compression results in a
temperature increase near the valve.
Industry has applied several different techniques to measure
this local temperature increase. These include penetrating the
valve cover to place the transducer near the valve, thermocouple
washers underneath the cover nuts or secured to the cover with a
small screw, penetrating the valve cover, penetrating the cylinder
wall near the valve cover, etc. Although effectiveness differs
somewhat across these techniques, all successfully provide an
indication of increased temperature.
Relating Valve Temperature to Valve ConditionThe rise in temperature of the valve or valve cover depends on the
mass of re-compressed gas and the ratio of compression this gas
experiences. So long as the compression ratio remains constant,
an increase in mass flow results in more heat transfer to the cover
and higher temperature. In a single cylinder arrangement with a
control valve that controls only on pressure, the compression ratio
remains relatively constant. In contrast, as valve failure progresses
in a multi-stage arrangement, the compression ratio of the cylinder
in distress drops as the other stages begin to pick up load. The
decrease in compression ratio, even as leak mass flow increases
due to deteriorating valve condition, results in less heat being
available and a decrease in valve temperature.
GE Measurement & Control | GER-4491C (01/15) 1
Figure 1. Reciprocating compressor suction valve. Top shows valve closed and bottom shows valve open.
2
From 12NOV2002 08:56:21 To 28NOV2002 08:56:21
From 12NOV2002 08:56:21 To 28NOV2002 08:56:21
From 12NOV2002 08:56:21 To 28NOV2002 08:56:21
From 12NOV2002 08:56:21 To 28NOV2002 08:56:21
From 12NOV2002 08:56:21 To 28NOV2002 08:56:21
LP Stg 2 DischWRecip Compres LP Stg 2 Disch SW Recip Compres LP Stg 2 Disch SERecip Compres LP Stg 2 Disch SERecip Compres LP Stg 2 Disch TempRecip Compres
NA
NA
NA
NA
NA
Temperature
Temperature
Temperature
Temperature
Temperature
12NOV2002 08:56:20 177 deg F NAHistorical12NOV2002 08:56:20 170 deg F NAHistorical12NOV2002 08:56:20 184 deg F NAHistorical12NOV2002 08:56:20 175 deg F NAHistorical12NOV2002 08:56:20 213 deg F NAHistorical
INVALID DATA
08:5612NOV2002
08:5614NOV2002
08:5616NOV2002
08:5618NOV2002
08:5620NOV2002
08:5622NOV2002
08:5624NOV2002
08:5626NOV2002
08:5628NOV2002
TIME : 12 Hours /div
0
100
200
300
AMPL
ITU
DE:
20 d
eg F
/div
0
500
1000
1500
0 20 40 60 80 100
TDC
5 %/divDisplaced Volume
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
100
psig
/div
Synch
From 12NOV2002 06:12:16 To 12NOV2002 06:12:16
Synch
From 12NOV2002 06:12:16 To 12NOV2002 06:12:16 1385.3 psig0 %
LP Stage 2 West (CE) Displaced VolumeRecip Compressor Tra LP Stage 2 West (CE)Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE) Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE)Displaced VolumeRecip Compressor Tra
Historical
Reference
Historical
Reference
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
Synch
From 24NOV2002 06:13:29 To 24NOV2002 06:13:29
Synch
From 24NOV2002 06:13:29 To 24NOV2002 06:13:29 1099.6 psig0 %
LP Stage 2 West (CE) Displaced VolumeRecip Compressor Tra LP Stage 2 West (CE)Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE) Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE)Displaced VolumeRecip Compressor Tra
Historical
Reference
Historical
Reference
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
0
500
1000
1500TDC
5 %/divDisplaced Volume
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
100
psig
/div
0 20 40 60 80 100
TDC
Synch
From 18NOV2002 09:00:18 To 18NOV2002 09:00:18
Synch
From 18NOV2002 09:00:18 To 18NOV2002 09:00:18 1100.4 psig0 %
LP Stage 2 West (CE) Displaced VolumeRecip Compressor Tra LP Stage 2 West (CE)Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE) Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE)Displaced VolumeRecip Compressor Tra
Historical
Reference
Historical
Reference
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
0
500
1000
1500
5 %/divDisplaced Volume
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
100
psig
/div
0 20 40 60 80 1000
500
1000
1500
5 %/divDisplaced Volume
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
100
psig
/div
0 20 40 60 80 100
Synch
From 13NOV2002 09:26:21 To 13NOV2002 09:26:21
Synch
From 13NOV2002 09:26:21 To 13NOV2002 09:26:21
LP Stage 2 West (CE) Displaced VolumeRecip Compressor Tra LP Stage 2 West (CE)Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE) Displaced VolumeRecip Compressor Tra LP Stage 2 East (HE)Displaced VolumeRecip Compressor Tra
Historical
Reference
Historical
Reference
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
MACHINE SPEED: 276 rpm
TDC
0 %1322.8 psig
Figure 2. Failing discharge valve.
Over the next few days, the cover skin temperature of the
distressed valve begins to drop. By 24 November, the distressed
valve cover skin temperature has fallen to 215ºF. If valve
temperature correlated accurately with valve condition, one would
expect the condition of the valve to have improved.
In fact, as the PV diagram in the top right shows, valve condition
has further deteriorated resulting in a significant deviation
between the indicated and theoretical curves as well as a further
reduction in the compression ratio of the cylinder.
At this point, the rod load and rod reversals had dropped near the
limits recommended by the compressor OEM. For this reason the
plant shut the compressor down for overhaul.
Secondary Temperature Effects of Valve FailureThe previous example focused the relationship between the
temperature of the distressed valve cover and valve condition.
The recirculation of gas at a particular valve changes not only the
temperature of the local valve cover, but also the temperature
profile of other components of the cylinder.
A failing suction valve provides a good example of the secondary
effects introduced by a valve failure. Figure 3 shows the valve
cover temperatures on the crank end in the left panes, and head
end in the right panes. On all trends, temperatures group together
until the morning of August 19th.
3
For an example of this phenomena consider a high-pressure
hydrogen cylinder instrumented with cylinder pressure, discharge
temperature, and valve cover skin temperatures. Figure 2 shows a
valve failure progression timeline for this cylinder.
The top left Pressure versus Volume (PV) curve shows the cylinder
pressure profile on 12 November. The plot shows good agreement
between the indicated cylinder pressures and theoretical curves.
Referring to the trend plot across the top of Figure 2, it can be
observed that on 12 November the discharge valve cover skin
temperatures and the discharge temperature lie close to each
other. Together, these observations indicate effective sealing by
the piston rings and cylinder valves.
On 13 November a leak develops in one of the crank end discharge
valves. This can be seen in the PV diagram in the lower left of the
plot where the actual pressure rises faster than the theoretical
pressure. Valve cover skin temperature of the “LP Stage 2 Disch W”
valve rises quickly from 180ºF to 208ºF.
At this point, the failure has a minimal impact on compression
ratio. The valve failure did not adversely impact rod loads or rod
reversals, so the plant decided to continue with operations.
By 18 or 19 November, the distressed valve cover skin temperature
reaches a maximum of 255ºF. The PV curve, shown in the lower
right of Figure 2, shows that the failure now begins to have a more
noticeable impact on the compression ratio of the cylinder. The
rod load and rod reversal of this cylinder and the other cylinders
servicing the compression stream were still acceptable, so the
plant continued to operate.
GE Measurement & Control | GER-4491C (01/15)
4
Figure 3. LP stage 1 valve cover temperature trends.
LP STG 1 Suct NWRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Suct WRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Suct SWRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Suct TempRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 Historical
11:0114AUG2008
11:0118AUG2008
11:0122AUG2008
TIME : 12 Hours /div
20
deg
F/di
vA
MPL
ITU
DE:
0
100
200
300
14AUG2008 15:32:19 104 deg F NA
14AUG2008 15:51:41 103 deg F NA
14AUG2008 15:35:31 107 deg F NA
14AUG2008 15:21:29 100 deg F NA
LP STG 1 Suct NERecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Suct ERecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Suct SERecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Suct TempRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 Historical
11:0114AUG2008
11:0118AUG2008
11:0122AUG2008
TIME : 12 Hours /div
20
deg
F/di
vA
MPL
ITU
DE:
0
100
200
300
14AUG2008 15:57:27 112 deg F NA
14AUG2008 15:33:03 120 deg F NA
14AUG2008 15:38:49 107 deg F NA
14AUG2008 15:21:29 100 deg F NA
LP STG 1 Disch NWRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Disch WRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Disch SWRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Disch TempRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 Historical
SAMPLE FILTERING
11:0114AUG2008
11:0118AUG2008
11:0122AUG2008
TIME : 12 Hours /div
20
deg
F/di
vA
MPL
ITU
DE:
0
100
200
300
14AUG2008 15:12:26 180 deg F NA
14AUG2008 15:21:25 184 deg F NA
14AUG2008 15:10:01 190 deg F NA
14AUG2008 15:23:45 215 deg F NA
LP STG 1 Disch NERecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Disch ERecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Disch SERecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 HistoricalLP STG 1 Disch TempRecip Compresso From 14AUG2008 11:01:38 To 25AUG2008 11:01:38 Historical
SAMPLE FILTERING
11:0114AUG2008
11:0118AUG2008
11:0122AUG2008
TIME : 12 Hours /div
20
deg
F/di
vA
MPL
ITU
DE:
0
100
200
300
14AUG2008 14:32:04 173 deg F NA
14AUG2008 15:25:33 173 deg F NA
14AUG2008 15:30:08 192 deg F NA
14AUG2008 15:23:45 215 deg F NA
-19
38
93
148
11
deg
C/d
ivA
MPL
ITU
DE:
-19
38
93
148
11
deg
C/d
ivA
MPL
ITU
DE:
-19
38
93
148
11
deg
C/d
ivA
MPL
ITU
DE:
-19
38
93
148
11
deg
C/d
ivA
MPL
ITU
DE:
5
Figure 5. Cylinder pressure and crosshead acceleration waveforms, after valve failure.
LP Stage 1 CE Synch Crank AngleRecip Compressor Train From 19AUG2008 06:09:20 To 19AUG2008 06:09:20 Historical MACHINE SPEED: 276 rpmLP Stage 1 CECrank AngleRecip Compressor Train Reference MACHINE SPEED: 276 rpmLP Stage 1 HE Synch Crank AngleRecip Compressor Train From 19AUG2008 06:09:20 To 19AUG2008 06:09:20 Historical MACHINE SPEED: 276 rpmLP Stage 1 HECrank AngleRecip Compressor Train Reference MACHINE SPEED: 276 rpmLP STG 1 Xhead W Synch Crank AngleRecip Compressor Train From 19AUG2008 06:09:20 To 19AUG2008 06:09:20 HistoricalLP STG 1 Xhead W Filtered Sync Crank AngleRecip Compressor Train From 19AUG2008 06:09:20 To 19AUG2008 06:09:20 Historical
300
400
500
600
700
0 100 200 300 20 Degrees/div
Crank Angle
TDCTDC
0 Degrees358.5 psig
0 Degrees358.5 psig
0 Degrees600.9 psig
0 Degrees600.9 psig
-4
-2
0
2
4
G'S
0.5
g/di
v
-2
-1
0
1
2
G'S
0.2
g/di
v
POU
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R SQ
UAR
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GAU
GE
20 p
sig/
div
Figure 4. Cylinder pressure and crosshead acceleration waveforms, before valve failure.
Figure 4 shows cylinder pressure curves and crosshead
accelerometer signals for this cylinder, typical for the time period
prior to the morning of August 19th. The close agreement between
the theoretical and indicated pressure signifies effective cylinder
trim sealing. Further, the high frequency crosshead accelerometer
signal shows only discrete events associated with normal valve
opening and closing.
Referring back to Figure 3, the consistency across the trend line
ends on the morning of the 19th. At this point, the plots show
relative changes in temperature trends. The “LP STG 1 Suct NE”
trend line in top right pane displays the most significant change;
however other points also show changes. For example, the “LP STG
1 Suct E” and valve cover temperature rises as do the head end
discharge valve cover temperatures, “LP STG 1 Disch NE/E/SE.”
The sudden change in relative temperature values indicates a
change in the sealing ability of the cylinder trim components. As
discussed above, this results in recirculation of gases and a local
increase in valve cover temperature. Given the relatively high
change in the “LP STG 1 Suct NE” temperature relative to the other
changes, one can reasonably associate the valve failure with this
valve cover. The rise in the “LP STG 1 Suct E” temperature, adjacent
to “LP STG 1 Suct NE”, results from the re-circulating gas heat
effect spreading to other valve covers.
The 20°F plus rise in the head end discharge valve group, “LP STG
1 Disch NE/E/SE” deserves attention as well. Either one or more of
the discharge valves has a leak, or there is something about the
leaking suction valve that changed the operating conditions of the
discharge valves.
Figure 5 shows the indicated cylinder pressure curves and
crosshead acceleration after the suction valve leak began. The
slower rise in pressure during the compression stroke on the
head end indicates a leak from the cylinder to a low-pressure
reservoir, such as the suction manifold. The high frequency content
crosshead accelerometer waveform, shown on the top, shows
a rise in amplitude as the difference between internal cylinder
pressure and suction valve manifold pressure increases. This rise
in amplitude results from internal cylinder gas leaking across the
valve into the suction manifold. The features of this plot confirm
that only a suction valve leak exists at this time.
With the possibility of a discharge valve leak eliminated, only the
scenario of a leaking suction valve causing the rise in the discharge
valve cover temperatures remains. At first glance, it seems unlikely
that the suction valve could impact the performance of the
discharge valves. The connection lies in the re-circulating gases
underneath the suction valve cover. While some of this gas does
stay local to the valve cover, large portions of the gas re-enter the
cylinder to be compressed, resulting in a higher effective suction
temperature for that end of the cylinder. Since the compression
ratios remain the same on both ends of the cylinder, the discharge
gas temperature for the head rises with respect to the crank end
valve cover temperatures.
LP Stage 1 CE Synch Crank AngleRecip Compressor Train From 19AUG2008 00:58:59 To 19AUG2008 00:58:59 Historical MACHINE SPEED: 276 rpmLP Stage 1 CECrank AngleRecip Compressor Train Reference MACHINE SPEED: 276 rpmLP Stage 1 HE Synch Crank AngleRecip Compressor Train From 19AUG2008 00:58:59 To 19AUG2008 00:58:59 Historical MACHINE SPEED: 276 rpmLP Stage 1 HECrank AngleRecip Compressor Train Reference MACHINE SPEED: 276 rpmLP STG 1 Xhead W Synch Crank AngleRecip Compressor Train From 19AUG2008 00:58:59 To 19AUG2008 00:58:59 HistoricalLP STG 1 Xhead W Filtered Sync Crank AngleRecip Compressor Train From 19AUG2008 00:58:59 To 19AUG2008 00:58:59 Historical
-4
-2
0
2
4
G'S
0.5
g/di
v
-2
-1
0
1
2
G'S
0.2
g/di
v
300
400
500
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700
0 100 200 300 20 Degrees/div
Crank Angle
POU
ND
S PE
R SQ
UAR
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GAU
GE
20 p
sig/
div
TDC
0 Degrees358.3 psig
0 Degrees358.3 psig
0 Degrees655.8 psig
0 Degrees655.8 psig
GE Measurement & Control | GER-4491C (01/15)
Relying on Valve Temperature Alone for Cylinder ConditionValve temperature, combined with a trending tool, can provide
a good indication of a failing valve at the onset of failure. As
the failure progresses, valve temperature becomes a poor
predictor of valve health. Valve leaks may also result in secondary
temperature effects in other parts of the cylinder, making it
difficult to confidently pinpoint the leaky valve. Further, it does not
provide any insight into the forces acting on the compressor (i.e.,
rod load and rod reversal), making it difficult to understand the
stress the failure places upon the compressor. Nor does cylinder
pressure provide sufficient information to pinpoint which valve on
a particular end of a cylinder has failed. For these reasons, valve
temperature measurement’s primary value is as a supporting
evidence tool in PV analysis, but is not sufficient by itself to fully
understand and manage the cylinder’s condition.
Review of Valve Temperature Installation ArrangementsThree main approaches in valve temperature monitoring have
gained acceptance. These three approaches are:
1. Valve cover skin temperature
2. Valve cover temperature
3. Internal valve temperature
6
The following sections describe the measurements in detail along
with the advantages and disadvantages of each approach. Table 1
on the following page summarizes the discussion.
1. Valve Cover Skin TemperatureIn this temperature arrangement, a small hole drilled and tapped
in the valve cover provides anchorage for a fastener securing a
washer-style thermocouple to the valve cover. Figure 6 shows this
type of arrangement. Obviously, this arrangement provides ready
access for maintenance and reduced retrofit effort.
The approach does limit temperature sensor options as only
thermocouple temperature sensors have been offered in this
configuration. Further, it is not possible to install an explosion-proof
housing around the element, if plant hazardous area requirements
dictate such an arrangement.
The impact of the ambient environment has the potential to reduce
the effectiveness of the measurement. For example, consider the
valve temperature mapping shown in Figure 7. This end of the
cylinder has three discharge valves. Two of the valves, “LP Stg
Disch NE” and “LP Stg Disch NE”, lay at an angle with respect to the
true horizontal axis. The LP Stg Disch E valve is horizontal.
Figure 6. Valve cover skin temperature.
Neither radiative nor conductive heat transfer modes provide
significant cooling for valve covers; however, convective cooling
does provide noticeable heat transfer. The angled valves allow
hot air near the surface of the valve cover to rise more easily
than does the true horizontal surface of the “LP Stg Disch E” valve
cover. This results in a higher temperature for those valve covers
oriented in the true horizontal plane. For example, the 6-9 degree
spread shown in Figure 8 for a cylinder in good condition is typical
for discharge valve cover arrangements like that represented
in Figure 7. The dependence of valve cover skin temperature on
valve cover orientation adds uncertainty to the measurement. Skin
temperature elements experience exposure to the elements. Figure
9 shows the val ve cover skin temperature over a 48-hour period.
This valve cover skin temperature data shows a high degree of
variation around 8:00 am on the 3rd of July. As the Pressure versus
Volume (PV) curves on the right show, cylinder condition remained
good throughout this time period.
The valve covers on the side show more variation as they receive
more wind than does the valve on the bottom of the cylinder. The
10-15°F variation in valve cover temperature over a short period of
time due to elemental exposure is typical for most valve cover skin
temperature installations.
7
DTC/RTD Valve cover skin temperature Valve cover temperature Internal valve temperature
Installation effort Minor Moderate Major
Effect of variables other than valve condition on measurement Major Moderate Moderate
Installation cost Minor Minor-Moderate Major
Allows explosion proof housings? No Yes Yes
Effort of removal for valve maintenance Minor Minor-Moderate Minor-Moderate
Temperature Sensor TC TC/RT
Table 1. Valve Temperature Installation Arrangement Comparisons.
Figure 7. Valve cover skin temperature layout.
GE Measurement & Control | GER-4491C (01/15)
8
17:0002JUN2006
01:0003JUN2006
09:0003JUN2006
17:0003JUN2006
01:0004JUN2006
TIME : 2 Hours /div
50
100
150
200
250
300
NA
NA
NA
NA
03JUN2006 07:51:49 160 deg F NA
03JUN2006 07:59:37 177 deg F NA
03JUN2006 08:52:17 176 deg F NA
03JUN2006 07:48:54 207 deg F NA
LP Stg 1 Disch NE
LP Stg 1 Disch E
LP Stg 1 Disch SE
LP Stg 1 Disch Temp
AM
PLIT
UD
E:10
deg
F/d
iv
01:0002JUN2006
09:0002JUN2006
Synch
From 03JUN2006 07:16:33 To 03JUN2006 07:16:33 Historical MACHINE SPEED: 276 rpm
TDC
0%709.2 psig
LP Stage 1 EastDisplaced VolumeRecip Train LP Stage 1 EastDisplaced VolumeRecip Train
Historical MACHINE SPEED: 276 rpm
Reference MACHINE SPEED: 276 rpm
300
400
500
600
700
800
0 20 40 60 80 100 5 %/div
Displaced Volume
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
20 p
sig/
div
Synch
From 03JUN2006 08:16:33 To 03JUN2006 08:16:33 Historical MACHINE SPEED: 276 rpm
TDC
0 %713.1 psig
LP Stage 1 EastDisplaced VolumeRecip Train LP Stage 1 EastDisplaced VolumeRecip Train Reference MACHINE SPEED: 276 rpm
300
400
500
600
700
800
0 20 40 60 80 100 5 %/div
Displaced Volume
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
20 p
sig/
div
Figure 9. Valve cover skin temperature (left side) and cylinder PV curve (right side).
INVALID DATA
19:4630MAY2006
19:4606JUN2006
19:4613JUN2006
19:4620JUN2006
19:4627JUN2006
19:4604JUL2006
19:4611JUL2006
TIME : 24 Hours /div
AM
PLIT
UD
E:10
deg
F/d
iv
50
100
150
200
250
300
NANANANA
24JUN2006 04:45:03 106 deg F NA 24JUN2006 04:28:36 105 deg F NA 24JUN2006 03:18:43 105 deg F NA 24JUN2006 04:35:22 102 deg F NA
LP Stg 1 Disch NE LP Stg 1 Disch E LP Stg 1 Disch SELP Stg 1 Disch Temp
300
400
500
600
700
800
0 20 40 60 80 100
5 %/divDisplaced Volume
TDC
POU
ND
S PE
R S
QU
AR
E IN
CH
GA
UG
E20
psi
g/d
iv
LP Synch
From 02JUN2006 03:18:11 To 02JUN2006 03:18:11 Historical MACHINE SPEED: 276 rpm LP
MACHINE SPEED: 276 rpm0 % 697.0 psig
LP Stage 1 EastDisplaced VolumeRecip Train LP Stage 1 EastDisplaced VolumeRecip Train
Figure 8. Head end head discharge valve temperature trends (left side) and cylinder PV curve (right side).
2. Valve Cover TemperatureThe valve cover skin temperature installation approach can be
modified slightly to allow explosion proof housings as well as to
reduce the effects of exposure. Figure 10 shows two examples of
this valve approach, referred to as valve cover temperature.
In either case, a dimple or shallow hole receives the temperature-
sensitive portion of the transducer. The installation shown in
the top pane does not require explosion-proof fittings allowing
a bayonet connector with an armored cable style temperature
9
transducer to be used. In the case where the plant hazardous area
classifications require explosion-proof fittings an explosion-proof
head is installed into the bracket and flexible conduit run from this
head to the junction box.
Valve cover temperature has the advantage of not requiring
significant cover modification; however, the installation—especially
in the case of the explosion-proof fittings—somewhat complicates
maintenance activities compared to valve cover skin temperature
installations.
Figure 11 shows a photo of a typical non-explosion proof
installation. In this installation, a compression-style tube fitting
threads into the valve cover and secures the temperature element
rather than a bayonet connector. Although this installation requires
more effort than the valve cover skin temperature approach,
valve cover temperature typically experiences less influence from
orientation and environmental effects. The reduced external
influence can be demonstrated by considering the data provided
by the sensor arrangement of Figure 11 on a large hydrogen
booster compressor in a refinery. (Note: The controls on this
compressor include hydraulically actuated “stepless” unloaders,
so the PV curves will appear altered from those of conventionally
operated compressor cylinder valves).
Figure 10. Valve cover temperature (top) and valve cover temperature with explosion proof fittings (bottom). Figure 11. Valve cover temperature installation.
GE Measurement & Control | GER-4491C (01/15)
10
Figure 12 shows the valve temperature map for throw 4. The cylinder
has three (3) suction valves and three (3) discharge valves on each
end. Stepless unloaders have been installed on the suction valves.
Figure 13 shows the valve cover temperature trend for the head
end discharge valves from 05 Dec. to 09 Dec. Compared to Figure
8, it can be observed that plot shows closer agreement between
the temperatures (~5-7°F difference) for valve cover temperatures
regardless of orientation. Note that the PV curves show a slight
suction valve leak, which the temperature trends in Figure 14
confirm to be Valve #56.
Figure 12. Throw 4 valve cover temperature maps.
SAMPLE FILTERING
11:0005DEC2006
11:0006DEC2006
11:0007DEC2006
TIME : 4 Hours /div
11:0008DEC2006
11:0009DEC2006
50
100
150
200
250
300
AMPL
ITU
DE:
10 d
eg F
/div
90° Left Temperature 05DEC2006 10:00:13 187 deg F NA From 05DEC2006 11:00:00 To 09DEC2006 11:00:00 Historical
90° Left Temperature 05DEC2006 09:48:59 180 deg F NA Historical
90° Left Temperature 05DEC2006 09:53:56 185 deg F NAHistorical
From 05DEC2006 11:00:00 To 09DEC2006 11:00:00
From 05DEC2006 11:00:00 To 09DEC2006 11:00:00
Valve #50 N/A Valve #54 N/A Valve #55 N/A
0
100
200
300
400
0 20 40 60 80 100 5 %/divDisplaced Volume
TDC
Synch
From 05DEC2006 13:45:58 To 05DEC2006 13:45:58 Historical MACHINE SPEED: 360 rpm
Reference MACHINE SPEED: 360 rpm
0 % 407.4 psig
0 %407.4 psig
1stStage-HE4 Displaced VolumeTRAIN K-20 1stStage-HE4Displaced VolumeTRAIN K-20
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
20 p
sig/
div
0
100
200
300
400
0 20 40 60 80 100 5 %/div
Displaced Volume
TDC
Synch
From 09DEC2006 10:06:13 To 09DEC2006 10:06:13 Historical MACHINE SPEED: 360 rpmFrom 09DEC2006 10:06:13 To 09DEC2006 10:06:13
Reference MACHINE SPEED: 360 rpm
0 %399.8 psig
0 %399.8 psig
1stStage-HE4 Displaced VolumeTRAIN K-20 1stStage-HE4Displaced VolumeTRAIN K-20
POU
ND
S PE
R SQ
UAR
E IN
CH G
AUG
E20
psi
g/di
v
Figure 13. 1st stage head end valve temperature trend and head end PV curves.
11
Figure 15. Internal valve temperature installation.
SAMPLE FILTERING
11:0005OCT2006
11:0019OCT2006
11:0002NOV2006
TIME : 48 Hours /div
11:0016NOV2006
11:0030NOV2006
0
50
100
150
AMPL
ITU
DE:
10 d
eg F
/div
90° Left Temperature 05OCT2006 11:00:00 86 deg F NA From 05OCT2006 11:00:00 To 09DEC2006 11:00:00 Historical
90° Left Temperature 05OCT2006 11:00:00 90 deg F NA From 05OCT2006 11:00:00 To 09DEC2006 11:00:00 Historical
90° Left Temperature 05OCT2006 11:00:00 87 deg F NAFrom 05OCT2006 11:00:00 To 09DEC2006 11:00:00 Historical
Valve #49 N/A Valve #48 N/A Valve #56 N/A
Figure 14. Suction valve temperature trends, head end.
3. Internal Valve TemperatureRe-circulating and re-compressing the gas gives rise to the
higher temperature observed at the valve cover. The internal
valve temperature design approach moves the sensor closer to
the valve where the gas first returns to the manifold. Figure 15
shows a typical design for a non-explosion proof installation. A
slight modification would be required to the thermowell to allow
installation of an explosion-proof head.
A penetration in the valve cover allows for a thermowell to be
installed, close to the valve. Within the thermowell, an RTD or TC
provides the actual temperature measurement and sensing.
The proximity of the sensing element to the valve provides better
response time compared to either valve cover skin temperature
or valve cover temperature. In addition, in most cases the
measurement provides data less influenced by environmental
factors than either of the other two measurements.
For many installations, temperature data from this arrangement
typically varies by 2-3°F, better than either of the other two
GE Measurement & Control | GER-4491C (01/15)
12
SAMPLE FILTERING
10:1128DEC2006
10:1104JAN2007
10:1111JAN2007
10:1118JAN2007
TIME : 24 Hours /div
50
100
150
200
250
300
AMPL
ITU
DE:
10 d
eg F
/div
45° Right 28DEC2006 21:43:13 79 deg F NA From 28DEC2006 10:11:41 To 22JAN2007 16:11:41 Historical
90° Left 28DEC2006 21:43:13 80 deg F NAFrom 28DEC2006 10:11:41 To 22JAN2007 16:11:41 Historical
1st Stg CE Disch #3 Recip Compress 1st Stg CE Disch #4 Recip Compress
Figure 16. Internal valve temperature trend.
SAMPLE FILTERING
10:1128DEC2006
10:1104JAN2007
10:1111JAN2007
10:1118JAN2007
TIME : 24 Hours /div
60
80
100
120
140
45° Right 28DEC2006 10:11:41 77 deg F NA From 28DEC2006 10:11:41 To 22JAN2007 16:11:41
90° Left 28DEC2006 10:11:41 76 deg F NAFrom 28DEC2006 10:11:41 To 22JAN2007 16:11:41
1st Stg CE Suct #1 Recip Compress1st Stg CE Suct #2 Recip Compress
AMPL
ITU
DE:
5 de
g F/
div
0
200
400
600
800
1000
0 20 40 60 80 100 5 %/div
Displaced Volume
Synch
From 29DEC2006 06:43:02 To 29DEC2006 06:43:02 Historical MACHINE SPEED: 327 rpm
Reference
TDC
0 %651.5 psig
0 %651.5 psig
1st Stg CE Pres Displaced VolumeRecip Compressor Tra 1st Stg CE PresDisplaced VolumeRecip Compressor Tra MACHINE SPEED: 327 rpm
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
20 p
sig/
div
0
200
400
600
800
1000
1200
0 20 40 60 80 100 5 %/divDisplaced Volume
Synch
From 22JAN2007 11:23:43 To 22JAN2007 11:23:43 Historical MACHINE SPEED: 327 rpm
Reference MACHINE SPEED: 327 rpmTDC
0 %643.2 psig
0 %643.2 psig
1st Stg CE Pres Displaced VolumeRecip Compressor Tra 1st Stg CE PresDisplaced VolumeRecip Compressor Tra
POU
ND
S PE
R SQ
UAR
E IN
CH
GAU
GE
50 p
sig/
div
Figure 17. Crank end suction internal valve temperature and PV curves.
approaches. Figure 16 shows this data and how closely the two
crank end discharge internal valve temperature trends track.
In some cases, it has been observed that the sensitivity of the
temperature sensor to transient conditions within the valve
assembly (i.e., dirt, debris, etc.) creates changes in the valve
temperature trend that do not correlate with the overall health
of the valve.
Figure 17 shows data from one such case. From 29 December
onward, the data shows the temperature of valve “1st Stg CE Suct
#2” increases away from the other suction valve temperature.
This usually indicates a leaking valve. The PV curves should show
a deteriorating suction valve as well. The PV curve in the top right
pane of Figure 17 shows the data at 29 December and the lower
right shows the data 22 January 2007. Although both curves do
show a minor leak, the cylinder pressure curve does not change
over the time period of the valve temperature trend plot, as would
be expected for a leaking valve.
References[1] Leonard, Stephen M. “Increasing the Reliability of Reciprocating
Compressor on Hydrogen Service,” Hydrocarbon Processing,
January 1996.
[2] Manurung, Togar MP, et. al. “Reliability Improvement of a
Reciprocating Compressor in an Oil Refinery.”
[3] Smith, Tim. “Quantum Chemical Uses Reciprocating Compressor
Monitoring to Improve Reliability,” Orbit Magazine, June 1996,
pp. 13-16.
[4] Silcock, Don. “Reciprocating Compressor Instrumented for
Machinery Management,” Orbit Magazine, June 1996, pp. 10-12.
13GE Measurement & Control | GER-4491C (01/15)
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GER-4491C (01/15)