Lesson 01 PDF

SHAFT ALIGNMENT AND VIBRATION ANALYSIS

Lesson 1 Code: Sabic – M22B 1

LESSON 1

INTRODUCTION TO SHAFT ALIGNMENT Shaft alignment is a technical skill that is not common in the construction and maintenance

professions, but categorized more like a specialty. It requires unique and expensive

measurement instruments, some calculation capability, and relies heavily on experience for

successful results on heavy, high-speed, or high-temperature machines. This training

course will provide an integral training knowledge and experience of shaft alignment to

solve misalignment problems in rotating machinery. Emphasis shall be laid on ways to

analyze, identify and correct the root causes of misalignment, unbalancing and vibration to

achieve precise operation, and improving machinery performance.

Vibration monitoring and analysis are useful tools for predicting incipient mechanical,

electrical, and process-related problems within plant equipment, machinery, and

continuous-process systems. Therefore, they are the most often used predictive

maintenance technologies. Vibration analysis can provide the means to first schedule

maintenance and ultimately to eliminate the need for corrective maintenance tasks.

Vibration analysis can be used to evaluate all equipment within a plant. The monitoring of

the condition of machinery can significantly reduce the costs of maintenance. Firstly it can

allow the early detection of potentially catastrophic faults which could be extremely


2 Code: Sabic – M22B Lesson 1

expensive to repair. Secondly it allows the implementation of condition based maintenance

rather than periodic or failure based maintenance. In these cases significant savings can be

made by delaying scheduled maintenance until convenient or necessary. This training

course is designed to expose the techniques of vibration analysis of machinery, with the

aim of improving machinery monitoring and diagnosis and to implement latest standard

systems and procedures as a tool for achieving precise operation, and improving machinery

performance. Emphasis shall be laid on topics relevant to basics of vibration, vibration

measurements, vibration analysis, international standard system and assess machinery

condition. It provides valuable information and knowledge of the principles and procedures

of condition based monitoring and machine condition monitoring, with focus placed upon a

range of topics, e.g. machinery vibration response, data acquisition procedures, transducer

selection & mounting, signal conditioning, data displays, machinery condition evaluating

and analysis and computer application in vibration analysis and condition monitoring. The

objective of this training course is to prepare attendees to be better analysts and gain

understanding of vibration principles and techniques and add to their practical knowledge of

machines.

Who Should Attend:

The training program is designed and targeted to engineers and technicians who are

dealing with the operation and maintenance of rotating equipment and totally new to shaft

alignment and who are running alignment and wish to improve their knowledge and skills.

And for all interested and using vibration and equipment condition monitoring for identifying

and correcting the machinery problems. And for maintenance engineers, maintenance

planners, supervisors and managers and senior technicians involved in machine’s condition

monitoring and vibration measurement and analysis.



Introduction to Shaft Alignment

What is shaft alignment?

Shaft alignment is the positioning of the rotational centers of two or more shafts such that

they are co-linear when the machines are under normal operating conditions. The Process

of Adjusting a piece of machinery so that its shaft will be in line with the shaft of the

machine to which it coupled (The Stationary Machine). Alignment is a critical aspect of

operation and the techniques used should be properly understood. Misalignment is the

main cause of Machine Potential Failure Shaft alignment is a technical skill that is not

common in the construction and maintenance professions, but categorized more like a

specialty. It requires unique and expensive measurement instruments, some calculation

capability, and relies heavily on experience for successful results on heavy, high-speed, or

high-temperature machines. Side Effect of Misalignment

• Bearing failure

• Coupling Failure, even in flexible types

• Internal heating

• Shaft Fatigue

• Seal Leakage

• High energy consumption

• Bearing failure

• Vibration

Misalignment causes excessive vibrations. It is, by far, the leading cause of machinery

malfunctions, downtime and maintenance (but often not identified as the root cause). There

is also no testing or certification of alignment craft people. With no common training, no

certification, and no common standards, it should come as no surprise that there is large

variability in the results. The guidelines for when to require alignment checks are:

1. All new shaft coupled equipment.

SHAFT ALIGNMENT

AND VIBRATION ANALYSIS

2. After repair work is done that disturbs shafts or bearings, and before energizing.

3. Whenever vibration indicates the need.

4. Periodically on critical equipment

Fig. 1-1. The most important requirement for any shaft alignment system is repeatability of the

readings. This is evaluated with a 360 deg repeatability test. It is also a good way to

evaluate a fixture system when considering a purchase. Basically, measuring systems that

do not return to zero (within 0.002 inch) after a 360 deg rotation should be rejected. Be

suspicious of plastic straps or other flexible fixture components. The choice of measuring

systems and methods is up to the aligner. The two fundamental choices are dial indicators

or lasers. Dial-indicator systems are the most useful because they can be used to measure

shaft run out, bearing alignment, and soft foot directly. All of the above measurements are

required by the standard, and needed to assure a goo(l-running machine, but not attainable

with lasers. Lasers require batteries, are not intrinsically safe for use in explosive

environments, and cannot do face-and-rim measurements.

Correcting Common Problems Time is spent on collecting vibration data on hundreds of machines, But not on actually

correcting the problems. Those involved with the PDM implementation do a lot of analysis

may not be involved in the correction of the problems they have identified.




How to utilize these data?

First step: Determine which pieces of equipment are problems and which are not. The vibration limit of

0.3 ips ( 7.6 mm/s) is a good break point to use. All equipment 0.3 ips (7.6 mm/s) or higher

should be repaired if the number of equipment at or above 0.3 ips is too large to tackle, a

further prioritizing process may be necessary.

Next Step: Breaking down the equipment over the limit by type..

Fig. 1-2. Categorized Equipment Failures.

Of the 109 machines over the limit pumps and fans seem to have the biggest problems.

Third step: Looking into the work performed on pumps and fans can often reveal a facility-wide or

systemic problem. For example, the facility that reported this data further investigated pump

problems. The result indicated that there was little or no alignment of coupled machinery

being performed.

Fourth step: Deeper investigation revealed that the plant’s only dial indicator (used in precision

alignment) was damaged and locked away in a machinist’s toolbox. The facility purchased

SHAFT ALIGNMENT


new indicators and trained every mechanic in proper alignment techniques. As stated

previously, the most common problems found in rotating machinery through vibration

analysis are (in approximate order) misalignment, imbalance, bearing damage, and

looseness. Grouping all problems together can start to reveal other systemic problems.

Investigations can help facility management focus on the top problems that can be solved,

with additional training, new methods, or new equipment.

Fig. 1-3. Types of Misalignment

Explanation of offset and angularity

Fig. 1-4.




There are two components of misalignment-angular and offset.

Explanation of Vertical Angularity

i. Positive Vertical Angularity

Fig. 1-5. ii. Negative Vertical Angularity

Fig. 1-6.

SHAFT ALIGNMENT

AND VIBRATION ANALYSIS Explanation of Horizontal Angularity i-Positive Horizontal Angularity

Fig. 1-7.

ii-Negative Horizontal Angularity

Fig. 1-8.




Explanation of Offset i. Positive Vertical Offset

Fig. 1-9

ii. Positive Horizontal Offset

Fig. 1-10.

SHAFT ALIGNMENT


iii. Negative Vertical Offset

Fig. 1-11. iv. Negative Horizontal Offset

Fig. 1-12.




Angular misalignment: This occurs when the shaft center-lines are out of parallel, although they may intersect at

the coupling. Angular misalignment sometimes referred to as “gap” or “face,” is the

difference in the slope of one shaft, usually the moveable machine, as compared to the

slope of the shaft of the other machine, usually the stationary machine. The units for this

measurement are comparable to the measurement of the slope of a roof (i.e., rise/run). In

this case the rise is measured in mils and the run (distance along the shaft) is measured in

inches. The units for angular misalignment are mils/1 in. As stated, there are two separate

alignment conditions that require correction. There are also two planes of potential

misalignment-the horizontal plane (side to side) and the vertical plane (up and down). Each

alignment plane has offset and angular components, so there are actually four alignment

parameters to be measured and corrected. They are horizontal angularity (HA), horizontal

offset (HO), vertical angularity (VA), and vertical offset (VO).

Fig. 1-13.

SHAFT ALIGNMENT


Fig. 1-13. Contd.

Parallel, Offset misalignment:

This occurs when the shaft center-lines remain parallel, but are offset Offset misalignment,

sometimes referred to as parallel misalignment, is the distance between the shaft centers of

rotation measured at the plane of power transmission. This is typically measured at the

coupling center. The units for this measurement are mils (where 1 mil = 0.001 in.).

Fig. 1-14.

Fig. 1-15.


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