Reciprocating Compressor Valve

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.


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.


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




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





0

500

1000

1500TDC


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





0

500

1000

1500


POUNDSPERSQUAREINCHG

AUGE

100psig/div

0 20 40 60 80 1000

500

1000

1500



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





TDC

0 %1322.8 psig


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.


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


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


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


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


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


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


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


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


AUGE

20psig/div

Figure 5. Cylinder pressure and crosshead

acceleration waveforms, after valve failure.


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.


8/14

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.


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


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


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.


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


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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.


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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


0 %407.4 psig

0 %407.4 psig

1stStage-HE4Displaced VolumeTRAIN K-201stStage-HE4Displaced VolumeTRAIN K-20


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


0 %399.8 psig

0 %399.8 psig

1stStage-HE4Displaced VolumeTRAIN K-201stStage-HE4Displaced VolumeTRAIN K-20


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


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



Valve #49N/AValve #48N/AValve #56N/A

Figure 14. Suction valve temperature trends, head end.


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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


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


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Vol 29 No 1 2009 ORBIT 29

RECIP TIPS

SAMPLE FILTERING

10:1128DEC2006

10:1104JAN2007

10:1111JAN2007

10:1118JAN2007


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


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.

Reciprocating Compressor Valve

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