OVER ROLLING OF FRANCIS TURBINE by swenthomasovelil

VIEWS: 87 PAGES: 19

									INTRODUCTION
             Hydraulic turbine is the machine, which use the
energy of water, and convert into mechanical energy. The
mechanical energy developed by a
Turbine is used in running an electric generator, which is
directly coupled to
the shaft of turbine. The electric generator thus develops
electric power.

             Francis turbine is a mixed flow type reaction
turbine. It is a reaction
Turbine due to the reason that at the entrance to the runner,
only a part of the
Available energy of water is converted into kinetic energy
and a substantial
Part remains in the form of pressure energy .It is called
mixed flow type due to
the reason that water enters the runner at the outer periphery
in the radial direction and leaves at the center in the
direction parallel to the axis of rotation of the runner. It is
named in honor of James B Francis an American engineer.
WORKING PROCEDURE OF FRANCIS TURBINE
               The water from the penstock enters a scroll
casing [also called
spiral casing] which completely surrounds the runner .The
purpose of this casing
is to provide uneven distribution of water around the
circumference of turbine
runner ,maintaining an approximately constant velocity for
the water so distribu-
ted .In order to keep the velocity of water constant through
out its path around
the runner ,the cross section area of the casing is gradually
decreased .The casi-
ng is made of a cast steel ,plate steel ,concrete or concrete
and steel depending
upon the pressure to which it is subjected .Out of these plate
steel scroll casing
is commonly provided for turbines operating under 30m or
higher heads .
               From the scroll casing the water presses
through a speed ring or
Stay ring .It consists of an upper and lover ring held
together by series of fixed
Vanes called stay vanes .the number of stay vanes is usually
taken as half the
number of guide vanes .The speed ring has two functions to
perform .It ………
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des ,which may be subjected to cavitation erosion ,are made
of stainless steel .This reduces the cost of the runner
And at the same time ensure the operation of the runner
with aminimum amount of maintenance .The runner is
keyed to the shaft which is usually of forged steel .
The torque produced by runner is transmitted to the
generator through the shaft
Which is usually connected to the generator shaft by a
bolted flange connection .
The water after passing through the runner flows to the tail
race through a draft tube
A draft tube is a pipe or a passage of gradually increasing
cross sectional area
Which connects the runner exit to the tail race .It is may be
made of cast or plate steel or concrete .It must be air tight
and under all condition of operation its lower end
Must be submerged below the level of water in the tail race
. The draft tube has 2
Purposes
          (1)It permits a negative or suction head to the
established at the runner exit
thus making it possible to instal the turbine above the tail
race level without loss of head
          (2) It convert a large proportion of velocity energy
rejected from the runner into
useful pressure energy .


----------------------------------FIGURE----------------

PREVIOUS CONDITION OF FRANCIS TURBINE
      BHP 5
      RPM 1500
      Brake drum circumference 950mm
      Head 15m
      Pump size 100x100             HP 15
      Guide vane adjustment 2.5mm
             Initially it was on good condition .And it was
giving almost 5BHP power .There
Were …………………… operation of the turbine .It was
giving good efficiency on load and no load
Conditions .It was giving 1500rpm of speed on load and no
load conditions .It was on smooth operating
 condition .
CURRENT CONDITION OF FRANCIES TURBINE
           The turbine is not working very well .After
running some period it suddenly stop .We are not
 getting 1500rpm of speed on loaded conditions .The
turbine is only able to give 3BHP of power on no load
conditions .There is plenty of noise due to improper
working of the turbine .There is jerking sound also .
It is not giving good efficency even at no load conditions
.There is heat generated in the outer casing
Of the turbine
OVER ROLLING PROCEDURE
              By analyzing the condition of the turbine we
understood that the main problem is in the internal
Moving parts of the turbine .It is due to the fact that the
turbine was out of good performance .
              We started disassembling the parts of the
turbine one by one .And we found out the fact that
Improper operation of the turbine is due to the damage of
oil seal and bush which rolls over the shaft .
Due to the continuous operation of the turbine the oving and
rotating parts are allowed to lose their original
Shape That is because of friction between the rotating parts
.There will have enormous amount of heat
Due to friction of the rolling bodies .This heat generated
will try to lose the original shape of the bodies .
              Thus two main reasons of damage of the turbine
is that
      (1) Friction between rolling parts .
      (2) High heat generated due to improper lubrication of
the system .heat will be generated due to friction too .
              Due to the above two reasons oil seal of the
turbine has been damaged .Also the bush of the turbine
Was out of the friction .The material used for bush was
phosphor bronze .
              Replaced the wear out oil seal and bush by
proper one .Proper amount of lubrication is done to the
Internal meshing parts of the turbine .Disassembled parts
are properly joined .finally all the settings for the turbine
Was once again checked .
CONDITION OF THE TURBINE AFTER OVER
ROLLING
           Now the turbine is working very well .It is giving
almost 5BHP of power .Its efficiency while loaded and
No load conditions are improved very well .We are getting
1500rpm of speed at loaded and no load conditions .
There is no noise while turbine on run .There is no jerking
sound due to improper alignment as before .No even at the
Drastic condition also the turbine is running very well
.There is no heat generated in the casing of the turbine .It is
Giving high output power .Due to lubrication of the system
by grease there is considerable gain in efficiency .
Friction and heat generated due to friction is almost
eliminated due to lubrication .By conducting several test on
The turbine various graph shapes were analyzed .The
shapes obtained is in accordance with the standard
Shapes of the graphs




SUGGESTIONS AND IMPLIMENTATIONS
(1)Give proper lubrication to the entire system .
(2)Give proper cooling or arrange cooling water system .
(3)Start the turbine with only no load .
(4)Do not allow the turbine to run under drastic conditions .
(5)Load the turbine after it has been reached steady .
(6)Fluctuations in speed are noted with tacometer .
(7)Periodically cheak weather there is noise while the
turbine is running .
(8)Proper maintenance work should be done at the right
time .
(9)Stop the turbine only after removing load .
(10)There should be considerable time difference between
two consecutive operation of the turbine
(11)The operator should be very careful about the operation
.
(12)Try to avoid heavy load on turbine .
(13)The fit between oil seal and bush should not be highly
tight .
(14)The material of the bush should be phropher bronce .
(15)Guide vanes and valves are properly operated in order
to get good working condition .
INFERENCE
          From the over rolling procedure we have seen the
fact that we should give proper
Lubricating system to turbine .Also the arrangement for the
cooling water should be properly
Used Thus by running the turbine by its proper working
conditions we will get good work out put
From the turbine .

								
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