FIELD OF THE INVENTION
The present invention generally relates to axial fans, in particular to an axial fan
impeller blade bearing assembly for thermal power plants. More particularly, the
invention relates to a multi jack hydraulic testing device for hydraulic testing of
fan impeller blade bearing assembly.
BACKGROUND OF THE INVENTION
In a power plant primary air fans, forced draught fans and induced draught fans
are used. The types of Fan consists of suction chambers, impeller housing,
Diffuser, Shafts impellers and Blades. Impellers are hydraulic pressure test
before final balancing. The impellers are fabricated by welding of various
components then it is going for stress relieving. After stress relieving the
impellers are machined by vertical boring operating in vertical turret Lathe and
line boring operation. After Completion of both vertical turret lathe and Line
boring then all the required holes are drilled and tapped. Finally the impellers
are moved to rough balancing then go for blade bearing assembly. After
completion of blade bearing assembly then 10 bar pressure 30 minutes duration
of hydraulic pressure leak test is done on blade shaft assembly segment (Figure
1 and Figure 2). The hydraulic test is conducted by one hydraulic pump with one

isolated valve and pressure gauge. After completion of one segment then the
unit is dismantled and go for another segment. Like all the 23 segments are
tested one by one. After completion of all 23 segment then the impellers are sent
for final balancing.
Axial fans are Primary Fan Forced draught Fans are used to supply air through
air pre-heater for heating the coal and carry the coal powder to the furnace, and
an induced draught fan is used to remove the flue gas from the furnace, and all
the three type of Axial Profile Fan are designed to withstand high pressures,
where precise flow control are required. This requires high reliability and
continuous running for months together. All the impellers are machined after
fabrication then first balancing (rough balancing) is to be done in a balancing
machine. After completion of blade bearing assembly, the impellers are leak
tested (Figure 1 and Figure 2) at 10 bar pressure for 30 minutes duration. In
prior art, the leak test is carried out for a single hole in one cycle of testing.
Totally 23 holes are to be leak tested. The disadvantages of this process is that
more time is taken to complete the leak test. After passing the hydraulic test,
the impellers are sent to final balancing.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a multi jack
hydraulic testing device for hydraulic testing of fan impeller blade bearing
assembly which reduces the time for hydraulic test of fan blade bearing
assembly.

Another object of the present invention is to propose a multi jack hydraulic
testing device for hydraulic testing of fan impeller blade bearing assembly which
reduces the time for hydraulic test of fan blade bearing assembly which improves
the productivity of the thermal plants.
SUMMARY OF THE INVENTION
According to the invention, there is provided a multi jack hydraulic testing device
for hydraulic testing of fan impeller blade bearing assembly which reduces the
time for hydraulic test of fan blade bearing assembly. The modified testing
device of the invention is provided with a plurality of isolated valve with
corresponding number of pressure gauges such that multiple drilled holes of a
fan blade assembly, can be leak-tested at a single testing cycle. The present
invention allows testing of all the 23 segments of the blade assembly at one
stroke within 30 minutes duration. So in the present invention the cycle time is
30 minutes only. By the new device, the testing cycle time is reduced to 62.83%.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows photographic view of Hydraulic leak test of impeller assembly
according to prior art.
Figure 2 shows a Schematic diagram for Hydraulic leak test according to the
prior art.

Figure 3 shows photographic view of Hydraulic leak test by the inventive device
Figure 4 shows Schematic diagram for Hydraulic leak testing by the device of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
After completion of machining the impellers are rough balanced. Then the
impellers are moved to clean room for blade bearing assembly. After completion
of blade bearing assembly for all 23 segments, each segment is to be tested for
oil leak (Figure 1 and Figure 2). For 30 minutes duration with 10 bar pressure.
According to the invention, the hydro testing device is redesigned with at least
23 outlets and corresponding numbers of isolated valves and pressure gauges.
Thus, the hydraulic pressure test for all 23 segments are done at the same time
as shown in (Figure 3 and Figure 4) instead of one by one testing by earlier
method (Figure 1 and Figure 2). According to the invention the time required to
complete he hydraulic pressure test for all 23 segment is reduced from 11.5 hrs
to 0.5 hrs.

WE CLAIM :
1. A multi jack hydraulic testing device for hydraulic testing of fan
impeller blade bearing assembly, comprising :
a hydraulic pump with a plurality of outlets;
a plurality of impeller blades fixed on a test bed;
a plurality of isolating valves and a plurality of pressure gauges
provided on the test bed; and
the plurality of outlets from the hydraulic pump each separately
connected to each of the plurality of impeller blades via each of said
plurality of valves and pressure gauges;
wherein the number of pump outlet, isolating valve, pressure gauge and
impeller segment is identical so as to substantially reduce the testing cycle
of a complete fan blade assembly.