Havec thrust monitor system

4/2/2020 HAVEC - Thrust Monitor System
https://www.havec.eu/en/offer/industrial-automatics/thrust-monitor-system.html 1/16
(https://www.havec.eu/)
THRUST MONITOR SYSTEM
Thrust Monitor System. A new way of
approaching the problems of roller skew and
thrust control in rotary equipment.
Rotary cooler, dryer, granulator or kiln -
support roller thrust monitoring.
Bearing failures and high rates of tyre and roller
surface wear due to high thrust loads are a thing
of the past.
From our experience the number one problem for
all industries operating rotary units is roller skew
and thrust control.
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Even when the simple physics of action – reaction,
roller adjustment, change of thrust – is well
understood, failures still occur. Obviously it all
comes down to alignment. On analyzing alignment,
the closer one looks, the more one may lose
confidence in the results.
Installation of real-time thrust monitoring system
allow to extend the lifetime of components
(support rollers, bearings, thrust rollers, tires etc.)
by more than 10 years.
Advantages of TMS:
Before (sign of excessive wear)
After (shiny surfaces – sign of perfect alignment)
No unplanned stoppages of rotary equipment

SYSTEM PRINCIPLE
Two versions of support roller bearings
Journal or sleeve bearings and spherical roller
bearings, a type of anti-friction bearing.
The typical kiln uses journal bearings. The housings
for these types of bearings also incorporate
separate thrust bearings. The roller assembly is
such that the distance between the thrust bearing
uphill to downhill leaves room for shaft to float
axially (uphill to downhill) nominally about 6 – 12
mm. This is purposely done to facilitate identification
of the rollers’ neutral skew position by simple
adjustment and observation without the need to
make any alignment measurements. When the
skew of the rollers drives the tyre and shell uphill,
the roller will drive itself and end up sealing itself
No excessive axial force
Significantly longer lifetime of components
24/7 condition monitoring
Detection of potential problems at an early stage
Constant alignment control

downhill. This is the normal and expected position
for the roller to be in whenever skew is applied and
the corresponding thrust bearing absorbs the load.
When the roller is than adjusted to reverse the
skew, as soon as it crosses the neutral position, the
forces also reverse and the roller starts moving
uphill. No matter what size of roller, be it 500 mm or
3000 mm dia., adjustment of less than 0.1 mm
across the neutral point will cause the roller to shift
positions. Tis technique is therefore employed to
locate each roller’s zero skew position. The
measurement required is to use dial indicators to
track the bearing adjustments.
Kilns with more substantially designed thrust roller
mechanism(s) are designed to run with neutrally
skewed support rollers, reliving them of the stresses
and subsequent wear when forced to run in a
skewed position. These are often referred to as full
thrust units.
A few kilns and most other trunnion roller supported
equipment, such as non-refractory lined rotary
coolers, dryers and granulators, make heavy use of
anti-friction bearings, namely spherical roller
bearings. Their application comes with two notable
handicaps. Firstly, there is no meaningful axial travel
by which to easily observe shaft position in
response to roller adjustment. This makes finding
the neutral skew position difficult by traditional
methods of alignment measurement. Secondly,
there is no separate thrust bearing. Spherical roller
bearings are capable of accommodating limited
thrust loads. Unfortunately, it does not take much
skew on a roller to introduce enough force to
overload it and cause it to fail. Excessive thrust
loads are exacerbated by the low speed of rotation
of rollers, which is usually no more than 50 rpm.
This may miserably slow to get the lubricant to
function effectively. As consequence, failures of
spherical roller bearings are much more common
than failures of journal bearings.

Traditional alignment
At the fundamental level, this requires only two
things:
The limit in measurement accuracy is not the quality
of the instruments brought to the task, which can be
capable of great accuracy. Rather, measurement
accuracy is also very dependent on the quality of
the target object. This can be a shaft, a bearing, a
bearing housing, a roller face and centerline. Given
the nature of the equipment to be dealt with and the
way it is installed, there are no pristine surface to
measure to. Moreover, the centerline almost always
requires the use of parallel offsets. Every additional
step adds more opportunity for imprecision.
Other factors, which are totally ignored when
carrying out such alignment measurements, are tyre
flex, tyre wobble, and base flex. All of which means
that, if one were actually capable of measuring
alignment to an accuracy of 0.1 mm, it would have
to be done at least three different times witch the
shell rotated 120o between each set of
measurements. The results would then be
averaged. When was the last time anyone saw that
done?
Some industries run what this author calls super
fast units, i.e. those at 6 to 12+ rpm. For them,
alignment never seems to be good enough, so they
resort to applying oil to the tyres. Oil is the
forgiveness option: if the alignment is reasonable,
Exact bearing elevations
Exact bearing location with respect to a centerline,
corrected for precise, prevailing roller, and tyre
diameters.

bearing failures are avoided. Oil acts to reduce, if
not completely eliminate, thrust due skew. Oiled
units should, therefore, never have their rollers
skewed. If, then, the thrust roller is not capable of
carrying the full thrust load of the unit and requires
the roller skew to protect it, the oil presents a
contradictory situation.
With oil applied to the running surfaces of tyres, this
forgiveness factor lulls one into a false sense of
security, believing that precise alignment is not
essential. However, oil is a fair weather friend: its
presence is not guaranteed to be uniform over the
long haul. A puff of dust and it becomes a grinding
compound; if the surface runs dry then there is no
forgiveness for bad alignment. That is why, even
with liberal amounts of oil applied to the tyre faces,
bearing failures abound. This scenario has become
routine in many plants. A bearing fails and when a
new roller assembly is put in place, it is done with
minimal concern for alignment or adjusting the
alignment for the inevitable difference in roller
diameters. This is not shoddy workmanship: it is
often the only available response to production
pressures and the very limited resources available
with which an alignment can be quickly verified.
For fast units, a roller with properly sized
bearings, well aligned and running without
surface oil, should run trouble-free an average
of 10 years.
Measure force not position
Bearing position is relative; axial force is
absolute.

While the best traditional methods may yield
passable results, there is no immediate feedback
confirming whether the set bearing location is
optimum. By measuring force in real-time, the
optimum bearing position announces itself.
Bearings fail when subjected to high loads, specially
high axial loads: why not then measure those loads
directly rather than assuming that a position of
minimized axial load has been set without such
confirming feedback?
Aligning the rollers based on real-time Thrust
Monitor System yields the neutral skew position of a
roller within 0.03 mm with 100% reliability.
Acceptable alignment usually only requires 0.1 mm
resolution provided its direction is verified as
positive. This method is therefore more precise than
the best “measured positions” normally produce.
How can the claim of 100% reliability be
substantiated? Simply because the measured
forces are observed in real-time and the response
to a 0.03 mm move is immediately seen. Alignment
by standard position measurement has no
immediate real-time feedback in response to a roller
adjustment.
How can it be said that alignment by the method of
thrust monitor system is more precise than standard
position alignment measurement? It is simply
judged by putting one method against the other.
Firstly, do the best standard alignment by position
measurement. Next, fit the thrust sensors to the
rollers and rotate the unit. If the alignment is correct,
a rotary unit requiring skew will have equal axial
load on each roller that just balances gravity, which
can be seen by the load on the thrust roller. If the
rotary unit is horizontal, then the axial load on each
roller should be near zero.
In almost three years of such testing, not a single
occasion arose where further adjustment, which
usually included shimming, was not required. In half

these cases, the adjustments were significant, i.e.
shim and skew correction of 3 mm or more.
Roller slope
The common cause for misalignment
For rollers fitted with spherical roller bearing, the
most common problem contributing to a
misalignment is inaccurate roller slopes. If the roller
slope is not correct, there is no subsequent
procedure that can be done to make up for it. Kilns
with sleeve bearings, particularly those with fixed
sleeve arrangements, have a very tight slope
installations tolerance usually in the order of
+/-0.02% from designed slope. With fixed sleeves
there is no self-alignment and shimming is not
permitted, so every effort is made to set the bases
precisely. Because spherical roller bearings are not
needed. Nothing could be further from the truth.
Slopes should still be set to within +/-0.02% of
designed slope, otherwise a roller set for optimum
skew will have limited face contact.

Tyre and roller surface reconditioning
Recommended for reliable alignment and bearing
failure prevention
To do a proper job of alignment, resurfacing by
grinding worn tyre and roller faces is recommended.
Alignment without resurfacing may result in less
than 70% face contact so wear will continue.
Grinding without alignment does not correct the
underlying problem that led to the need for
resurfacing. The two are inextricably linked: one
cannot do one without the other and expect the best
value for money.
To align via Thrust Monitor System, flat cylindrical
roller and tyre are recommended.
Thrust Monitor System
Alignment that eliminates all the guesswork
The basic principal of this procedure is that axial
thrust force, which results from roller skew, reverses
direction with change in direction of rotation. A

roller, however minutely skewed, creates a
measurable thrust force, either pushing the roller
downhill or pushing it uphill. Reverse the direction of
the shell rotation and the roller’s axial force also
reverses. This axial force can be plotted graphically,
in real-time, and roller adjustments as small as 0.03
mm can be easily identified. When there is no
appreciable change in thrust level going from a
clockwise (CW) rotation to a counter clockwise
(CCW) rotation, then the roller is certified to be in
the truly neutral position.
In practice, with all the sensors mounted, the shell is
rotated in its normal direction (e.g. CW). Depending
on the speed of rotation, after a few minutes all the
rollers will settle out at some level of thrust. At that
point, the drum is stopped and then turned in the
reverse direction. Immediately, all thrusts reverse
and settle out at a new level. Each roller is then
adjusted in turn until its change in thrust from CW to
CCW rotation is minimized. If the surfaces have not
been reconditioned , the tapers must be identified
by circumferential tape measurement and extracted
from the shim calculation. One of the prime reasons
for resurfacing is to avoid this unnecessary
complication as well as those caused by
convex/concave surfaces.

Once this is done for each of the four rollers, they
will all be sitting in their neutral position. Two things
now become apparent.
Firstly, the effects of the tyre wobble will be seen.
This is roughly a sinusoidal thrust pattern imposed
on each roller. For half of rotation, the tyre pushes
the roller in one direction and for the other half the
tyre pushes the roller the other way. All tyres
wobble: only the degree of wobble varies.
Secondly, upon careful examination of the quality of
contact between tyre face and roller face, any
persistent gap throughout one rotation is a clear
indication of roller slope error. This can be the only
possible explanation if the tyres and rollers have
been reconditioned. Such gaps, excluding cyclical
gaps from tyre wobbling can now be carefully
measured (after the unit is shut down and locked
out) using feeler gages from which a simple
calculation yields the required shim thickness
needed to achieve 70% face contact or better.
One the most difficult problems one faces to have a
roller’s skew set to zero thrust and then see it run
with poor face contact. The overwhelming tendency
is to readjust the skew for better face contact. This
is so easy to do but is always wrong. Minimal if not
zero skew is primary. Running with poor face
contact is far more tolerable than add skew.
Correcting the face contact requires eliminating any
face tapers and then shimming one of the roller’s
bearings to attain full face contact. This method of
correcting rollers slope has shown itself to be far
superior to any attempts at absolute measurement
with respect to a design slope using auto levels,
slope blocks/machinists level, or inclinometers.
With full thrust units, alignment is now complete.
However, most units do not have thrust rollers
robust enough to operate continuously in this state
and must be “floated”. Floating simply means that a
small amount of skew is introduced on each support

roller to counter the pull of gravity. With the ability to
graphically view the thrust levels in real-time, the
roller adjustments can be made so that each roller
can be exactly in skew to share the load equally.
When one pair of rollers supports more weight than
the other pair, then equal load does not correspond
to equal skew. This aspect of final adjustment is
also not available by standard position
measurement alignment.
A drum is said to be floating when the thrust tyre
leaves the lower thrust roller for a short period
during each revolution. This intermittent contact is
caused by the tyre wobble.
With the Thrust Monitor System permanently
installed, “float” adjustments may be modified for
load and speed once the unit has been put into full
operation.
Going forward, the system becomes an early
warning system, operating over the plant’s network
to alert of any change in bearing’s thrust load. To
assist with this, a local LED panel indicates each
roller’s thrust level by a string of lights: white for
neutral, green for normal float load, red for alarm. In
this way, the operator in the control room is kept
abreast of thrust level, and it is also clearly
displayed to all who walk by the operating unit.
Assessment of the condition of roller skew is
therefore reduced to a single glance at the control
panel.
Operating the unit after aligning it in this manner
and following it by continuous monitoring will result
in realizing maximum service life of all the rollers
and bearings.
The system is designed as an active web page
and so it is accessible anywhere on the local
network/internet via web browser (i.e. MS
Internet Explorer).

Conclusion
Aligning a unit by Thrust Monitor System does not
take any more time than conventional methods. In
many installations, the drums are powered using a
variable frequency drive (VFD). The VFD allows
reversing rotation at a push of a button, although
things like backstops and one-way clutch coupled
auxiliary drivers would have to be temporarily
disconnected. No VFD installed? No problem: these
are readily brought to site and quickly wired in for
temporary use.
For kilns with journal bearings there is no need for
rotation reversal to set zero skew.
There is one minor drawback to the Thrust Monitor
System procedure: it does not yield the actual shell
slope. This is an academic consideration only,
within the range of adjustment that can be made on
any roller: given the length of the bolt slots in the
base, the shell slope cannot be significantly altered.
What is assured, however, is that whatever the shell
slope is, each roller is precisely set to that slope.
Alignment by Thrust Monitor System is not just
another way to do alignment: it is a fundamental
change, a paradigm shift in alignment technology.
Its simplicity and positive real-time feedback makes
its use the intuitive choice. It virtually guarantees
that bearing failures and high rates of tyre and roller
surface wear due to high thrust loads are a thing of
the past.
INSPECTION OF ROTARY KILNS
(HTTPS://WWW.HAVEC.EU/EN/OFFER/INSPECTION-OF-ROTARY-
KLINS.HTML)

Hot kiln alignment - the main area of our actions shall be to conduct mechanical
inspection and to specify activities (measurements, exchanges, repairs,
modifications, etc.) which should be performed to attain and maintain high
effectiveness of the rotary kiln's operation.
TECHNOLOGY TRANSFER
(HTTPS://WWW.HAVEC.EU/EN/OFFER/MEASUREMENT-
TECHNOLOGY.HTML)
We hold a specialist hardware and software used for professional measurements.
Application of relevant tools allows for effective diagnosis and monitoring of
machinery and equipment operation.
INDUSTRIAL AUTOMATICS
(HTTPS://WWW.HAVEC.EU/EN/OFFER/INDUSTRIAL-AUTOMATICS.HTML)

We developed high precision measurement systems to allow to monitor current
status of equipment and to plan maintenance activities. Hence, malfunctions and
breakdowns can be reduced both in respect of their intensity and frequency.
INDUSTRIAL MEASUREMENTS AND CONTROL
(HTTPS://WWW.HAVEC.EU/EN/OFFER/INDUSTRIAL-MEASUREMENTS-
AND-CONTROL.HTML)
We provide a wide scope of measurement services addressed to many industry
branches. Highly precise measurements are the starting point for analyses and
regulations supporting the work of machinery and equipment.
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Havec thrust monitor system

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