This document summarizes an industrial case study where Shree Cement Limited performed on-site machining of a fan shaft without removing the impeller or needing external assistance. A bearing on a cement plant fan developed irregular vibrations due to wear on the shaft. Rather than taking the equipment offsite for repair, the company machined the shaft onsite by installing supports to hold the shaft securely, mounting a lathe toolhead, rebuilding the shaft through multiple welding and machining steps, and verifying the new shaft dimensions before reinstalling the bearing. This innovative onsite repair approach helped minimize downtime and costs for the cement plant.

1. INDUSTRIAL CASE STUDY:
THE CEMENT INDUSTRY
PREPARED BY
MAUSAM SHARMA
with assistance from
RAHUL MUNDRA
SHREECEMENTLTD.

2. Plant : Shree Cement Limited
Location : Ras
Site : Unit – 8 Kiln Section
Equipment : Cooler ESP Fan
Induced Draft Fan
750 rpm – variable frequency drive
Case : On-site shaft solution
ABSTRACT
This paper elaborates on-site machining procedure carried out for the first time in entire
Shree Group. This case is related to one of the ID fan in kiln section, at Line 8. Fan non-drive
end bearing responded to irregular vibrations in July 2014. Detailed analysis of non-drive end
bearing was conducted; concluding bearing was loose on shaft and housing. Considering
plant downtime, bearing was gripped on shaft using metal putty and shims were added to grip
bearing outer race on housing. However this was not a long term solution for the problem.
Within time, the shaft was taken for machining and the procedure was carried out at site itself
without any external assistance. It outlines the innovation and unconventional ways used by
SCL for productivity improvement, to reduce downtime and cost cutting.
Plant Overview
Shree Cement Ras Plant is located in the village Ras, Pali District, around 150 kms from Jodhpur.
It has eight cement lines (Line 3 to Line 10) and three grinding units , two ball mills and one
vertical roller mill: Line 3 to Line 8 are designed for annual production of 1 MT each and Line 9
& 10 both are designed to have an annual capacity of 2 MT. Two ball mills are designed with
annual capacity of 4 MT each and vertical roller mill of 3 MT per year.

3. Case History –
In July 2014, during shutdown inspection
of Cooler ESP Fan bearing, non-drive end
bearing was found loose in housing and
bearing clearance was also observed in
upper limit range. So decision was made to
change the bearing. Further it was also
noted that bearing inner was loose on shaft
i.e. bearing inner race was running freely
on the shaft and on the other hand shaft
size was also reduced at the bearing seat.
When shaft dimensions were measured,
shaft dimension were down by 0.7mm
with actual shaft dimension of 100mm.
Fig 1 – Bearing loose in housing and shaft
Considering plant down time, metal putty
was applied on the shaft to ensure
adequate gripping action between shaft
and bearing inner race. Also shims were
added to hold bearing outer race with
bearing housing. Although this was not a
long term solution for the problem but
considering production loss, temporary
arrangement was done.
Observations –
Since July 2014, Cooler ESP fan was kept
under close surveillance. Scheduled
vibration readings were done along with
regular physical inspections. However no
abnormality was observed till October
2014.
On 22nd
October 2014, vibrations went up
to 3.8 mm/s in horizontal direction in non-
drive end bearing. Detailed analysis was
conducted for fan non-drive end bearing
and it was suggested to inspect fan non-
drive end bearing internally in the next
available opportunity.
Bearing Inspection –
Soon there was a shut at Line-8 due to
excess clinker stock, which presented an
opportunity for us to inspect fan impeller
conditions and bearing condition. When
non-drive end bearing was inspected
internally, it was seen that the shaft wear
had increased to 1.4 mm.
Fig 2 – Bearing seat found wear
A meeting was held with Mr. S.C.
Maheshwari (Joint VP, Operations) to
discuss the fault and possible maintenance
solutions. Taking out the impeller and
machining it at workshop involved long
time, manpower and expertise guidance.

4. As a result, it was decided to make
necessary arrangements at site to re-build
the shaft in-situ, without taking out the
impeller.
On-Site Machining –
a. Shaft holding: First of all Shree
Cement made the necessary
arrangements to install a bearing at
the location between non drive end
bearing seat and fan casing, to
support the rotation of shaft while
machining is performed at non
drive end bearing seat. Here the
shaft size was 120mm, so we
decided to use bearing (22224 CC)
and bearing housing was designed
as per availability of space.
Along with this extra bearing, a
jack bolt arrangement was also
equipped with bearing housing
base plate to align the impeller
shaft to obtain precise machining.
Fig – 3 Alternate bearing setup
b. Variable Frequency Drive:
In order to rotate the shaft at 20-80
rpm for the purpose of machining
and building up, we needed a
variable frequency drive.
Fortunately the fan motor is
designed as a variable frequency
drive; as a result we need not to
install an external variable
frequency drive.
c. Mounting of tool post: In order to
machine the shaft, a lathe machine
tool post was mounted. To ensure
the accuracy and precision of the
shaft after the machining process, it
was ensured that the movement of
tool post was parallel to the axis of
the shaft with the help of the dial
indicator.
Fig – 4 Tool post mounted at site
d. Rough machining: To re-build the
shaft, it was essential to machine it
for a level and smooth surface.
Shree cement started machining the
shaft at the maximum possible
shaft speed of 80 rpm and with a
depth of cut of 0.10 mm at a feed
rate of 0.1mm/rev. The machining
process continued until a smooth
and level surface was achieved on
shaft.

5. After cutting, emery paper
was used to smooth the shaft
surface texture. On completion of
the rough machining process, the
shaft was 98 mm in diameter, with
an under-cut of 2 mm.
Fig 5- Rough machined shaft
e. Rebuilding the shaft: However
Shree Cement had performed
machining on shaft in past times
but on-site this was the first time in
the entire group. It was a challenge
to uniformly make a build up at the
undercut portion of shaft. However
the electrode material compactable
to shaft material was not available
in local market. It was decided to
carry the built-up job with Mild
Steel Welding Electrode 6013
3.0mm. The surface of the shaft
was pre-heated to a temperature of
90o
C before commencement of
welding.
Welding was done in radial
direction at a uniform rate.
Engineers were continuously
monitoring the shaft temperature
and cooled compressed air was
used to keep the shaft temperature
optimum as per welding operation.
After 7 layers of welding shaft had
a diameter of 105 mm.
Fig 6 – Actual shaft dimension
Fig 7 – Built-up on shaft
f. Final machining: Final machining
was conducted on the shaft using a
precise cutting tool. After attaining
a shaft size of 100.10mm
machining was finalized. Emery
paper was used to get the shaft
diameter to 100mm with a
tolerance of +0.02 mm.

6. Fig 8 - Final machining
g. Measurements: Shaft diameter
was measured at different positions
with tolerance range between
+0.02 to +0.03 mm was obtained.
Fig 9 – Shaft after final machining
Fig 10 – Micron reading on shaft
h. Mounting of bearing: The bearing
was heated to 150o
C and was
mounted on shaft. The housing was
fixed in the position. When the
temperature of the bearing reduced
to ambient temperature, the
clearance was measured with a
feeler gauge.
i. Operational test: After final
fitment of the bearing, fan was
running on its bearing drive.
Vibrations reading were observed
in all three directions and were
found satisfactory.
Results –
After the job was successfully completed
and the bearing mounting was done, the
vibration reading measured at 95% fan
speed were –
Motor
Drive End Non Drive End
Horizontal: 0.46 mm/s 0.46 mm/s
Vertical: 0.31 mm/s 0.35 mm/s
Axial: 0.35 mm/s 0.26 mm/s
Fan
Drive End Non Drive End
Horizontal: 1.08 mm/s 1.60 mm/s
Vertical: 0.32 mm/s 0.50 mm/s
Axial: 0.54 mm/s 1.30 mm/s
Conclusion – Overall this challenging
job was performed successfully
throughout, within the plant itself without
any external assistance. The successful
maintenance of the shaft resulted into
morale boost up of maintenance engineers
and thus marking an assurance for the
company to withstand future challenges.