FIELD OF THE INVENTION
The present invention relates to an axial fan impeller and particularly relates to
an improved process in a device for measurement of Axial Fan blade moment in
a power plant.
BACKGROUND OF THE INVENTION
For thermal power plant capacity ranging from 200 MW to 1000 MW, the
primary Air Fans, Forced Draught Fans and Induced Draught Fans are required
to run the power plant. The above type of Fans consists of suction chambers,
impeller housings, Diffuser, Shafts, Impellers and Blades. All type of Blades are
first moment sorted and then fixed with impellers.
The Fans used in the thermal power plant are called Primary Air fans, Forced
Draught fans and Induced Draught Fans which consists of a shaft with bearing
assembly, a plurality of impellers, and a servomotor. The shaft (rotor) is
accommodated with Cylindrical Roller bearing. In addition, two Angular Contact
Ball bearings are arranged on the driven side in order to absorb the axial thrust.
Double contact Tele-thermometers and double resistance thermometers are used
to monitor the bearing temperature. These thermometers are connected to
signaling instruments at the site. Lubrication and cooling of these bearings are
ensured by a circulating pump and an oil bath. Simmer rings are always

installed, filled with grease. The oil ventilated through a tube oil return pipe, is
recycled into an oil reservoir. The ventilation hood is mounted on the reservoir.
For Axial fans, there is at least one Primary Air Fan, and a Forced draught Air Fan
is used to supply the air through a air pre-heater for heating the air which in turn
is used to dry coal and carry the coal powder to the furnace, wherein an induced
draught fan is used to remove the flue gas from the furnace, and all the three
types of Axial Profiled Fans are designed to withstand high pressures, where
precise flow control are required. A high reliability is required for the fans due to
their continuous running for months together. The Primary Air Fan, Forced
draught fan are having aluminum alloy blades, and the Induced Draught Fan is
having Casting Blades used for their assembly. All the Impellers are balanced
with high accuracy. So the Blades alone are balanced by means of a moment-
measurement operation. The blades are moment sorted using a process called
MOMENT SORTING OPERATION.
In prior art, the blades are fixed with a moment measurement device by using 4
numbers of bolts and nuts. The digital balance in the moment measurement
device must show Zero reading. The actual moment of the blade is shown in the
digital balance, after removing the fulcrum in the moment measurement device.
Then, the blade is removed from the moment measurement device by
unscrewing the fasteners and another blade is fixed on the moment
measurement device for moment measurement. The major disadvantage in the
prior art, is that at the time of fixing and removing the fasteners from the blade
base, the base of the blades get damaged and also take more time for

completing the moment measurement process. To overcome the above an
improved process in a device for measurement of Axial Fan blade moment in a
power plant, is necessary.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved process in a
device for measurement of Axial Fan blade moment in a power plant, is
necessary, which eliminates the damage to blade during movement
measurement of the fan blades.
Another object of the present invention is to an improved process in a device for
measurement of Axial Fan blade moment in a power plant, is necessary, which
reduces the time for mounting and dismounting of Fan blades in a moment
measurement device.
A still another object of the present invention is to propose an improved process
in a device for measurement of Axial Fan blade moment in a power plant, is
necessary, which allows an improvement in the quality of the final product.
A further object of the present invention is to propose an improved process in a
device for measurement of Axial Fan blade moment in a power plant, is
necessary, which improves the productivity.

SUMMARY OF THE INVENTION
In thermal power plant Primary Air fan, Forced Draught fan and Induced
Draught Fans are used. All types of fan having impellers and blades for their
operation. The impellers are fabricated by welding of various components, and
then relieved. After stress relieving, the impellers are machined by vertical boring
operation and line boring operation. After Completion of both vertical boring and
Line boring, then the required holes are drilled and tapped. Finally, the impellers
are moved to rough balancing before sending for blade bearing assembly.
Hydraulic test is carried out while undertaking the blade bearing assembly and it
is now ready for final balancing. The impellers are balanced without mounting
the blades with permissible accuracy. Similarly, the blades used in the impellers
for Primary Air fans and Forced draught fans are aluminum alloy casting are
subjected to various machining and drilling operation. After completion of the
machining process, blades are inspected by frequency tuning.
Upon completion of the frequency tuning operation, the blades are sent for
moment measurement. First, the weight of the blades are measured and
accepted with 10% weight variation. Then the individual blades are mounted in
a moment measurement instrument and noted the reading in balance. One set of
blades is moment measured one by one and the balance reading is noted
against their serial number. Then all the readings with serial number is fed in a
software program then the blades are sorted according to their bottom measured
weight. Then the serial number of the blades with batch identify numbers are

punched in the bottom of the blades. According to the invention, the blades are
mounted in the moment measurement instruments using two taper pins with
coiled spring and two locking pins, which eliminates the damage in the base of
the fan blades, and further expedites the process of moment measurement.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : Schematic diagram of a Socket Head M16 of prior art.
Figure 2 : shows a tapper pin with a locking pin and coiled spring according to
the invention.
Figure 3 : Moment measuring instrument view-1.
Figure 4 : Moment measuring instrument view -2.
DETAILED DESCRIPTION OF THE INVENTION
Axial Profile fans consist of an impeller with blades at its peripherals. According
to the invention, the impellers are balanced via mass added or reduced without
fixing of the blades in the balancing machine. The blades are moment measured
instead of balancing, with a separate instrument, then with the help of software
program the serial number for its position is allotted. Moment measurement of
the blades are done to ensure that the rotor, and the impeller with blades

together is balanced, i.e. mass distributed uniformly. In moment measurement,
moment of each and every blades are noted in the instrument. All the tabulated
readings are fed into a measurement software. The output of the software
represent the position of each and every blade such that the mass get
distributed uniformly for the rotor at site.
The unbalance control in axial fan rotor warrants unbalance moment of the blade
to be sorted within a specified limit. For this the moment of each blade needs to
be measured in an instrument.
A moment measurement device consists of mountings arranged in a sea saw
manner for fan blades with lever and fulcrum. The lever with a hanging weight is
fixed on a frame with a support base. And a digital balance is placed on the
support base.
The individual blades are mounted in the moment measurement device and the
balancing reading is noted. One set of blades (i.e. 14, 16, 18, 20, 23 ad 24
numbers) is moment measured one by one and the reading is noted against their
serial number. Then all the readings with serial number is fed to a software
program then the blades are sorted according to their moment measurement
weight. Then the serial number with batch identify numbers are punched in the
bottom of the blades and packed the batch as one set and sent to the respective
site.

In prior art, one blade is mounted in the moment measurement fixture for fixing
the blade by means of 4 numbers of M16 screws and ratchet type spanner
figure 1. Around ~ 8000 blades are manufactured and supplied to various
customers in a year. So by means of 32000 times we tighten the screws for
fixing and removing of blades. And also it creates more stress to working
employee and time. In the present invention two numbers of taper pin with
coiled spring and two numbers of locked pin as shown in Figure 2 are used in
place of 4 numbers of screws as shown in the Figure 1 without using of any
spanner. Edge of Blades are restored in good condition by using of taper pins.

WE CLAIM :
1. An improved process in a device for measurement of Axial Fan blade
moment in a power plant, is necessary, the device comprising a plurality
of mounting arranged in sea-saw manner for mounting of the fan blades,
a lever with a hanging weight fixed on a frame of a support base, a
fulcrum, a digital balance placed on the support base, and a computer
apparatus with a software program, the process comprising the steps of :
mounting individual fan blades on the device and the moment
measurement weight noted, each fan blade of individual set of blades
assigned with a serial number,
feeding the data to the computer apparatus and sorting out the fan blades
based on individual moment measurement weight; and
punching a batch number including said serial number on each sorted fan
blade,
wherein each fan blade is mounted on the device and fixed by means of two
taper pins with coil springs including two locked pins, which allows avoiding

damage to the fan blades during mounting, measuring, and dismounting on and
from the device.