The purpose of this method statement is to explain the various steps involved in lifting the Settling Tank shells by Jack Lifting Method.
Prepare work permits, JSA and working procedure for approval prior to commencing work. Organize job safety meeting with all concerned to brief the planned work activities and discuss their associated risks.
All lifting gears such as wire slings, web slings, shackles etc shall be inspected and shall come with the valid load test certificate prior to lifting. All personnel that will be involved with the works shall review the Job Safety Analysis, Work procedure and conduct tool box meeting immediately before commencement of work.
Ensure all personnel are equipped with appropriate PPE for the right job especially for personnel working at height to wear safety harness, hand gloves and vest.
Barricade the work area with red and white tape, sufficient warning sign boards, work permit and JSA at Work site. Only authorized personnel are allowed to be within the area during the lifting and erection works.
Erect Scaffolding/ install temporary support and platform to ensure works accessibility.
Following equipment shall be used.
- Hydraulic Cylinder Type BW 12-200
- Lifting Capacity 12tonnes
- Maximum lift height 100mm.
- Weight Approx. 25kg
- Lifting Trestle with Two Supporting Stay legs
- Safe Working load 12tonnes
- Maximum lift height 2.5m or 3m
- Total unit weight approx. 200kg
- Largest component Approx. 75kg
- Jack rod 40 mm diameters
Erection by Jacking Method
- Mark the shell I/S diameter and fix the elevators on the annular plate.
- Tack the guide on the elevators.
- Weld the lifting cleats. (2 nos. /Jack; capacity of hydraulic jack-12 MT; For settling Tank – 38Nos (Min.), Export Tank – 55Nos (Min.).
- Weld the pad plates. ( 1 no for trestle & 2 no’s for stay member)
- Install trestle and stay member. Length of the trestle to be checked according to shell heights.
- Connect the high pressure hosepipes from power pack to each jack.
- Give electrical power connection to power pack and start jacking.
- Continue jacking till the assemble is lifted to a height of 50 mm more than the width of the shell course to be erected next.
- Erect the shell course by using crane or by any mechanical means.
Tank erection Sequence
- Sand Blast , complete Painting On Bottom Surface of Annular Plates
- 6th Shell – Painting on outer surface one coat – and Bottom Plate along with complete painting
Compression Ring Painting on outer surface one coat
- Center Column along with complete painting
- Trusses And Cross Girder along with complete painting – Lift Assembly
- 5th Shell along with one coat painting
- Wind Girders / Foam Chambers/ Stair case along with one coat painting /Roof Plat form / Roof Nozzles – LIFT
- 4th Shell along with one coat painting
- Wind Girders / Nozzles / Stair case along with one coat painting /Balance Roof Plat form along with one coat painting, Nozzles – LIFT( Partially)
- On 4th Shell – ( Only on 4th Shell) Oil through support bracket fabrication, Oil through bottom plate fabrication with shell plate, Oil through vertical plate fabrication with support bracket. Oil through plates shall be pre fabricated as per drawing and Sand blasted. Sand blasted surfaces shall be protected with the help of adhesion tape to protect the sand blasted surfaces from rust. Bottom of the oil through surface shall be fully welded with support bracket of oil through, balance structural work of Oil through after erection of 1st Shell on nozzle portion.
- 3rd Shell
- Nozzles / Stair case/Balance Roof Plat form – LIFT
- 2nd Shell
- Nozzles / Stair case/ – LIFT
1st Shell Plate erection with one coat painting external to the tank – (Only following plate erection shall be taken preliminary
1. One plate on Inlet nozzle N3 @ 180 ° area Plate S1A -25 mm Thk
2. One Plate S1A 25 mm Thk @ 90 ° to Nozzle N3
3. One Plate S1A 25 mm Thk @ 270 ° to Nozzle N3
After installation above plates, following activities to be taken up,
1. Oil suction bucket assembly shall be installed along with all structural support.
2. Fixing of base plates on the tank shells and oil bucket for support of Bumper supports to hold Main Distribution and lateral distribution supports.
3. Main distribution holding supports shall be drilled for bolting holes as per drawing before welding on base plates on shells & suction bucket assembly.
4. Marking shall be done for welding of 8 mm x 300 mm x 300 mm base plates for supports for Steam pipe on entire Bottom plates as required.
5. Fabricate all Steam Pipe Supports in workshops as per drawing and keep ready for installation.
6. Fabrication of Steam pipe ( Flange to flange) spools shall be kept ready for assembly inside the tank along with U- clamps. Also supports shall be pre fabricated out side tank before erection along with pipe.
7. Base plate for Bumper assembly shall be fabricated on shell plate. Lateral distribution Bumper assembly shall be fabricated as per the drawing. Fabricated Bumper support to be welded to the shell as per the drawing.
8. Draw off sludge support shall be kept ready for assembly on the bottom of the shell dully painted as required.
9. While prefabricating the main and lateral distribution shells at work shop, please (ensure)fabrication of adjacent lateral distribution shell with respective main distributive shell shall also be completed to avoid local welding inside the tank.
10. Main and lateral distributor shells shall be one coat painted with Glass flake paint before shifting for assembly.
11. Assemble the main distributing shell with bumpers fixed on the shell.
12. After completion of alignment of main distributing shell , Seal weld shall be done for complete assembly of the Main distributive shall.
13. Similarly lateral distributive shell shall be aligned and seal welded.
14. After complete erection of main and lateral distributors, Oil through, oil suction buckets, and draw off sludge assembly with pipes – Now the inside of tank is ready for copper blasting.
15. Keep the shell -1 open (only with 4 plates in place and welded), start the copper blasting for entire shell plate, before start of blasting the shell plates, roof structure and plates shall be covered by appropriate coverage to avoid damage of paint due to copper grit striking the paint surface during copper blasting of shell plates.
16. VEGF (Vinyl Easter Glass Flake) paint holding primer is to be applied on the inside of the shell within 4 hrs from the time of completion of copper blast. Keeping the shell-1 open helps to avoid dust to escape from the tank so that during the painting, paint surfaces will not affected by dust contamination.
17. Now complete the copper blast of un-erected shell plates at bottom level ( level -1) and apply primer paint.
18. Erection of all shell plates now to be taken up and complete within 2 days of time.
19. Primer painting shall be done on weld joint,( shell course No1 and 2) after manual cleaning
20. After copper blast and primer painting, now the tank is ready for final paint coating of VEGF (Vinyl Easter Glass Flake).
21. Apply VEGF (Vinyl Easter Glass Flake) on the internal surface of shell and release for Holiday test as required.
QA/QC Testing ( NDT testing )
Following are the testing methods for fabrication works are followed for quality controls. Areas and type to be tested.
a. All butt welds horizontal joints – 10% Radiography
b. All T- Joints- 100% radiography.
c. Annular to Shell Plate – Chalk test by High Speed Diesel.
d. All fillet Weld – Vacuum tests 100 %.
e. RF pads for Nozzle – Pneumatic test.
However other than tests mentioned above, as per standards, following additional test are also taken up for higher quality standards. All fillet Welds and Butt welds – Shall be provided with 100% DP test to find the quality of the weld.