condition monitoring

1. CONDITION MONITORING AND VIBRATION ANALYSIS
NDT: NDT means Non-destructive Testing.
The use of non destroying techniques to determine the integrity of a material,
component, structure or quantitatively measure some characteristic of an object.
Nondestructive testing (NDT) is the process of inspecting, testing, or evaluating materials,
components or assemblies for discontinuities, or differences in characteristics without
destroying the serviceability of the part or system. In other words, when the inspection or
test is completed the part can still be used.
i.e. Inspect or measure without doing harm.
REASONS FOR USE OF NDT IN A CHEMICAL INDUSTRY
•To ensure Reliability of equipments.
.To reduce breakdowns and hence increase the profits by
maximum Capacity utilization & by reducing down time

2. CONDITION MONITORING
• Condition monitoring section has been established with a philosophy to
perform preventive /predictive maintenance to avoid any unwanted break
down. With this philosophy in mind a full -fledge cell was started with plant
.The data bank has been establised right from the initial stage where the
base data of all critical machines is well recorded and this shall be very
useful in future .Presently this section is geared to fulfill all the requirement
of a running plant and is very well equipped with manpower /instrument.

3. NDT AND CONDITION MONITORING IN NFL BATHINDA
Followings are the various activity which are being exercised in NDT Section :
1.Scheduled Vibration Monitoring and analysis of rotating machines.
2.Field, shop balancing.
3.Antifriction bearing and fault detection.
4.Physical Inspection.
5.Dye penetrant test.
6.Ultrasonic test of Metals.
7.Magnetic particle Inspection.
8.Alloy analysis of metals.
9.Metal/rubber hardness check.
10.Pinhole detection in lining/coating.
11.Thermography.
12.Metal thickness measurement from one side.
13.Non-ferrous coating thickness measurement.
14.Steam Trap performance monitoring.
15.System leak detection.
16.Welding Inspection for soundness.
17.Ferrite check of Austenitic weld.
18.Pre/post weld heat treatment.

4. Scheduled Vibration Monitorin and Analysis of Rotating Machines :
• Scheduled Vibration Monitoring and Analysis of Rotating Machines :
• .VIBRATION: It is the response of a system to an internal or external
force which causes the system to oscillate.
• Vibration parameter :
• Vibration of a rotating machine can be measured by measuring mainly displacement, velocity,
acceleration.
• 1.Displacement
• 2.Velocity
• 3.Acceleration
• 4.Frequency
• 5.Amplitude
• 6.Natural freqenecy
• 7.Resonace
• 8.Dof
• 9.Phase

5. • Scheduled vibration monitoring in NFL BATHINDA:
• Limits of Vibration :
• All the published standards are of a advisory nature only and depending upon the user of the
equipment various limits of vibration tolerances are set. The limits at NFL are set on following
considerations :
• As per ISO 10816. Standard
• CLASS -1 If motor (15 KW)
• CLASS -2 If motor (15 KW to 75 KW)
• CLASS- 3 Large Prime mover
• Thump rule
• 1.Horizontal-Unbalance
• 2.Vertical-Mechanical looseness
• 3.Axial-Misalignment
• 4. G value- Bearing health

6. Defects and their Resolution :
1. Unbalance :
It is the uneven distribution of mass about rotating centre line.
Manifestation of 1 x rpm with steady phase normally high in radial direction. But
for fan and blowers supported in cantilever position vibration is high in axial
direction. It can be corrected by adding or removing weight.
Causes Of Unbalance
Uneven distribution of mass of rotor.
Dirt accumulation on fan rotors.
Rotor eccentricity
Roller deflection, especially in paper machines
Machining errors
Uneven erosion and corrosion of pump impellers
Missing balance weights

7. SYMPTOMS OF UNBALANCE
Before going for balancing of a rotor we should know the symptoms of
unbalance. Following are the symptoms of unbalance :
a) Horizontal and vertical vibrations will be high. However, for an overhung rotor
axial vibration will be as well, perhaps as high or in some cases higher than the
radial vibration amplitude.
b)Predominant frequency of vibration will be 1xrpm.
c)The difference between horizontal and vertical phase readings will be 90
degree.
d)The amplitude of the harmonic frequencies in the radial directions will be less
than 50% of the 1xrpm frequency.
e)Orbit will be generally circular.
f)Phase will be of single reference mark.

8. Types Of Unbalance
Static Unbalance
Couple Unbalance
Overhang Rotor Unbalance
Static Unbalance
Detection:
1.Highest horizontal vibration
2.Amplitude increases as square
of speed.
3.Dominant frequency at 1x rpm
4.Horizontal to vertical phase
difference 900 on the same
bearing housing

9. Couple Unbalance
Detection:
• High horizontal & some times axial vibration
• Dominant frequency at 1x RPM
• 1800 phase difference between both bearings horizontal
as well as vertical direction.
Correction It requires two plane balancing

10. Overhung Rotor Unbalance
Detection:
• High horizontal & axial vibration
• Dominant frequency at 1x RPM
• Axial readings will be in phase but
radial phase readings might be
unsteady.
Overhung rotors might be having both
static and couple unbalance and each of
which requires correction.
Correction

11. Looseness : It occurs at 1 x rpm, 2 x rpm and 4 x rpm. High in the
direction of looseness with phase change at loose location.
Foundation may be the culprit for looseness and needs to be
eliminated first as the cause of high vibration
.
It alone can not create vibration but in the influence of Unbalance,
Misalignment, Bearing problems it amplify the amplitude.
It should be corrected first.
Types:
1. Structural frame/base looseness (1X)
2. Cracked structure/bearing pedestal (2X)
3. Rotating looseness - Loose bearing/improper fit between
component parts. (Multiple)

12. 1. Structural frame/base looseness (1X)
Caused by-
1. Structural looseness/weakness of machine feet, baseplate &
concrete base.
2. Deteriorated grouting.
3. Deterioration of frame or base
4. Soft foot.
5. Loose holding down bolts
Analysis- 1.
2.
3.
Dominant freq 1X. Similar to unbalance & misalignment.
Horizontal to vertical phase diff 00 or 1800 at the same
bearing housing.
1800 phase diff in the vertical direction between two
surfaces.

13. 2. Cracked structure/bearing pedestal (2X)
Caused by-
1. Crack in the structure or bearing pedestal.
2. Occasionally on some loose bearing housing bolts.
3. Loose bearing or improper component fit.
Analysis-
1. 2X RPM amplitude is > 150% of 1X RPM amplitude in radial
direction.
2. Amplitudes are somewhat erratic.
3. 2X RPM phase somewhat erratic.

14. 3. Rotating looseness
Caused by-
1. Loose rotor.
2. Bearing loose in the housing.
3. Bearing loose in the shaft.
4. Excessive bearing internal clearance.
Analysis:
1. Generates running speed harmonics up to 20X RPM.
2. Generates low amplitude frequencies of 1/2x (i.e. .5x, 1.5x,
2.5x…) and 1/3 x also.
3. Presence of 1/2x will indicate more advanced looseness
problems like presence of rub. It indicate other problems like
unbalance and misalignment.
4. Bearing loose on the shaft will generate 1x RPM peak.
5. Bearing loose in the housing will generate 4x RPM peak.

15. 2. Misalignment : When the centre line of two shafts in a machine train do not match exactly
misalignment exists. There are three types of Misalignment - Angular, offset, and combination.
Manifestation at 1 x rpm , 2 x rpm and 3X rpm with a difference in phase readings showing one
or two or three reference marks. Generally high in axial direction and can be confirmed with
phase analysis.
Causes Of Misalignment
•thermal expansion - Most machines align cold. Machine vibrations
•Machine vibrations
•Forces transmitted to the machine by pipe or
support structure.
•Soft foot.
•Direct coupled machined are not properly aligned.
•Poor workmanship.
•.

16. Types Of Misalignment
1. Off set
2. Angular
3. Skew - Combination of
offset & angular

17. Eccentric Rotor
When center of rotation is offset from geometric
center.
Dominant frequency 1X.
Horizontal to Vertical phase difference either 00
or 1800 at the same bearing housing (Both
indicate straight-line motion).

18. BENT SHAFT
.Bent shaft problems cause high axial vibration
.1X RPM dominant if bend is near shaft center
.2X RPM dominant if bend is near shaft ends
Phase difference in the axial direction will tend towards 1800
difference

19. SLEEVE BEARING
WEAR / CLEARANCE PROBLEMS
.Later stages of sleeve bearing wear will give a large
family of harmonics of running speed
.A minor unbalance or misalignment will cause high
amplitudes when excessive bearing clearances are
present

20. RESONANCE
Resonance occurs when the Forcing Frequency
coincides with a Natural Frequency
1800 phase change occurs when shaft speed
passes through resonance
High amplitudes of vibration will be present
when a system is in resonance

21. HYDRAULIC AND AERODYNAMIC FORCES
.Cavitations will generate random, high frequency
broadband energy superimposed with BPF harmonics
Normally indicates inadequate suction pressure
.Erosion of impeller vanes and pump casings may occur
if left unchecked
Sounds like gravel passing through pump

22. 1.Which frequencies exist and what are the relationships to the
fundamental exciting frequencies.
2.What are the amplitudes of each peak
3.How do the peaks relate to each other
4.If there are significant peaks, what are their source
SIGNATURE ANALYSIS

23. Spectrum Analysis Techniques
Step - 1
Collect useful information
History of machine.
Control room data - speed, feed, temperature, pressure etc.
Name plate details - bearing no, no of gear teeth etc.
Design operating parameters, critical speed.

24. Step - 2 : Identify the type of measurement procedure
Identify measurement type-Disp, Vel, Acc.

25. Measurement direction - Hori, Vert, Axial

26. Step - 3
Analyze:
1. Evaluate overall vibration reading of the entire
machine.
(a) Identify 1x RPM peak.
(b) Locate highest amplitude.
(c) What is the direction of the highest amplitude?
(d) What is the frequency of the highest amplitude?
2. See the values of Shock pulse, HFD etc.
3. See the trend - in case of sudden increase the
problem severity increases.
4. Analyze the frequency for possible defects.
5. Analyze the phase readings for confirmation if
necessary.

27. TROUBLESHOOTING PROBLEMS
UGA-102-A: CARBAMATE PUMP
DATE-21/08/2019 the vibration readings of UGA-101-A were following
15/3.0 15/6.5 8/2.0 10/4.0
10/2.0 8/3.5 6/2.0 8/2.0
15/3.0 13/4.0 5/2.0 8/2.4
Temp-T/F-60 DEGREE
T/R-88 DEGREE
OBSERVATIONNS: Unbalance
1.Beacause of steam leakage from labyrinth which was effecting bearing
pedestals and warm machine uneven
2.Beacause of steam leakage from labyrinth the condensation was happening
and condensate was being collected in the casing which at an interval of time
hitting the rotor

28. Remedies Recommended
1. Pedestal fans were placed on both one bearing to bring
temperature at equal stage.
2.Recommended opening of drain of the casing so that formed
condensate which is collected in the casing will come out
from the casing . The process was followed by regular time
interval.
after implementing the NDT recommendation the vibration
reading of UGA-101-A
10/2.8 8/2.6 8/2.8 12/3.0
6/2.0 6/1.8 6/2.0 8/2.0
8/1.8 9/2.5 6/2.0 5/2.0
Temp-T/F-55
T/R-53

29. TROUBLESHOOTING PROBLEMS
UGB-401
DATE-30/11/2019 the vibration readings of UGB-401
were following
80/12.0 90/14.0 35/5.0 45/6.2
15/2.0 40/6.5 80/11.0 80/12.0
30/4.0 20/6.8 40/3.2 20/4.0
OBSERVATIONNS: Unbalance
1.Frequencies of 1x order
2. Disturbed flow parameters
3.Suction internal recirculation & Cavitations.
Remedies recommended:
Check for flow parameters

30. The vibration readings of UGB-401 at
Suction valve open ,full fresh air taken
45/7.0 60/8.0 30/4.0 20/3.0
10/2.0 25/4.0 45/7.0 40/2.5
15/2.5 15/2.5 15/3.0 10/2.0