Valve Temperature Measurement for Reciprocating Compressors · For a suction valve, when the pressure inside the cylinder falls below the suction manifold pressure, the valve opens

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




Synch

From 24NOV2002 06:13:29 To 24NOV2002 06:13:29

Synch



Historical

Reference

Historical

Reference





0

500

1000

1500TDC


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



Historical

Reference

Historical

Reference





0

500

1000

1500


POU

ND

S PE

R SQ

UAR

E IN

CH

GAU

GE

100

psig

/div

0 20 40 60 80 1000

500

1000

1500


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


Historical

Reference

Historical

Reference





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


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


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


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


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

ND

S PE

R SQ

UAR

E IN

CH

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

600

700

0 100 200 300 20 Degrees/div

Crank Angle

POU

ND

S PE

R SQ

UAR

E IN

CH

GAU

GE

20 p

sig/

div

TDC

0 Degrees358.3 psig

0 Degrees358.3 psig

0 Degrees655.8 psig

0 Degrees655.8 psig


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.


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


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


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.


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


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


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


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


12

SAMPLE FILTERING

10:1128DEC2006

10:1104JAN2007

10:1111JAN2007

10:1118JAN2007


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


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)

GE Measurement & Control

1631 Bently Parkway South

Minden, NV 89423

+1 775.782.3611

www.ge-mcs.com/bently

©2015, General Electric Company. All rights reserved.

GER-4491C (01/15)

Documents

Valve Temperature Measurement for Reciprocating Compressors · For a suction valve, when the pressure inside the cylinder falls below the suction manifold pressure, the valve opens