reciprocating compressor valve
TRANSCRIPT
-
8/13/2019 Reciprocating Compressor Valve
1/14
16 ORBIT Vol .29 No.1 2009
RECIP TIPS
Valve Temperature Measurement
for Reciprocating Compressors
Brian Howard, P.E. Sr. Technical Manager Reciprocating Compressor Condition Monitoring GE Energy [email protected]
eciprocating 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 decadesis valve or valve cover temperature [3,4].
Properly understood and applied, this measurement provides valuable insight into reciprocatingcompressor 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 Application
The 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 seat 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 success-
fully provide an indication of increased temperature.
-
8/13/2019 Reciprocating Compressor Valve
2/14
Vol .29 No.1 2009 ORBIT 17
RECIP TIPS
Relating Valve Temperatureto Valve Condition
The rise in temperature of the valve or valve coverdepends 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.
Figure 1. Reciprocating compressor suctionvalve. Top shows valve closed and bottom
shows valve open.
WHEN RECIPROCATING
COMPRESSOR VALVES
FAIL, THEY CAN NO
LONGER PROVIDE
EFFECTIVE SEALING
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.
-
8/13/2019 Reciprocating Compressor Valve
3/14
18 ORBIT Vol .29 No.1 2009
RECIP TIPS
Figure 2. Failing discharge valve.
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 CompresLP Stg 2 Disch SWRecip Compres
LP Stg 2 Disch SERecip CompresLP Stg 2 Disch SERecip CompresLP 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 NAHistorical
12NOV2002 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
AMPLITUDE:
20
degF
/div
0
500
1000
1500
0 20 40 60 80 100
TDC
5 %/divDisplaced Volume
POUNDSPERSQUAREINCH
GAUGE
100ps
ig/div
Synch
From 12NOV2002 06:12:16 To 12NOV2002 06:12:16
Synch
From 12NOV2002 06:12:16 To 12NOV2002 06:12:161385.3 psig
0 %
LP Stage 2 West (CE)Displaced Volume
Recip Compressor TraLP Stage 2 West (CE)Displaced VolumeRecip Compressor TraLP Stage 2 East (HE)Displaced VolumeRecip Compressor TraLP 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 06:13:291099.6 psig
0 %
LP Stage 2 West (CE)Displaced Volume
Recip Compressor TraLP Stage 2 West (CE)Displaced VolumeRecip Compressor TraLP Stage 2 East (HE)Displaced VolumeRecip Compressor TraLP 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
POUNDSPER
SQUAREINCHG
AUGE
100psig/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 09:00:181100.4 psig0 %
LP Stage 2 West (CE)
Displaced VolumeRecip Compressor TraLP Stage 2 West (CE)Displaced VolumeRecip Compressor TraLP Stage 2 East (HE)Displaced VolumeRecip Compressor TraLP 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
POUNDSPERSQUAREINCHG
AUGE
100psig/div
0 20 40 60 80 1000
500
1000
1500
5 %/divDisplaced Volume
POUNDSPERSQUAREINCHG
AUGE
100psig/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 TraLP Stage 2 West (CE)Displaced VolumeRecip Compressor TraLP Stage 2 East (HE)Displaced VolumeRecip Compressor TraLP 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
-
8/13/2019 Reciprocating Compressor Valve
4/14
Vol .29 No.1 2009 ORBIT 19
RECIP TIPS
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 180F to 208F.
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 255F. 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.
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 215F. 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 signifi-
cant 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 Effectsof Valve Failure
The 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.
-
8/13/2019 Reciprocating Compressor Valve
5/14
20 ORBIT Vol .29 No.1 2009
RECIP TIPS
Figure 3. LP stage 1 valve cover temperature trends.
ValveTempEffects - Trend Plot [Figure03] Plot Number:__________Company: None Enterprise: ValveTempEffects
Job Reference:
LP STG 1 Suct NWRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Suct WRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Suct SWRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Suct TempRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:
11:01
14AUG2008
11:01
18AUG2008
11:01
22AUG2008
TIME : 12 Hours /div
20degF
/div
AMPLITU
DE:
0
100
200
300
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 100100100100
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 98 d98 d98 d98 d
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 104104104104
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 96 d96 d96 d96 d
LP STG 1 Suct NERecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Suct ERecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Suct SERecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Suct TempRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:
11:01
14AUG2008
11:01
18AUG2008
11:01
22AUG2008
TIME : 12 Hours /div
20degF
/div
AMPLITU
DE:
0
100
200
300
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 108108108108
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 114114114114
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 103103103103
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 96 d96 d96 d96 d
LP STG 1 Disch NWRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Disch WRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:
LP STG 1 Disch SWRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Disch TempRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:
SAMPLE FILTERING
11:01
14AUG2008
11:01
18AUG2008
11:01
22AUG2008
TIME : 12 Hours /div
20degF/div
AMPLITUDE:
0
100
200
300
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 175175175175
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 184184184184
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 186186186186
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 208208208208
LP STG 1 Disch NERecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Disch ERecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:
LP STG 1 Disch SERecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:LP STG 1 Disch TempRecip Compress From 14AUG2008 11:01:38 To 25AUG2008 11:01:
SAMPLE FILTERING
11:01
14AUG2008
11:01
18AUG2008
11:01
22AUG2008
TIME : 12 Hours /div
20degF/div
AMPLITUDE:
0
100
200
300
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 172172172172
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 177177177177
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 189189189189
14AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:3814AUG2008 11:01:38 208208208208
-
8/13/2019 Reciprocating Compressor Valve
6/14
Vol .29 No.1 2009 ORBIT 21
RECIP TIPS
LP Stage 1 CE SynchCrank AngleRecip Compressor Train F r om 1 9 AU G 20 08 0 0 :5 8: 59 T o 1 9A UG 20 08 0 0: 58 :5 9 H is to r ic al M AC HI NE S P EE D: 2 7 6 r pmLPStage1 CECrank AngleRecip Compressor Train Reference MACHINE SPEE D:276 rpmLP Stage 1 HE SynchCrank AngleRecip Compressor Train F r om 1 9 AU G 20 08 0 0 :5 8: 59 T o 1 9A UG 20 08 0 0: 58 :5 9 H is to r ic al M AC HI NE S P EE D: 2 7 6 r pmLPStage1 HECrank AngleRecip Compressor Train Reference MACHINE SPEE D:276 rpm
LP STG 1 Xhead W SynchCrank AngleRecip Compressor Train F r om 1 9 AU G 20 08 0 0 :5 8: 59 T o 1 9 AU G2 00 8 0 0: 58 :5 9 H is to r ic alLP STG 1 Xhead W Filtered SyncCrank AngleRecip Compressor Train F r om 1 9 AU G 20 08 0 0 :5 8: 59 T o 1 9 AU G2 00 8 0 0: 58 :5 9 H is to r ic al
-4
-2
0
2
4
G'S
0.5
g/div
-2
-1
0
1
2
G'S
0.2
g/div
300
400
500
600
700
0 100 200 300 20Degrees/div
CrankAngle
20psig/div
TDC
0 Degrees358.3 psig
0 Degrees358.3 psig
0 Degrees655.8 psig
0 Degrees655.8 psig
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 20F 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 compres-
sion 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 accel-
erometer 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.
Figure 4. Cylinder pressure and crosshead
acceleration waveforms, before valve failure.
LP Stage 1 CE SynchCrank AngleRecip CompressorTrain F ro m 19 AU G2 00 8 06 :0 9: 20 T o 19 AU G2 00 8 0 6 :0 9: 20 H is to ri ca l M AC HI NE S PE ED : 27 6 r p mLPStage 1 CECrank AngleRecip CompressorTrain Reference MACHINE SPEED: 276 rpmLP Stage 1 HE SynchCrank AngleRecip CompressorTrain F ro m 19 AU G2 00 8 06 :0 9: 20 T o 19 AU G2 00 8 0 6 :0 9: 20 H is to ri ca l M AC HI NE S PE ED : 27 6 r p mLPStage 1 HECrank AngleRecip CompressorTrain Reference MACHINE SPEED: 276 rpm
LP STG 1 Xhead W SynchCrank AngleRecip CompressorTrain From19AUG200806 :09 :20To19AUG2008 06:09:20 HistoricalLP STG 1 Xhead W Filtered SyncCrank AngleRecip CompressorTrain From19AUG200806 :09 :20To19AUG2008 06:09:20 Historical
300
400
500
600
700
0 100 200 300 20Degrees/div
CrankAngle
TDCTDC
0 Degrees358.5 psig
0 Degrees358.5 psig
0 Degrees600.9 psig
0 Degrees600.9 psig
-4
-2
0
2
4
G'S
0.5g/div
-2
-1
0
1
2
G'S
0.2g/div
POUNDSPERSQUAREINCHG
AUGE
20psig/div
Figure 5. Cylinder pressure and crosshead
acceleration waveforms, after valve failure.
-
8/13/2019 Reciprocating Compressor Valve
7/14
22 ORBIT Vol .29 No.1 2009
RECIP TIPS
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 under-
neath 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.
Relying on Valve TemperatureAlone for Cylinder Condition
Valve 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 measurements primary value is as
a supporting evidence tool in PV analysis, but is not
sufficient by itself to fully understand and manage the
cylinders condition.
Review of Valve Temperature InstallationArrangements
Three main approaches in valve temperature monitoringhave gained acceptance. These three approaches are:
1. Valve cover skin temperature
2. Valve cover temperature
3. Internal valve temperature
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 Temperature
In 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 ef fort.
The approach does limit temperature sensor options
as only thermocouple temperature sensors have been
offered in this configuration. Further, it is not possible toinstall an explosion-proof housing around the element,
if plant hazardous area requirements dictate such an
arrangement.
The impact of the ambient environment has the poten-
tial 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 dis-
charge 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.
-
8/13/2019 Reciprocating Compressor Valve
8/14
Vol .29 No.1 2009 ORBIT 23
RECIP TIPS
Figure 6. Valve cover skin temperature.
Valve cover skin temperature Valve cover temperature Internal valve temperature
Installation effort Minor Moderate Major
Effect of variables otherthan valve condition onmeasurement
Major Moderate Moderate
Installation cost Minor Minor-Moderate Major
Allows explosion proofhousings?
No Yes Yes
Effort of removal for
valve maintenanceMinor Minor-Moderate Minor-Moderate
Temperature Sensor TC TC/RTD TC/RTD
Table 1. Valve Temperature Installation Arrangement Comparisons.
-
8/13/2019 Reciprocating Compressor Valve
9/14
24 ORBIT Vol .29 No.1 2009
RECIP TIPS
Figure 7. Valve cover skin temperature layout.
Neither radiative nor conductive heat transfer modes
provide significant cooling for valve covers; however,
convective cooling does provide noticeable heat trans-
fer. 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 cov-
ers 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 valve 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 10-15F variation in valve
cover temperature over a short period of time due to
elemental exposure is typical for most valve cover skin
temperature installations.
INVALID DATA
19:4630MAY2006
19:4606JUN2006
19:4613JUN2006
19:4620JUN2006
19:4627JUN2006
19:4604JUL2006
19:4611JUL2006
TIME : 24 Hours /div
AMPLITUDE:
10
degF
/div
50
100
150
200
250
300
NANANANA
24JUN2006 04:45:03 106 deg F NA24JUN2006 04:28:36 105 deg F NA24JUN2006 03:18:43 105 deg F NA24JUN2006 04:35:22 102 deg F NA
LP Stg 1 Disch NELP Stg 1 Disch ELP Stg 1 Disch SELP Stg 1 Disch Temp
300
400
500
600
700
800
0 20 40 60 80 100
5 %/divDisplaced Volume
TDC
POUNDSPERSQUAREINCH
GAUGE
20psig
/div
LP Synch
From 02JUN2006 03:18:11 To 02JUN2006 03:18:11 Historical MACHINE SPEED: 276 rpmLP
MACHINE SPEED: 276 rpm0 %697.0 psig
LP Stage 1 EastDisplaced VolumeRecip TrainLP Stage 1 EastDisplaced VolumeRecip Train
Figure 8. Head end head discharge valve temperature trends (left side) and cylinder PV curve (right side).
VALVE TEMPERATURE MEASUREMENTS
PRIMARY VALUE IS AS A SUPPORTING
EVIDENCE TOOL IN PV ANALYSIS, BUT
IS NOT SUFFICIENT BY ITSELF TO FULLY
UNDERSTAND AND MANAGE THE
CYLINDERS CONDITION.
-
8/13/2019 Reciprocating Compressor Valve
10/14
Vol .29 No.1 2009 ORBIT 25
RECIP TIPS
17:00
02JUN2006
01:00
03JUN2006
09:00
03JUN2006
17:00
03JUN2006
01:00
04JUN2006
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 NA03JUN2006 07:48 :54 207 deg F NA
LP Stg 1 Disch NE
LP Stg 1 Disch E
LP Stg 1 Disch SELP Stg 1 Disch Temp
AMPLITUDE:
10degF/div
01:00
02JUN2006
09:00
02JUN2006
Synch
From 03JUN2006 07:16:33 To 03JUN2006 07:16:33 Histori cal MACHINE SPEED: 276 rpm
TDC
0%709.2 psig
LP Stage 1 EastDisplaced VolumeRecip TrainLP 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 1005 %/div
Displaced Volume
POUNDSPER
SQUAREINCHG
AUGE
20psig/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 TrainLP Stage 1 EastDisplaced VolumeRecip Train Reference MACHINE SPEED: 276 rpm
300
400
500
600
700
800
0 20 40 60 80 1005 %/div
Displaced Volume
POUNDSPER
SQUAREINCHG
AUGE
20psig/div
Figure 9. Valve cover skin temperature (left side) and cylinder PV curve (right side).
2. Valve Cover Temperature
The valve cover skin temperature installation approach
can be modified slightly to allow explosion proof hous-
ings 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. Theinstallation shown in the top pane does not require
explosion-proof fittings allowing a bayonet connector
with an armored cable style temperature 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
installationespecially in the case of the explosion-
proof fittingssomewhat 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-styletube 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 consider-
ing the data provided by the sensor arrangement of
Figure 11 on a large hydrogen booster compressor in a
-
8/13/2019 Reciprocating Compressor Valve
11/14
26 ORBIT Vol .29 No.1 2009
RECIP TIPS
Figure 10. Valve cover temperature (top) andvalve cover temperature with explosion proof
fittings (bottom).
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 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-
7F 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 11. Valve cover temperature installation. Figure 12. Throw 4 valve cover temperature maps.
-
8/13/2019 Reciprocating Compressor Valve
12/14
Vol .29 No.1 2009 ORBIT 27
RECIP TIPS
SAMPLE FILTERING
11:0005DEC2006
11:0006DEC2006
11:0007DEC2006
TIME : 4 Hours /div
11:0008DEC2006
11:0009DEC2006
50
100
150
200
250
300
AMPLITUDE:
10degF/div
90 Left Temperature 05DEC2006 10:00:13 187 deg F NAFrom 05DEC2006 11:00:00 To 09DEC2006 11:00:00 Historical
90 Left Temperature 05DEC2006 09:48:59 180 deg F NAHistorical
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 #50N/AValve #54
N/AValve #55N/A
0
100
200
300
400
0 20 40 60 80 1005 %/divDisplaced Volume
TDC
Synch
From 05DEC2006 13:45:58 To 05DEC2006 13:45:58 Histori cal MACHINE SPEED: 360 rpm
Reference MACHINE SPEED: 360 rpm
0 %407.4 psig
0 %407.4 psig
1stStage-HE4Displaced VolumeTRAIN K-201stStage-HE4Displaced VolumeTRAIN K-20
POUNDSPERSQUAREINCHG
AUGE
20psig/div
0
100
200
300
400
0 20 40 60 80 1005 %/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-HE4Displaced VolumeTRAIN K-201stStage-HE4Displaced VolumeTRAIN K-20
POUNDSPERSQUAREINCHG
AU
GE
20psig/div
Figure 13. 1st stage head end valve temperature trend and head end PV curves.
SAMPLE FILTERING
11:00
05OCT2006
11:00
19OCT2006
11:00
02NOV2006
TIME : 48 Hours /div
11:00
16NOV2006
11:00
30NOV2006
0
50
100
150
AMPLITUDE:
10degF/div
90 Left Temperature 05OCT2006 11:00:00 86 deg F NAFrom 05OCT2006 11:00:00 To 09DEC2006 11:00:00 Historical
90 Left Temperature 05OCT2006 11:00:00 90 deg F NAFrom 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 #49N/AValve #48N/AValve #56N/A
Figure 14. Suction valve temperature trends, head end.
-
8/13/2019 Reciprocating Compressor Valve
13/14
28 ORBIT Vol .29 No.1 2009
RECIP TIPS
3. Internal Valve Temperature
Re-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 f irst 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 measure-
ment 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 2-3F, better than either
of the other two 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 theother 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.
Figure 15. Internal valve temperature installation.
Figure 16. Internal valve temperature trend.
SAMPLE FILTERING
10:1128DEC2006
10:1104JAN2007
10:1111JAN2007
10:1118JAN2007
TIME : 24 Hours /div
50
100
150
200
250
300
AMPL
ITUDE:
10degF/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 NA
From 28DEC2006 10:11:41 To 22JAN2007 16:11:41 Historical
1st Stg CE Disch #3Recip Compress
1st Stg CE Disch #4
Recip Compress
-
8/13/2019 Reciprocating Compressor Valve
14/14
Vol 29 No 1 2009 ORBIT 29
RECIP TIPS
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 NAFrom 28DEC2006 10:11:41 To 22JAN2007 16:11:41
90 Left 28DEC2006 10:11:41 76 deg F NA
From 28DEC2006 10:11:41 To 22JAN2007 16:11:41
1st Stg CE Suct #1Recip Compress1st Stg CE Suct #2
Recip Compress
AMPLITUDE:
5degF
/div
0
200
400
600
800
1000
0 20 40 60 80 1005 %/div
Displaced Volume
Synch
From 29DEC2006 06:43:02 To 29DEC2006 06:43:02 Historical MACHINE SPEED: 327 rpm
Reference
TDC
0 %651.5psig
0 %651.5psig
1st Stg CE PresDisplaced VolumeRecip Compressor Tra1st Stg CE PresDisplaced VolumeRecip Compressor Tra MACHINE SPEED: 327 rpm
POUNDSPERSQUAREINCH
GAUGE
20psig/div
0
200
400
600
800
1000
1200
0 20 40 60 80 1005 %/div
Displaced Volume
Synch
From 22JAN2007 11:23:43 To 22JAN2007 11:23:43 Historical MACHINE SPEED: 327 rpm
Reference MACHINE SPEED: 327 rpm
TDC
0 %643.2psig
0 %643.2psig
1st Stg CE PresDisplaced VolumeRecip Compressor Tra1st Stg CE PresDisplaced VolumeRecip Compressor Tra
POUNDSPERSQUARE
INCH
GAUGE
50psig/d
iv
Figure 17. Crank end suction internal valve temperature and PV curves.
References
[1] Leonard, Stephen M. Increasing the Reliability of Reciprocating Compressor on Hydrogen Service, HydrocarbonProcessing, 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.