C. M. Consulting
P.O. Box 407
Odell, Oregon 97044
C. M. CONSULTING
A Division of Cliff Mansfield Incorporated
Trunnion & Tire Repair
In an earlier article I
talked about drier/mixer trunnion adjustment procedures. If followed, these
procedures can go a long way toward restoring the functionality of your
drier/mixer, hereafter referred to as the drum. There are instances, however, in
which no amount of adjusting will correct the problems exhibited by a particular
drum. Sometimes, the trunnions and tires are simply too worn to do their job or
the tires are scalloped so badly that the drum vibration is excessive. Wear is
the most common problem.
Badly worn trunnions like this one can be ground
This was the situation I encountered in early February at
Blythe Construction's Plant 3 in Pineville, North Carolina. The plant manager, Punkin Sowell, contacted me as a result of that article in the spring issue. His
crew was not having much success adjusting the trunnions on the plant and he
felt that I might be able to help them. I flew to North Carolina to inspect the
problem and recommend corrective measures.
The plant, a Gencor 400tph drummer, produces nearly 350,000
tons of hot mix per year and is well maintained and operated. My initial
inspection revealed some moderately worn trunnions and tires. As can be seen in
photo # 3, the discharge end trunnions were worn concave while the tire was worn
The result of this was that the drum was forced to try to climb out of a 'dish'
in the trunnion surfaces. The drum would climb the trunnion until gravity
exceeded traction, then the drum would slide back to its starting position and
the process would begin again. When tire/trunnion surfaces are worn to this
point no amount of adjustment is going to make the drum run correctly.
The burner end tire/trunnions exhibited a different problem.
The surface contact
was forced to the extreme downhill edge of both units. This was a result of the
trunnions being too close together. Apparently, at some point in the past,
someone decided that the drum needed more slope. Instead of shimming the drum
frame as recommended, they moved the trunnions closer together which raised the
burner end of the drum and caused the tire to ride at a bit of an angle to the
trunnions thereby preventing full surface contact. Over time the tire/trunnions
wore at the angle evident in the photographs.
When confronted with components worn to the degree that these
were, most companies would have shut down the plant and replaced both tires and
all the trunnions. The considerable cost of the parts is a minor consideration
when compared with the resulting lost production. Taking this into
consideration, I suggested to Jim Rynkewicz, Blythe's equipment manager, that we
build a machine, set it up and grind his trunnions and tires flat. I told him
that we could do it without interfering in on-going plant operations, a real
plus for a plant producing over 1,500 tons a day. After estimating the costs and
considering the alternatives he agreed to the plan.
Our first mission was to find some method of holding a
grinder stable while passing it evenly across the surface of the trunnions. For
this job we purchased a compound milling table, part # 6Z849, from Granger for
We then mounted it on a 1" thick steel plate which we clamped to the drum frame
with heavy duty clamps. Kurt Hartung
of Grob USA in Charlotte NC, handled the machine work and fabrication of the
mounts for the heavy duty Makita angle grinder which would perform the grinding
We installed the grinder with the disc 'edge-on', since we felt that this would
provide us with the most durable grinding surface and the least amount of
deflection to the disc which could cause us to grind a taper on the trunnions.
Once we were ready to begin, we set the milling table parallel to the trunnion
shaft centerline and locked it down.
Knowing that our grinding operations would require that the
drum be continually rotated while the grinding disk was in contact with the
trunnions, I worked out a system of signals with Brian Johnson, the plant
operator, so that I knew when he needed to hot-stop because of full silos. The
actual grinding operation took about
4 hours per trunnion.
Our drum is trunnion driven, so it is very important to make sure that all four
units ended up the same diameter. We did this by measuring them with a big
caliper, then grinding the trunnions to the size of the smallest one. All in
all, this entire operation was painless and easily accomplished without any
problems. And, best of all, the plant never missed one minute of production.
With all four trunnions nicely surfaced, it was time to turn
our attention to the tires. Early on I'd decided that our goal on the tires
would be to smooth them up as best we could, since they were not exactly round
but egg shaped due to heat distortion. To this end Kurt, Grob USA, built a tube
frame mount for our milling table
which set it up above the trunnions and allowed the grinder unobstructed access
to the tire. Grinding the tires required more patience and took
considerably longer than the trunnions. It took nearly 20 hours per tire, but we
ended up with a reasonably smooth surface that allowed us to adjust the
trunnion/tires as per factory specifications. The end result is that this plant
is now cranking out 2,000 to 3,000 tons per day without any downtime associated
with the tire/trunnions repairs.
This process is also useful for dealing with another, less
common drum tire problem, that of tire 'scalloping'. This problem, caused by
maladjusted trunnions, is illustrated in this picture.
The dark, ragged looking area
to the right on the tire is the surface which contacts the
trunnion. Since it is rough, or scalloped, it causes the drum to vibrate and
bounce badly. On plants where the switchgear is mounted on the drum frame the
vibration can cause problems with the electrical components 'dropping out' and
shutting down the plant. In extreme cases the vibration has been known to crack
and break structural supports for the drum and tires. It is strongly recommended that the trunnion
bearings be thoroughly greased after the grinding operations to flush out any
grindings around the bearing seals that could be drawn inside the bearing as it
cools down and pulls in expelled grease.
Estimated cost for repairs: Under $5,000 apiece for both
The prognosis: If kept properly adjusted, the tire/trunnions
on each plant should last many years into the future.
For additional information on this subject
or help with any problems encountered
contact Cliff Mansfield,
7:30am to 9:00pm Pacific Standard Time.
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