Vibration And Noise - ABB AMG 0180 User Manual

7.4.2 Vibration and noise

High or increasing vibration levels indicate changes in the machine's condition.
Normal levels vary greatly depending on the application, type and foundation of
the machine. The vibration measurements and levels are discussed in detail in
Chapter 5. Commissioning. Some typical reasons that might cause high noise or
vibration levels are:
•
Alignment, see Chapter 3. Installation and alignment.
•
Air gap, see Chapter 3. Installation and alignment.
•
Bearing wear or damage.
•
Vibration from connected machinery, see Chapter 5. Commissioning.
•
Loose fastenings, see Chapter 3. Installation and alignment.
•
Rotor imbalance.
•
Coupling.
Normal vibration levels
The following instructions are part of the following two ISO standards:
1. ISO 10816-3:1998 Mechanical vibration - Evaluation of machine vibration by
measurements on non-rotating parts: Part 3: Industrial machines with nominal
power above 15 kW and nominal speeds between 120 r/min and 15 000 r/min
2. ISO 8528-9:1995 Reciprocating internal combustion engine driven alternating
current generating sets: Part 9: Measurement and evaluation of mechanical
vibrations.
Measurement procedures and operational conditions
General procedures described in ISO 10816-1 are used, subject to the
recommendations listed below.
Measurements are usually made when the rotor and the main bearings have
reached their normal steady-state operating temperatures and the machine running
under specified conditions, e.g. at rated speed, voltage, flow, pressure and load.
If the measured vibration exceeds the acceptance criteria and excessive
background vibration is suspected, measurements should be made with the
machine shut down to determine the degree of external influence. If the vibration
with the machine stationary exceeds 25 % of the value measured when the
machine is running, corrective actions may be necessary to reduce the effect of
background vibration.
Measurement equipment
The measurement equipment must be capable of measuring broad-band r.m.s
vibration with flat response over a frequency range of at least 10 Hz to 1000 Hz,
in accordance with ISO 2954. Depending on the vibration criteria, this may
require measurements of displacement or velocity or combinations of these (see
ISO 10816-1).
Measurement location
Use a measurement location that is exposed and accessible during normal
operation. Make sure that there are no local resonances or amplification so that the
final measurements will reasonably represent the vibration of the bearing housing.
The locations and directions of vibration measurements should provide adequate
sensitivity to the machines dynamic forces. Typically, this will require two
orthogonal radial measurement locations on bearing cap or frame. Place the
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