Routine
inspection procedures indicate that
levels of noise or vibration on a product
have exceeded recommended limits
When?
- Tests can be carried
out by inspection and service personnel:
- As part of an end function
quality test after final assembly
- To verify conformance
after installation on site
- To confirm compliance
after the machine has been in service
for some time as part of a structured
maintenance routine
How?
The procedure is usually laid out by
the appropriate standard that is specified
for the type of machine (ISO, BS, ANSI,
API etc). The process usually involves
taking vibration measurements at each
bearing position along the machine’s
length and in each of two planes.
Because machines can be mounted in a
variety of positions the measurement
planes can be vertical and horizontal,
X and Y, axial and fore / aft etc.
If the product does not have easily
accessible bearing positions then any
location that is deemed to representative
of the quality can be used. These should
be easily identifiable and used consistently
by all operators and for all subsequent
tests.
Using the instrument template
generator, the AS-440 can be pre-installed
with the appropriate test settings indicating
machine type and measurement positions.
The acceptance limits can also be defined
by the user or a supervisor in accordance
with external international or internal
company standards.
The operator would select
a machine type to be tested from a menu
and would then be presented with a display
of the measurement positions to be recorded.
The operator would work through the
list, recording data until the machine
survey is complete.
For each measurement taken the recorded
values will be displayed together with
a colour coded pass / fail indicator.
This would reflect the health or quality
of the product.
Overall vibration readings and spectra
will be stored to memory for future
retrieval and analysis.
Once a standard has been
identified for use, then the measurement
procedure and vibration limits can be
made into a AS-440 test template using
the Check to Conformance configuration
tool. This one off exercise creates
a template. A survey is then made in
accordance with the template and readings
stored into a new file.
AS-440 templates are available for the
following popular standards:
ISO 10816 Parts 2-6 Mechanical
Vibration - Evaluation of machine vibration
by measurements on non-rotating parts:
- Part
2: Land based steam turbines
and generators in excess of 50 MW
with normal operating speeds of 1500
r/min, 1800 r/min, 3000 r/min and
3600 r/min.
- Part 3:
Industrial machines with nominal power
above15 KW and nominal speeds between
120 r/min and 15,000 r/min when measured
in situ.
- Part 4:
Gas driven turbine sets excluding
aircraft derivatives
- Part 5:
Machine sets in hydraulic power generating
and pumping plants
- Part 6:
Reciprocating Machines with power
ratings above 100 KW
ISO 8528 English
- Reciprocating internal combustion
engine driven alternating current generating
sets.
- Part 9:
Measurement and evaluation of mechanical
vibrations
ISO 13332
- Reciprocating internal combustion
engines.
Test code for the measurement of structure-borne
noise emitted from high speed and medium
speed reciprocating internal combustion
engines measured at the engine feet.
BS 4999-142 (1987) – General
requirements for rotating electrical
machines.
Specification for mechanical performance
vibration.
BS 4675-1 (1976) –
Mechanical Vibration in rotating machinery.
Basis for specifying evaluation standards
for rotating machines with operating
speeds from 10 to 200 revolutions per
second.
ANSI/HI 9.6.4-2000 –
American national standard for centrifugal
& vertical pumps
For vibration measurements & allowable
values.
Data Retrieval
and Analysis
Stored data can be transferred to a
PC via USB, Infra Red (IrDA), RS232
serial ports or memory card. The data
is in comma separated values (*.csv)
but will appear as a Microsoft Excel
spreadsheet.
The data can be used in various
ways. For example;
- Plotting vibration
data versus machines tested to trend
changes in quality
- Viewing vibration spectra
to make to diagnose a problem
- Archival of reference
vibration signatures for future comparison
with data taken after installation
or service period
- Plotting vibration
data versus time to trend changes
in machine health
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