REPAIR DISTORTION SHELL JOINTS

Dear Sir,
Could you send me the method of repairing the distortions in the shell and joints. How many times we can repair in a weld seam?. our client spec for peaking is 13 mm and banding is 7 mm only. we are suffering a lot . tank capacity is 20000m3.

Reply

• 

  lukman, on September 29, 2009 at 3:36 am said:

  1. Cutting weld metal using grinding machine in the buckling area vertical and horizontal weld

  2. Install Strong back according to Radius of Tank with Vertical position using Horse shoe

  3. Setting strong back to assure the plate buckling has been same with radius of tank

  4. Clean Gap of Shell Plate where Weld metal has been remove from Horizontal and Vertical weld location.

  5. Built up plate on the welding line if any length of plate has shortness because cutting of weld metal.

  6. After finish built up test weld metal with Dye Penetrant test to assure the weld is good and no crack.

  7. After all Built up finish and Gap of welding line is fine, fit up vertical joint and install stiffener / key plate in the location of buckling area

  8. After All Vertical Joint has been fit up and than weld the vertical joint, carefully from out side of Tank

  9. After finish weld from out side check the radius of buckling plate and setting again using stiffener and Key plate

  10. if Radius of Tank is “OK” continuous Back weld ( from inside tank)

  11. After finish Vertical welds and than check Peaking of Vertical welds, Measurement of Peaking must be not exceed tolerance by API 650

  12. After finis Vertical joint, conduct Horizontal joint follow same is Vertical joint procedure

  13. After all welding finish (vertical and horizontal) clean area from spatter and tack weld

  14. All Stopper and Strong back and other tools using for repair will be removed after plate cold

  15. After removed all temporary attachment to shell plate check Local deviations Peaking at Vertical weld joints and Banding at Horizontal weld joints and also roundness , refer to API 650

  16. A record or report of the Measurement and testing shall be complete and approved by Client.

Storage Tank (API 650) INSPECTION

Storage Tank (API 650)

Shop Fabrication Inspection

1        Material Receiving Inspection Report

Ø      Check visual (free of lamination & damage).

Ø      Check certificate (keaslian, Heat No & Plate No).

Ø      Check dimensional (Length, Thickness, Width & Diameter).

2        Marking

Ø      Check dimensional marking.

Ø      Check transfer heat no.

3        After Cutting

Ø      Check dimensional.

Ø      Check traceability (Heat No & Plate No).

Ø      Check Stamp Marking.

4        Rolling

Ø      Check visual (free of damage).

Ø      Check edge preparation.

Ø      Check Rolling radius.

5        Painting

Ø      Check material painting (batch no, self life, brand).

Ø      Check Ambient Condition (surface & whether).

Ø      Check DFT.

Field Erection Inspection

6        Dimensional Inspection

1        Peaking banding

Peaking measured using a horizontal sweep board 36 inch (900 mm) long. Tolerance of peaking shall not exceed ½ inch (12.7 mm).

Banding measured using a straight edge vertical sweep board 36 inch (900 mm) long. Tolerance of peaking shall not exceed ½ inch (12.7 mm).

2        Roundness

Ø      Check roundness at 0°, 45°, 90°, 135°, 180°, 225°, 270°, 325°

Ø      Radius measured at 1 foot above the bottom corner weld shall not exceed the following tolerance:

Diameter	Tolerance
< 40	±½”
40 – 150	±¾”
150 – 250	±1”
≥250	±1¼”

3        Plumbness

Ø      Check at 0°, 45°, 90°, 135°, 180, 225°, 270°

Ø      The plumbness of the top of shell relative to the bottom of the shell not exceed 1/200 of the total tank height.

Ø      The out of plumbness in one shell plate (single course) shall not exceed 1/250 of the course height.

7        Visual

      Visual examinations shall be carried out during all stages of fabrication to ensure that the completed fabrication meets COMPANY satisfaction and approval with particular attention being paid to the following:

A weld shall be acceptable by this kind of inspection if the conditions are fulfilled :

Ø      The weld has no crater cracks or other surface cracks.

Ø      The maximum acceptable undercutting is 1/64 inches of the base  metal for vertical joints, and 1/32 inches maximum for horizontal joints. For the welds that attach nozzles, manholes, clean-out opening, and permanent attachments, no undercutting exceeds 1/64 inches.

Ø      The frequency of surface porosity in the weld does not exceed one  cluster (one or more pores) in any 4 inches of length, and the diameter of each cluster does not exceed 3/32 inches.

Welds that fail to meet the criteria given in paragraph above, shall be reworked prior to hydrostatic testing as follows :

Ø      Defects shall be removed by mechanical means or thermal gouging  processes.

Ø      If the resulting thickness is less than minimum required as per hydrostatic test design conditions, re-welding is required.

Ø       The repair weld shall be visually examined for defects prior to reexamined by radiography.

8        NDT

1        Oil leak test

media solar, method spray, temperature ambient, holding period 4 hours.

2        Vacuum box test

            Vacuum testing shall conduct as follows:

Ø      Vacuum testing is conveniently performed by means of a metal testing box, 6 inches wide x 30 inches long, with a glass window in the top. The open bottom is sealed against the tank surface by a sponge-rubber gasket. Suitable connections, valves, and gauges should be provided.

Ø      Approximately 30 inches of the seam under test is brushed with a soap solution or linseed oil. The vacuum box is placed over the coated section of the seam,  and a vacuum is applied to the box. Bubbles or foam produced by air sucked through the welded seam will indicate the presence of porosity in the seam.

Ø      A vacuum can be drawn on the box by any convenient method, such as connection to a gasoline or diesel-motor intake manifold or to an air ejector or special vacuum pump.

Ø      Vacuum box tested using a test pressure at least 3 psi gauge or as specified on Company specification.

3        Radiography test

Ø      Radiographic examination method shall be in accordance with the ASME  section V, Article 2.

Ø      Radiographic inspection is required for shell butt weld, annular-plate butt welds, and flush-type connection with butt welds.

Ø      Inspection by radiographic method is not required for roof-plate or bottom-plate welds, for welds joining roof plates to top angle, the top angle to the shell plates, shell plates to bottom plates, or appurtenances to tanks.

Ø      Number and location of radiographic shall minimum as specified on API Standard 650, Section 6. Vendor shall submit proposal of number and location of radiographic to CONTRACTOR/COMPANY for review and approval.

Ø      The radiographers shall be certified by the manufacturer meeting the requirement as outlined by ASNT Recommended Practice SNT-TC-1A and its supplement.

Ø      Vendor shall submit the radiography test result to CONTRACTOR/COMPANY for review and approval. The penetrameter image as result of radiography shall clearly enough for visual examination on a radiograph viewer. The acceptance criteria of radiographs result shall be judged as specified on ASME Section VIII Div. 1, par. UW-51 (b).

Ø       Repairing defective welds shall be done by chipping or melting out the defects from one or both side of joint, as required, and proceed with re-welding. All repaired welds are subject to be re-tested as specified above.

4        Penetrant test

Ø      Liquid penetrant examination shall be performed in accordance to ASME Section V, Article 6.

Ø      Magnetic particle examiner shall meet the requirements on API Standard 650 par. 6.4.3.

Ø       The acceptance criteria and repair of defects shall be per ASME Section VIII, Division 1, Appendix 8, Par. 8-3, 8-4, and 8-5.

5        Ultrasonic test

Ø      Ultrasonic examination method shall be in accordance with ASME Section V,  article 5.

Ø      Ultrasonic examiner shall be qualified in accordance with as specified on API Standard 650 par. 6.3.3.

Ø       The acceptance criteria and repair of defects shall be per ASME Section VIII, Division 1, Appendix 12, Par. 12-3 and 12-4.

KICK OFF MEETING

Please kindly refer to attached Overall Schedule & Project Organization Chart_ Rev 1.1_20130828  for your perusal.

As per our Internal Kick Off Meeting, please kindly refer to below for the key action items of the projects for your attention & follow up:

Project General:

1.       Communication Channel, Organization Chart & Overall Schedule to be submitted to MES by end of August 2013

2.       1^st Monthly Progress Report to be submitted to MES by end of September 2013, cut-off date is 25 of the month

 SAFETY HEALTH & ENVIRONMENT

Engineering:

1.       Vender Document List (VDL) to be submitted to MES by end of August 2013

2.       General Assembly, Design Calculation, Material Specification & BQ for Purchasing of Main Plates to be ready by 16 September 2013

Procurement:

1.       PO to be issued for purchasing of Main Plates by 20 September 2013

2.       Estimate to Arrive (ETA) of Main Plates in Singapore shall be 1^st December 2013

Fabrication:

1.       Fabrication of Main Plates to be started in 1^st Week of December 2013

2.       1^st lot of Bottom, Roof & Shell Plates for TK-2961 to be ready to deliver to job site by end of December 2013 w/ Blasting & Painting

3.       Shop Assembly of Hopper (TK-2455) to be completed with NDE & Pneumatic Test by end of March 2014

Construction:

1.       Site Mobilization is on 2^nd of January 2014

2.       Commencement of construction works for TK-2961 to be on 3^rd January 2014

3.       Site Assembly of Hoppers (TK-2410) to be completed with NDE & Pneumatic Test by end of March 2014

4.       Site Construction of CRT (TK-2961) to be completed with NDE & Hydrostatic Test by end of May 2014

5.       Site Construction of CRT (TK-2261 & TK-2990) to be completed with NDE & Hydrostatic Test by end of June 2014

QA/QC

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