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है”ह”ह

IS 12633 (1989): First filling and emptying of pressuretunnels - Guidelines [WRD 14: Water Conductor Systems]

IS 12633 I 198'(Reaffirmed 2000)

Indian STandard

FIRST FILLING AND EMPTYING OFPRESSURE TUNNELS - GUIDELINES

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BUREAU OF INDIAN STANDARDSMANAK BHAVAN. 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Price Group :I

AMENDMENT NO.1 AUGUST 1992TO

IS 12633: 1989 FIRST FILLING AND EMPTYING OFPRESSURE TUNNELS - GUlDELINES

I Page I, clause 3.U. (I) ) -Insert tbe folloWingIllhe end:

'such IS lefl over ccncrete lumps. proJechons. protruding dowels. etc, Thesc,bOuldbe groundsmooth.'

IPage1, clause 3.1.1 (b) ) -Insert the following It the end:

'prdcJ1bl)' wllh rtSJD based hanleners,•

I Page1. clause 3.1.1 (c) ) -Inscrt Ihe Iollowmg Illbe end:

'IDd the boles Ior groulJng be SQIed perfectly Ind Ibe surface ground smooth.'

(Page 3, clause 7.1.1 ) - Insert Ihe followmg Illhe end:

'TJus 'hall apply to penstock and draft tube gales atso,

(RVD 14)ReP"'erapby VOl!,BIS,Now 0011.., Ind..

Water Conductor SYltelDl ~ctional Committee, BDC 58

FOREWORD

Thil Indian Standard was adopted by the Bureau of Indian Standards on 24 February 1989, afterthe draft finalized by the Water Conductor Sylteml Sectional Committee had been approved by theCivil Engineering Division Council.

The pressure tunnel is a part of water conductor IYltem and hence the filling and emptying is linkedwith overall planning of filling and emptying of the water conductor system.

The schedule of first filling and emptyin~ of tunnel for a project shall be prepared and discussedamong design and field engineers in detail before commencement of operation.

IS 12633 I 1989

Indian Standard

FIRST FILLING AND EMPTYING OFPRESSURE TUNNELS - GUIDELINES

1 SCOPE

1.1 This standard covers the guidelines andprecautions to be observed for first filling andemptying of the pressure tunnels of water con­ductor system of hydro-electric projects.

2 GENERAL2.1 Water conductor system of a hydro-electricproject generally consists of the following com­ponents:

a) Intake structure,b) Head race tunnels,c) Surge tank,d) Valve house,e) By-pass,f) Penstock,/presm re shafts,

g) Draft tube,h) Downstream surge tank, and

j) Tail race.

3 CHECK LIST

3.1 Before commencement of filling operation, itshall be ensured that all construction material,labour and d"partmental personnel are clearedfrom the entire water system. Before actuallyfiUing the system, the following checks ( 3.1.1 to3.1.9 ) shall be exercised.

3.1.1 Intake Structure

a) Trash-rack and air vent shall be cleanedand its cleaning device shall be checked.In projects where trash-rack cleaningdevice is not equipped, the racks shall beinspected manually.

b) Gateslstop logs shall be checked for theirseals, tracks, guides and smooth operationof gates. Filler valves shall also be check­ed, if provided.

c) Hoisting arrangements shall be checkedfor proper operation.

d) Automatic system for operation and alarm!shall be checked.

e) A telephone/wireless set shall be providedat gate with trained crews posted foroperation of gate.

3.1.2 Head Race Tunnel

a) It shaH be thoroughly inspected. All theCOJUtruction material/equipment shall be

removed and the tunnel cleared of allextraneous material.

b) It shall he repaired, wherever required.

c) It shall be ensured that all cold joints areproperly treated.

d) It shall be ensured that contact groutinghas been done in the prescribed reachesand shall be in accordance with the designrequirements.

e) It shall be ensured that consolidationgrouting has been done in the prescribedreaches and shall be in accordance withthe design requirements.

f) It shall be ensured that all the points, suchas, man-hole construction adits, etc, havebeen properly sealed/plugged in accord­ance with design requirements,

g) It shall be ensured that all the instrumentsrequired for observations before filling,during filling and after filling have beeninstalled at required locations and are inproper working order.

h) Drainage holes and dewatering pipe,wherever provided, shall be checked andit shall be ensured that these are function­ing properly and there is no particle flow.

j) It shall be ensured that proper arrange­ments for gradual filling and dewateringare functioning properly.

k) It shall be ensured that there is no obstruc­tion in the air vent pipes, where provided,and around outlet and inlet pipes.

m) It shall be ensured that the adit gates,where provided, are working and sealinghave been bolted/locked properly.

3.1.3 Surg'Tank

a) Gates/stop logs, wherever provided, in thesurge tank shall be checked for their seals,tracks, guides, etc, by lowering/ rat-ingin respective slots or all the slots. It isalso necessary to check filler valves toensure balanced operation of gates.

b) Hoisting arrangement for the above shallbe checked for proper operation.

c) Water level indicators, automatic systemfor operation and all the alarms shall bechecked.

d) Drainage glllleries, if provided, around thesurge tank shall be cleaned.

18 12633 I 1989

e) Man holes, construction aditl, etc, shall beproperly plugged in accordance with thedesign requirement.

f) AIr vent shall be clear of any obstructiong) It shall he ensured that the lnstrumenu

needed for observation before filling, duringfilling and after filling are installed atrequired places and are in working order

NOTE - Tho above rhecka apply to upstream a. won asdowrutteam mrge tanka

3.1.4 Pens/ocks/Pressur, Shafts

a) Entire length of penstocks/pressure shaftsshall be thoroughly cleaned. The penstocksshall be painted and completed in allrespects and inspected for before filling thewafer.

b) All the machine inlet valves shan hechecked for proper operation,

c) All the bolts of man-holes shall be checkedand tightened.

d) All the bolts of the seals of expannonjoints of penstocks should be tested andteam kept ready with required kit to carryout tightening a. required in case of leak­age.

e) In case of rockers provided as supports forpenstocks, these should be set and greasedfor free movement.

f) Any instruments provided in pressureshafts or on anchor blocks shall bemonitored.

~) It shall be ensured that grouting holes areproperly plugged and repainted.

h) It shall be ensured that the air vents areclear of any obstruction and air valves areworking properly.

j) It shall be ensured that filling anddewatering systems are working properly.

3.1.5 Draft Tubes

a) All the draft tubes shall be clean andready for running.

b) Draft tube gates and their hoistingarrangement shall be checked for theirsmooth operation.

3.1.6 Tall Race

The fcllowrng checks 10 addiuon to thosementioned in 3.1.2 shall be carried out·

a) The temporary cofterdam on downstream,if any, shall be removed.

b) Pumps for dewatering the tail race shouldbe ready at hand.

c) The area around the tail race should becleared of all obstructions for any imme­diate movement of equipment.

d) After dry testing of draft tube gates,water should be filled in tall race by

pumping and followin~ systems in powerhouse be checked f01 proper functioning:

I) Operation of draft tube gates underwater,

2) Cooling water system for power house,3) Pressure filters In the power house,4) Draft tube dell atermg system,

5) Emulsifier pumps in the power house,and

6) All drainage and dewatering system.e) In case of any malfunctioning, the tad

race may be emptied by pumping andrefilled after rer tifying the defects.

f) The tall race and draft tube shall be filledup to minimum water level hefore the startof initia] fillmg.

3.1.7 Valve House

The follo.... ing checks shall be carried out onvalves before fillmg operation is started:

a) All hydraulic and electrical systems shouldbe checked

b) The air inlet valve and vacuum breakingvalves should be cleared for overflow ofany water.

c) The drain from the valve house should becleared for overflow of any water.

d) The communication between valve houseand power house shall be tested.

e) The control system from the control roomto the valve house shall be checked andtested for proper operation.

5.1.8 Pow" House

a) All pra-comrrussiomng test in the dry stageshall be completed in all respects andcertified by the manufacturer and theerector.

b) The staff required for the operation ofpower plant shall be In position and assumethe specific duties.

c) Adequate number of spare dewateringpumps shall be in posiiion at various floorsof the power house.

d) All temporary stofs provided during theconstruction shal be removed and testedagainst full tail race level.

e) All drainage and dewatering pumps shallbe conditioned and made in operationalcondition

f) Turbine seals shan be tested and checkedfor perfect sealing.

g) Inlet valve seals shall be tested and check­ed for perfect sealing

h) Alternative source of power supply forworking all auxiharies in the power houseshall be ensured 24 hours.

2

j) Electrical over head crane shall be inoperating condition and tested.

k] All vacuum valves and air release valveand drainage valves shall be tested.

m) The security staff and security arrangementshall be completed to restrict the entry ofunauthorized person in the power house.

n) The staff fur operation and maintenanceof the power house shall be in position andfull compliment shall be detailed on shiftduties belore rmtial fillmg starts.

:J.l.9 By-Pa.s

a) The garcs'stoplogs, where provided, shallbe checked for their seals, track, guides,etc, by lowcung raismg in respective slotsor all the slots as the case may be.

b) It shall be ensured that the liners andembedded metal works are paintedproperly.

c) It shall be ensilled that dlainage arrange­rnent around the by-pass has been providedin accordanee with design requirements.

d) It shall be ensured that the air vents areclear of any obstruction.

e) It shall be ensured that arrangement forgradual filling/dewatermg are functioningproperly

f) It shall be ensured that the alarm systemindicating the sta: t of by-pass arrangementis working properly.

4 LOCATION OF OBSERVATION POINTS

4.1 Before filling the water conductor system,the observation points shall be judiciously locatedat convenient places along the aystem. Suchpoints may be located near the tunnel plugs( such as, those at intermediate adits in a longtunnel) and in the Vicinity of the surge shaft andalong the penstocks slopes (say, in the upperexpansion chamber). Observation points shallalso be located at water systems, such as, existingsprings, water level in wells, retaining walls, etc,in lower cover reaches and monitored after filling.If any leakage is observed at the observationpoint or an appreciable drop in surge tank waterlevel is seen, the same shall be reported andattended to immediately. Since minor leakagesthrough plug concrete may be anticipated,grouting equipment, such as, grout pump', pipes,nozzles, drilling machine, cement, sand, water,etc, shall be kept handy for urgent requirements.

5 COMMUNICATION FACILITIES

5.1 Communication facilities, such as, walkie­talkie andjor telephone shall be provided at theintake as well as at all observation points so thatimportant messages may be flashed across easilyand quickly without any loss of time.

IS 12633 I 1989

6 CHECKS BEFORE START OF FILLING

6.1 Obtain final clearance ensuring that noman or material of any kind has been left In thetunnel and other works. The engineer in-chargeshall himself inspect the tunnel and other worksand ensure that no material or equipment hasbeen left inside, before he orders closing of accessdoorsj man holes.

6.2 Check that access door.manholes are properlyclosed and locked.

6.3 Check that all the draft tube gates are In

raised position.

6.4 Check that all the main inlet valves areclosed.

6.5 Check that the guide vanes of all the machinesare closed with 011 pressure applied (Apply gene­rator brakes to prevent creeping, if necessary).

6.6 Check that the surge shaft gates/stoplogs arein open posiuon.

6.7 Check the reaervoir level. The filling shouldonly start when the reservoir level is at or abovethe minimum permissible level.

7 FlLUNG OF THE SYSTEM

7.1 General

Filling is normally done from the downstreamend of the water conductor system, that is, themachine inlet valve. However, in case of longhead race tunnel, where a surge shaft is provided,the system shall be filled initially up to the surgeshaft, if provided with gates, otherwise up to theemergency valves downstream of valve. Theportion of water conductor system between theemergency valves downstream of shaft and themain inlet valve provided just upstream of themachine may be filled up only afrer detectionand rectification of leakage upstream of thebutterfly valve.

7.1.1 The water conductor system shall be filledat very slow rate so that the internal pressureincreases gradually and the surrounding condi­tions get sufficient time for stabilization.

7.1.2 In case of gated arrangement, the leakageon gates shall be checked and ascertained for theefficacy of the seals.

7.1.3 The water conductor system shall be filledat a slow rate so that there is no scope forthe air to get entrapped, compressed and thenreleased.

7.2 IJlidal FUUul

7.2.1 Depending upon the length of the system,number of probable seepage observation pointsand filling req uirements, the total time taken tocomplete the initial filling shall be estimated.This can be calculated and arrived at once the

3

IS 12633 I 1989

volume of water required to fill the system isknown.

7.2.2 Following steps shall he followed for initialfilling:

a) Gates of intake shall be lowered and pondlevel maintained at desired level with thehelp of spillway gates and/or other dis­charge outlets.

h] Surge shaft gales/bulterfly valve andmachine inlet valve gate shall be keptclosed.

c) If filling i, to he done by crack opening,intake gate shall he raiser! lip to the heightcalculated by e>timating the dischargerequirements for filling up the system inthe programmed schedule of time frameof filling. The velocity should be restric­ted to about 6 Ill/sec. The crack-openingwould generally be of the order of 20 to40 mm, Thus, in order to limit the velo­city through the gate, water level in thereservoir should not be marc than 300 to500 mm above the crest level of the intakesill.

d) Surge shaft gates;butterfly valves, machineinlet valves, penstocks couplings., etc, shallbe checked and tested.

c) The tunnel shall be filled in appropriatepre-determined steps of water head so thatexcessive tension in the lining i. avoided,The steps may be worked out on the basisof known properties of the surroundinglock mass.

C) A waiting period of at least 48 h shall U,:allowed between first and second steps offilling and of at least 24 h between eachsubsequent ~teps of fillin~ to get thesurrounding strata surchai ged with wafer

g) Watel levels in the SUI ge tank shall berecerdecl concurrently during ihe fillin!;operation.

h) At the end of each sfep of fiJling, theintake ~f.Ile~ shall be closed and waterlevels in the surge tank shall be observedevery hour. The loss of water from tunnelthrough d rainagc galleries around SlIrgelank and leakage through machine inletvalve shall abo be noted.

J) Clo~1' monitoring of instruments ;IlSlalkdin head I ace tunnel, 'urge tank and pen­stock ~hall he done before, during andafter filling of the system.

k) After the watel conductor system IS filled,t-he reset voir level shall he rnaintained atthe lowest level. The water level shall heraised slowly in the I eservoir till it reachesthe maximum reservoir level.

m) If the drop in water level is more at anystep, the reasons for leak Igc shall be inves­tigated and remedial measures should betaken. Next filling steps shall only betaken after ensuring that drop in waterlevel in the prsceding 'Iep is within thepre-determined limit>.

p) All gates, uoplogs, obser vation points,values and expansion poinn un penstocksshall be monitored for leakage dui ing andafter filling.

7.3 FUlial of Tail Race Syuem

7.3.1 The tail race shall be filled U t' to the rn unmum tail ..... ater level gradually. In r ase of po weihouses having a clerp setting, the filling of thetail race may have to b~ accompliahed by pump­ing water into it from a Source located near thetail race.

8 EMPTYING THE SYSTEM

8.1 If quantity of leakage or any other situationwarrants emptying the tunnel or entire waterconductor system, following procedure and pre­caution, shall be adopted:

a) Close all the intake gates,

b) Emptying of the tunnel shall be donethrough the by· pass. However. if no by­pass is provided, the water shall be dis.charged through the turbine.

c) Before emptying the system through theturbine, it shall be ensured tbat the turbineis just sufficient to run the machine at noload and the generator is not being cnn­nected.

<I) Rate of emPtYing the tunnel shall be<lower than the rate of filling. Emptyingof the tunnel shall be done in steps. In nocase, the number of steps in emptying'hall be less than tl·r II umber of stepsfollowed in filling. The number of stepsmay be increased if 1\ smaller dischargeIS to be passNI through Ihe machines.

e) Suitable waiting period shall be allowedbetween each step of emptying.

9 PRECAUTIONS BEFORE ENTERINGTHE TUNNEL AFTER EMPTYING

9.1 Un emptying the access dOOI! manhole, theremay be ventilation due to the stork ellect of thesurge shaft This may clear limited areas oneither side of the surge shaft. Other areas maybe oxygen deficient, contain hydrogen sulphidealld{or methane. The water in the tunnel hasbeen ~radllally lowered, giving t nue for any gases( C02. CO, CH~. 802, H2S) m 'hf' water 10 b':liberated.

9.2 Keep the access door/manhole open for 12 hto permit fresh air draft imide the tunnel andthus to bring humidity to a safe level for humanbreathing.

9.3 Do no! enter the tunnel without carryingpersonal monitoring equipment and have breath­ing apparatus Within reach. Under no circum­stances, less than two persons shall enter or move

IS 12633 I 1989

within the ad it or any section of the tunnel.

9.i Send an advance party with gum boots,raincoats, torch lights for a distance of 500 m(or less if they feel uneasy) only and reportback. Dependll.g upon the condition of waterand slush. carry out regular Inspection either onfoot or on a vehicle WIth spot lights mounted onit.

5

~-- ~- -- ~ --.

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Doc : No. BDC 58 ( 4467 )

Ameadm_tl I...eelSiace Pabllcatioll

Amend No. Date of Issue

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