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 t resulting g thickness is less than n minimum required as per hydrosstatic test de esign co onditions, re e-welding iss required. Ø Th he repair weld w shall be visually examined for defectts prior to reexamined by
ra adiography.
8 NDT 1 Oil leak test m media solar,, method sp pray, tempe erature amb bient, holdin ng period 4 hours. 2 Vaccuum box test t Vacuum testing sha all conduct as a follows: Ø Vacuum testing t is co onveniently performed by meanss of a meta al testing bo ox, 6 inches wide x 30 incches long, with w a glass window in the t top. The e open botto om is a the e tank su urface by a sponge e-rubber gasket. Suitable sealed against connectio ons, valves, and gauge es should be e provided. Ø Approxima ately 30 inch hes of the seam s under test is brusshed with a soap solutio on or linseed oil. o The vacu uum box is placed p overr the coated section of the t seam, and a a vacuum is i applied to o the box. Bubbles B or foam produ uced by air sucked through the welde ed seam willl indicate th he presence e of porosityy in the seam m. Ø A vacuum m can be drawn on the box by b any con nvenient method, such as connectio on to a gassoline or die esel-motor intake manifold or to an a air ejecttor or special va acuum pum mp. Ø Vacuum box b tested using u a test pressure at a least 3 pssi gauge or as specifie ed on Company y 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
API 650 Tank Joint Welding & Inspection for Field Erected ASTs Butt welded steel tanks have been a main stay in the field of constructing above ground storage tanks for decades. Around 1936, welded steel tanks overtook riveted tanks as the preferred method in new above ground storage tank construction. In step with this change, API standards were published to guide construction of such tanks for adequate safety and reasonable economy. Now in its twelfth edition, API 650 is the current standard to which welded steel tanks are built. This standard covers the minimum requirements for materials, design, fabrication, erection, welding, and inspection for constructing a new above ground storage tank.
Following this trend in constructing new welded storage tanks, between 1960 and 1990 many of the old riveted tanks were being cut down and reconstructed as welded tanks. The economics of this process became less attractive after the catastrophic tank failure of a reconstructed tank in 1986. In January of 1991, the API 653 Standard was published and addressed the criteria by which welded or riveted tanks should be dismantled and reconstructed. This Standard also addresses the need for tank inspections, repairs, or alterations on existing tanks. In building welded steel above ground storage tanks, different welding processes can be used. Shield Metal Arc Welding (SMAW) or better known as stick (arc) welding was the leading welding process and still very common today for construction of above ground storage tanks. The SMAW process is versatile and very well suited to the environment of field erected work.
Submerged Arc Welding (SAW) became popular in the tank industry in the early 1980s. This process was used on lap welded bottoms and roofs and butt welded shell joints. The first use of this process took many years of education to develop a method of welding that would be clean of porosity under the surface of the weld. Many tank builders abandoned this method of welding on bottoms due to the inability to control moisture from the bottom side of the lap plates. However, the use of preheat in the winter time has made this a very successful way of the welding the girth (round) seams connecting one shell course to the next. This method of welding, known as Three O’Clock welding (3-O’Clock), delivers good clean and smooth penetration and provides a more uniform weld. The submerged arc weld blends and merges well with the two plates being joined and also provides X-ray quality welds. API 650 section 9 requires all welding on above ground storage tanks to be done in accordance with the manufactures Weld Procedure Specifications (WPS) and the supporting Procedure Qualification Record (PQR). Welding operators are tested and certified in accordance with the tank builders welding procedures. Welds on newly constructed above ground storage tanks are subjected to various types of inspection. Radiographic (x-ray) testing is performed to prove that the welding operators are in compliance with the welding procedure. The radiographic method is used on the shell butt weld joints, annular plate butt joints, and flush type connections with butt joints. This method is not used on the bottom and roof lap joints, top angle joints, man-way necks, shell to bottom joints, structural joints, and appurtenances. Welds examined by radiography are judged as acceptable or unacceptable by the standards of ASME section VIII. Section 8 of API 650 provides criteria for determining the number of shots to be taken for each welding operator based upon the thickness, number of shell courses, number of T joints, and the linear feet of vertical and horizontal welds completed. The storage tank owner/operator has the right to select the locations of the x-rays based on the Section 8.1.2 criteria. All tank shell welds should also be cleaned and visually checked from both sides of the joint making sure weld joints are free of defects such as craters, pinholes, undercut, and under fill. Excessive weld reinforcement or overlay should be ground smooth along with the removal of all arc strikes, weld spatter, fit up, and scaffold strap burrs to include replacing any parent metal that might have been lost in the process of removing the bracket straps, nuts, and fit up equipment. Vacuum box testing is the most common way of testing the tank floor weld seams for leaks. Care should be taken in ensuring all floor welds are visually checked to be complete and free of any slag, weld burrs, and other defects such as pinholes, undercut, and under fill before the vacuum testing is performed.
The shell to floor/bottom joint is visually inspected in the same manner. When one side of the welded joint is complete, the most common weld test is to apply a high flash point penetrating fluid such as diesel fuel to the opposite side. The welded side is then checked for any visible signs of wicking. If any repairs are required, the penetrating fluid test is performed again before the other side is welded. Appurtenances, including inlet and outlet nozzles, should also have a good visual check making sure welds are free of defects. Air pressure is then applied through a quarter-inch pipe threaded tell-tale hole in the re-pad. Soap suds are then brushed or sprayed onto all sides of the re-pad and both sides of the penetration where the weld attaches the pipe nozzle to the shell. The welds are visually checked for small air bubbles penetrating the soap solution. Once the welds on a new above ground storage tank pass all of these weld inspection processes, the tank is ready for service. If repairs are needed on a tank during its lifetime, similar weld inspection methods are used for the particular type of weld repair performed.
Dome Roof with Internal Floating Roof October 23, 2009 by ferrysibarani Pictures below are sequential procedure of tank erection in one of my project. This project titled Installation and Erection of Knock Down Tank in Brunei Methanol Project, Negara Brunei Darussalam. Project owner is Brunei Methanol Company Sdn. Bhd., with Mitsubishi Heavy Industries Ltd. as Main Contractor and PT. Rekayasa Industri is the Sub-Contractor. Consortium of PT. Bangun Bejana Baja and Adinin Works and Engineering is the manufacturer of 15 units Knock Down in this project. One of the biggest tank that built in the project is Product Methanol Tank with type Dome Roof with Internal Floating Roof, shell size 63 metres inside diameter and 18 metres height, dome roof radius is 50.4 metres, and internal floating roof diameter is 62.6 metres. Tank construction was done from September 2008 to October 2009.
Bottom plate consist of annular, rectangular, and sketches plate. The annular plate is the outer plate which on top of it the shell plate will be installed. Butt joint type welding connection used for annular to annular plate, and shall be 50% radiographic test. Rectangular and sketches plate was welded using fillet weld and all joint shall be 100% vacuum box tested.
Fit-up of bottom plate usually using temporary welding to plate using nut and u-bar, then bullpen used to make the overlap plate flat to each other.
After plate fit-up finished, the work continue with fillet welding. Welder classification for this welding is welder 1G.
The first installation of shell plate. Rigging using 2 automatic clamps (vertical clamp) with spreader bar.
Nozzle connection installation to shell plate. After welding completed, the welding shall be Post Weld Heat Treatment (PWHT).
Finished installation shell course #1 and #2 completed with vertical weld butt-joint.
Horizontal weld between shell course #1 and #2 and so on will be done by Automatic Girth Welding (AGW) Machine.
Dome roof ground assembly. Install the rafter and continue with roof plate welding. There are 24 block of roof will be assembly, 12 of them will be ground assembly and block in between section will install inside tank.
Some part of shell plate #1 and #2 was removed as entry access for crane and material, it is call door sheet.
Centre column support installation. This part will support the centre rafter of the dome roof which is the part that all roof block will be connected into.
Finish assembly of centre support and installation centre rafter on the top.
First installation of dome roof block. Roof block lifted by 300 Ton Crane.
Adjusted lower part of the roof block into the outer support.
Adjusted upper part of the roof block into the centre rafter.
Finished installation of the first 4 numbers of roof block (beautiful, isn’t it). It is important to keep the balance between installations section by section.
Overtime work for catch-up schedule, but only welding work without any rigging or fit-up.
In between roof block assembly. Manlift basket used to install and weld rafter. Rafters erected by crane from outside tank.
Roof plate installation in between roof block. The first 3 section roof plate were install from inside tank before finished rafter in between block. The 4th and 5th roof plate installed from outside tank.
Last shell course (#8) installation with tension bar. Last shell course and tension bars were assembled on workshop to decrease welding work on height.
Installation of roof plate in between block was remaining in the door sheet area. This part welded the last due to entry access for crane only available through door sheet.
Finished dome roof assembly viewed from inside tank. Dome roof now ready to be lifted up to the tension bar by air raising method. The roof will float due to air pressure inside tank increased by blower through shell nozzle.
This picture showing the completion of air raising process of dome roof, and dome roof completely fixed to the tension bar.
Single deck internal floating roof assembly on process. This floating roof consists of general part and pontoon compartment. Floating roof supported by permanent pipe support with height approximately 2 metres. During construction the floating roof temporary supported then will be raised up by water to the correct elevation.
Pontoon compartments work as the buoy of the floating roof. These compartments shall be fully tested by oil leak test to ensure 100% leak proof.
Floating roof assembly finished and ready to be raised up. Next preparation will be closing all the shell manhole and nozzles and fill up the tank with water.
Water raising finished and the floating roof already setup on the permanent pipe support, locked with stud bolt.
Accessories of tank such as roof periphery platform, spiral and roof stairway, piping for fire fighting, etc. continue assembled prior to hydrostatic test.
Hydrostatic test was to fill the tank with water to the design pressure to ensure there is no leaking in the tank as well as to check the stability of the tank foundation. After all inspection finished, the water inside tank discharged.
Touch-up primer coat for welding area to be finished prior to applying final coat.
The tank installation finished. Awesome, isn’t it? Well, that’s it! I hope all of the reader enjoyed to read it
