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Proposed Vibration Monitoring And Analysis Engineering Essay

Vibration is a broad capable country that has continued to pull research over the old ages because of its import in about every aspect of daily life. From aircraft patterning to constructing design in temblor prone parts of the universe ; from plus status monitoring in assorted industrial workss to wheel reconciliation and alliance at the local auto garage, an application of the cognition of quiver rules can be observed.

The quiver of an object can merely be referred to as the oscillating motion of that object about a average equilibrium place.

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The gesture is brought approximately by the application of some force or excitement. Common illustrations of this phenomenon include the gesture of plucked guitar strings, the gesture of tuning forks, and the shaking felt at the station floor when a train base on ballss, the agitating observed on the route when a heavy truck base on ballss or the rattle of the route workers ‘ impact cock. Some quiver nevertheless is non every bit pronounced as the illustrations given. For case houses and Bridgess vibrate every bit good. Normally, these quivers can non be detected by simply looking. When the excitement is big plenty, the vibrational gesture can be seen and this would likely ensue in the prostration of the construction.

From the foregoing, it can be seen that some quiver is utile while some is destructive. The failure or devastation brought about by quiver is non an immediate 1. Vibration finally leads to a fatigue failure and this should be of involvement to the operators and upholders of works equipment.

For the care applied scientist or plus direction practician, these facts about quiver can be translated to intelligent and informed determinations for industrial workss. With legion different devices, quiver degrees on works equipment can be detected, measured and recorded. It is possible to analyze the informations collected to find the status of an plus and even predict an at hand failure. All revolving or stationary works equipment have acceptable quiver degrees stipulated by criterions such as the International Organization for Standardization ( ISO ) Codes or developed in-house by Vibration Monitoring Engineers. A divergence from the acceptable quiver degrees is an indicant of the oncoming of impairment which is unwanted. This cognition gives insight into the existent status of a piece of equipment, eliminates guessing and enables the care applied scientist to be after a fitting response to the plus ‘s impairment. Such control and planning can take to a immense economy in care costs, prevent unneeded downtime, better safety and public presentation for any plus.

Furthermore, quiver monitoring and analysis incorporates some advanced techniques for the find of the root cause of frequent machinery failures. Using these techniques can intend the difference between changeless dislocations and good plus handiness.

It is the aim of this study to supply a clear cut proposal as to how to work out the job of the frequent failures of the Yoho High Pressure ( H.P. ) Flare Scrubber Pumps by the application of these advanced quiver analysis techniques and besides supply a method for supervising the status of the pump to pre-empt any impairment that can jump surprises. This will guarantee a decrease in present care costs and relieve the work load of care forces whose clip is tied up with the attention of these pumps.

Case Study and job Description

The Yoho H.P. Flare Scrubber pumps are perpendicular, turbine, submerged pumps that transfer cured liquids from the Flare Scrubber vas to the chief petroleum oil production heading on the Yoho offshore oil and gas installing. The pumps are submerged in barrels that receive provender from the H.P. scrubber vas by gravitation. The cured liquid is a mixture of H2O and light petroleum oil. There are three pumps on skid and these pumps are critical to works operations. One pumps runs at a clip and an extra pump or the other two pumps can be put in service, if the demand arise due to an increasing degree of liquid in the H.P. Flare Scrubber. In the event of an outage of all three pumps, the works could lose production to the melody of one hundred 1000 barrels of rough oil per twenty-four hours ( 4100 barrels/hour ) .

The pumps were commissioned in 2006 at works start-up and hold had legion failures since. They have proven undependable and soon a contractor ‘s pumps ( which are portable and of a different design ) , are relied upon to execute their map. There have been occasions when all three pumps are in a province of disrepair.

These pumps normally run swimmingly for a piece and so go noisy, vibrate and eventually neglect. After a pump fails, it is taken out of the hole, sent to the shore-base for fix, sent back to the platform for reinstallation and so reinstalled. Probes of the legion failure instances reveal that the pump bearings, riser line drives and bushings have worn out given room for shaft drama, impeller harm and mechanical seal failure. Installation, fix and rebuild processs have been scrutinized and checked for quality. This has non yielded any dividends nevertheless, as the pumps maintain neglecting after two or three months in service.

Fig. 1. overleaf shows a cut-away subdivision of the pumps. The diagram is supplied by the makers but is simplified as the existent H.P. Flare Scrubber pump has six impellers, a top column of 11inches length, two intermediate columns of 30 inches length, a bottom column of 30 inches length, and a pump bowl assembly of 36.25 inches length.

The length of the pumps makes it hard for remotion and installing and as such care practicians, works operators and works direction have been invariably distressed by the frequent failure of these pumps.

Fig. 1. Gould Pump Model VIC-T ( beginning ITT-Gould Product catalogue, [ online ] www.gouldspumps.com/pump_VIC.html [ Accessed 6th May 2010 ]

Pump Specification

Manufacturer: ITT-Gould

Head shaft Length: 129 Inchs

Head shaft Diameter: 1 Inch

Seal Method: Mechanical Sealing wax

Drive: 40 HP Electric Motor

Differential Pressure: 200 Pounds per square inch

Capacity: 180 Gallons per Minute

Revolutions per minute: 3000

Impeller: 5 Weathervanes, Enclosed

Failure and Maintenance History

The tabular array below shows the failures and some care activities performed on the three H.P. Flare Scrubber Pumps over a biennial period. The rows 69, 71, 72, 90,91,97,98,102,103 and 110 show times when none of the three pumps were operational. The cost of this inaccessibility of the pumps is multiplex. It ranges from the loss of production of about one hundred 1000 barrels of rough oil per twenty-four hours, to punishments for non-compliance with environmental ordinances and most significantly, safety.

Signal-to-noise ratio

Date

EVENT/ACTIVITY

EQUIPMENT TAG

NO. OF PUMPS AVAILABLE

COMMENTS/ FINDINGS

1

11-Jan-06

HP Flare Scrubber Pump B Auto Operation job

YP-G-180

3

A

2

12-Jan-06

Trouble-shooting of LSLL-6207 on HP Flare Scrubber

YP-G-180

3

A

3

1-Mar-06

PM on HP Flare Scrubber Pumps A and B

YP-G-180A/B

3

A

4

11-Mar-06

Pumps Operation Started

YP-G-180A/B /C

A

Earliest recorded day of the month of petroleum and produced H2O motion with YP installations

5

5-Jun-06

Test-run HP Flare Scrubber Pump C with quiver group, QIT to find cause of inordinate quiver

YP-G-180C

3

Expecting consequence

6

7-Jun-06

Investigating cause of inordinate quiver on HP Flare Scrubber Pump C

YP-G-180C

3

Vibration traced to damaged Mech. Sealing wax

7

9-Jun-06

Removed HP Flare Scrubber Pump C for fixs

YP-G-180C

2

A

8

9-Jun-06

Unblocked strainers on HP Flare Scrubber Pumps A & A ; B

YP-G-180A/B

2

A

9

12-Jun-06

Rectified hapless discharge and noisy operation on HP Flare Scrubber Pumps A & A ; B

YP-G-180A/B

2

A

10

19-Jun-06

PM on HP Flare Scrubber Pump A

YP-G-180A

A

A

11

3-Jul-06

Completed installing of HP Flare Scrubber Pump C

YP-G-180C

3

A

12

4-Jul-06

Removed HP Flare Scrubber Pump B for fixs in QIT

YP-G-180B

2

A

13

15-Jul-06

Remove and clean HP Flare Scrubber Pump C suction strainer

YP-G-180C

2

A

14

12-Aug-06

Remove and clean HP Flare Scrubber Pump C suction strainer

YP-G-180C

2

A

15

24-Aug-06

Remove and clean HP Flare Scrubber Pumps A & A ; C suction strainer

YP-G-180A/C

2

A

16

27-Aug-06

Rigged out HP Flare Scrubber Pump A and transferred to lading bay

YP-G-180A

1

A

17

30-Aug-06

Rigged in HP Flare Scrubber Pump B after QIT fixs

YP-G-180B

2

A

18

2-Sep-06

Removed shaft matching on HP Flare Scrubber pump B, removed motor and installed motor from pump Angstrom

YP-G-180A/B

2

Electricians look intoing high electromotive force on motor

19

3-Sep-06

Transfer motor, pump and all associated parts from YP-G-180B to G-180A

YP-G-180A/B

1

A

20

4-Sep-06

Installed pump caput, motor and shaft hub on HP Flare Scrubber Pump A

YP-G-180A

1

A

21

5-Sep-06

Carried out matching runout cheques, impeller lift ( Reinstallation ) on pump Angstrom

YP-G-180A

2

A

22

8-Sep-06

PM on HP Flare Scrubber Pump C

YP-G-180C

2

A

23

11-Sep-06

Remove and clean HP Flare Scrubber Pump C suction strainer

YP-G-180C

2

A

24

29-Oct-06

Bleed off gas from HP Flare Scrubber Pump C suction and discharge line

YP-G-180C

2

A

25

12-Nov-06

Replacement of Mech. Seal on Pump C

YP-G-180C

1

A

26

13-Nov-06

Removed HP Flare Scrubber Pump C for fixs in QIT

YP-G-180C

1

A

27

28-Nov-06

Reinstallation of Pump C

YP-G-180C

1

A

28

2-Dec-06

Completed installing of HP Flare Scrubber Pump C and test-ran it.

YP-G-180C

2

A

29

21-Dec-06

PM on HP Flare Scrubber Pumps A and C

YP-G-180A/C

2

A

30

6-Feb-07

Commenced installing of pump B

YP-G-180B

2

A

31

7-Feb-07

Continued installing of pump B

YP-G-180B

2

Expecting Mech. Sealing wax

32

24-Apr-07

Installation of Mech. Seal on Pump B

YP-G-180B

2

A

33

25-Apr-07

Completed Mech. Seal Installation of Pump B

YP-G-180B

3

A

34

28-Apr-07

Troubleshoot overload trip mistake on Pump B

YP-G-180B

3

A

35

30-Apr-07

Rechecked alliance of Bump B

YP-G-180B

3

A

36

1-May-07

Rectified overload trip on Pump B- cleaned recess strainer

YP-G-180B

3

Discharge line was filled with sand and sludge

37

14-May-07

Mech. Seal replacing on Pump C

YP-G-180C

2

Shaft worn around Mech Seal

38

15-May-07

Rigged out HP Flare Scrubber Pump C for fix at QIT

YP-G-180C

2

A

39

27-May-07

Troubleshoot high quiver on Pump B

YP-G-180B

2

A

40

30-May-07

Removed HP Flare Scrubber Pump B for fixs in QIT

YP-G-180B

1

A

41

1-Jun-07

Assessed stuffs for stiff valves associated with pumps

YP-G-180A/B /C

1

A

42

3-Jun-07

Reinstallation of Pump C

YP-G-180C

1

A

43

6-Jun-07

Completed Pump C Installation

YP-G-180C

2

A

44

7-Jul-07

Reinstallation of Pump B

YP-G-180B

2

A

45

10-Jul-07

Completed Pump B Installation

YP-G-180B

3

A

46

13-Jul-07

Troubleshoot frequent tripping of Pump B

YP-G-180B

3

Electric motor job. This was fixed

47

21-Jul-07

Rigged out HP Flare Scrubber Pump A and transferred to lading bay

YP-G-180A

2

A

48

22-Jul-07

Rigged out HP Flare Scrubber Pump B and installed in A barrel

YP-G-180A/B

1

Pump B becomes Pump A

49

23-Jul-07

Alliance and commissioning of Pump A

YP-G-180A

2

A

50

26-Jul-07

Remove and clean HP Flare Scrubber Pumps A & A ; C suction strainers

YP-G-180A/C

2

A

51

10-Aug-07

Rigged out HP Flare Scrubber Pump A and transferred to lading bay

YP-G-180A

1

A

52

17-Aug-07

Commenced installing of pump Angstrom

YP-G-180A

1

A

53

18-Aug-07

Continued installing of pump Angstrom

YP-G-180A

1

A

54

22-Aug-07

Alliance and commissioning of Pump A

YP-G-180A

2

A

55

11-Sep-07

PM on HP Flare Scrubber Pump A

YP-G-180A

2

A

56

17-Oct-07

Removal and resettlement of Pump A to Pump B barrel

YP-G-180A/B

2

Pump A becomes B

57

21-Oct-07

Investigate low discharge force per unit area on Pump B

YP-G-180B

2

A

58

22-Oct-07

Replacement of Mech. Seal on Pump C

YP-G-180C

2

A

59

23-Oct-07

Rigged out HP Flare Scrubber Pump B and transferred to lading bay

YP-G-180B

1

A

60

24-Oct-07

Rigged out Pump A barrel for leak fixs by FMS

YP-G-180A

1

A

61

25-Oct-07

Rigged in Pump A barrel after leak fixs by FMS

YP-G-180A

1

A

62

28-Oct-07

Commenced installing of pump Angstrom

YP-G-180A

1

A

63

29-Oct-07

Completed installing of pump Angstrom

YP-G-180A

2

A

64

31-Oct-07

Remove stiff hub from Pump B Motor

YP-G-180B

2

A

65

3-Nov-07

Remove Motor to W/Shop to bore and tap broken bolts of Motor Fan Cover

A

2

A

66

29-Dec-07

Remove damaged pump C and commenced installing of refurbished pump

YP-G-180C

1

A

67

30-Dec-07

Rig out Pump C due to miss of keyway on shaft

YP-G-180C

1

A

68

1-Jan-08

Transferred bad pump to lading bay for QIT W/Shop

A

1

A

69

8-Jan-08

Removed HP Flare Scrubber Pump A for fix in QIT

YP-G-180A

0

A

70

9-Jan-08

Installed Flare Scrubber Pump A

YP-G-180A

1

A

71

10-Jan-08

Removal of Pump A

YP-G-180A

0

Pump stiff.

72

12-Jan-08

Commenced installing of pump Angstrom

YP-G-180A

0

A

73

13-Jan-08

Completed installing of pump Angstrom

YP-G-180A

1

A

74

27-Jan-08

Rigged in Pump B and commissioned same

YP-G-180B

2

A

75

4-Mar-08

PM on HP Flare Scrubber Pumps A & A ; B

YP-G-180A/B

2

A

76

13-Apr-08

Removal and resettlement of Pump A to Pump C barrel

YP-G-180A/C

1

Pump A barrel leaking petroleum from cut bleed line. Pump A becomes C

77

14-Apr-08

Commenced installing of pump C

YP-G-180C

1

A

78

15-Apr-08

Completed installing of pump C

YP-G-180C

2

A

79

17-Apr-08

Rigged out HP Flare Scrubber Pump B and transferred to lading bay

YP-G-180B

1

A

80

A

A

A

A

A

81

18-Apr-08

Removal of dust from Pump barrel

YP-G-180B

1

A

82

21-Apr-08

Commenced installing of pump B

YP-G-180B

1

A

83

22-Apr-08

Completed installing of pump B

YP-G-180B

2

A

84

9-May-08

Commenced set uping out Pump C

YP-G-180C

1

A

85

10-May-08

Completed set uping out Pump C

YP-G-180C

1

A

86

17-May-08

Commenced installing of pump C

YP-G-180C

1

A

87

18-May-08

Completed installing of pump C

YP-G-180C

2

A

88

20-May-08

Rectified failure to raise on Pump B

YP-G-180B

2

A

89

23-May-08

Rigged out HP Flare Scrubber Pump B for QIT fixs

YP-G-180B

1

A

90

26-May-08

Rigged out HP Flare Scrubber Pump C for QIT fixs

YP-G-180C

0

A

91

27-May-08

Commenced installing of pump B

YP-G-180B

0

A

92

28-May-08

Completed installing of pump B

YP-G-180B

1

A

93

13-Jun-08

Commenced installing of pump C

YP-G-180C

1

A

94

14-Jun-08

Completed installing of pump C

YP-G-180C

2

A

95

17-Jun-08

Rigged out HP Flare Scrubber Pump B for QIT fixs

YP-G-180B

1

A

96

17-Jun-08

Troubleshoot failure to raise on Pump C

YP-G-180C

1

A

97

18-Jun-08

Rigged out HP Flare Scrubber Pump C for QIT fixs

YP-G-180C

0

A

98

20-Jun-08

Commenced installing of pump B

YP-G-180B

0

A

99

21-Jun-08

Completed installing of pump B

YP-G-180B

1

A

100

22-Jun-08

Reconfirmed Pump B alliance

YP-G-180B

1

A

101

24-Jun-08

PM on HP Flare Scrubber Pump B

YP-G-180B

1

A

102

26-Jun-08

Rigged out HP Flare Scrubber Pump B for QIT fixs

YP-G-180B

0

A

103

30-Jun-08

Commenced installing of pump B on freshly designed base

YP-G-180C

0

FMS welding / design inaccurate. Pump pulled out to C-Barrel

104

1-Jul-08

Completed installing of pump C

YP-G-180C

1

A

105

5-Jul-08

Swapped Barrel B to ‘A ‘ Position

YP-G-180A

1

A

106

11-Jul-08

Investigated unusual noise on Pump C

YP-G-180C

1

A

107

22-Jul-08

Worked with FMS to measure alteration of Pump bases

YP-G-180A/B /C

A

A

108

26-Jul-08

Installed pump Angstrom

YP-G-180A

2

A

109

29-Jul-08

Removed pump C

YP-G-180C

1

A

110

31-Jul-08

Commence remotion of Pump A

YP-G-180A

0

A

Fig.2. Failure and Maintenance Summary for H.P. Flare Scrubber Pumps, YP

Literature Review

Graham and Nurcombe ( 2003 ) , observed that many perpendicular submergible pump failures happen instead out of the blue, without due warning and rough economic climes and competition has become an inducement for equipment operators to want to acquire the best service out of their equipment. This translates to higher life anticipation with works equipment and as such status supervising engineerings such as Vibration, Lubricant and Exhaust gas analyses have become really popular to forestall unwanted and unplanned machinery outages. Of the afore-mentioned techniques, Vibration analysis they say, is likely the most of import because of its proved efficaciousness and global credence in many industries.

In a instance history of submergible pumps at Saudi Aramco, they highlighted the demand to cognize the status of the pump internals which were submerged in liquid and are normally without status monitoring. ISO codes specify that bearings be monitored but this is non straight done for submerged pumps because the bearings are usually unaccessible. Alternatively, ISO allows measurings to be taken from the accessible parts of the machine i.e. from the Electric motor and the downside of this is that plentifulness of quiver information gets losing or attenuated. A batch of the mistakes associated with perpendicular submergible pumps nevertheless arise from those unaccessible places e.g. cavitation, flow induced quiver etc. , and as such supervising the status of the submersed parts straight provides a valuable beginning of information for predictive and diagnostic steps that can do large cost nest eggs for equipment operators.

They have developed and tested transducers and quiver monitoring equipment which can be used to straight acquire information from the submerged pump parts.

It is non plenty merely to supervise the quiver status of these pumps nevertheless. The job at manus is that of the frequent failures of the H.P. Flare Scrubber pumps from the very clip they were commissioned. Installing the submergible quiver monitoring devices would decidedly assist to foretell the failures but would make nil to place the implicit in cause of the frequent failures. So, the failures might be predicted but would go on often however. The root-cause of these failures demands to be identified so that a permanent solution can be developed. Vibration analysis besides makes this possible.

Sinha ( 2008 ) shows that site installing of machines has effects on their quiver and dynamic features, even when they are good designed. He points to the fact that many freshly installed machines vibrate severely and neglect often merely as has been described in the debut and in the care history of the H.P. Flare Scrubber pumps. Hence it is of import to decide any machine installing jobs if equipment handiness is desired. A quiver analysis and dynamic word picture technique known as Modal Testing can be used to uncover the natural frequences of the machine installing assembly and the operating velocity checked to see if near to any of the natural frequences. Operating machines at velocities at or shut to structural natural frequences brings about resonance which is seen as inordinate quiver. This trial makes it possible to place the right places on the construction to use stiffening in order to cut down quiver by modifying the structural natural frequences. He gave some illustrations were these had been done successfully to extinguish frequent machinery failures.

DeMatteo ( 2001 ) presents a instance survey of how the quiver analysis methods of Modal Testing and Operating Deflection Shape have been used to work out the job of inordinate quiver on perpendicular pumps which are similar to the H.P. Flare Scrubber pumps.

A common yet enfeebling mistake for these pumps is cavitation. A mentioned earlier, it occurs at the submersed parts of this pump where there is no status monitoring as of the present. Cavitation is a phenomenon that takes topographic point in these kinds of pumps when the impact of a fall ining vapor of the fluid been pumped causes harm to the impellers and other pump internals. Vapour-bubbles can be formed within the wired fluid at low force per unit area pump internals as a consequence or restricted suction, fluctuating liquid degrees of the H.P. Flare Scrubber vas etc. When these bubbles move on to higher force per unit area countries within the pump, they collapse and cause harm to the pump. Wilcoxon Research says that, “ The prostration of the bubbles is a violent procedure that creates an impacting action inside the pump. This impact will excite high frequence resonances in the pump construction. ” For this ground, they advocate the usage of quiver detectors in pumps. Cernetic ( 2009 ) says in the same vena, that quiver signals should be used to observe cavitation at the early phases of development since this phenomenon causes pump harm and a decrease in efficiency.

From the foregoing, the instance for forestalling failures is being made and the demand for Condition Based Maintenance ( CBM ) emphasised. Prickett and Eavery ( 1991 ) compared preventative care and Breakdown care with CBM. CBM is shown to be cheaper and as such is required for the H.P. Flare Scrubbers if concern profitableness and equipment handiness are desired.

Overview of Proposed Vibration Monitoring and Analysis Based Solution to Frequent Failures

First and first, it must be ascertained that the site installing of the three pumps is non doing any quiver jobs. The Vibration analysis techniques of Modal Testing and Operating Deflection Shape are proposed for usage to find the root-cause of the frequent failures. Modal proving on the one manus would demo structural natural frequences, node points and manner forms for the three pumps. The manner form is the warp of the construction at any natural frequence. This information would assist to find: if operating velocity is perilously close to the structural natural frequences, the dynamic feature of the construction and the points of least or no warp on the construction ( nodes ) – where supports or stiffening may be added in order to relieve quiver degrees. The Impact cock method shall be used to transport this trial out, in situ.

The Operating Deflection Shape ( ODS ) on the other manus, would as the name implies show the warp of each pump construction at the operating frequence of 50Hz ( 3000RPM ) . In other words, the ODS would demo the consequence of the operating velocity on assorted parts of the construction and it can be seen if points on the construction vibrate in stage or non. Should parts of a construction non travel in stage with the other parts, destructive burden can happen which can give rise to frequent failures.

Transporting out these trials as mentioned above would place jobs with the installing. Solving the installing jobs would extinguish the frequent failures. The solution as mentioned earlier, normally involves the application of supports in identified places or the stiffening of bing supports.

After the installing jobs are taken attention of, it is proposed that for good mounted quiver detectors are put in topographic point. For the open parts of the pump assembly i.e. the electric motor, it is proposed that two accelerometers be mounted at each of the antifriction bearing lodging countries. The accelerometers would be stud mounted at each bearing lodging at right angles apart. Having these accelerometers installed in add-on to the analysis of the generated signals would do it possible to observe bearing mistakes at their incipient phases, such that something could be done to forestall a more dearly-won harm to the whole pump assembly.

As for the submersed parts of the pump, i.e. the journal bearings, the shaft, the impeller/bowl assembly, the Bently Nevada designed submergible propinquity investigations are proposed for usage to supervise the quiver and give diagnostic and prognostic capablenesss for such mistakes as cavitation, impeller harm, weariness shaft cleft, instability etc. , which are the common mistakes of machinery such as these and can merely be detected by submersed detectors. Understanding what goes on in the pump hole is critical to maintaining the pump healthy. For case cavitation can be detected on clip with these investigations, procedure conditions changed and the dependability of the pumps maintained. The quiver information collected by these detectors would be analysed and used to do quality determinations sing the needed care responses. Analysis techniques would include frequence spectrum analysis, envelope analysis, polar secret plans, orbit secret plans etc.

This three prong attack is strongly believed to extinguish the frequent failures, cut down the overall care costs and assist in guaranting the handiness of the three H.P. Flare Scrubber Pumps.

The techniques shall be expounded in more item within this study and all the necessary tools and quiver signal processing methods shall be specified.

In-Situ Modal Testing for the Pumps

This quiver trial is to uncover any jobs with the installing of the pumps which might be responsible for the frequent failures experienced within the past few old ages. In this trial, the natural frequences, manner form and nodes will be determined for each pump construction.

An instrumented cock would be used to provide impact or energy to each construction at a known frequence and responses measured. When there is resonance, elaboration would be seen in the response spectrum. A Frequency Response Function ( FRF ) is obtained utilizing the force and the response spectra. The response can be represented as:

FRF= = A + J B

Where A= Real Part, B= Imaginary Part and Phase =

At Resonance, the exciting frequence from impact cock = Natural Frequency of Pump Structure.

A 0, B gives the Mode Shape, and Phase 90A°

The computations are performed and graphs displayed by the FFT ( Fast Fourier Transformation ) Analyzer as shown below.

Fig. 3. Time sphere and frequence sphere signals. ( Beginning: M14 Lecture Notes, 2010, MSc Maintenance Engineering and Asset Management, University of Manchester )

The FRF shows frequence extremums which may or may non be structural natural frequences. However, for the structural natural frequences, the relationships shown supra would all use. The existent portion of the curve ( A ) would go through through nothing and the stage would alter by 90A° . The fanciful portion of the FRF gives the manner form.

So, the needed equipment for the unmoved average testing of the pump constructions are as follows:

Some accelerometers positioned along points on a pump construction ( accelerometers can be secured by magnetic agencies )

An instrumented cock

An FFT Analyzer

Cable connexions for cock and accelerometers to analyzer

Post Processing Software.

The diagram below shows the layout for the trial. The instrumented cock is used to excite the pump construction and the responses taken from the measuring points and analysed to give all the information required i.e. manner form, nodes and natural frequences.

Fig.4. Schematic of Vertical Pump Impact Test

Fig. 5. Impact Test and Modal parametric quantities ( beginning: Richardson M.H. ( 1997 ) , “ Is It a Mode Shape, or an Operating Deflection Shape ” , Sound and Vibration Magazine, 30th Anniversary Issue. )

Fig.6. Mode shapes from Imaginary Part of FRF ( beginning: Richardson M.H. ( 1997 ) , “ Is It a Mode Shape, or an Operating Deflection Shape ” , Sound and Vibration Magazine, 30th Anniversary Issue. )

Fig.7. Example of manner form obtained from pump modal proving. ( Beginning: Sinha J.K. , ( 2008 ) , “ Vibration-based Diagnosis Techniques Used in Nuclear Power Plants: An Overview of Experiences ” , Nuclear Engineering and Design, Elsevier B.V. , Volume 238, Issue 9, pp. 2439-2452.

From the attendant manner forms and ascertained natural frequences, penetration can be obtained as to the exact places for stiffening application or mass remotion in order to alter the natural frequences. Experience has shown that resonance in these kind of instances is due to the intimacy of the operating velocity ( runing frequence or 1x ) or multiples thereof, to one or more structural natural frequences. For the pump described in fig.7. above, the job was solved welding a thick home base to the stool in order to stiffen it and by put ining extra u-bolts on the discharge line.

Operating Deflection Shape

The Operating Deflection Shape ( ODS ) merely shows how much the pump construction is traveling at a peculiar frequence ( most significantly, the normal runing velocity ) and how much difference there is in stage between different points of the pump construction as it operates.

The set-up is merely as was used for the average testing. The difference nevertheless, is that the instrumented cock is non used to excite the construction. Alternatively the machine would be run at its normal operating velocity and quiver informations collected from the accelerometers is fed to the multi-channel analyser. The end product from the analyser is so fed into the computing machine which would hold installed specializer package for ODS show. The show would demo the existent quiver form of the construction. It would be clearly seen, if the pump construction is flexing, if parts are traveling out of stage with one another etc. It would be seen if any status exists which contributes to frequent failures.

Fig.8. Example of Software Animation of ODS FRF informations. ( Beginning: Richardson M.H. ( 1997 ) , “ Is It a Mode Shape, or an Operating Deflection Shape ” , Sound and Vibration Magazine, 30th Anniversary Issue. )

It is proposed that both Modal Testing and ODS analysis be carried out by contractors who are specializers in the country of survey and have a proved path record of success.

Proposed Permanently Mounted Vibration-based Condition Monitoring System

Fig.9. Set-up of Proposed Permanently mounted quiver monitoring system for the H.P. Flare Scrubber Pumps ( Influenced by Fig.5. , Graham K.M. and Nurcombe B. , ( 2003 ) , “ Vertical Water Pumps- What ‘s Happening Down The Hole ” , Orbit Magazine, 1Q 2003, pp. 4-9 )

Fig. 10. Orthogonally mounted propinquity investigations [ on-line ] Available from: hypertext transfer protocol: //zone.ni.com/reference/en-XX/help/372416A-01/svtconcepts/obt_tbs_shctln/ [ Accessed 6th May 2010 ]

The proposed for good mounted quiver monitoring and analysis system for each pump would hold the followers:

Four Bently Nevada 330400 Accelerometers mounted as shown on the diagram

Four 3300XL 8mm submerged Proximity Probes mounted in Custom Housings ( two each for two different journal places along shaft length )

A Bently Nevada 1900/65 General Condition Equipment Monitor

A tacho-sensor for shaft place mention ( from any reputable manufacturer- Bently Nevada, SKF, Endevco )

and,

A laptop with the Bently Nevada System 1 version 6.5 Diagnostic package installed for the analysis of information collected by any of the proctors.

The accelerometers would be used to mensurate the quiver degrees of the anti-friction bearings on the pumps ‘ electric motors while the submersed propinquity investigations would mensurate shaft quiver, within the impeller shell and intermediate columns. All the transducer information would be collected by the 1900/65 proctor for each equipment. The proctors are designed for uninterrupted monitoring and readouts from them can be checked from clip to clip by dedicated forces or works operators.

Besides, these proctors have the capableness of being tied into bing works control systems such that quiver warning degrees and danger bounds for each pump can be announced in control suites via hearable dismaies or visible radiations when these degrees are breached. Additionally, there is the capableness to configure trips and closures in the instance of high quiver degrees occasioned by mistakes such as cavitation. The proctors can be installed near to the equipment in sheltered enclosures, utilizing a short overseas telegram tally. The System 1 package is capable of advanced quiver analysis through the usage of shows such as Bode Plots, Spectral shows, Polar secret plans, Envelope analysis, etc. It is besides capable of informations acquisition and storage which makes swerving possible. Detailed specifications for the assorted equipment are supplied in the appendix.

Signal Conditioning and Processing

As is good known, the end product from the accelerometers and propinquity investigations are linear and clip sphere signals. These have to be converted to digital end products and frequence sphere signatures for mistake diagnosing to be carried out. This is achieved by the Fast Fourier Transformation ( FFT ) algorithm. Analyzing the frequences shown in a spectrum is indispensable for understanding implicit in machinery mistakes, as certain mistakes have distinguishable frequence features. For case, pump revolving velocity would be shown in the frequence spectrum and mistakes on the shaft could be presented as multiples of revolving frequence. The Bently Nevada 1900/65 proctor and System 1 package facilitate this.

Fig. 11. Time sphere and frequence sphere signals. ( Beginning: M04 Lecture Notes, 2010, MSc Maintenance Engineering and Asset Management, University of Manchester )

The quiver measuring devices have been chosen carefully to understate the noise and unwanted intervention to measuring signals. The Bently Nevada 1900/65 has the capableness for low base on balls filtering and high base on balls filtering and these can be configured to accommodate user demands. This helps to extinguish the aliasing consequence and other instrument related noise. ( See merchandise specification sheet in appendix for inside informations ) .

There is besides the capableness for envelope analysis by the usage of criterion or enhanced demodulation. This is supported by proctor and analysis package and is peculiarly utile for the early sensing of mistakes on the electric motor anti-friction bearings.

Diagnosis Software Display Plots and Uses

The following show some of the show plots that can be generated by the diagnostic package:

Bode

Performance map

Rotor stator profile

Rotor form

Hydro air spread

Phasor

Histogram

Octave

Casacade/Full Casacade

Current values

Bar graph

Machine train diagram

Alarm/System event list

Trend / Multivariable tendency

Tabular list

Time base ( with option for superposition

of baseline informations )

Orbit / Time base ( with option for

superposition of baseline informations )

Orbit ( with option for superposition of

baseline informations )

Shaft mean center line

Spectrum / Full spectrum ( with option

for superposition of baseline informations )

Ten vs. Y

Waterfall / Full waterfall

Polar/Acceptance part

Of the list above, accents would be placed on the Bode, Polar, Orbit, Shaft mean centreline and Waterfall secret plans. These secret plans can be used during normal and transeunt machine conditions to expose the normally experient mistakes.

The Bode secret plan is really utile in placing the critical velocity ( natural frequence ) of a machine, as it shows the quiver behavior of the said machine during start-up or shut-down ( transeunt conditions ) .

Fig. 12. Bode Plot Example. [ Online ] Available from: hypertext transfer protocol: //zone.ni.com/reference/en-XX/help/372416A-01/svtconcepts/bode_polar_plots/ [ Accessed 6th May 2010 ]

The polar secret plan gives the amplitude of 1X ( machine RPM or runing frequence ) and its stage difference from the mention place. The amplitude and stage behaviors can be interpreted to existent equipment wellness or defect.

Fig. 13. Polar Plot illustration [ online ] Available from: hypertext transfer protocol: //zone.ni.com/reference/en-XX/help/372416A-01/svtconcepts/bode_polar_plots/ [ Accessed 6th May 2010 ]

The Orbit secret plan hints out how the shaft is revolving within the bearing. This tells how much clearance exists between shaft and bearing wall. This information is priceless as it can be used to find bearing load alterations and the oncoming of bearing wear.

Fig. 14. Orbit Plot illustration [ online ] Available from: hypertext transfer protocol: //zone.ni.com/reference/en-XX/help/372416A-01/svtconcepts/obt_tbs_shctln/ [ Accessed 6th May 2010 ]

The Shaft centreline secret plan is used in much the same manner as the orbit secret plan in that it can be used to state how much wear has happened within a bearing. The secret plan checks the concentricity or eccentricity of shaft running within a diary bearing, as the name implies.

Fig. 15. Shaft Centerline secret plan illustration [ online ] Available from: hypertext transfer protocol: //zone.ni.com/reference/en-XX/help/372416A-01/svtconcepts/obt_tbs_shctln/ [ Accessed 6th May 2010 ]

The Waterfall secret plan is utile during the transeunt machine operations. It shows how frequency constituents such as 1X, 2X, 3X etc alteration with clip or any other variable. The information obtained can be used to do good judgements as to existent machine conditions.

Fig. 16. Waterfall plot illustration [ online ] Available from: hypertext transfer protocol: //integratedpro.com/content/ ? p=1114 [ Accessed 6th May 2010 ]

Diagnosis Chart

Mistake

Steady province Characteristic

Transient State Characteristic

Shaft hang-up

0.3 X shown in frequence spectrum,

Funny Orbit secret plan forms and discontinuities thereof.

Imbalance

Merely 1X is seen in frequence spectrum, 1X additions with clip and the Phase angle alterations

Bode Plot remains the same, There is no alteration in critical velocity or stage angle when compared with the healthy status.

Misalignment ( or Preload in the instance of unstable bearings )

1X,2X,3X,4X etc are shown in frequence spectrum, Phase angle remains changeless

The orbit secret plan will non change with velocity and polar secret plan remains the same.

Crack

1X, 2X, 3X, 4X etc are shown in frequence spectrum and these continually alteration in amplitude. The stage angle alterations every bit good.

There is amplitude and phase alteration of 1X constituent in the polar secret plan,

The orbit secret plan alterations from a figure eight form to a cringle incorporating a little cringle.

Bend

Merely 1X is seen in frequence spectrum, 1X additions with clip and the Phase angle alterations

A signal alteration of stage takes topographic point at critical velocity.

Mechanical Diarrhea

Presence of 0.3X, 0.5X, 1X,1.5X,2x, 2.5X in frequence spectrum

Motor Bearing Damage

Bearing Characteristic Frequencies would be seen in spectrum

Fluid induced instability

The presence of 0.45-0.48 X in spectrum when fluid natural frequence is approached by circumferential velocity of fluid, stand foring Oil Whirl.

The presence of 0.45-0.48 X in spectrum when fluid natural frequence is approached by circumferential velocity of fluid, stand foring Oil Whirl

Oil Whip consequences when Pump System rotor natural frequence peers fluid ‘s.

Fig. 17. Diagnosis Chart for common mistakes ( Beginning: Sinha J.K. , M14 Lecture notes 2010, MSc Maintenance Engineering and Asset Management, University of Manchester )

Fault Diagnosis Process

The overall quiver degrees measuring would be the first phase of protection for the pumps. The ISO recommends the usage of RMS values of speed for overall quiver measuring. Limits for acceptable quiver would be set and configured into the Bently Nevada 1900/65 proctors in footings of Velocity ( RMS ) . These proctors can denote when the bounds have been breached and this would motivate farther probe and trials. These bounds can be obtained from ISO tabular arraies or decided upon in-house by the care applied scientist. The proctor would demo which peculiar detector or detectors has detected a mistake.

Furthermore, the proctor and diagnosing package proposed are capable of informations acquisition and storage which make it possible for swerving. The tendencies would be observed hebdomadal and when a set quiver bound is approached, the frequence of review is increased and trials such as the 1s mentioned before can be carried out to determine the mistake type, so a fitting care response can be planned.

Fig. 18. Swerving illustration ( beginning: M04 CBM Lecture notes ( 2010 ) , MSc Maintenance Engineering and Asset Management, University of Manchester )

The mistake diagnosing chart would be used in concurrence with the FMEA diagram, 1900/65 proctor event logs and assorted applicable show secret plans ( frequence spectrum shows, Bode secret plan, Polar secret plan etc ) to corroborate the exact mistake of the pumps. Pump related frequences would be noted such that when they appear in the frequence spectrum, they can easy be identified.

FMEA, Symptoms of identified impairment mechanisms

Potential Failure Mode

Potential Effectss of Failure

Potential Failure Causes

Symptoms of identified impairment mechanisms

1

Antifriction Bearing mistake ( Electric motor )

Bearing Seizure, Misalignment,

Damage to motor shaft, Mechanical seal failure.

Poor lubrication, Resonance

High Frequency Hump seen in Frequency spectrum related to bearing lodging natural frequence

2

Shaft Cracks

Shaft Fracture, Loss of pump action

Resonance, Manufacturing defects

1X, 2X, 3X, 4X etc are shown in frequence spectrum. These addition in amplitude over clip.

3

Cavitation

Impeller Damage, Reduced end product, Pump loss.

Process disturbances, Gas lock in Pump Barrel

Noisy operation, High frequence extremums in spectrum

4

Imbalance

Excessive Vibration, B

Damage to bearings and Impellers, Pump loss.

Wear, Impeller harm

1x constituent in frequence spectrum which increases in amplitude over clip.

5

Journal Bearing Wear

Lateral shaft drama, Shaft harm

Matching misalignment

Noisy operation, Lateral shaft drama,

6

Impeller Damage

Reduced end product, Pump loss, Imbalance,

Improper assembly,

Cavitation, Flow-induced quiver

Blade Passing frequence nowadays in frequence spectrum ( 5X,10X etc )

7

Bent Shaft

Bearing harm, High quiver

Matching misalignment, Resonance

Axial quiver, 1X presence in frequence spectrum

8

Matching Misalignment

Resonance, Damage to pump internals, Mechanical seal failure, Loss of pump.

Improper assembly, Resonance

1X,2X,3X,4X etc are shown in frequence spectrum

9

Shaft hang-up

Damage to pump internals, Mechanical seal failure, Loss of pump.

Matching misalignment

0.3X, 0.5X presence in quiver spectrum secret plan

10

Diarrhea

Damage to pump internals, Mechanical seal failure, Loss of pump.

Resonance, Improper Assembly

The presence of 0.5X, 1X, 1.5X, 2X, 2.5X etc in frequence spectrum

Fig. 19. FMEA tabular array for pump and motor assembly.

Cost and Man-Power Implications of Vibration Monitoring and Analysis Set-up

The monetary values given are estimations based on monetary values obtained from assorted cyberspace shopping web sites. They are non unequivocal as Bently Nevada gives monetary values based on different functionality demands and applications worldwide.

Item

Measure required for all three pumps

Unit Price ( $ )

Price ( $ )

Accelerometer, Bently Nevada 330400

12

500

6000

Monitor, Bently Nevada 1900/65

3

2500

7500

Submersible Proximity investigations, Bently Nevada

12

1000

12000

Tacho Sensor, Bently Nevada

3

300

900

Laptop

1

1000

1000

System 1 Diagnostic Software Licence, Bently Nevada

1

20000

20000

Training for quiver applied scientist ( from bing care administration )

2500

Entire Price $ 49,900

Fig.20. Cost breakdown of needed equipment for for good mounted quiver monitoring and analysis system.

At lease one applied scientist with accomplishments for quiver monitoring and analysis would be required to supervise the whole set-up. He must be trained and competent in the usage of assorted show secret plans, signal processing and conditioning, for mistake designation and sensing.

This cognition can besides be used on other critical works equipment such as the gas turbines and the centrifugal gas compressor.

The dynamic word picture trials are to be contracted out to see service suppliers with the equal hardware and package for real-time life of vibrational gesture. It is estimated that the cost of this service would be circa $ 100,000. This brings the expansive sum of the proposed quiver programme from the frequent pump failures solution to for good installed status monitoring to about $ 150,000.

Benefits and Limits of the proposed Vibration-based Condition Monitoring System

The proposed set-up for monitoring and analyzing the quiver from the pumps has rather a figure of benefits.

From the concern point of position, it is an investing because it can forestall dearly-won failures. The dollar value of the pumps ‘ failure within the biennial period considered in this study easy exceeds $ 1million when fix costs, trim parts, logistics and man-hours expended are considered.

For the care administration, the presence of these vibration-based status monitoring equipment, makes it possible for care to be pro-active instead than reactive. Furthermore, frequent failures are eliminated which give room for better planning and more clip for effectual and efficient care.

The cost of the quiver monitoring and analysis equipment can be seen to be a little monetary value to pay for plus handiness, enhanced productiveness and even safety.

The restriction to the proposed system is the accomplishment, cognition and competency of the applied scientist or applied scientists who are in charge of the set-up. The signals for any mistake status would ever be picked up by the monitoring equipment. The proper and accurate diagnosing of mistakes and subsequent care determinations made are the remit of the applied scientist ( s ) responsible for the vibration-based status monitoring programme. In add-on, quiver monitoring equipment could neglect and necessitate replacing.

Decision

A glimpse through the summarised failure and care history of the H.P. flair scrubber pumps for a two twelvemonth period reveals the sum of resources expended on them and their hapless handiness. Clearly so, something new and different from the old attacks should be attempted.

This proposed system covers all the grounds- from installing jobs check, procedure vagaries that cause cavitation, to common mistakes experienced by revolving machines such as bearing defects and matching misalignments to advert a few.

Besides, the proposed methods are tested and trusted and can lend to nest eggs in care cost, works handiness and safety which are cardinal public presentation indexs for most industrial workss.

Appendix i- Bently Nevada 1900/65 Monitor

[ Online ] Available from: www.ge-energy.com/prod_serv/products/oc/en/bently_nevada.htm [ Accessed 6th May 2010 ]

Appendix ii- Bently Nevada 330400 Accelerometers

[ Online ] Available from: www.ge-energy.com/prod_serv/products/oc/en/bently_nevada.htm [ Accessed 6th May 2010 ]

Appendix iii- Bently Nevada System 1 Diagnostic Software

[ Online ] Available from: www.ge-energy.com/prod_serv/products/oc/en/bently_nevada.htm [ Accessed 6th May 2010 ]

Appendix iv- Vibration Severity Limits for Machines

Fig. 21. ISO 10816 Vibration Severity Limit Chart

Appendix v- Submersible Proximity Probes

[ Online ] Available from: www.ge-energy.com/prod_serv/products/oc/en/bently_nevada.htm [ Accessed 6th May 2010 ]

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