leakage of miv

8/22/2019 Leakage of MIV

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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.

leakage of miv

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