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Optiwave analysis Introduction
THE EVER INCREASING DEMANDS FOR HIGHER production rates, paper quality, sheet uniformity, and machine efficiencies has lead to an increased demand for machine optimization. One of the tools used to optimize the wet end of the paper machine is the stock approach diagnostic evaluation more commonly referred to as a pulsation analysis.
The purpose of a stock approach diagnostic evaluation is to define those variables contributing to the non-uniform delivery of stock to the wire. Uniform delivery of stock is essential to uniform machine direction basis weight control.The non-uniform delivery of stock onto the wire can be a result of consistency, pressure, total head, vibration, control, or speed instability.
Optiwave analysis
Introduction (cont’d)
Through the introduction of High speed mass mearement by FiberScan (1024 sample/sec) now is possible to detect any period variation directly on wire ;electronic data is simultaneously taken regarding machine performance. Simultaneous sampling of multiple signals is essential to determine the propagation of the variations through the system
Frequency
Frequency, is the number of vibrations in a certain time, e.g. cycles per second, when the unit Hz (Hertz) is used or cycles per minute (cpm).
Amplitude
Amplitude, in the case of pressure pulsations is the magnitude of the pulsations.
Optiwave analysis
Source of pulsation in paper machine approach system
Screen • design and quality of the rotating elements, foils and screen basket Piping • design and supports Mechanical vibration • pipes which are not well supported • pumps, screens or other components which are not well fixed to the building • building itself Pump drive • gear box • coupling • variable speed control System design • overlapping operating frequencies: pump and screen • resonant frequency pump and system (e.g. pipes) • control by throttling valve • control by by-pass Headbox feed pump • quality of design and manufacturing, especially of the impeller • relative position of duty point to BEP (Best Efficiency Point) • suction condition (NPSH)
Optiwave analysis
Optiwave analysis
FiberScan™
Host Software FiberScan™
The FFT analysis can be easily done during the drainage check. An additional instrument set-up allow an high speed sampling (up to 1024) for at least 7 sec. An FFT analysis have to be performed in all the machine measuring position
FF
T
Optiwave analysis
Main screen
Set Menu
FFT Menu
Optiwave analysis
fft
Mass variations
1000
1100
1200
1300
1400
1500
1600
1700
2000 2200 2400 2600 2800 3000
msec
db
•Host Software to download data as a xlc.file or simply as a bitmap file
•The results are displayed in time domain or as a FFT
Time: mmsecond
Amplitude: decibel Gain: decibel
Frequency: Hertz
Optiwave analysis
Data Requested @ first approach
• Machine speed ( wire and reel)
• Paper Basis weight ( dry and total)
• Headbox pressure
• Fan pump rpm
• Jet drag
Optiwave analysis
Paper picture showing a transversal barring defect
High Speed FFT Analysis Case 1: Fan Pump Problems
FFT spectrum @ point 1
A B C
1 2 3 4
5
Picture of the Top Former where the FFT analysis was conducted
FFT spectrum @ point 2
High Speed FFT Analysis Case 1
A B C
1 2 3 4
5
FFT spectrum @ point 3
FFT spectrum @ point 4
High Speed FFT Analysis Case 1
Picture of the Top Former where the FFT analysis was conducted
High Speed FFT Analysis Case 2: Fan Pump Problems
1 2 3 4 5
FFT spectrum @ point 1 Forming board - 734m/min
FFT spectrum @ point 2 Multifoils - 734m/min
44 Hz
44 Hz
1 2 3 4 5
FFT spectrum @ point 4 Vacufoil 3 - 734m/min
FFT spectrum @ point 3 Vacufoil 2 - 734m/min
FFT spectrum @ point 5 Suct box 5 - 734m/min
44 Hz
44 Hz
44 Hz
High Speed FFT Analysis Case 2: Fan Pump Problems
1 2 3 4 5
40,5 Hz
40,5 Hz
FFT spectrum @ point 1 Forming board - 675m/min
FFT spectrum @ point 5 Suction box - 675m/min
High Speed FFT Analysis Case 2: Fan Pump Problems
43,5 Hz
1 2 3 4 5
FFT spectrum @ point 4 Multifoils - 675m/min 836rpm
FFT spectrum @ point 4 Multifoils - 675m/min 706rpm
High Speed FFT Analysis Case 2: Fan Pump Problems
0,18 Hz
High Speed FFT Analysis Case 3: Sheet Instability @ PU
FFT spectrum @ point 2 4th suction box - 670m/min
1 2
0,18 Hz - Zoom in
FFT spectrum @ point 2 4th suction box - 670m/min
1 2
High Speed FFT Analysis Case 3: Sheet Instability @ PU
High Speed FFT Analysis Case 4 Couch roll vibrations
Periodical variation : 2,73 Hz harmonics
fft
Wire speed : 413 m/min
Mass variations
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
2000 2500 3000 3500 4000
msec
db
Periodical variation :2,29 Hz harmonics
fft
Wire speed : 348 m/min
Mass variations
1000
1100
1200
1300
1400
1500
1600
1700
1800
2000 2200 2400 2600 2800 3000
msec
db
Test 2: 04-03-09
High Speed FFT Analysis Case 4 Couch roll vibrations
High Speed FFT Analysis Case 5 stock pulstion
Periodical variation : 82,5 Hz harmonics
fft 1 2 3 4 5 6 7 8 9 10
Wire speed : 841 m/min
Wire speed : 910 m/min
Periodical variation : 82,5 Hz harmonics
High Speed FFT Analysis Case 5 stock pulstion
