Engineering Article (3)

Vibration as Measurement Object in Predictive Maintenance

And

Predictive Maintenance Basic Procedure Based on Vibration Measurement

Predictive maintenance (PdM) is maintenance method which is based on actual machine condition. In this maintenance method, there are several measurement objects which are commonly used such as vibration, pressure, sound, oil viscosity, temperature, etc. However, measurement object selection is really depended on the type of machine. For example, measurement objects for common rotary machine are different from those which are used for steam boiler. For common rotary machine, measurement objects which are commonly used are vibration, sound, and performance. For steam boiler, measurement objects which are used are leakage, temperature, pressure, and spark detection.

Now, let’s take an emphasis on rotary machine since this type of machine is commonly used in industry. Based on practical experience and many research results, vibration is the best PdM measurement object for rotary machine. In rotary machine, dynamic forces, which act on the machine, generate machine vibration response. These dynamic forces are generated by fault which is inside the machine. Because of that, machine vibration response can be used for machine fault early detection since its level correlates with the machinery fault severity.

Basically there are several particular steps which should be done in predictive maintenance based on vibration level monitoring. First step is vibration data collection process. The vibration data is measured in time domain (waveform). The vibration measurement can be done either periodically or continually.  After vibration measurement is done, the second step is vibration data analysis using FFT algorithm. FFT (Fast Fourier Transform) is algorithm which converts vibration waveform (time domain) into vibration frequency spectrum in frequency domain. By having vibration frequency spectrum, we can continue to the next step which is vibration signature observation. Vibration signature is the vibration response frequency component which has high magnitude in frequency domain. This frequency component represents the type of machinery fault that exists in the machine. Based on this observation result, machine condition diagnostic (the third step) is done. This diagnostic encompasses fault source prediction. Furthermore, the prediction result is compared with other analysis results which come from other PdM object measurement such as temperature and pressure. The last step is breakdown time prediction. If the maximum overall vibration level (OVL) is known, the breakdown time can be predicted using overall vibration level curve trending. From this information, we can calculate the available time which can be used to prepare reparation procedure and spare parts procurement and hence the reparation process can be well prepared.

Engineering Article (2)

MAINTENANCE PHILOSOPHIES

There are three basic maintenance philosophies:

1.      Breakdown or run-to-failure maintenance

2.      Preventive or time-based maintenance

3.      Predictive or condition-based maintenance

1.         Breakdown or Run-to-Failure Maintenance

The basic principle of this maintenance philosophy is to allow the machinery to operate or run until failure occurs. The corrective action is to repair or replace the damaged machinery part. It is very obvious that this maintenance technique is not suitable for critical machine. This maintenance philosophy has its advantages and disadvantages.

Breakdown maintenance has two advantages. The first advantage is that it does not need periodic maintenance activity. In this technique, corrective action will be done after the machine fails. Thus, the maintenance cost for this philosophy is low. It has been discussed in the previous paragraph that the corrective action is to repair or replace the damaged part of the machine which is not critical for production process. So, the second advantage is it does not interrupt the production process.

On the other side, this maintenance philosophy has some disadvantages. The first disadvantage is it can cause the production process stopped if it is applied to the critical machine. The second disadvantage is people in industry tend to increase the number of spare parts and this condition will lead industry to the increase of spare part procurement cost. In addition for the two previous disadvantages, the late corrective action can cause another failure.

From the previous explanation, it can be concluded that breakdown maintenance philosophy has big risk to be applied in industry. Because of that, people in industry prefers to use preventive and predictive maintenance.

2.         Preventive or Time-Based Maintenance

This maintenance philosophy is suitable for critical machine. In this philosophy, overhaul is done at certain time which is scheduled before. Similar to the breakdown maintenance, preventive maintenance has advantages and disadvantages.

The first advantage of this method is it lengthens the machinery lifetime. By applying scheduled inspection, machinery fault can be avoided and this condition makes the machinery lifetime becomes longer. The second advantage is the number of spare parts can be reduced and the procurement cost is lower than the cost in the previous philosophy. This advantage makes preventive maintenance is preferable to breakdown maintenance.

Preventive maintenance also has several disadvantages. The first disadvantage is unnecessary overhaul can happen. Unnecessary overhaul means corrective action which is done when there is no machinery fault exists. This overhaul is wasteful and can trigger another machinery fault. In addition, the second disadvantage is failure can occur because of imperfect reparation.

3.         Predictive or Condition-Based Maintenance

Predictive maintenance is maintenance method which is based on actual machinery condition. This method has several characteristics. The first characteristic is predictive maintenance replaces scheduled overhaul with periodic machinery condition based monitoring activity. Another characteristic is overhaul is done if the machine diagnostic process shows dangerous result. Similar to the two previous method, predictive maintenance has advantages and disadvantages too.

The first advantage is by applying this maintenance method, machinery fault can be detected earlier and failure can be avoided. In addition, the second advantage is predictive maintenance reduces number of unnecessary overhaul. Thus, it can reduce the maintenance cost and lengthen the machine operational time.

On the other hand, this method has also disadvantages. The first disadvantage is this method need early investment related to machinery diagnostic tools and equipments. The last disadvantage is industrial training is needed for employee who takes a part in this predictive activity. Thus the factory must spend some money for this training cost.

Engineering Article (1)

Misalignment Basic Knowledge

Misalignment is the condition when there is deviation of shaft position from its collinear axis or from the reference shaft position.

Misalignment can occur in two basic forms: parallel and angular misalignment. In parallel misalignment, the deviation of shaft position from the reference shaft position is called as offset. For angular misalignment, the deviation is called as gap.

In industrial world, misalignment usually occurs as the combination of the two previous basic forms, i.e., parallel and angular misalignment.

Source : Piotrowski, John, Shaft Alignment Handbook, 3^rd edition., CRC Press, USA, 2007.

PERSONAL INFORMATION

FELIX BOB WIJAYA

ADDRESS:

Jl. Mentor 88

Bandung  40175

MOBILE:

+6285624644639

EMAIL:

fbw_mechanical@yahoo.com

Personal Information

Place and Date of Birth:         Bandung, 21 October 1989

Nationality:                             Indonesian

Sex:                                         Male

Marital Status:                        Single

EDUCATION

2007-2011:            Institut Teknologi Bandung (ITB), Bandung, Indonesia

                             • Bachelor of Science in Mechanical Engineering

                             • Graduated with the GPA 3.80 of 4.00

                             • Qualification: Cum Laude (2^nd of the class)

                             • Final Year Project: Rigid Coupling Bolt Vibration Signature in Rotating Shaft with   

                               Parallel Misalignment

2004-2007:            Saint Angela High School, Bandung, Indonesia

WORKING EXPERIENCE

Aug 2011 – Present:  Research Assistant in Dynamic Laboratory, PRI, ITB 

• Research focuses in misalignment vibration signature analysis for industrial predictive maintenance. 
• Research project:   Parallel Misalignment Analytical Model Development

June-July 2007:      Design Engineer (Internship) at PT. Nusantara Turbin dan                                      Propulsi Indonesia

·          Two month internship as required for Job Training Course at Institut Teknologi Bandung (ITB)

·          Project: Preliminary Finite Element Modeling of JT8D Low

Pressure Compressor.

PART TIME JOB

July 2010:       Teaching Assistant in Basic Vibration Training for Industry, Dynamic Laboratory, PRI, Institut Teknologi Bandung (ITB)

July 2011:     Teaching Assistant in Basic and Advanced Vibration Training for Industry, Dynamic Laboratory, PRI,  Institut Teknologi Bandung (ITB)

ORGANIZATION AND COMMITTEE EXPERIENCE

2007-2011:      Member of Catholic  Student Union, Institut Teknologi Bandung (ITB)

2004-2007:      Staff of High School Intra Organization, Saint Angela High School

2006-2007:      Physics Olympiad Participant (3^rd grade Senior High School)

2005-2006:      Physics Olympiad Participant (2^nd grade Senior High School)

2004-2005:      Physics Olympiad Participant (1^st grade Senior High School)

                                                                                                                          

award

        2^nd Best Student in Mechanical Engineering Department, ITB (2011)

SKILLS AND INTERESTS

•       Computer literacy: Microsoft Office,  MATLAB, Inventor, and FEMAP with Nastran

•       Language proficiency:

• English:  Good (TOEFL : 440)

• Bahasa Indonesia: Excellent

•       Soft skills:

• Good team player with good communication skill

• Fast learning on new things

• Self motivated

• Maintain good performance even under pressure

• Strong analytical and interpersonal skill

• Basic knowledge in vibration analysis

·           Trainings:

• Basic Programming for Signal Processing Using MATLAB (2010)

• Advance and Basic Vibration Training for Industry (2009)