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Operation Instructions BAL EKTG/04e Visum 10/10 T/fr Page 1 of 18

Transformer BushingType EKTG

Mounting

Operatingand

Maintenance Instructions

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Operating Instructions BAL EKTG/04e Visum 10/10 T/fr Page 3 of 18

CONTENT

1 Description.................................................................................................. 41.1 Construction................................................................................................................41.2 Design.........................................................................................................................51.3 General Operating Conditions ....................................................................................61.4 Mechanical Stress.......................................................................................................6

2 Montage...................................................................................................... 72.1 Status of dispatch .......................................................................................................72.2 Handling......................................................................................................................72.3 Lifting and Errection...................................................................................................82.4 Preparation for Installation ..........................................................................................82.5 Mounting of a screen on the trans transformer side **................................................9

3 Mounting of the bushing on the transformer.............................................. 103.1 Grounding of the bushing flange...............................................................................11

4 Putting into operation................................................................................ 114.1 Ventilation at the bushing flange...............................................................................114.2 Evacuation of the transformer...................................................................................114.3 Recommended tests before putting into operation....................................................114.4 Electrical measurements...........................................................................................114.5 Test tap....................................................................................................................124.6 Voltage tap**.............................................................................................................13

5 Maintenance............................................................................................. 135.1 Recommended maintenance and checks.................................................................135.2 Cleaning....................................................................................................................145.3 Cleaning after coating wirh oil...................................................................................145.4 Electrical measurements...........................................................................................155.5 Measuring procedures ..............................................................................................155.6 Equipment.................................................................................................................155.7 Limits ........................................................................................................................15

6 Possibilities of repair................................................................................. 167 Storage..................................................................................................... 178 Disposal after end of operation ................................................................. 18

** optional, see specification

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Connection Contact plate

Condenser coreHigh gloss varnish

SF6 side

Connecting flange for SF6 -substation

Test tap

Connecting flange for transformer

Transformer side

Condenser coreSurface oil coated

Connecting termial

Electrical screen, removable(optional, see specification)

1 Description1.1 Construction

Fig.1

Fig.2

Fig.3

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The main insulation of the transformer bushing EKTG is an

insulating body (4). It is made of a special paper impregnatedunder vacuum with epoxy resin and coaxially placed gradinglayers made of aluminium foil to guarantee uniform voltagedistribution along the insulating body (5).

This insulating body is upholstered and secured againstdisplacement impregnated directly onto the copper conductorbolt (6).

The high voltage connection (1) is made of a copper connectingplate with threaded bores. It is designed for direct screwconnection to the current carrying components of the SF6-

substation. Underneath this connecting plate there is a threadedring (2) which with the help of screws guarantees side pressure inthe thread of the connecting plate also fixed by screws, thusproviding contact.

Underneath there is a special sealing chamber with a liquidsealing (3) encapsuled between two sealing rings. It is made ofhigh viscosity silicone oil, which due to its excellent adhesivefeatures secures high gas tightness even in case of lowtemperatures.

The bushing flange (9) is sealed directly onto the insulating bodywith its SF6-side flange plate by SF6-resistant sealing rings. Thetransformer side flange plate (11) is sealed with oil-resistantsealing rings (12). Both flange plates are fixed to the central partof the flange by screws.The flange is equipped with the test tap (10) and the air releasevalve (13). This valve seals a circular ring chamber within theflange. Its purpose is to allow gas release in case of leakingsealings on the SF6-side to prevent building of high gas pressureon the transformer side sealings.Displaced to the test tap on the transformer side flange plate or inthe flange neck the transformer ventilation screw (14) is located.

On the transformer side end of the insulating body there is asealed O-ring (15). It prevents transformer oil from penetrating intothe area between conductor bolt and insulating body. It is notaccessible from outside.

The transformer side current connection is designed as round oroptional** as flat connecting terminal.(16)

The contact area is shielded by an electrical screen (17). It iseither part of the bushing** or it is located in the transformer

** optional, see bushing specification

1.2 DesignFig.4

Fig.5

12

3

4

5

6

7

89

10

11

12

13

14

15

16

17

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Application: Bushing for installation in transformers with direct connection toGIS

Classification: Epoxy resin impregnated paper, capacitive gradingSF6- substation transformer - bushing

Ambient temperature: SF6- side : - 30* up + 60C **Transformer side: daily mean value + 90C, limit value 100 C **

Immersion medium: SF6 side: SF6or SF6/N2*Transformer side: transformer oil of all common types acc. to

standard

Oil level below bushing flange: max. 15 mm

min. gas pressure: 250 kPa**max. oil pressure: 200 kPa gauge

Possibility to evacuate: No restrictions regarding level and time

Corrosion protection: All armatures and fixing materials made of corrosion-resistantmaterials

Marking: According to IEC 60137 / IEC 601639 **

Packing: Wooden crate, ventilated, bushings protected by styro-foamcushions below the flange and both ends, sealed in plastic foilwith inlaid dehydrating bags

* < 25C gas mixture in special cases see bushing specification** standard values, modifications see bushing specification

1.3 General Operating Conditions

1.4 Mechanical Stress

On the high voltage side connection:

Test bending load: < 245 kV 3000 N 245 kV 4000 N *Operating load: 50% of the values for test bending loadOn the bushing flange: for bending moment refer to IEC 601639

* standard values, modifications see bushing specification

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2 Montage2.1 Status of dispatch

2.2 Handling

.

The bushing is transported in a ventilated wooden crate(1). It is supported by styro-foam cushions (2) located inthe flange area. Additionally in case of bigger bushingsthe flange is supported and fixed by wooden crossbeams.(4)

The whole bushing is covered with a plastic foil with inlaiddry bags.(3)

Packed like this the bushing can be stored in dry roomscovered by a roof for 12 months.

When the bushing is packed in aluminium coated foilinstead of plastic foil it can be stored for 24 monthsunder the same conditions.

Proper long term storage, e.g. for spare parts, can onlybe achieved by metal protections tanks on both sides ofthe bushing. Both tanks are filled with dehydrating bagsand nitrogen. The tanks are equipped with test valves,which allow to test the condition by using test equipment.(see item 7)

Fig.6

Fig.7

To remove the bushing from the crate it may be lifted onthe flange only and put down either on the flange or onthe insulating body close to the flange.

It is not permitted to put the bushing down on thetransformer end and/or on the gas side end. Even in caseof an upholstering there is the danger of cracksdeveloping in the insulating material, which may beinvisible, but jeopardize operation of the bushing.

With the ends unprotected the bushing can be handledoutside for a short period of time during dry weather.Longer storage, e.g. during rain is not permitted. Thematerial RIP is hygroscope and absorbs moisture on itssurface, which has a negative influence on the operatingbehaviour in the transformer.

In case you detect bushings with clear signs of theinfluence of moisture, please contact the manufacturer.See comparative picture on the left side (Fig.7).

1

2

3

4

Surface influenced b moisture

Dry surface

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2.3 Lifting and Errection

.

.

2.4 Preparation for Installation

Fig.8

Fig.9

Use the lifting eyes to lift the bushing. There are either

removable ring screws or lifting eyes on the bushingflange.

After installation of the bushing the removable ringscrews have to be removed. The threaded bores haveto be closed by plastic caps.

The bushing is always lifted on the flange with liftingequipment. Due to the bushing design the center ofgravity is always in the area of the flange, therefore it issufficient to guide the longer end of the bushing withone hand during the lifting procedure. As a rule thelonger part of the bushing is the transformer side,therefore when it is lifted it will move into this directionand in this position is suitable for installation in thetransformer.

By no means the bushing must be put down on theinsulator end for erection purposes.

After the bushing was lifted from the crate it has to beput down on the flange or on both sides close to theflange on upholstered supports. The plastic foil isremoved do not use a knife, because the surface ofthe insulator may be damaged.

If the bushing is equipped with an electric screen whichis not yet mounted to the bushing, it has to be put downin such a way that assembly of the connection can bemade after installation (see 2.5).

Bushings type EKTG always have an undetachable

current conductor. Therefore the connection in thetransformer has to be made as plug connection withcontact sleeves or as screw connection with accessthrough a mounting hole in the transformer.This design is necessary because a leakage test iscarried out on the bushing in the factory. Subsequentmounting works on a design with detachable bolt wouldnot guarantee tightness.

Instructions of the transformer manufacturer regardingmounting connection have to be obeyed.

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2.5 Mounting of a screen on the trans transformer side **

The screen fastening is made of two discs, one of them is

movable guided via pins and pressed tight with a recoilspring. In the screen made of epoxy resin with embeddedshield three brass pins are inserted. When inserting thescreen with its pin into the corresponding openings ofthe outer disc and by a turn to the right hand side thediscs are pressed apart. When turning the screen furtherthe pins will rest in a special fastening slit.

Movable disc

Opening for insertion with inclination

Fastening slit

Opening to push through the whole screen

Fixed disk

Mounting of the screenThe screen has to be located towards the fastening thatthe pins are positioned opposite to the opening in thedisc. These openings are asymmetrically positioned to

avoid wrong installation of the screen. Turn the screenuntil it can be inserted. With a turn to the right until thepins snap into place the screen is mounted.

Demounting of the screenBy turning the screen to the left it is removed from the pinfastening, then proceed turning until the openings in thedisc release the screen.

Pushing the screen throughFor easy mounting of the current connections the screencan be turned before putting it on to the discs in such a

way that it can be guided through the through-goingopenings of both discs and by slightly turning can be putdown on the upper disc (mainly when the bushing is invertical position).For mounting purposes proceed as described above.

The turning directions always refer to the position on thebottom side in front of the screen.

** if a screen is provided for the bushing, if necessary, refer toThe bushing specification

Fig.10

Fig.11

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3 Mounting of the bushing on the transformer

The given values are reference values and referto bolted joints with stainless steel screws.

Applicable only for flange joints with O-ring sealand metallic contact of the parts. If used with flat

gaskets, adequate external brace support isrequired.

Fig.12

Fig.13

Fig.15

Mounting of the bushing on the transformer is carriedout on the transformer side according to theinstructions of the transformer manufacturer. Differentconnecting techniques have to be taken into account.In case of a design with connecting plug wheninserting the bushing take care that the plug is locatedvertically and in the center of the contact sleevebefore it is lowered. This also applies for a bushing inhorizontal mounting position.In case of screw connections with connecting terminalbefore mounting the screen has to be movedaccordingly. Torques of the screws have to be chosen

acc. to the table.Sealing of the bushing flange is made according to theinstructions of the transformer manufacturer, the sameapplies to the torques for the fastening screws of thebushing flange. If there are no instructions, pleaserefer to the table on the left.

The connections on the SF6-side are differentdepending upon the installation design. Proceedaccording to the rules and instructions of the GIS-manufacturer.The surface of the insulator and the metal surfaces of

the flange which are in contact with the SF6-gas haveto be free of oil and grease and clean (also see 5.3).For cleaning purposes use cleaning cloths free offluffs. For this reason the surface of the insulator ishigh gloss varnished.

If there are adjusting problems regarding the angleposition of the high voltage contact plate, this platecan be turned in a range of 30. To adjust theposition slightly loosen the locking screws (Fig.15/1) inthe contact terminal, it can now be turned in therequired direction. After that the screws have to be

fastened with a torque wrench acc. to the table(Fig.14) on the adjoining side.The locking screws pull a threaded ring (2) against thecontact plate (3), which is screwed to the conductorbolt with a thread. By fastening the locking screws thethread of the contact terminal is pressed to theconductor bolt and guarantees safe current transition.This manipulation directly influences the currentcarrying capacity of the bushing! Therefore it has tobe reported in writing in the mounting reports.

1 2 3

screw torque (Nm) torque (kpm)

torque (Nm)M8 12M10 25M12 50M16 100M20 200

Fig.14

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3.1 Grounding of the bushing flange

4 Putting into operation4.1 Ventilation at the bushing flange

4.2 Evacuation of the transformer

4.3 Recommended tests before putting into operation

4.4 Electrical measurements

The bushing flange has grounding screws. Through groundingbands or wires the flange has to be connected to thetransformer tank. Apart from following several national rulesthis secures a safe galvanic connection.

To remove possible air bubbles in the area underneath thebushing flange open the air release screw to enable the air toescape. The ventilation screw does not have to be removedcompletely, it is flattened at its lower end, thus allowingventilation. For the same reason the air release screw (Fig. 16)has a lateral bore.

As the bushing has an undetachable current conductor, thereare not other possibilities for air release.

If evacuation of the transformer is necessary, there are norestrictions regarding level and duration up to operating

temperature of the bushing. The material RIP is suitable forsuch treatment.

Only a visual check of the visible parts of the bushing forpossible damages is possible. All screws have to be fastenedaccording to the rules, the cap of the test tap has to be closedtightly.As the bushing was subjected to a leakage test in themanufacturers factory, gas as well as oil leakages, further

testing prior to putting into operation is not required.

By the final tests carried out in the manufacturers factory thebushings are tested and certified suitable for operation.But it makes sense and is recommended to carry out a so-called reference measurement on site. This guarantees that incase of later control measurements the meauring conditionsare unchanged and comparable results are achieved. This is

only possible, though, when the connection on the gas side isinterrupted.

Depending upon the design of thebushing the transformer ventilationis located either on the outer rim ofthe transformer side flange plate

(Fig. 16), on the side of the flangeneck (Fig. 17) or in case of big

flange plates in front on top of the

flange plate

Fig.16

Fig.17

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4.5 Test tapDesign of the test tap on bushing type EKTG

Design A older type (Fig.18)Design B new type (Fig.19)

With the test tap the last grading layer of the capacitivegrading is led out insulated (1) by means of a smallbushing. The removable cap (2) has a contact sleeveor spring (3) in which the connecting pin (4) providesreliable grounding when the cap is closed tightly. The

cap has an O-ring sealing (5) to guarantee a moisture-free inner volume of the test tap.During normal operating conditions this connection isalways grounded. For measurements of the bushing incase of de-energized transformer the measuring leadis connected to the pin to determine capacity anddissipation factor.

The test tap is not self-grounding! Therefore duringoperation the cap has always to be tightly closed!Operation with open test tap leads to a destruction of

the small bushing (1) in the test tap with influence onthe inner volume of the bushing and following damage!

TEST TAP

DESIGN A

Connecting pin (4)

Bushing (1)

Cap (2)

Sealing (5)

Grounding spring madeof non-corrosive steel(3)

DESIGN B

Cap (2)

Contact sleeve (3)

Sealing (5)

Bushing (1)

Connecting pin (4)

Fig.18

Fig.19

There are transformers where such measurements arecarried out during the final test of the transformer. In

this case comparative data is available already.

Bushing capacity as main capacity C1 and the electricaldissipation factor tan delta are measured. Measurementof the capacity between the last grading layer and theflange is possible, but it does not allow any statementabout the main insulation, it only shows the condition ofthe test tap area.Description of the procedure see item 5.4 ff

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4.6 Voltage tap**

5 Maintenance

5.1 Recommended maintenance and checks

If the bushing has a voltage tap (Fig. 20), not the last

but the last but one layer of the capacitive grading isled out galvanically. Due to the higher output voltageof approx. 6 kV the insulating bushing is correspon-dingly bigger. Above that the volume around thisbushing is filled with oil for permanent voltage output.In the cap (1) there is a contact spring (2) to ground theconnecting pin (3) of the bushing (4). The cap isequipped with an O-ring sealing (5) to guarantee amoisture-free inner volume.During normal operating conditions this connection isalways grounded. For measurements of the bushing incase of de-energized transformer the measuring leadis connected to the pin to determine capacity anddissipation factor.

The voltage tap is not self grounding! Therefore the caphas always to be tightly closed during operation.Operation with open connection leads to a destructionof the insulation of the bushing (4) in the voltage tapwith influence on the inner volume of the bushing andfollowing damage!

For permanent connection of voltage tap equipment,

which fits with its connecting plug onto the externalthread of the bushing (2), after mounting the innervolume has to be filled with oil through the oil fillinghole , take into account approx. 2-3 cm3 volume for oilexpansion.

** Optional, see bushing specification

Fig.20

The bushing is free of maintenance. Check andmaintenance only refers to the visible and accessiblearea of the flange with respect to corrosion or damagesof the varnish. These checks should be carried outduring the regular transformer revisions.

VOLTAGE TAP

Cap (1)

Oil filling screw (6)

Sealing (5)

Connecting pin (3)

Bushing (4)

Contact spring (2)

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3 2 1

5.2 Cleaning

5.3 Cleaning after coating with oil

Due to its encapsulation apart from the flange area thebushing is protected against environmental influences.

Therefore, apart from the flange area, no cleaning isrequired.

Fig.20If during mounting or delivery it is noticed that the gas sidesurfaces are coated with oil and it is not sure that the oilhas not penetrated into gaps, cleaning as described isrecommended.

In the flange area (Fig. 21) all gaps, grooves (1) and screwsinks (2) are sealed with sealing material by themanufacturer. Here only remainders of oil have to beremoved with a solvent.

Only the gap on the high voltage side between connectingplate and insulating body is not sealed and must becleaned. Procedure see Fig. 22

1 2

CLEANING AFTER COATING WITH OIL(Fig.23)

- Loosen and remove locking screws (1)- Remove contact plate (2)- Remove threaded ring (3)- Make front side of the insulating bodyincluding ring groove and all removed partfree of oil with cleanser.

- Fasten threaded ring (3) in the same position

as before disassembly- Fasten contact plate (2) with screws andadjust position of the bores with reference tothe threaded ring. Take care that a gap ofmin. 1 mm remains between front side of theinsulating body and contact plate and contactplate and threaded ring.

- Insert locking screws (1) and fastened themwith a torque wrench acc. to the table Fig. 14

- For precise position of angle see 3.0

Fig.21

Fig.22

Due to the encapsuled installation arrangement electricalmeasurement is difficult or not possible at all. For such a

measurement either the GIS-substation section has toprovide access to voltage feed of the measuring equipmentthrough an opening, while the section itself is interrupted, orthe whole encapsuling including high voltage connection hasto be removed.

This kind of electrical control measurement we recommendafter the first 10 years of operation and after that dependingupon the measuring results in shorter intervals.

Control measurement on bushings require a certainexperience with measuring equipment, test set up and

interpretation of the test results. For some part this is a resultof the relatively small capacity values, the influence of theenvironment is rather low, though, due to the existing metalencapsulation. The measurement of the electrical dissipationfactor can be influenced by humidity, weather etc.

Fig.23

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C

deltaC(%

)

tandelta(%

)

tan delta = f (T) delta C = f (T)

00

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7

6

5

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3

2

1

HSP - RIP

-20 -10 0 10 20 30 40 50 60 70 80 90 100

5.4 Electrical measurements

5.5 Measuring procedures

5.6 Equipment

5.7 Limits

Measurements on bushings require experience with measuring

equipment, test set up and the interpretation of measurementresults.This is for some part due to the relatively small capacitancevalues, which are corrupted by the ambient influence of theenvironment alone. The measurement of the dielectricdissipation factor can be influenced by the voltage feed on theGIS-side by humidity, weather etc.

Mainly the measuring procedures differ by the coupling of themeasuring signal. In case of so-called not groundedmeasurements the test voltage is applied to the conductor ofthe bushing and the measuring signal is taken at the test tap ofthe bushing.The grounded measuring procedure is applied, if the bushingwhich has to be measured does not have a test tap. This is notapplicable for the bushing type EKTG.The devices required for the measurement are usuallyequipped specifically for the measurement of bushings. Themeasurement methods are described in comprehensivemanuals.

Measuring equipment is available from several manufacturers.Data can be found in the internet or enquired at HSP.(Fig.24)

For the measurement the influence of the ambient temperaturehas to be taken into consideration. In the diagram on the leftside for C and tan delta the variation through temperature isshown. (Fig.25).

For the material RIP, resin impregnated paper there are limitvalues for the deviation of the capacitance and the dielectricdissipation factor with relation to the new value.This value is reliably deducted from the referencemeasurement described under 4.4.

In case the deviations are larger than mentioned in the tablebelow, HSP has to be contacted in any case. When there arevery large deviations the bushing may have to be taken out ofoperation.

Voltage level C-Deviation< 123 kV 10 %123 kV 5 %245 kV 3 %420 kV 1 %

Guide value tan delta 0.004 0.006

Example of mobilemeasuring equipment

Fig.24

Fig.25

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6 Possibilities of repairThe bushings type EKTG are made of several parts which

can be disassembled, therefore repairs are possible. Theserepairs will mainly be replacements of sealings on the gasand on the transformer side of the bushing. For repairpurposes the bushing has to be demounted. Only in case themain sealing on the SF6-side of the flange is concerned,there may be the possibility that it can be replaced while thebushing is mounted.

These operation and maintenance instructions are valid forbushings type EKTG, therefore in case of a repair differentsectional drawings and parts lists are required. Bothdocuments can be ordered from HSP in case of a repairquoting the serial and the specification number and will besent immediately. (Example of a sectional drawing and aparts list (Fig. 26). Above that depending upon the repairrequirements short instructions can be given.

General measures in case of repairDisassembly has to be made in a dry and dust-free room.The bushing is placed with its insulating body on woodensupports situated close to the bushing flange. The flangeplate on the SF6side is sealed with silicone and dependingupon the design the fastening holes are sealed with siliconeas well. Remove this sealing material before you start with

disassembly.After repair an electrical test has to be carried out in anycase to guarantee that the bushing was not damaged duringthe works. (C, tan delta and p.d. measurements up reducedtest voltage).On the insulating body itself no repair can be made. In caseof an internal failure we recommend to return the bushing tobe manufacturer, who has suitable means and measuresand professional investigation methods. But even in case ofmore simple repairs a return to the manufacturer may bereasonable.

Fig.26

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7 Storage

Fig.27

In its original packing the bushing can be stored up to 12months in dry rooms. In case it is packed in aluminium coatedfoil with inlaid dehydrating bags, it can be stored up to 24months.

Long term storage, e.g. as spare bushing, is possible onlywith a protection tank (Fig. 27) on the gas side as well as onthe transformer side. The material RIP is hygroscope and canabsorb moisture, especially during long periods of storage.The protection tank is made of spray-galvanized steel sealedby O-rings and fixed to the flange by screws. The tank has ascrew opening with non-return valve (Fig.27). The gas side of

the bushing can be stored in dry nitrogen only, therefore itmakes sense to fill the transformer side with nitrogen as well,here dehydrating bags are added. A small excess pressure ofmax. 15 kPa is sufficient. In terms of approx. 1 year thepressure should be check with a pressure gauge (Fig.28)

NON-RETURN VALVE (Fig.28)The non-return valve is made of a valve body (1) with a movablevalve cone (2) This valve cone is pressed against the conical gasketface by a cup spring column. From outside the non-return valve issealed with an additional locking screw (3). The valve opens when

the filling valve is screwed in. The tip of the filling valve pressesagainst the cone and opens it. When releasing the valve is closedagain by the pressure of the springs.

FILLING VALVEThe filling valve (4) (Fig. 29) is equipped with a pressure gauge forpressure measurement. It is screwed into the valve body by a thread. It is possible instead of a pressure gauge to connect a hosewith a suitable and common hose nipple to re-fill gas instead of apressure gauge.

HANDLINGRemove the locking screw with a screw driver. After loosening the

screw it has to be pulled out of the bore, because it is fixed by aradial O-ring. After that the filling valve is screwed in until the valveopens. Take care that after the works have been finished thelocking screw is inserted and fixed again.

Protection tank

open closed

4

3

1

2

Fig.28

Fig.29

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8 Disposal after end of operation

The bushing does not contain any liquids, the parts are neithertoxic, self-inflammable nor physically detrimental. All partscan be disposed of as common industrial waste.

Following components:- Epoxy resin impregnated special paper with

aluminium foils as layers- Armatures made of aluminium or copper alloys- Conductor bolts made of E-Cu- Fastening elements, test tap, screws etc. made of

non-corrosive steel, aluminium alloy or brass- Silicone elastomere (sealings)

In case the flange plates are fixed by screws to the centralpart of the flange for easier disposal they can be removed.

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Bal Ektg 04e