leakage of miv
TRANSCRIPT
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LEAKAGES OF MIV
Unit-3 & Unit-4 machines were re-commissioned on 21st October 2002 and
17th Jan 2003 respectively after R & M works by Toshiba & Mitsui & Co, Ltd, Japan.
The MIV of Unit -1 & 2 were replaced by new one but for Unit -3 & 4, the old MIV
were overhauled by M/S Toshiba, Japan during R & M works in 2001-02. Subsequently
it was found that some leakages appeared in the MIV of Unit -3 & 4, whereas MIV in
unit -1 & 2 were performing properly till date. It was observed that these leakages of
Unit 3 & 4 kept on increasing day by day and at present leaking heavily at the rate of
0.4 Cubic metres/sec (400 litres/sec).During the recent inspection, it was found that the leakages have increased for
Unit-3 & 4 to a great extent that it is not possible to enter the spiral casing for closer
inspection as shown in Exhibit -1, while it was also found that there were no leakages
for Unit -2 as shown in Exhibit -2. When the machine was idle, it was observed from the
Discharge meter located in the Draft Tube that the reading was 0.4 cubic metres / sec
i.e. the wastage of water. Based on this discharge meter reading, the calculation was
prepared which ultimately shows the actual loss in Rupees per year at Rs 1.68 cr as per
annex--I.
It is therefore very much necessary that the above two MIVs be also replaced by
the new Horizontal Thru Flow Type complete with Servomotor, Coupling Bolts & Nuts,Flanges, Installation materials, Mounting materials, Oil piping, etc except Bypass
Valve which have already been replaced during R&M. Since the Power Station was
built and renovated by M/S TOSHIBA Ltd, Japan, the original manufacturer, so it is
proposed that the above MIVs be procured from M/S Toshiba, Ltd, Japan.
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It was seen that, if the MIV were replaced, the total cost will be recovered
within three years time and it will also save the Turbines, etc from further damages.
AnnexI
CALCULATION OF DISCHARGE
P = 9.8 x Q x H (as per annexII)
Where
P = power in kw
Q = discharge in cubic metre per sec.
H = effective head in metre.
Here
P = unknown
Q = 0.4 cubic metre/sec (as per the present reading in the meter)
H = (h max + h min)/2 = (169+130)/2 = 149.50 m (as per annexV)
Therefore,
P = 9.8 x0.4 x 149.5 kw
= 586.04 kw
Taking
1.The average idle condition of the machine = 15.75 hrs/day (as perannexure-III)
2.Cost of energy per unit = Rs 2.494 P (as per annex-IV)3.Number of machine (i.e leakages) = 2
Therefore Loss in Rupees for one year
= Rs (586.04 x 15.75 x 2.494 x 2 x 365)
= Rs 16804559.28
(Say) = Rs 1.68 crores.
(Rupees one point six eight crores.)
N.B. Amount of Leakages were considered during idle hours only.
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Idle Hours of Unit-3 & Unit-4 machines wef Jan-06 upto Jul-06 ofStage-I
Month/Year
Unit-3 Unit-4No.of
daysTotal
AvailableHours
RunningHours
IdleHours
TotalAvailable
Hours
RunningHours
IdleHours
Jan-06 744:00:00 151:48:00 592:12:00 744:00:00 545:07:00 198:53:00 31
Feb-06 672:00:00 24:45:00 647:15:00 672:00:00 404:06:00 267:54:00 28
Mar-06 744:00:00 62:47:00 681:13:00 744:00:00 375:59:00 368:01:00 31
Apr-06 720:00:00 63:39:00 656:21:00 720:00:00 252:24:00 467:36:00 30
May-06 744:00:00 72:19:00 671:41:00 744:00:00 237:02:00 506:58:00 31
Jun-06 720:00:00 226:21:00 493:39:00 720:00:00 580:43:00 139:17:00 30
Jul-06 744:00:00 93:49:00 650:11:00 744:00:00 404:43:00 339:17:00 31
Total 5088:00:00 695:28:00 4392:32:00 5088:00:00 2800:04:00 2287:56:00 212
Average Idle Hours per day = (4392:32 + 2287:56) / 2 x 212
= 15:45:21 Hrs
= 15.75 Hours (say)
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EXHIBIT: 1
VIEW OF MIV LEAKAGES IN CLOSED CONDITION AS SEEN FROM THE MANHOLE
FIG.1: UNIT-4
FIG. 2: UNIT-3
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EXHIBIT: 2
VIEW OF MIV LEAKAGES IN CLOSED CONDITION AS SEEN FROM
THE MANHOLE:
FIG. 3: UNIT-2
FIG. 4: UNIT-2
VIEW OF MIV IN CLOSED CONDITION AS SEEN FROM INSIDE THE SPIRAL
CASING / DOWNSTREAM SIDE.
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EXHIBIT: 3
FIGURE SHOWING THE LOCATION OF MIV (MAIN INLET VALVE) WITH RESPECT TO
PENSTOCK & TURBINE OF THE POWER PLANT.
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EXHIBIT: 4
FIG: 1. MIV IN FULLY CLOSED POSITION.
FIG:2. MIV IN FULLY OPENED POSITION.
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CONCLUSION
The loss due to the leakages of the MIVs in Unit 3 & 4 is quite
significant which cannot easily be ignored. In fact if both the MIVs are
replaced as early as possibly the whole expenditure including the cost of newMIV, Servomotor, plus taxes, interest, etc could be recovered within two
years from the date of re-commissioning of the Unit.
If the MIVs of Unit-3 & 4 are not immediately replaced, then the loss
will definitely increase, thereby causing more loses than projected at present.
At present also with so much leakages in the MIV, then the question of
attending or inspection of the Turbine section including Guide Vanes
adjustment, runner blades, draft tubes, etc is out of question.
Since the inspection/repair of the above parts are of vital importance
for the running of the Hydel Power Station, I would very much like to
recommend for complete replacement of the above MIV at the earliest in
order to avoid any further loss and damages to the turbines and last but not
the least for the safety of all the personnel in the power station.