Production efficiency and output
can often be improved by increasing machine speed and changing
the machine’s configuration. In some paper machines,
these steps raised paper speeds from 800 to 2000 m/min. After
these modifications, machine and plant components that for
years have run smoothly may unexpectedly develop premature
wear on shafts, gear teeth and bearings, or fail altogether.
Increased vibration and resonances may reduce operating reliability
and the service life of drives and machines. An excessive
level of disturbing vibrations can even reduce the quality
of manufactured and processed products. Figure 1 identifies
rolling mill drive components that often exhibit an increase
in vibrations and disturbing vibrations.
Fig. 1: Sources of vibration excitation in a rolling mill
Experienced maintenance engineers begin early to search
for methods of reducing vibrations to ward off premature wear
and fatigue fracture.
If the problem is with resonance, excitations must be minimized
and/or mass-to-stiffness ratios selectively changed. Which
particular measures are effective and suitable? Usually, a
specialist is asked to determine the vibration cause on a
single day of measurement and based on that makes a recommendation
on how to minimize vibration. But what if the disturbing vibration
doesn’t occur on the measurement day? Waiting around
on site for it to arise is far too costly.
It is for cases like these that PRÜFTECHNIK offers
short-term telediagnosis services. A rented VIBNODE
might be installed on the affected machine for four weeks,
for example. The Diagnostic Center then remotely identifies
and characterizes the disturbing vibrations and searches for
relationships to the operating and process conditions. The
photo on the left shows a VIBNODE system on a marine propulsion
plant. During sea trials, this temporary online CMS was used
to continuously record the vibration conditions on the port
and starboard drives and activate the frequency analyses.
With an Internet connection, the measurement results can be
transmitted from VIBNODE to the Diagnostic Center by eMail.
Drive and process conditions are measured around the clock,
making if possible for PRÜFTECHNIK diagnosis specialists
to recognize atypical operating and vibration conditions without
having to be on-site.
Figure 2 shows vibrations on a roll drive. A natural frequency
was excited at 1800 m/min. Continuous measurements revealed
an increased level of vibration, which ceased after a new
roll with greater stiffness was installed.
Fig. 2: Reduction in vibration on a paper machine |
