Storage Tank Inspection API 650
Shop Fabrication Inspection
1.Material Receiving Inspection Report
- Check visual (free of lamination & damage).
- Check certificate (keaslian, Heat No & Plate No).
- Check dimensional (Length, Thickness, Width & Diameter).
2.Marking
- Check dimensional marking.
- Check transfer heat no.
3.After Cutting
- Check dimensional.
- Check traceability (Heat No & Plate No).
- Check Stamp Marking.
4.Rolling
- Check visual (free of damage).
- Check edge preparation.
- Check Rolling radius.
5.Painting
- Check material painting (batch no, self life, brand).
- Check Ambient Condition (surface & whether).
- Check DFT.
Field Erection Inspection:
1.Dimensional Inspection
a) 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).
b) Roundness:-
- Check roundness at 0°, 45°, 90°, 135°, 180°, 225°, 270°, 325°
- Radius measured at 1 foot above the bottom corner weld shall not exceed the following tolerance:
c) Plumbness:-
- Check at 0°, 45°, 90°, 135°, 180, 225°, 270°
- The plumbness of the top of shell relative to the bottom of the shell not exceed 1/200 of the total tank height.
- The out of plumbness in one shell plate (single course) shall not exceed 1/250 of the course height.
2.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 :
- The weld has no crater cracks or other surface cracks.
- 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.
- 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 :
- Defects shall be removed by mechanical means or thermal gouging processes.
- If the resulting thickness is less than minimum required as per hydrostatic test design conditions, re-welding is required.
- The repair weld shall be visually examined for defects prior to reexamined by radiography.
3.NDT
a.Oil leak test:-
media solar, method spray, temperature ambient, holding period 4 hours.
b.Vacuum box test:-
Vacuum testing shall conduct as follows:
- 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.
- 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.
- 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.
- Vacuum box tested using a test pressure at least 3 psi gauge or as specified on Company specification.
c.Radiographic Test:-
- Radiographic examination method shall be in accordance with the ASME section V,
- Article 2.
- Radiographic inspection is required for shell butt weld, annular-plate butt welds, and flush-type connection with butt welds.
- 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.
- 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.
- The radiographers shall be certified by the manufacturer meeting the requirement as outlined by ASNT Recommended Practice SNT-TC-1A and its supplement.
- 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).
- 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.
d.Penetrant test:-
- Liquid penetrant examination shall be performed in accordance to ASME Section V, Article6.
- Magnetic particle examiner shall meet the requirements on API Standard 650 par. 6.4.3.
- 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.
e.Ultrasonic test:-
- Ultrasonic examination method shall be in accordance with ASME Section V, article 5.
- Ultrasonic examiner shall be qualified in accordance with as specified on API Standard 650 par. 6.3.3.
- The acceptance criteria and repair of defects shall be per ASME Section VIII, Division 1, Appendix 12, Par. 12-3 and 12-4.