PVM Training Presentation Session 1 - 2014 Secure
-
Upload
diaccessltd17172961 -
Category
Documents
-
view
6 -
download
1
description
Transcript of PVM Training Presentation Session 1 - 2014 Secure
![Page 1: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/1.jpg)
PVM Training
Module 1 - Pipework Vibration
![Page 2: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/2.jpg)
Objectives & Outcomes
• Gain knowledge of vibration and specifically piping vibration.
• Learn how to identify potential risks & failure mechanisms.
• Learn how to measure and quantify vibration risk.
![Page 3: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/3.jpg)
Contents – Module 1
• General Vibration– What is Vibration / Fatigue– Amplitude and Frequency– Natural Frequency– Vibration Excitation– Vibration Measurement
• Pipework Vibration– Risks– Main Pipe
•Excitation Mechanisms•Fretting
– Small Bore•Poor Geometry Examples•SBC Supports
– Pipework Vibration Criteria
![Page 4: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/4.jpg)
General Vibration
![Page 5: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/5.jpg)
What is Vibration ? Video
• An oscillating motion about a reference position• Frequency is a measure of the number of cycles of this motion during a
period of 1 second – SI unit: Hertz (Hz)• Vibration occurs due to dynamic effects of tolerances, clearances,
rolling/rubbing contact and out of balance forces in mechanical systems• Vibration is often destructive, but is sometimes generated intentionally to
perform a task
Damping, ζ Stiffness, K
Mass, MX
![Page 6: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/6.jpg)
What is Vibration ?
Stiffness (k)
Mass (kg)
mass
mass
Time
Max Positive +
Max Negative -
AM
PLI
TUD
E
Pea
k
RM
S
Pea
k to
Pea
k
PeakRMS *2/2Root Mean Square ‘useful’ unit of amplitude in a sine wave -
![Page 7: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/7.jpg)
Frequency
• A vibrating system’s motion can consist of:
– a single component occurring at a single frequency, e.g. a tuning fork, or
– Several components occurring at different frequencies simultaneously, e.g. a car, engine, exhaust, road noise, suspension etc
• In practice the second case is correct for the majority of vibrating systems
• When looking at the different frequency components in a vibrating system, frequency analysis is required.
![Page 8: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/8.jpg)
Time & Frequency Domains – Single Frequency
-1.5
-1
-0.5
0
0.5
1
1.5
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Time (sec)
Am
plitu
de
0
0.2
0.4
0.6
0.8
1
1.2
0 25 50 75 100 125 150 175 200
Frequency (Hz)
Am
plitu
de
Period
Frequency = 1 / Period
![Page 9: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/9.jpg)
Time & Frequency Domains – Multiple Frequencies
-30000
-20000
-10000
0
10000
20000
30000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Time (s)
Am
plitu
de
• Random Vibration with energy distributed over a wide frequency range
From Disorder (time history)…..
To Order (frequency domain)….
![Page 10: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/10.jpg)
Important Measurement Units
• SI Unit for frequency measurement is number of cycles per second (Hertz). • Other common frequency unit is RPM – revolutions per minute.• To be understood, it is essential that units state both the parameter and
amplitude measure being used e.g.:
Velocity - mm/s RMS
Acceleration - g (peak)
Displacement - mm (peak to peak)
![Page 11: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/11.jpg)
Natural Frequency & Resonance
• Natural Frequency
• Very little energy is required to excite the natural frequency of a system, as the system ‘wants’ to respond at this particular frequency. If damping is present then this will dissipate the dynamic energy and reduce the vibrational response.
massstiffness spring
21 :frequency Natural
nf
![Page 12: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/12.jpg)
Natural Frequency & Resonance – Video Tacoma Narrows
![Page 13: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/13.jpg)
Vibration Excitation - Recap
• Excitation can either be tonal i.e. energy is only input at discrete frequencies, or broadband i.e. energy is input over a wide frequency range.
• Tonal Excitation – ResonantExcitation frequency matches a natural frequency then a resonant condition is said to exist. All excitation energy is available to ‘drive’ the natural frequency of the system
• Tonal Excitation – ForcedExcitation frequency does not match a system natural frequency, then vibration will still be present at the excitation frequency, although at much lower levels than the resonant condition. High levels of vibration will occur only if the excitation energy levels are high, relative to the stiffness of the system.
• Broadband ExcitationIf the excitation is broadband then there is a probability that some energy will be input at the system natural frequencies. Generally, response levels are lower than for the purely resonant vibration case described above because the excitation energy is spread over a wide frequency range.
![Page 14: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/14.jpg)
Measurement Techniques – Why Do We Measure Vibration?
• Vibration amplitude and frequency data provide good correlation to dynamic strain.• To be able to identify sources of undesirable vibration.• To avoid excitation of resonances in certain parts of the system.• To use for condition monitoring. • To construct or verify computer models of structures & systems.
![Page 15: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/15.jpg)
Fatigue
• Progressive and localized structural damage that occurs when a material is subjected to cyclic loading
![Page 16: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/16.jpg)
Fatigue Assessment
For an F2 category weld
Stress Range = 35 N/mm2
= 2.3% Probability
17.5N/mm = 0.1% Probability BS7608
Stress Ratio SR Classification Action
SR < 0.5 OK None
0.5 < SR < 1 CONCERN NDT. Modify at the earliest opportunity
SR >= 1 PROBLEM NDT. Modify immediately
![Page 17: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/17.jpg)
Pipework Vibration
![Page 18: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/18.jpg)
Root Cause of Reported Leaks
0
5
10
15
20
25
30
Degradationof materialproperties
Corrosion /Erosion
Fatigue /Vibration
IncorrectInstallation
Operator Error InadequateProcedures
Inadequateequipment
Inadequateisolation
Proceduralviolation
Line blockage
Perc
enta
ge o
f all
Inci
dent
s
Fatigue /Vibration
![Page 19: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/19.jpg)
Main Pipe Vibration – Excitation
Excitation• There are a variety of excitation mechanisms which can be present in a
piping system including;
•Flow Induced Turbulence
•Mechanical Excitation
•Pulsation
![Page 20: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/20.jpg)
Flow Induced Turbulence Excitation
• Turbulence will exist in most piping systems. The dominant sources are found at major flow discontinuities, such as: partially closed valve, short radius or mitred bends, tees or reducers. This in turn generates potentially high levels of Broadband Energy, which is typically concentrated at lower frequencies (below 100 Hz)
Fluid Velocity Profile Kinetic Energy
![Page 21: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/21.jpg)
Mechanical Excitation
• Most of the problems encountered have been with reciprocating compressors & pumps. Dynamic forces load the pipework connected or cause vibration of the supports which in turn excites the pipework connected. Normally high levels of vibration and failures only occur when the natural frequency of the pipework system coincides with the running speed (or harmonics) of the machine.
• Transmission– Problems can also occur on pipework which shares supports with either the
machinery or associated pipework, but is not part of the system which involves the excitation.
![Page 22: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/22.jpg)
Pulsation Excitation
• Fluids within piping systems also exhibit natural frequencies – Acoustic.
• Pressure pulsation is a tonal form of excitation whereby dynamic pressure fluctuations are generated in the process fluid at discrete frequencies.
• If these frequencies coincide with a structural natural frequency of the pipework system high vibration can occur.
•Typical sources of Pulsation are:Reciprocating Pumps & CompressorsCentrifugal Compressors (Rotating Stall)Flow over bodies within flow – (thermowells)Dead Leg Branches
![Page 23: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/23.jpg)
Potential Failure Mode: Identifying Fretting Issues
• Typical locations to be considered include:– U-bolt pipe clamps, particularly where there is no resilient layer (e.g. tico pad)– Resting supports– Deck penetrations – Loose insulation cladding– Contact between pipes (partial clash)– Pipework in contact with other equipment items (e.g. cable racks, handrails,
other fittings, etc)– Temporary supports (e.g. scaffold poles, chain blocks etc.)
• Where fretting is identified, the items in contact should be separated and appropriate inspection performed to quantify any damage which has been sustained.
![Page 24: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/24.jpg)
Examples of Fretting
The screw and nut used to mount a temp gauge in contact with pipe, resulting in penetration of sch. 160 pipe
Pipeline contact to cable rackresulting in fretting damage
U-bolt is attached to the connection on a reducer section and is not lined and susceptible to fretting damage
![Page 25: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/25.jpg)
Pipework VibrationSmall Bore
![Page 26: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/26.jpg)
Small Bore
• Excitation generally from the main pipe as previously described
• Geometry significantly effects the response– Length– Diameter– Type of fitting– Number & size of valves– Parent pipe schedule– Location
![Page 27: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/27.jpg)
Example of High Risk Geometry
Necked down connection and large cantilevered mass
Large cantilevered mass with poor geometry
![Page 28: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/28.jpg)
Example of High Risk Geometry
Support to first flange, however, large mass assembly overhang
Large cantilevered mass with poor geometry
![Page 29: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/29.jpg)
Example of High Risk Geometry
![Page 30: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/30.jpg)
Example of High Risk Geometry
![Page 31: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/31.jpg)
Clamp – Inadequate Supports
Connection braced at small bore pipe using flat bar, no support
provided to the valve and potential punch through threat.
Brace only protects welded connection to parent pipe. Down stream elbow welded connection
unprotected
![Page 32: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/32.jpg)
Clamp – Inadequate Supports
Connection handcuffed to adjacent pipe rather than parent
pipe
Connection braced to deck. Combination of static (axial) loading and vibration leading
to failure
![Page 33: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/33.jpg)
Clamp – Adequate Support
• Clamp provides restraint in both the horizontal and vertical direction.
• No overhanging mass of the valve
![Page 34: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/34.jpg)
Clamp – Maintenance & Inspection
• Example of critical clamp not been re-instated correctly after intervention work on line
• Disadvantage of Bracing Everything– High cost– Risk of corrosion– Risk of loosening resulting in ineffectiveness– On-going maintenance is required
![Page 35: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/35.jpg)
Welded Web Supports
• Example of SBC fully supported using welded webs
• Thin-wall PipeworkPotential failure location when high
frequency vibration present
![Page 36: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/36.jpg)
Piping Vibration Criteria
•Industry standard curves basedon 25 years experience in thepetrochemical industry
•Frequency Weighted
![Page 37: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/37.jpg)
Pipework Vibration - Experience
![Page 38: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/38.jpg)
Piping Vibration Criteria
ACTION
OK No action required, vibration levels are acceptable
CONCERN The level of vibration, above which, further analysis is required to determine if modifications must be undertaken to prevent possible high cycle fatigue failure
PROBLEM The level of vibration, above which, modifications must be undertaken immediately to prevent high cycle fatigue failures
Doosan Power Systems application of the pipework vibration curves is to calculate
the overall RMS value over the entire frequency range, acting at the lowest
dominant frequency, and compare it to the curves to determine the classification.
![Page 39: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/39.jpg)
Solutions – What Role Can you Play…
• Keep your eyes and ears open• Pipework vibrating• Leaks / drips• Noise, especially tonal• Changes from yesterday / last trip
Don’t assume someone else is dealing with the concern!
![Page 40: PVM Training Presentation Session 1 - 2014 Secure](https://reader030.fdocuments.us/reader030/viewer/2022013101/55cf8579550346484b8e650d/html5/thumbnails/40.jpg)
Questions
Any Questions