Rêbaza Darçûna Piramên Transmîsyon
Bêrên çar sernîşan ên sererastkirinê da çavkantinan çelîkan û ku li jêr têne nîşan kirin:
Rêzikê ya build-up an jî piece-by-piece.
Rêzikê ya section.
Rêzikê ya ground assembly.
Rêzikêya helicopter.
Build Up Method of Transmission Tower Erection
Ev rêzik ji bo sererastkirina çavkantinan çelîkan 6.6 kV, 132 kV, 220 kV, û 400 kV di Hindistanda de her têke pêk hatiye bikar an îro biniyê:
Materiyalên çavkantinan dikare bi rêzikê knocked down derbas be û hêsan û pirwer bike werdibe.
Nayê zoravê têkebûn ne ku crane û yake têkebûn.
Etkariya sererastkirina çavkantinan dikare di her cûra de û her demê re bigere.
Herînê xebatê bi hêsan.
Ev rêzik ji bo sererastkirina çavkantinan member by member derbas dike. Memberên çavkantinan di navbera de bi rêzikê erection sequence derbas dike ku hewce ne ku li gorî vaxtê bibin. Sererastkirina ji paşê derbas dike.
Memberên corner leg ên herêmî ya paşê ya tower dikare sererast bikin û guard off bikin. Jî hêj ji berê divê du corner leg section û yake ya herêmî bi rêzikê bolted together di navbera de bikin û sererast bikin.
Cross braces ên herêmî ya paşê ku di navbera de girîn dibin û wekî unit bi rêzikê raised bikin û bi memberên corner leg angles sererast bikin. Herêmî ya paşê ya tower ên paşê dibin û horizontal struts (belt members) eger heye, bi rêzikê bolted in position bikin. Ji bo assembly ên herêmî ya duyem ên tower, du gin poles dikare bi rêzikê placed bikin û herêmî ya diagonally opposite corner legs.
Du poles ên wan bi rêzikê bikaranîn û parts ên herêmî ya duyem ên tower bikin. Leg members û braces ên herêmî ya duyem dikare hoisted bikin û assembled bikin. Gin poles dikare shifted bikin û bi corner leg members on the top of the second section to raise the parts of the third section of the lower in position for assembly. Gin poles are thus moved up as the tower grows.
Ev process dikare devam bike ta tower komplet sererast bike. Cross-arm members assembled on the ground and raised up and fixed to the main body of the tower. For heavier towers, a small boom is rigged on one of the tower legs for hoisting purposes. The members/sections are hoisted either manually or by winch machines operated from the ground.
For smaller base towers/vertical configuration towers one gin pole is used instead of two gin poles. In order to maintain speed and efficiency, a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members, keeping the member’s incorrect position on the ground and assembling the panels on the ground which can be erected as a complete unit.
Section Method of Transmission Tower Erection
Di rêzikê ya section de, sections ên mezin ên tower assembled on the ground and the same are erected as units. Either a mobile crane or a gin pole is used. The gin pole used is approximately 10 m long and is held in place by means of guys by the side of the tower to be erected.
The two opposite sides of the tower section of the tower are assembled on the ground. Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into position on bolts to stubs or anchor bolts.
One side is h held in place with props while the other side is being erected. The two opposite sides are then laced together with cross members and diagonals; and the assembled section is lined up, made square to the line. After completing the first section, the gin pole is set on the top of the first section. The gin rests on a strut of the tower immediately below the leg joint. The gin pole then has to be properly guyed into position.
The first face of the second section is raised. To raise the second face of this section it is necessary to slide the foot of the gin on the strut of the opposite face of the tower. After the two opposite faces are raised, the lacing on the other two sides is bolted up. The last lift raises the top of the towers.
After the tower, the top is placed and all side lacing has been bolted up all the guyed are thrown off except one which is used to lower the gin pole. Sometimes whole one face of the tower is assembled on the ground, hoisted, and supported in position. The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted.
Ground Assembly Method of Tower Erection
Ev rêzik ji bo sererastkirina tower bi rêzikê assembly on the ground and erecting it as a complete unit. The complete tower is assembled in a horizontal position on even ground. The tower is assembled along the direction of the line to allow the cross arms to be fitted. One slopping ground, however, elaborate packing of the low side is essential before assembly commences.
After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location, and set on its foundation. For this method of erection, a level piece of ground close to footing is chosen from the tower assembly.
This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of the complete tower on the sloping ground may not be possible and it may be difficult to get the crane into position to raise the complete tower.
In India, this method is not generally adopted because of the prohibitive cost of mobile crane, and the non-availability of good approach roads to tower locations.
Helicopter Method of Transmission Tower Erection
Di rêzikê helicopter de, transmission tower erected in section. For example, the bottom section is first lifted on to the stubs and then the upper section is lifted and bolted to the first section and the process is repeated till the complete tower is erected.
Sometimes a completely assembled tower is raised with the help of a helicopter. Helicopters are also used for lifting completely assembled towers with guys from the marshaling yards where these are fabricated and then transported one by one to line locations. A helicopter hovers over the line location while the tower is securely guyed.
The ground crewmen connect and tighten the tower guys. As soon as the guy wires are adequately tensioned the helicopter disengages and files to the marshaling yard. This method is adopted where the approach is very difficult or to speed up the construction of the transmission line.
Tightening of Nuts and Punching of Threads and Tack Welding of Nuts of Transmission Towers
All nuts shall be tightened properly using correct sized spanners. Before tightening it is ensured that filter washers and plates are placed in relevant gaps between members, a bolt of proper size and length are inserted and one spring washer is inserted under each nut.
In the case of step bolts, the spring washer shall be placed under the outer nut. The tightening shall be carried on progressively from the top downwards, care being taken that all bolts at every level are tightened simultaneously. It may be better to employ four persons, each covering one leg and the face to his right.
The threads of bolts shall be projected outside the nuts by one to two threads and shall be punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time. If during tightening a nut is found to be slipping or running over the bolt threads, the bolt together with the nut shall be changed outright.
Painting of Joints of Transmission Tower
For galvanized towers is coastal or highly polluted areas, the joints shall be painted with zinc paint on all contact surfaces during the course of erection.
Checking the Verticality of Erected Transmission Towers
The finally erected tower shall be truly vertical after erection and no straining is permitted to bring it in alignment. The tolerance limit for vertical shall be one in 360 of the tower height.
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