Vibration Analysis Overview
It has been shown many times over that
the vibration of an operating machine provides far more information about the
inner workings of that machine than any other type of nondestructive test. A
bearing that has a small developing fault will cause a tell-tale change in the
machine's vibration, as will a weight imbalance condition, a shaft or coupling
misalignment, or any of a myriad of other faults.
With virtually all building owners and
operators seeking reductions in plant maintenance manpower, as well as greater
efficiency of all maintenance practices, the value of vibration analysis has
become more obvious in recent years. Vibration analysis provides a thorough
evaluation of all moving parts of one's plant equipment and machinery, can
identify root causes as well as specific machine faults, and most importantly,
is capable of correctly identifying those machine faults when or actually
before they first appear.
Diagnostic Advantages Of Vibration Analysis
Vibration analysis, properly applied,
allows the detection of small developing mechanical defects long before they
become a threat to the integrity of the machine, and thus provides the
necessary lead time to suit the needs and schedules of the plant operators /
management. In this way, plant management has control over the machines, rather
than the other way around. Properly applied, vibration analysis offers the
following significant benefits:
First of the many benefits of vibration
analysis is the ability to avoid the more common method of plant maintenance
known as "Run to Failure." Substantial savings are possible if a machine
is shut down for repairs before a catastrophic failure occurs. Repair costs
typically triple if machines are allowed to run to failure versus, for example,
the planned replacement of a bearing found to be worn prior to its failure.
Most plant operators have experienced problems where the bearings have had to
be cut from the shaft, and where the rotor had to be re-worked to repair the
damage caused by a resulting major failure.
- Quality Assurance Of New Installations And
Of New Or Overhauled Equipment
It is well known that many machines
contain hidden defects when newly installed. These defects can range from
improper installation caused by poor footings and poor alignment, to defective
parts within the machine itself - such as bad bearings, bent shafts, and so
forth. A proactive maintenance program will include testing on even new
installations for the purpose of verifying that the equipment in question meets
a specific standard. The same standards are applied to rebuilt and overhauled
equipment.
This type of testing can also help
establish specific performance specifications, which, in some cases, may be
more stringent than the equipment manufacturer's specifications and tolerances.
It is possible to write vibration acceptance criteria into purchasing
specifications to insure quality materials and workmanship, and then verify
contract performance. Verifying equipment integrity and performance has become
a major issue given minimal design and construction techniques now frequently
used by contractors to provide cost savings.
Class design problems built into new
installations or replacement machinery can waste many man-hours trying to
identify the source of the problem, as well as add unexpected expenditures for
parts and repairs. Vibration analysis offers an excellent method of avoiding
lengthy trouble shooting before you accept new machinery.
- Reactive vs. Proactive
Maintenance
The early warning of emerging machine
faults allows an engineering department to plan for repairs, to order parts,
and to schedule the appropriate personnel to perform the work. This minimizes
downtime and the related adverse effects to plant operations common to
providing an emergency response. As the engineering staff becomes more
efficient, and reduces their "Fire Fighting" response to maintenance
demands, they will be better able to meet other preventive maintenance
schedules - thereby increasing overall department efficiency.
- Just-In-Time Parts Inventory
The predictive machine condition
information provided by an established vibration program allows
"Just-In-Time" inventories to be implemented while reducing risk.
Instead of paying exorbitant costs for rush orders and overnight shipping,
parts may now be ordered when problems first appear - thereby being available
just prior to the scheduled repair. Vibration analysis allows equipment
reliability to be maintained, but without the need to maintain an expensive and
often redundant parts inventory.
- Avoid Calendar Based
Maintenance
"If it ain't broke, don't fix it"
is still a very popular saying in the plant and building maintenance industry.
This implies that you should wait until a machine fails. Yet, such
"Run-To-Failure" type maintenance actually increases repair costs and
overall operating expenses tremendously.
Calendar-based maintenance, the most
commonly used maintenance program, results in the repair of healthy machinery
in many cases, and can be costly in parts and manpower. Calendar based repairs
can only be justified with strong historical evidence supporting machine life
cycles. In contrast, vibration analysis identifies only that specific equipment
which is reaching a defective condition.
- Increase Mean Time Between
Failures
Root cause failure analysis using
vibration techniques is a proven method in achieving a higher Mean Time Between
Failure (MTBF). Many machine problems cause increased vibration levels that
actually create other problems. For example, misalignment and/or imbalance
causes high vibration levels which overload the bearings. Eventually, the
bearings fail, but replacing the bearings represents only half the maintenance
required. In fact, the machine should also be aligned and/or balanced properly,
or the next set of bearings will wear out prematurely as well. As longer MTBF
periods become reality, maintenance schedules can be realistically adjusted.
Vibration analysis information of a plant
site allows management to make decisions based on known machine condition. As a
result, planning budgets can now be justified with vibration analysis results.
Resources are directed on a need basis and unnecessary maintenance functions
may be avoided.
On the average, 5-15% of the total energy
consumption of a mechanical plant is wasted due to the operation of equipment
at less than optimum conditions. This results in heat production. Two dominant
causes of energy being converted to heat instead of horsepower is the
misalignment and/or imbalance of rotating machinery. The detection of both
conditions are two of the easiest diagnostics to determine via spectral
analysis of vibration data.
Common Applications
Vibration analysis, is the single best
indicator of a machine's condition, and is commonly utilized in the commercial
and industrial sector for monitoring the following rotating and reciprocating
equipment:
- Belt, Chain And Coupling Driven
Equipment
- Fluid Drive Couplings
- Generators
- Centrifugal And Propeller
Pumps
- Rotary Thread And Sliding Vane
Pumps
- Axial Piston Pumps
- Purifiers
- Reduction Gears
- Diesel Engines
- Turbochargers
- Fans and Blowers
- Turbines
- Centrifugal, Reciprocating, And Screw
Compressors
- Motors - AC And DC
- Gear Boxes
Recommended Levels of Testing
In order to get the best results from a
vibration analysis program, regular equipment testing is required. When the
program is first set up it will generally provide only a small set of data to
evaluate. In the worst case, there may be only one set of reference data from
only one individual piece of equipment. At best, a number of examples of the
same given machine type will provide a larger sample of data for analysis and
comparison. As each machine is re-tested and another cycle of data collected,
the accuracy for evaluating equipment condition will improve.
Clearly, a successful vibration program
is dependant upon an accurate accumulation of data over time. How often data
should be collected is generally dictated by how critical your equipment is to
your specific operation. Each time a reading is performed on a particular piece
of equipment, the success rate of your vibration analysis program increases and
the better your chances are of allowing yourself to forecast equipment
problems, schedule corrective action and avoid catastrophic failure. Generally
speaking, in most applications, the minimum data collecting frequency is
quarterly. Semi-annual testing may be appropriate to some non-critical
equipment types.
Reporting Criteria
East Coast Industries, Inc. employs one
of the most powerful vibration software packages available on the market today.
Instead of offering a generic report showing the good or bad waveform results
for each piece of equipment, ECI produces an in-depth client specific analysis
- including any appropriate recommendations.
Our final report includes actual spectrum
graphics, specific data derived from all test locations, and a complete
explanation of its importance. The final result is a professional, ready for
presentation report filled with the information necessary to not only justify a
repair, but to pinpoint the origin of the problem and the replacement parts
required.
Field Testing
Vibration analysis can usually be
accomplished during normal business hours. Depending on the individual
building's operational procedure, the equipment type and it's availability,
approximately 25 pieces of machinery can be tested during a normal business
day. The one time attachment and set-up of the vibration pad, and recording of
all equipment operating data is typically performed prior to beginning the
testing program.
While in the field collecting data, we
simultaneously perform automated diagnostics to identify any significant
faults. These findings, if any, are immediately referred to the appropriate
operating personnel. An in-depth analysis of all collected data is performed;
producing a final report within 7 to 10 business days. This report provides a
wealth of information allowing the building professional to make the proper
business decisions based on actual hard data, rather than guesswork and
assumption.
Pricing Guidelines
Fees are based upon the equipment type,
number and frequency of pieces tested, and include a full color report with all
supporting documentation. Additional report copies are available upon request,
and all reports are archived by ECI for a period of five years.
Fees vary from $40 to $200 depending on
the complexity of the equipment and the ability to access all necessary areas
within the property to tag and test approximately 25 pieces per each day. A
motor/pump or motor/fan combination is considered a single piece of equipment,
and one time set-up fees generally apply. Vibration testing that is located
outside the immediate New York City area is priced at the same rate, but with
the addition of actual expenses for travel and hotel accommodations.
Report Samples
A selection of reprinted pages from a
typical client report can be accessed from the navigation bar at the left, and
is provided in order to illustrate the level of detail we provide. Although
such high detail is requested by many clients, summary information in the form
of written text and graphics is also provided.
Graphed summaries are particularly useful
for identifying various trends which may exist, and for comparing and
evaluating the cumulative data derived from all test locations. A separate
priority worksheet is provided, and lists all test locations in need of
corrective action. All equipment problems and visually observed defects are
documented with a photograph and commented upon.
Each report offers both an executive
summary as well as a detailed discussion of our findings. Written
recommendations and corrective measures are also made addressing any equipment
deficiencies identified in the report. A photograph of each piece of equipment
showing the actual test area is incorporated into each detail page of the
report in order to better identify the test site to the reader, and to aid
follow-up testing or future investigators.
Since a high level of detail is provided
in each ECI vibration report, and because we do not always have the opportunity
to present our findings personally, we provide the written explanation and
background information necessary to understand its content as best possible. A
typical report will cover between 100 and 125 pages, and is written and
arranged in an user friendly easy to read format.
Each report is preceded with a thorough
explanation of the testing procedure, equipment used, basic theory of vibration
analysis, and necessary assumptions related to our testing and reporting
procedure. Due to the fact that our vibration analysis testing reports are
often submitted past a wide range of individuals including building owners,
property managers, operating engineers, and consulting engineers, we have
always strived to provide information ranging from the most basic conclusions
to the most detailed technical information.
For further, more detailed information
regarding the actual testing procedures used, please view our
Vibration Testing and
Reporting Specifications.
Testing
Services