METHOD OF TOWER ERECTION

1.             PURPOSE

1.1.        The purpose of this document is to explain the methods used for Tower Erection works.

2.             SCOPE

2.1.        This procedure applies to all personnel who are involved in and are responsible for the execution of Tower Erection works.

3.             DEFINITION

3.1.        Nil.

4.             REFERENCE

4.1.        Technical Specification and Contract Agreement of 500 KV Transmission Line jawa 1 CCP project.

5.             SAFETY

5.1.        All work will be carried out in accordance with the WTE Health, Safety and Environment procedure.

5.2.        The following Personel Protective Equipment (PPE) must be provided :

·     Hard Hat (Safety Helm)

·     Gloves

·     Safety Belts double lanyards type.

5.3.        Climbing

Unattached movement is NOT permissible. Access up and down the climbing leg / stepbolts is carried out using double lanyards or a fall rope and slide chuck mechanism (cobra). When traversing across a tower to a work position, it is an essential requirement that the climbers must be securely attached to a safe anchorage at all times.

5.4.        Working

It is an essential requirement that when at the work point, the person is in a secure position attached to a safe anchorage at alltimes.

5.5.        Climbing Belt and Lanyards

All climbers must use a climbing belt with two lanyards. Belt and lanyards should be checked daily for obvious damage, broken stitches cuts or wear. Checking on safety hooks and buckles should also be carried out daily.

5.6.        All workers have a responsibility to work safety according to the Company Guidelines. lnparticular they must :

Ø   Wear the safety equipment provided.

Ø   Check that the lower earthing is connected.

Ø   Check their equipment daily and request the replacement of faulty items.

Ø   Climb down from the tower during rain.

Ø   Never erect the tower if the foundation is not backfilled.

Ø   Not work at night unless special provisions have been made.

Ø   All Lifting Hooks must have an approved safety catch.

Ø   All type of steel wire rope and nylon rope must be tension tested before use.

Ø   At every 3 towers erection, bamboo derrick must be checked against crack and rope lightening.

Ø   Anchorage must use anchor drill or other strong tools.

Ø   lf you are not sure about the anchor drill (example : rock area), please install the- spare anchor drill (2 pieces) at back.

Ø   lvlaximum lifting capacity for bamboo derrick is 400 Kg.

Ø   Maximum lifting capacity for 70 ft aluminium denick is 1.000 Kg.

Ø   Maximum lifting capacity for modified 25m Tesmec aluminium derrick model number FAL 320 is 1000 Kg.

Ø   Maximum lifting capacity for WTE 21m lattice steel derrick is 1.000 Kg.

5.7.        ln the event that a winch bond becomes snagged on the tower, the lift should be stopped and the tension reduced on the bond before releasing the snagged portion of the bond.

5.8.        The foreman an is responsible for implementing this erection safety procedure. ln addition, a person should be appointed "banksman" to observe and direct the lifting operations involving the winches.

6.             MATERIALS

6.1.        The following materials are required for Tower Erection :

Ø  Angle Steel work.

Ø  Plates.

Ø  Nuts, Bolts and Washers.

Ø  Anti Climbing Devices.

6.2.        All materials are hot dip galvanized and care must be taken to avoid damaging, scratching or marking this protective coating. Any defect in the galvanizing should be reported immediately.

6.3.        All materials are issued to site from the store. The procedure for storage, batching and issue of tower materials to site is described in the Work lnstruction for store.

6.4.        All materials should be checked for compliance with the specification before leaving the store.

6.5.        MATERIAL TRANSPORTATION

6.5..1.     Material is transferred from the site store to the tower location by using truck or any othersuitable means. Smaller truck may be used, for example, where road access is very narrow.

6.5..2.     lf there is no access road access, the steelwork should be carried from the nearest roadside point to tower location by hand carry.

6.5..3.     The materials unloaded at the tower site must be stacked on timber batons, for ease of lifting and to keep the steelwork clean (any dirt must be washed / brushed off).

6.5..4.     The steelwork should be laid out in the sequence it is required for tower erection.

6.5..5.     Special care must be taken to avoid damaging the steelwork in any way. Scratches can berepaired using 'Cold calvanizing Paint' as approved bythe Engineer. Steelwork with major damage must be replaced.

7.             PREPARATION FOR TOWER ERECTION

7.1.        The tower foundation must be back filled before starting any tower erection.

7.2.        The foundation concrete must have reached a strength of specification.

7.3.        The surveyor must check the following stub dimensions :

Ø  Back to back (face and diagonal).

Ø  Relative levels of top of stubs.

Ø  Slope of stubs.

As shown in work sheet for foundation work.

7.4.        The tower earthing must be installed according the drawings. Make sure that tower earthing has been installed before erection and has to be measured after erection finished.

7.5.        Assembly of steelwork on the ground should be carried out in dedicated areas to avoid people working overhead.

7.6.        Good housekeeping (i.e. keeping the site tidy) should be maintained during the tower erection operation.

8.             PROCEDURE FOR ERECTION OF AA TOWER

8.1.        The main equipment and plant required are :

Ø  Winch and Bond.

Ø  Derrick

Ø  Spanners.

Ø  Derrick guys.

Ø  Stakes.

Ø  Snatch blocks.

Ø  Nylon rope.

Ø  Pullifts.

Ø  Lifting hooks complete with safety catch.

8.2.        The derrick is manually handled into resting position on the chimney of one leg. Head guys and winch bonds are fitted as shown on the sketch below :

8.3.        The head guys must be secured to a ground anchor such as Molex Anchors or concrete blocks at a safe distance from the derrick. The foreman must select appropriate locationsand check they are correctly installed. lt is not acceptable to use trees of any type for ground anchors.

8.4.        The winch must be anchored to the ground using either stakes, molex anchors.

8.5.        LEG EXTENSIONS

8.5..1.     The first lift is the main leg which fits immediately above the stub. After lifting into position and bolting up the splice plates and bosom angles, a holding out rope is fixed to the top of the main leg to maintain the correct slope.

8.5..2.     The derrick is then moved to the next leg and the operation described in 8.5.1 is repeated.

8.5..3.     The horizontal and bracing bars, that fit between these legs are then lifted into position.

8.5..4.     The derrick is moved on to the remaining legs, in turn and operations 8.5.1 & 8.5.3 are repeated until all 4 leg extensions are in place with all the horizontal and bracing members.

8.6.        BODY EXTENSIONS

8.6..1.     The bamboo derrick is then lifted to the first horizontal at one of the main legs. The winch bond passes through a snatch block at the bottom of the main leg used by the derrick and through a second snatch block at the top of the derrick.

8.6..2.     The same procedure as described in 8.5.1 to 8.5.4 is followed to compiete the bodyextension.

8.6..3.     Providing the derrick is 14m long it may be possible to lift the two adjacent main legs into position by leaning the derrick towards each leg by adjusting the derrick head guys. Head and foot holding out ropes are attached to each main leg to manuver them into position. ln this way the derrick will only be moved to one other leg. However, the derrick must not normally lean more than 15" to the vertical.

8.7.        COMMON PORTION

8.7..1.     The derrick is lifted, as required, to each new level of the tower.

8.7..2.     All material can be lifted into position by the derrick fixed at one leg. The derrick is leaned over, as required, by adjusting the derrick head guys.

8.8.        CROSSARMS

8.8..1.     The cross arms are lifted into place when the common portion body is complete.

8.8..2.     The earth wire cross arms are lifted first.

8.8..3.     The top, middle and bottom cross arms are lifted in two sections (an outer and an inner section). The outer section is lifted into position with the winch bond passing through a snatch block on the earth wire cross arms take off plate.

9.             PROCEDURE FOR ERECTION OF ANGLE (DD / DDR / EE} TOWERS

9.1.        The main equipment and plant required are :

·           2.5T winch (Capstan Winch) and bond.

·           Type of derrick : 70'Aluminium derrick or Modified 25m, Tesmec Aluminium derrick model number FAL 320 or WTE 21m lattice Steel derrick.

·           1.5T Tirfors.

·           1.5T Pull Lifts.

·           Head guys.

·           Wallace toggles.

·           3m and 4m . 12mm Wire rope slings.

·           1.5m x 16mm Wire rope slings.

·           1T & 1.5T SWL D Shackles.

·           Anchor drill.

·           Snatch blocks.

·           Nylon rope

9.2.        The procedure for lifting the steel work into position is the same as for described in section 8. however, since the tower material is heavier and the base size of angle towers is wider, a larger aluminium derrick is used. The 'floating derrick' methods is used with guys connected to the main legs of the towers.

9.3.        The following safety considerations should be considered at all times.

·           The derrick should be lifted into the wind.

·           The derrick should not be used at an angle > 30˚ to the vertical.

·           Lifting hooks shall be completed with safety catch.

9.4.        The following operations 9.5 and 9.6 describe the additional information required ti lift lhe derrick into position and subsequently raise the derrick to new levels of the tower.

9.5.        RAISING DERRICK TO THE VERTICAL POSITION

9.5..1.     This is a straight forward operation, which requires good co-ordination to avoid accidents. Lt is important that the Senior Erection Supervisor attends every lifting operation.

9.5..2.     The derrick is laid out and assembled with its foot on a base plate at the centre of the tower. Slings are used to anchor lhe base plate to the existing stubs.

9.5..3.     The winch is positioned by the supervisor to suite the site conditions. lt is important that the winch operator has good visibility to all lifting operations.

9.5..4.     While the derrick is lying on the ground, four guys are pulled out from the head of the derrick. They are positioned at 90˚ to each other and anchored at a distance equal to the height of the derrick.

Item	Description	Qty	Item	Description		Qty
1	Aluminium derrick 70 Feet or WTE 21m lattice steel derrick	1	7	Erectionn Winch bond dia. 12mm with length 250m		1
2	77m , 8 ,12mm wire rope guys	4	8	4m * 12mm wire rope sling		2
3	3m * 12mm wire rope sling	4	9	1T SWL "D' Shackles		4
4	2.5T SWL Erection Winch	1	10	Tirfor 1.5T		4
5	A-Frame for erection bond	1	11	1.5m * 16mm wire rope slings		4
6	Anchor drill	15	12	1.5T SWL "D' Shackles		18

9.5..5.     A falling derrick is then positioned over the base plate. This is typically an a frame made up from two main legs. lt is common practice to connect a sling from the a frame to the derrick to control its fall once the derrick rises above the top of a frame.

9.5..6.     The winch bond is passed through the head of the a frame and head to the derrick and caught off at the base plate.

9.5..7.     The derrick is now ready for lifting. Before this operation begins the senior supervisor will check :

·      All the guys are correctly positioned with men at each anchor position.

·      The bonds and guys are not obstructed.

9.5..8.     The derrick is slowly raised by the winch. The side guys should be monitored to ensure that the derrick rises in line with the winch.

9.5..9.     When the derdck is above 45˚ the rear guy should be very closely monitored. lt need to be applied quickly if there is a danger of the derrick falling over towards the winch but otherwise should have some slack to that it does not work against the winch.

9.5..10. After the derrick has reached the vertical position all four guys are caught off and the derrick is ready to begin lifting operation.

Item	Description	Qty	Item	Description	Qty
1	Aluminium derrick 70 Feet or WTE 21m lattice steel derrick	1	7	Erectionn Winch bond dia. 12mm with length 250m	1
2	77m , 8 ,12mm wire rope guys	4	8	4m * 12mm wire rope sling	2
3	3m * 12mm wire rope sling	4	9	1T SWL "D' Shackles	4
4	2.5T SWL Erection Winch	1	10	Tirfor 3.5T	4
5	A-Frame for erection bond	1	11	1.5m * 16mm wire rope slings	4
6	Anchor drill	15	12	2.5T SWL "D' Shackles	18

9.6.        RISING DERRICK TO HIGHER LEVEL

9.6..1.     When the derrick is lifted off the base plate it becomes a “floating” derricks. It is supported from pennants connected to all four tower legs. The head guys pass through the blocks at the top of the main legs and continue to the stubs where they can be adjusted by tirfors.

9.6..2.     Position on the main legs is chosen to fix the pennants. This is chosen to ensure :

·      One - third of the derrick remains inside the erected tower.

·      The pennants hang at an angle of < 30˚ to the derrick.

9.6..3.     The derrick is lifted using a "Lazy" bond connected from the winch through a block at the top of one main leg and on to the bottom of the derrick.

9.6..4.     The head guys are released as the derrick is lifted. When the derrick has been raised to the correct height the pennants are connected and the head guys caught off.

9.6..5.     The derrick is then ready to re-start lifting operation.

10.         TOWER CHECKING

10.1.    After completion of the tower erection all bolts must be checked tightness, This operation should follow a logical sequence from bottom to top of the tower to ensure all bolts are checked.

10.2.    The supervisor should complete and sign the Post Erection Inspection Form.

11.         EXCEPTION

11.1.    ln the steep area or narrow area, to pull the derrick can use the kick back system (Different with the normal procedure on Point 9.5)

12.         RECORD

12.1.    Post Erection lnspection.

12.2.    Certificate of Tower Earlhing

13.         APPENDIX

13.1.    Work Flow for Tower Erection.

13.2.    Post Erection Inspection Form.

TOWER ERECTION WORK FLOW