ADASH Ltd.
Adash 4300 – VA3Pro
For further technical and contact information visit www.adash.com, email: [email protected]
63
Appendix B: Standards for vibration measurements
Using standards is a frequent topic in vibration diagnostics. As there are a lot of different types of
machines it is
impossible to determine the critical limits of vibrations for a wide range of machines. Its reliability would be then
low. It could happen that you would repair a machine unnecessarily. The standards should rather be determined
for a narrow range of machines.
Adash Limit Values
Adash limits are not rewritten from any existing standard. It is a result of more than 20 years of the Adash
engineering team's experience. It is difficult to invent a critical value definition which would be simple (which
means not many parameters such as speed, power, bearing type, machine type and so on) and reliable.
In the figures below you can see how to derive Adash limit values. There are three levels of machine condition
defined: GOOD, ALERT (Machines that lay in this range are not acceptable for a long period of operation, they
can be operated until time when they can be repaired) and DANGER (Vibration values in this range are
considered as very dangerous and machines should not be operated). The corresponding colours are taken
from traffic lights - green, yellow and red.
All limit values are related to the speed value. Low speed machines should generate lower vibration than higher
speed machines.
You can find three particular areas in the graphs below. The GOOD condition is the area up to the yellow line
which means operation without restriction. The area above the yellow line and under the red line is the ALERT
condition. It is possible to operate the machine but is has to be checked more frequently and it is necessary to
determine the source of the worse condition and plan the repair (for instance change the bearing) or
maintenance (balancing, alignment). The area above the red line is the DANGER condition and the machine
should not be operated. The first figure contains the values for overall machine condition. The value of overall
machine condition can determine unbalance, misalignment or mechanical looseness. They are called “overall”
because we can measure them on most of the measuring points on the machine. The second figure contains
the limit values of roller bearing condition. This condition is local and can be measured only on the appropriate
bearing house.
It is easy to understand the graphs below. It is necessary to know the speed. The instrument (A4900)
determines the speed automatically or it can be entered manually by the user. Look at the graph and find the
point on the horizontal axis which corresponds to the speed. You will find an intersection with the yellow and red
lines above this point. Projections to the vertical axis will determine limit values for yellow (ALERT) or red
(DANGER) states. If the measured value is lower than the yellow value the condition is GOOD – green. If the
value is above the yellow value and under the red value then the condition is ALERT – yellow. If the measured
value is higher then the red value then the condition is DANGER – red.
