You offer the software for automatic diagnostics of rotating
machine units such as bearings, impellers, gear wheels and so on. Are all these
units really diagnosed similarly in different types of machines? The question
asked by the representatives of the metallurgical plants during the annual
meeting of maintenance service managers of metallurgical industry.
The question is answered by
Natalia A. Barkova:
The peculiarities of diagnostics of the same units in
different machine types certainly exist and they are taking into account in the
proposed software. These peculiarities can be divided into three main aspects:
by rotation frequency,
by machine construction peculiarities,
in what stage of the specified operation life the machine
or its unit is diagnosed.
So when the diagnostics is made for a machine with rotation speed of several RPM
then it is made by middle frequency vibration, but when the rotation speed is
about several revolutions per second it is made by low and high frequency
vibration.
According to the constructive peculiarities the machines are divided firstly by
those where each unit is accessible for vibration measurements and those where
many diagnosed units have no access for measurements and the vibration there has
to be measured on a significant distance from the optimal control points. In the
first case it is possible to diagnose in detail each unit separately, in the
second case it is necessary to diagnose a group of units jointly creating a very
special diagnostic programs. Such programs are designed and customized for
example for some types of aviation engines and certain types of gas pumping
machines in gas industry.
By different stage of specified service life the machines are divided on three
main groups. The first group includes the machines just after manufacturing
(maintenance), not run-in, with possible manufacturing and mounting defects. The
second group includes the permanently controlled machines with possible defects
of wear that are detected in the incipient stage of development and are watched
up to their repair. The third part includes the machines that are diagnosed for
the first time before their repair with the aim of flaw detection.
In the first and third cases the standards of unfalty and faulty units are
automatically constructed by a group of machines of similar type, and in the
third case the possibility of machine dangerous condition appearance is
additionally taken into account when the main methods of detailed diagnostics
may already not work and give incorrect results.
In the second case the standard of unfalty machine (unit) is automatically
constructed on the results of preceding intermittent vibration measurements and
the symptoms and defect levels are defined a priori by the results of special
diagnostic investigations with the possibility of these levels following
corrections. In this case it is possible to achieve the most reliable results.
Its own peculiarities has the transport machine and unit diagnostics. For this
type of diagnostics are produced even special diagnostic systems which are often
called the stand systems. They have two peculiarities. The first one is the
result of limitations on the transport mode of operation during the procedure of
diagnostics. It is made not during the transport movement it means not when the
transport has the specified optimal revolution rate and loads applied to the
diagnosed units. The second peculiarity is in often absence of the data
concerning the vibration and noise that could be obtained during periodical
measurements. Consequently the diagnostics is usually made according to the
rules concerning the flaw detection of the equipment that came for repair, viz.
according to the rules for the third group of diagnosed equipment.
