va example technical report

7/25/2019 VA Example Technical Report

1/14

Dynaseq Monitoring Group Greenfield Business Centre Greenfield Holywell Flintshire North Wales CH8 7GR

TEL: 01352 710600 FAX: 01352 710703 Email: [email protected] Web: www.dynaseq.co.uk

Vibration Analysis Report

AN Other Company Limited, Example Report:25th October 2011.

Report Content s):

Run Up/Coast Down Analysis on Calorifier Pumps

Details of Engineer, Site Representative and Report Author

Report Prepared By

Tony Riseley

Dynaseq Monitoring Group Phone+44 (0) 1352 710600Greenfield Business Centre Fax +44 (0) 1352 710703Greenfield, HOLYWELL Email [email protected]. North Wales. Web www.dynaseq.co.uk

Date of Survey(s):25th October 2011.

Our Reference Number:ANCL11-08.


2/14

Dynaseq Monitoring Group Greenfield Business Centre Greenfield Holywell Flintshire North Wales CH8 7GRTEL: 01352 710600 FAX: 01352 710703 Email: [email protected] Web: www.dynaseq.co.uk

2

Table of Contents

PART ONE: The Report Section

Introduction Page 3

Site details, diagrams and additional notes.

Run Up / Coast Down Analysis on Sensitising Calorifier Pumps Page 6

Site details, diagrams and additional notes.

PART TWO: Discussion

Conclusions Page 10

Advice and recommendations

Further Remarks Page 11

Basic concepts of vibration analysis and other details


3/14


3

Part

1Report Section

Introduction; Machine Listings; Site Details and Relevant Data

Introduction

Preface

A real-time run up/coast down analysis was requested by AN Other Company to investigate the vibration

levels occurring on the Sensitising P1023A and P1023B 82C Calorifier Pumps since installing a variable

speed drive (VSD) inverter on the installations.

The purpose of this survey was to determine if there were any significant increases in vibration amplitude

when operating at certain speeds, where an offset motor misalignment has been identified on regular

occasions during the routine condition monitoring inspections.

Machine Listings

The following machinery located within the Sensitising Plant at AN Other Company has been monitored during

the course of the survey as follows:-

(a) Ten individual horizontallymounted belt driven2.1b (Upper Plant Room) SensitisingBox Section

Fans, each of approximately 2920 RPM, 15 kW capacity and labelled consecutively from No. 1through to

No. 10and identified as follows: (i) K1102; (ii) K1107; (iii) K1103; (iv) K1108; (v) K1104; (vi) K1109; (vii)

K1105; (viii) K1110; (ix) K1106 and (x) K1111.

(b) One single horizontallymounted 2.1b (Upper Plant Room) SensitisingExtraction Fan, identified as:

K1118, of 960 RPM, 11.0 kW capacity.

(c) Two individual horizontallymounted belt driven2.1a Sensitising (Lower Plant Room) Main Conditioner

Fansas follows: (i) Main Conditioner Fan No. 1 K1101of 1460 RPM, 25 Hp capacity and (ii) AuxiliaryConditioner Fan No. 1 K1117of 1460 RPM, 22.0 kW capacity.

(d) Two identical horizontallymounted variable-speed, direct-coupled 2.1 a Sensitising (Lower Plant Room)

82 C Calorifier Pumps, identified as: P1023A and P1023B, each of 2950 RPM, 40 Hp capacity.


4/14


4

Data Collection

The machines were monitored using an SKF DC460 dual channeldigital FFT analyser which is a combined

portable data collector and sophisticated signal analyser, capable of detecting the following fault types:

bearing damage

lubrication problems

imbalance

positional misalignment

angular misalignment

loading anomalies

looseness

gearbox component wear/damage

conveyor belt tracking

resonance and structural related problems

foundation movement

coupling damage

excessive stress points

inadequate support

application problems

hysteresis whirl

faulty belt drives

The analysis conducted on site highlights any of the above fault types and on detection will be documented in

this report, stating the exact defect, cause and severity.


5/14


5

Spectrum Analysis: Description and Purpose

Before presenting this report in further detail, it may be necessary to explain some of the terminology used

when referring to the recorded spectra:

Velocity Spectrum

Velocityis movement expressed in terms of time and in our case, measured in mm/sec.. The ISO10816-3

vibration severity standardcategorises certain types of machinery (in accordance with capacity; rotational

speed and operating circumstances) into certain zonessuch as: Excellent; Acceptable; Unsatisfactory

and Unacceptable.

Acceleration Spectrum

Accelerationis the rate of change ofvelocity(in other words, movement per second per second) and is

measured in G. Acceleration is a high frequencyspectral signal relating to typical faults such as: bearing

fatigue; gear wear; complex or multiple component damage; excessive loading anomalies and aerodynamic

related problems on rotors or impellers.

Enveloped Spectrum

Envelopingis the relatively new technique, which filtersandprocessesthe normal high frequency

characteristics naturally produced by the combinedcomponents of a bearing. In the past, conventional

techniques only permitted the analysis of the overallsignal, which could actually indicate an array of anomalies

other than a bearing defect. This method became an increasingly unreliable and misleading technique,especially when levels began to rise - for example, it was impossible to distinguish between a genuinebearing

defect and a typical loading related problem.

When utilising the envelopingtechnique, the following processes take place:

The complexsignal is demodulatedby use of a band pass filtercentred on the resonant carrier waveform.

The entire process is enveloped(half wave rectified). The individualcomponents of a bearing such as faulty

inner/outer races; cages and rollers/balls are now detectable at specific frequencies.

The technique is particularly useful on slow running machinery (e.g., below 10 RPM) where conventional

methods fail to produce any relevant signals to analyse.

The investigation can now be classified into the following areas:

1. Site Details.

2. Vibration Measurements on the machines.


6/14


6

Run Up / Coast Down Analysis on Calorifier Pumps

Inspection of the Supporting Structure and Operating System

The Calorifier Pumps selected for monitoring appeared to be adequately placed upon suitable foundations and

supporting structures. Hence, the survey was primarily concerned with the vibration levels obtained from the

machine itself as opposed to foundations and structural related problems.

Run Up / Coast Down Analysis

During this particular test, the 2.1a Sensitising Plant 82C Calorifier Pumps P1023A and P1023B were allowed

to operate from standstill to full rotational speed (run up analysis) and from full speed down to standstill (coast

down analysis). The purpose of these tests was to highlight any shaft critical frequencies, random impacts

and/or other anomalies that can easily be missed using stationary signal analysis alone.

Data was collected in real-time at each of the following monitoring positions: (i) motor non drive end

(horizontal)and (ii) motor drive end (horizontal). It has long been suspected that these pumps have been

operating close to a shaft critical frequency since installing a pressure sensitive variable speed drive on each

installation, whereby an offset misalignment of the motor has been observed during the routine condition

monitoring surveys at approximately 81 - 85 % operating speed.

Figure 1:Photograph identifying the dual channel sensor locations on the

non drive endand drive endpositions of the 2.1a Sensitising Plant 82C

Calorifier Pump motor, using magnetic mounted accelerometers connected

to an SKF DC460 analyser.

The following results were obtained during the coast up analysis at 2x rotational frequency from the motor non

drive endand motor drive endbearings, all within the horizontalplane:-


7/14


7

Coast Up/Down Analysis Results on 2.1a Sensitising 82C Calorifier Pumps P1023A and P1023B

Freq. Pump P1023A Pump P1023B

Notes and observationsmtr-nde mtr-de mtr-nde mtr-de

Hz mm/s mm/s mm/s mm/s

73.4 2.73 2.63 1.36 2.49 Both motors operating normally

75 3 2.86 1.45 2.59 -

76.6 3.32 3.05 1.60 2.52 -

78.1 4.49 4.24 2.01 3.04 First observation of significant 2x rpm vibration on P1023A motor

79.7 7.12 6.71 2.42 3.75 P1023A motor now operating above ISO 10816-3 Unusable Zone

81.3 9.39 8.63 3.42 5.27 First observation of significant 2x rpm vibration on P1023B motor

82.8 7.32 6.66 4.86 7.51 Both P1023A & P023B operating above the ISO 10816-3 Unusable

84.4 4.99 4.65 6.61 10.2 Decreasing amplitudes on P1023A & increasing amplitudes on P1023B

85.9 4.36 4 7.15 10.9 P1023A Satisfactory Zone / P1023B Unusable Zone

87.5 3.57 3.12 6.19 9.32 P1023B continuing to operate in the ISO 10816-3 Unusable Zone

89.1 2.61 2.46 5.15 7.6 P1023B continuing to operate in the ISO 10816-3 Unusable Zone

90.6 2.61 2.36 4.22 6.1 P1023B operating in the ISO 10816-3 Unsatisfactory Zone

92.2 2.52 2.15 3.48 4.92 P1023B operating in the ISO 10816-3 Unsatisfactory Zone

93.8 2.17 1.79 2.87 3.95 Both motors operating normally

95.3 1.78 1.42 2.63 3.45 -

96.9 1.64 1.33 2.43 3.21 -

98.4 1.40 1.19 2.18 2.83 -

Table 1:Table 1 identifying potential shaft critical frequencies (measured in Hz) and velocity amplitudes (measured in mm/sec. RMS) during the

run up / coast down analysis conducted on the motor non drive end and motor drive end monitoring positions of the Sensitising 2.1a 82C

Calorifier Pumps P1023A and P1023B. The dark green, light green, yellow and red boxes correspond with the ISO Vibration Severity Standard:

10816-3 Group 3 (15 kW300 kW pump with external driver rigid mount) ratings of: Excellent, Satisfactory, Unsatisfactory and Unusable

consecutively.

As observed in the table above, there is a potential shaft critical zone between the operating speed of 2351 -

2490 rpm (79.7% - 84.4% running speed) occurring on Pump P1023A and 2399 - 2720 rpm (81.3% - 92.2%

running speed) occurring on Pump P1023B, culminating in the highest velocity amplitude of 10.9 mm/sec. at

85.9 Hz (2xrotationalfrequency) on the motor drive endbearing of Pump P1023B. The prolonged use of

these motors operating in this speed range should be avoided if possible.

The following pages contain the coast up spectral analysis obtained from each motor and clearly illustrate the

problem area.


8/14


8

P1023A 82 C Calorifier Pump Run Up Analysis

Figure 2:Run Up Analysis conducted on the motor non drive endbearing of 2.1a Calorifier Pump P1023Ashowing significant emergence of 2x rpm

vibration (misalignment) at 81.3 Hz (corresponding to 81.3% operating speed) over a 131 second sample (32768 samples/21 spectra/40KHz spacing).

Figure 3:Run Up Analysis conducted on the motor drive endbearing of 2.1a Calorifier Pump P1023Ashowing significant emergence of 2x rpm vibration

(misalignment) at 81.3 Hz (corresponding to 81.3% operating speed) over a 131 second sample (32768 samples/21 spectra/40KHz spacing).


9/14


9

P1023B 82 C Calorifier Pump Run Up Analysis

Figure 4:Run Up Analysis conducted on the motor non drive endbearing of 2.1a Calorifier Pump P1023Bshowing significant emergence of 2x rpm

vibration (misalignment) at 85.9 Hz (corresponding to 85.9% operating speed) over a 131 second sample (32768 samples/21 spectra/40KHz spacing).

Figure 5:Run Up Analysis conducted on the motor drive endbearing of 2.1a Calorifier Pump P1023Bshowing significant emergence of 2x rpm vibration

(misalignment) at 85.9 Hz (corresponding to 85.9% operating speed) over a 131 second sample (32768 samples/21 spectra/40KHz spacing).


10/14


10

Part

2Discussion

Advice and Recommendations

1 Recommendations for 2.1a 82 C Calorifier Pumps P1023A & P1023B

2.1a Sensitising 82 C Calorifier Pumps P1023A & P1023B - URGENT PRIORITY (operating at

shaft critical frequency)

The Sensitising 82 C Calorifier Pumps P1023A and P1023B proved to be operating above the

Unacceptable Zone as specified by the Vibration Severity Standard: ISO10816-3.

The Coast Up/Coast Down Analysis clearly highlighted a potential shaft critical zone between the operating

speed of 2351 - 2490 rpm (79.7% - 84.4% running speed) occurring on Pump P1023A and 2399 - 2720 rpm

(81.3% - 92.2% running speed) occurring on Pump P1023B, culminating in the highest velocity amplitude of

10.9 mm/sec.at 85.9 Hz (2xrotationalfrequency) on the motor drive endbearing of Pump P1023B (should be

less than 4.5 mm/sec.).

The prolonged use of operating these motors in this speed range should be avoided if possible; there is a

potential risk of the internal rotor catching the stator or secondary induced mechanical damage may be causedto the coupling or bearings.

There are three solutions to overcome this problem:-

1. Operate the pumps at 100% speed only (the motors in use are not dynamically balanced to run at any

other speed).

2. Operate the pumps outside the shaft critical speed zone in each case (highlighted above).

3. Replace BOTH motors and fit a variable speed rated motor to each installation.

If there is any aspect of this report you wish to discuss in greater detail, or any further points you would like to raise yourself, thenplease do not hesitate to contact Tony Riseleyon Tel. 01352 710600or [email protected].
mailto:[email protected]:[email protected]:[email protected]:[email protected]


11/14


11

Further RemarksBasic Concepts of Vibration Analysis

What is Vibration?

Introduction

Vibration is the disturbance from equilibrium, which propagates in time from one place to another and exists in

all rotating and reciprocating machinery. An ideal machine would produce no vibration at all because all

energy would be channelled into the machine function. A good design will produce low levels of inherent

vibration, however, as the machine wears, foundations settle and parts deform, subtle changes in the dynamicproperties of the machine begin to occur. Shafts become misaligned, parts begin to wear, rotors become

unbalanced and tolerances increase. All of these factors are reflected in an increase in vibration energy, which

dissipates throughout the machine, excites resonance and puts considerable strain on bearings. Cause and

effect reinforce each other and the machine progresses towards ultimate breakdown.

A machine may contain many complex vibrations, made up of a wide-range of superimposed sinusoidal and

random components. This multi-complex signal can be broken down into its constituent frequency

components by using F.F.T. analysis (Fast Fourier Transform) commonly referred to as a Spectrum. The

following table highlights the many common faults and their characteristic frequencies in terms of rotation

speeds:

Nature of Fault Frequency of DominantVibration (Hz=rpm/60)

Direction Remarks

Rotating members out ofbalance

1 x rpm RadialA common cause of excess vibrationin machinery.

Misalignment & Bent ShaftsUsually 1 x rpm; Often 2 xrpm and sometimes 3 or 4 xrpm

Radial & Axial A common fault.

Damaged rolling elementbearings (ball, roller etc.)

Impact rates for theindividual bearing

componentAlso vibrations at highfrequencies (2 to 60 KHz)often related to radialresonance in bearings

Radial and Axial

Uneven vibration levels, often withshocks. Impact Rates f (Hz)

Outer Race defect: f(Hz) = n/2 x fr(1-

BD/PD x Cos )

Inner Race defect: f(Hz) = n/2 x fr(1+BD/PD x Cos )

Ball defect: f(Hz) = PD/BD x fr [1-

(BD/PD x Cos )2]

N = number of balls or rollersfr= relative rev./s between races


12/14


12

Journal bearings loose inhousing

Sub-harmonics of shaft rpm,exactly or 1/3 x rpm

Primarily RadialLooseness may only develop atoperating speed and temperature(e.g. turbo machines).

Oil film whirl or whip injournal bearings

Slightly less than half shaftspeed (42% to 48%) Primarily Radial

Applicable to high speed (e.g. turbo)machines.

Hysteresis Whirl Shaft critical speed Primarily Radial

Vibrations excited when passingthrough critical shaft speed aremaintained at higher shaft speeds.Can sometimes be cured bychecking tightness of rotorcomponents.

Damaged or worn gearsTooth meshing frequencies(shaft rpm x number ofteeth) and harmonics

Radial and Axial

Sidebands around tooth meshingfrequencies indicate modulation (e.g.eccentricity) at frequencycorresponding to sideband spacings.Normally only detectable with verynarrow-band analysis and cepstrum.

Mechanical looseness 2 x rpmAlso sub and inter-harmonics, as forloose journal bearings.

Faulty belt drive 1,2,3 & 4 x rpm of belt RadialThe precise problem can be usuallyidentified visually with the help of astroboscope.

Unbalanced reciprocatingforces and couplings

1 x rpm and/or multiples forhigher order imbalance

Primarily Radial

Increased turbulenceBlade and vane passingfrequencies and harmonics

Radial and AxialIncreasing levels indicate increasingturbulence.

Electrically induced

vibrations

1 x rpm or 1 or 2 times

synchronous frequency Radial and Axial

Should disappear when turning off

the power.

Figure 6:Table identifying common machinery faults and characteristic frequencies in terms of rotational speed.


13/14


13

Evaluation of Rotating Machine Condition using ISO10816-3 Vibration Severity Standard

The ISO Committee have completely revised the old ISO2372 Vibration Severity Standard for evaluating in-

situ performance of rotating machines. The new standard: ISO10816-3accommodates the many changes thathave taken place in the design and operating frequencies of modern process machinery.

The vibration criteria in this standard applies to the machine sets, with for example steam turbine or electric

drives, having a capacity above 15 kW and operating between speeds of 120 RPM and 15000 RPM. Machine

sets covered by this standard include: (i) Steam Turbines with a capacity up to 50 MW; (ii) Steam turbine sets

with a capacity greater than 50 MW and speeds below 1500 RPM; (iii) Rotary Compressors; (iv) Industrial gas

turbines up to 3.0 MW capacity; (v) Pumps of centrifugal, mixed or axial flow type; (vi) Electrical motors of any

type and (vii) Blowers or fans, not of lightweight sheet metal construction.

Classification according to Machine Type and Application

Significant differences in the design; type or bearings and support structures requires a separation into

different groups. Machines in these groups may have horizontal, vertical or inclined shafts and can bemounted on rigid or flexible supports.

Group 1:Large machines rated above 300 kW; electrical machines with a shaft height H 315 mm. Group 2:Medium machines with a rated power above 15 kW up to and including 300 kW: electric machines with a

shaft height 160 mm H 315 mm. Group 3:Pumps with multi vane impeller and separate driver, rated above 15 kW capacity. Group 4:Pumps with multi vane impeller and integrated driver, rated above 15 kW capacity.

ISO10816-3 Vibration Severity Standard

RMS RMSV

elocity

10-1000Hzr>600rpm

2-

1000Hzr>120rpm

11 0.447.1 0.28

4.5 0.18

3.5 0.11

2.8 0.07

2.3 0.04

1.4 0.03

0.71 0.02

mm/sec. inch/s

rigid flexible rigid flexible rigid flexible rigid flexible FOUNDATION

Pumps > 15 kW radial, axial, mixed flowMedium sized

machines 15 kW

va example technical report

Documents