Al Jabber Prec Precis isio ion n Engi Engine neer erin ing g
Proc-No – SVT-001 L.L. L.L.C. C.
Rev- 0
Oct 2006
0
M.D
D.L
W.D
Issue date
Revision
Prepared By
Reviewed By
Approved By
Page 1 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
TABLE OF CONTENT
1.0
FOUNDATION
3
2.0
ERECTION
5
3.0
INSPECTION AND TESTING
13
4.0
GENERAL SITE NOTES
17
Page 2 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
1.0 FOUNDATION
PAGE
1.1.
CHECK OF FOUNDATION
4
1.2.
API CODE REQUIREMENTS
4
Page 3 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
1.1.
CHECK OF FOUNDATION
For a tank to have a shell,which is true, circular and free from buckles and flat spots,the foundation must remain level as the tank shell is being erected.For this reason the foundation shall be checked,not only at the commencement of operation,but several times during the various stages of the tank construction. Which ever type of construction is chosen,the surface immediately under the shell plates shall be laid so that the difference in level does not exceed ± 3mm in 9 meters and ± 6mm in total periphery. An indication that the tank is settling unevenly is the apperence of gaps in the circumferential seams,and the departure of the shell from the perpendicular.If these signs appear,no attempt should be made close the gap by pulling with key plates and wedges.The tank level should be checked and corrected by leveling if necessary. Before commensing erection the foundation as provided must be fully surveyed tp confirm that sode tolerance have been achieved.In addition all caedinal points,center points,cut outs in the tank foundation for sumps and clean out doors must be marked and checked for orientation and radius. If the tank design has column-supported roof,confirm that the general condition and slop of the foundation is in accordance with job requirements. Note: The above survey is limited to confirming acceptance of the base profile and orientation.It does not accommodate acceptance of the base intergrity. If the tank is designed having clean out doors insure that foundation is recessed to receive the bottom reinforcing plate thickness. 1.2. API CODE REQUIREMENTS 1.2.1. Control Perpendicular To Shell Maximun deflection related to theoretical middle level Concrete ring foundation On total periphery : On 10m Zone :
± 6mm ± 3mm
Normal Asphalt foundation On total periphery : On 3m Zone :
± 12mm ± 3mm
1.2.2. Control Of The Rest Of The Foundation In relation to theoretical middle profile ( with or without slope ) ± 50mm
Page 4 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
2.0
ERECTION
PAGE
2.1.
BOTTOM PLATES
6
2.2.
SHELL PLATES
7
2.3.
POSITION OF ON SITE OPENINGS
9
2.4.
STAIRS,INTERMIDATE PLATFORMS AND HAND RAILS
10
2.5.
SHELL STIFFENNERS AND SECONDARY WIND GIRDERS
10
2.6.
SHELL CURB ANGLE
11
2.7.
CONE ROOFS
11
Page 5 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
2.1. BOTTOM PLATES 2.1.1. Annular Plates Lay annular plates at the correct orientation and setting out radius ( + 12mm ) and recheck on flaring butts prior to welding to ensure they comply with required gap. Butt straps should be placed under the annular butts prior to flaring.The butt straps should not be tack welded to the underside of annular plates. Fit strong back channels at butt joints and pin them securely to maintain the required gap. Tack weld annular plates to butt straps.
To prevent downward peaking of the butt during welding,the joint should be raised approximately 50mm off the foundation.This will also afford access to radiographic testing. Fully weld all butt joints. Radiograph welded joints.Note: No. of welded joints to be examined to be determined as per submitted inspection and test plan and/or code requirements. 2.1.2. Bottom Plates From the cardinal points and using a chalk line mark off the centerlines. Mark the centerlines using a chalk line on the center plate.Place the plate in position insuring that centerlines of plate and foundation are matching. Continue laying the strake longitudinal across the tank diameter. Note: Always mark the plate short center line at this stage,and ensure that the lines are matching together. Progressively lay subsequent runs of plates and always ckeck that minimum weld lap is maintained till reaching the other end. During plates laying ensure that short transverse seams are tacked always. Longitudinal seams may be tacked sufficiently to prevent movements of plates during errection. Flaring of bottom joints before tack welding bottom plates together to be performed by using site erection equipment. At plate junctions and joggles bend top plate to suit. 2.1.3. Welding Of Bottom Plates Commencing at center start welding short transverse seams working towards the tank perimeter completing single or multi pass welds at this stage. Once sufficient transverse seams have been welded the temporary tacks in the long seams may be broken,and longitudinal seams may be tack welded again starting at the tank center and working towards the perimeter in a sequence in which alternate seams will be welded ( Welding should be from center outwards ).After reaching perimeter the remaining welding seams may be flaired,tack welded and then welded.This sequence is performed tominimize distortion. Page 6 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
At plate junctions and joggles insure that the fillet size is increased to take account of increased thickness. Note: Do not weld bottom plates to annular plates at this stage. 2.1.4. Tanks Without Annular Plates. Follow the same procedure for bottom plates ( 2.1.2 ). Joggle all sketch plates until top of plates is level in order to receive shall plates. Follow same welding sequence as ( 2.1.3 ). 2.2.
SHELL PLATES. Note: The following is dependent on the number of tiers called for the tank design.
2.2.1. Setting Of Bottom Course. Using a chalk line draw off from the center point the setting out circumference of the first tier on the bottom plate. Note: To determine the setting out radius use the following formular s/o radius = radius + shell gap X no.of butts Π Punch the drawn line on bottom plates by using center punch so it remains permanent through out errection. Distrubute sufficient erection nuts around established circumference line both inside and outside with allowance for 1st tier plate thickness. Weld erection nuts in position. Erect the 1st tier plates in position at there given orientation in working drawings. Weld sufficient working nuts to the inner side of each shell plate at both vertical ends maintaining suitable distance from the welding edge. Align the shell plates to each other with shim plates and wedges.The shim plates thickness should match the given welding gap in working drawings. Secure the 1st tier shell plates to the bottom plates by means of the erection nuts and key pin and the shell plates to each other by means of key plates all wedged to previousely welded erection nuts. Position sufficient temperory supports between the 1st tier plates and bottom plates to maintain its verticality during erection and weld them in place. Page 7 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
Note: This tier must be properly aligned, plumbed and leveled at its top edge prior to further shell plate erection to insure tank shape. Do not tack weld 1 st tier shell plates to the bottom plates at this stage. 2.2.2. Erection Of Remaining Tiers. Erect the 2nd tier shell plates connected together as mentioned above for 1st tier,also by aligning the horizontal seam between two tiers by means of appropriate size shim plate corresponding to welding gap given in working drawings. Stage the vertical joints by the distance given in working drawings,normally one third of the plate. During erection,suffecient vertical joint aligners and horizontal joint channel aligners must be placed in position and the seams wedged outwards as necessary to counteract inwards peaking caused by initial manual welding of the outside. Check the alignment between the 1st tier and 2nd tier by means of using a plumb from top of 2 nd tier to bottom of 1st tier. Commence tack welding of the 1st tier followed by 2nd tier vertical seams.
After the completion of vertical seam welding,commence tacking the horizontal seam between 1st and 2nd tiers.Upon completion commence welding the seam. Commence tack welding the 1st tier shell plates to the bottom plates after the completion of horizontal seam welding between 1st and 2nd tier,ensuring that the shell plate radius confirms to code requirements. Note: During fairing the 1 st tier plates to the bottom plates use the tolerances mentioned to maintain and correct the measured verticality between 1 st and 2nd tiers. Commence welding the 1st tier to the bottom plates (Corner Weld ) on the outside,then to the inside. (Note: Diesel test to be performed prior to welding the inside. After completion of the corner weld,commence welding the bottom plates to the annular plates.( Note: this is to be performed if the tank is designed with annular plates). Erect the 3rd tier shell plates connected together to the 2nd tier as mentioned above for the 2nd tier. Commence flaring,tack welding and then welding the 3rd tier vertical seam. After the completion of the vertical seam welding,commence flaring,tack welding and then welding the horizontal seam between the 2nd and 3rd tiers. Repeat the same steps of 3rd tier for the erection of the remaining tiers. Page 8 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
General Notes: Upon the erection of any tier and before tack welding check for verticality by means of plumb between top of tier and bottom of 1st tier. Holes in platework to assist in erection are not permitted. Lugs,nuts and other devices to assist in erection may be tack welded to the tank plates,but all such attachments required only for the purpose of erection shall be ultimately removed and any noticeable projection of weld metal remaining shall be carefully ground or chipped away.Plates shall not be gouged or torn in the process of removing attachments,and any indentations caused thereby shall be filled with weld metal and ground flush with the plates surface,but this practice should be avoided as much as possible. Tack welds of vertical seam of tier plates must follow closely behind their erection and flaring. Tack welds used in vertical and horizontal joints between shell plates and in the horizontal joint between the 1st tier and the bottom plates shall be ground away and shall not remain in the finished weld. Special precautions must be taken while welding “T” joints to minimize repairs.To this end its essential to check fit up at tee joints. In case of welding the horizontal joint by means of automatic welding machine,tee joints mat be gouged or ground away and rewelded manually at the top of the vertical seams and short distance either sides on the horizontal seams. 2.2.3. Staging
2.3.
Each tier must be staged inside or outside to give sufficient access during erection and welding.The location of staging is dependant on the shell plate edge preparation.If the edge preparation is prepared to the outer tank side then staging should be done inside the tank or the other way round. Only in exceptional circumstances will sufficient staging be supplied to cover the entire tank.Successive movements for erection and or dismantling of staging will therefore be normal. For welding of vertical seams welders covered bogies suspended from and run around the top of the tier being welded are to be provided. Where automatic machine welding of horizontal seams is adopted no staging is required on the outside but access to the outside of the vertical is provided by using welders covered bogies. POSITIONING OF ON SITE OPENINGS. Note: Always ensure that the latest orientation drawings are to used for location of fittings. For circular type reinforcing plate,tell tale hole to be located on the horizontal centerline. Bottom tier outlets should be made after completion of the welding of the first circumferential joint. The positioning of the openings must be determined based on the reference point 0° , 90° , 180° and 270°.After marking off the openings and prior to cutting final inspection for the orientation and elevation should be witnessed by client/Consultant/Third Party Inspection.
Page 9 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
Adequate stiffening should be fitted on the inside of the shell associated with fittings particularly on thin shell plates and with large fittings prior to welding i.e.vertical and horizontal bearings. On installation and flairing of fittings,but prior to welding a check witnessed by client/Consultant/Third Party Inspection shall be applied to insure fittings are installed radial or tangential as defined by working drawings. 2.4.
STAIRS,INTERMEDIATE PLATFORMS AND HAND RAILS
2.4.1. Spiral Stairs. Where spiral stairs are supplied,it is essential in addition to establish the start and finish point as per the latest orientation drawings,that the location of the stair treads are marked on the tank shell such that any problems of location can be identified prior to the erection of stair treads. Note: For marking treads location,start at the top platform and progress downwards. Erection for stairs should commence at the tank base and progress upwards. On completion of the stair construction all welding should be visually examined and handrail butts ground to a smooth profile. 2.4.2. Ladders Where ladders are supplied ( with or without cage ) it is essential to establish the position of the ladder as per the latest orientation drawing. Mark and fit the ladder brackets at there correct location. Weld the brackets and visually inspect the welds after completion. 2.4.3. Hand Rails.
After the completion of roof erection mark the p osition of the roof handrail location starting at the top platform. Erect the handrail post as per working drawing details by means of tack welding. Erect the top,mid amd guard rails as per working drawing details. After completion and flaring of rails commence welding. On completion of the roof rail construction all welding should be visually examined and handrail butts ground to a smooth profile. 2.5.
SHELL STIFFENERS AND SECONDARY WIND GIRDERS. Shell stiffeners and secondary wind girders shall be erected after the erection of the requisite tier or alternatively tacked to shell plate prior to erection of the tier. It is important to check the elevation of stiffeners and secondary wind girders are in accordance with working drawings. 10 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
It is important that the shape and alignment of butts are checked prior to welding to ensure that deformation will not be locked onto tank shape.All welding must be completed and visually inspected prior to water test. 2.6.
SHELL CURB ANGLE. Curb angles may either be tack welded to the respective tier plates prior to or after erection of the tier.In either case butt displacement and curd height must be checked against the working drawings,but before welding of the curb angle commences.However it is essential that the section of tier joint covered by curb angle approx.450 mm are welded prior to the curb angle being fully to the shell. Visual inspection shall be applied to curb angle butts after flaring to ensure alignment and preparation is acceptable.Any local flat spots at the curb angle should be removed before welding.These butt joints should be welded before welding the circumferential welds to the tier plates. Note: Curb angle butt welds should be visually re-examined after hydro test to ensure that no defects have developed.
2.7. 2.7.1
CONE ROOFS. Column Supported Roofs. From the cardinal point mark the radial line for the start position of the columns and mark the individual column based on the tank bottom. The roof columns should be prefabricated at a suitable convenient time and location in order not to inflect delays in construction program.The columns should visually inspected at fabrication point to ensure that the sever bowing has not taken place and rectification action to be taken prior to erection. Columns base should positioned at the predefined locations on the tank bottom.Columns may be erected prior to completion of shell erection if this is to be of advantage to program completion. In such case the column will be required to be erected from the tank center out and in fill structure progressively erected to assist in stabilizing the structure.Area associated with base support for columns must be visually and vacuum box tested prior to commencement of roof structure.The maximum out of plumbness for columns shall not exceed 1/200 of column height.
In case of wind loading and to assist in safe erection of column guy wires must be used with suitable displacement.Distortion of tank bottom can occur due to guying but may be limited by ensuring that guy wires are tied back to key plates or anchors positioned close to base of columns in the adjacement rings such that the weight of columns can assist counteracton of displacement due to guying. Progressive construction of roof structure in fill will afford release of the major numbers of guy wires to be used. All bolted connection should be tightened as work progress.Once shell plate welding of vertical seams of the last tier has been completed and shell support cleats have been erected and welded at their correct orientation then the outer ring of girders can be installed,in which case all temporary guy wires can be removed. Page 11 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
When the column erection is actioned sfter the completion of shell plate construction,it is recommended that the column be erected from the shell,progressively in filling the associated structure. On completion of structure erection the columns should be welded to their respective bottom anchors. II)
Roof Plate Erection. Once the curb angle welding has been completed,roof plates may be laid similarly to the laying of the botton plates,i.e.commence at the center stack.Alternatively plating may commence from the tank shell moving progressively up the roof opposite sides. In either case it is important to ensure that plates lap,orientation and layout are in accordance with working drawings. Welding of roof seams should be treated in accordance with sequence of bottom seams lap type welding.
III)
Roof fitting Erection. Note: Always ensure that the latest orientation drawings are used for location of fittings. Roof fittings should be installed after bulk of roof lap welding has been completed. The positioning of the openings must be determined based on the reference point O°,90°,180° and 270°.After marking the openings and prior to cutting,final inspection for orientation and radius should be witnessed by client/Consultant/Third Party Inspection.
2.7.2.
Rafter Supported Roofs. I)
Rafter Support Erection. Prior to the erection of the roof structure,all welding of shell plates including curb angles should be completed. From a cardinal point,mark on the upper inner side of last tier shell plates ( around the circumference ) the position of the rafter support cleats at the correct orientation. Erect and weld the rafter support caleats on the pre located marking.
On ground level commence the assembly and welding of the roof structure if bolted connection is provided install all bolts and tighten,then lift the whole structure into position to line up with the preinstalled shell/rafter cleats.
II) III)
Tighten all bolted connection between the rafter structure and the supporting cleats. Roof Plate Erection. Follow the same procedure for the column supported roof. ( 2.7.1 II ). Roof Fitting Erection. Follow the same procedure for column supported roof. ( 2.7.1 III ). Page 12-17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
3.0
INSPECTION AND TESTING.
3.1.
INSPECTION
14
3.2.
TESTING
15
PAGE
Page 13 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
3.1.
INSPECTION.
3.1.1. Weld Inspection I) Inspection for quality of welds shall be made by the radiographic method. The quantity of radiographic shots to be determined as specified in the approved Code requirements. Complete joint penetration and complete fusion is required for welds joining shell plates together. Where visual inspection by the client/Consultant/Third Party inspector indicates unsatisfactory welds between shell plates,acceptance or rejection shall be based on inspection of radiography.
II)
Fillet Welds. Inspection for quality of welds shall be made by Magnetic Particle Inspection. (MPI/DPT). The quantity of ( MPI/DPT ) to be determined as specified in the approved Code Requirements. Where visual inspection by the Client/Consultant/Third Party inspector indicates unsatisfactory acceptance or rejection shall be based on inspection of ( MPI/DPT ).
3.1.2. Dimensional Tolerances. Note. The purpose of the following tolerance is to produce a tank of acceptable appearance and to permit proper function of floating roofs if the tank is designed so.These tolerances may be waived by agreement with the client/consultant representative.All tolerances to confirm to API 650 latest edition. A. Plumbness:The maximum out of plumbness on top of the shell relative to the bottom of the shell shall not exceed 1/200 of the total height. The Plumbness measured between top and bottom of 1st tier and top of any subsequent tier and bottom of 1st tier to confirm to the above. Note. Verticality to be measured at one point per plate preferably at plate center. B. Roundness: Radius measured at 1 foot above the bottom corner weld shall not exceed the following tolerances.
Page 14 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
Tank Diameter (Meters )
Radius Tolerance ( mm )
◄ 12 From 12 to ◄ 45 From 45 to ◄ 76 ≥ 76
± 13 ± 19 ± 25 ± 32
C. Peaking: Peaking at vertical welded joints shall not exceed 13 mm.Peaking at vertical weld joints shall be determined by using a curved straight edge 900 mm long. D. Banding : Banding at horizontal welded joints shall not exceed 13 mm.Banding at horizontal weld joints shall be determined by using a vertical straight edge 900 mm long. 3.1.2. Inspection General Notes. Welding joints shall be checked for fit up and stiffenings prior to commencement of welding.Visual inspection shall be performed at all stages of construction.Back gouges shall be also inspected to ensure sufficient weld metal has been removed to accommodate quality welding. Prior to radiography the welds shall be inspected visually to confirm surface profile and scars removal is acceptable. If any repairs are to take place in welded joints,this should be actioned immediately and the types of defects investigated to establish cause and remedy. Its essential that all radiography and any inspections keeps pace with welding thus ensuring that trouble is detected and resolved as quickly as possible and eliminating welding work going out of control. All welds must be clearly marked with weld numbers and welders initials. 3.2. TESTING 3.2.1. Bottom Plate Testing. After welding of the bottom plate has been completed ,all welds must be tested to ensure that the tank bottom is free of leaks.This can be achieved by using a vacuum box,which enables any leaks in the seams to be positively located by visual inspection. The test must be made prior to surface coating is applied and hydro testing. Prior commencement of testing all welded seams shall be clean and free from slag. For detection of leaks,soapsuds shall be applied to all bottom plates seams. Diesel testing to be performed on the weld between bottom and shell plate ( corner weld ).After the completion of the outer side of corner weld,diesel is to be sprayed from the inner side and checked the following day for leaks.
Page 15 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
3.2.2. Roof Plate Testing. Note: This is to be performed only in the case of GASTIGHT tank roof design. For roof plate testing follow the same procedure for the tank bottom testing ( Vacuum Box ). Tanks with peripheral circulation vents or free open vents,shall receive only visual inspection on its welded joints.In case of any suspected welds agreed further methods of inspection shall be taken on suspected areas. 3.2.3. Reinforcing Plate Testing. Visual inspection to be performed upon completion of welding and cleaning of reinforcing plate. Pneumatic testing to be performed and leaks to be detected by means of soap suds.(Note: this is not performed on roof reinforcing plate). 3.2.4. Water Testing. After the entire tank is completed and as a final action prior to the introduction of water,the complete tank bottom i.e.seams and plates should be visually inspected to ensure that no damage or defects have occurred since the vacuum test was applied. Note: Visual examination of shell to bottom welding should be done in conjunction with bottom examination. Particular attention should be applied to. 1. Bases associated with support column. 2. Areas associated with pads on attachment. 3. Areas associated with bottom sumps. 4. Joggles. Water testing should be performed prior to connection of permanent external piping to the tank. Prior to the introduction of water, the area of shell to bottom externally must be swept clean of any debris and where possible,surface water should be removed.The presence of any casual water should be reported immediately to client and site management,such that any measures deemed necessary can be taken to remove this water.Special emphasis must be placed on areas associated with cellar sumps.The flooding of areas of this type can deem the test as unacceptable. Water testing to be performed as specified in the approved code requirements.
Page 16 of 17
Al Jabber
Proc-No – SVT-001
Precision Engineering l.L.C.
Rev - 0
4.0.
GENERAL NOTES. 1.
Welding consumables shall be delivered to site in sealed containers and checked on receipt to establish that.
Containers are sound. Containers are identified as per mill test certificate. 2.
3. 4. 5. 6. 7. 8. 9.
10.
Site team must advise project management as to any discrepancy or damage such that steps can be taken to make up the possible short full of supply.Welding electrodes,which require baking,shall be treated as per manufacturere recommendation prior to issue. Damaged or unidentified welding consumables shall not be used irrespective of types. Rebaking shall be in accordance with manufacturer recommendation.Surplus electrodes other than low hydrogen types shall be returned at the completion of each shift to storage area. Welding consumables should be generally drawn in reasonable quantities from bulk order. Issued electrodes to welders must be stored in welders quivers while welding work is going on. Storage facilities must be kept tidy and clean. In the case of wind loading it is recommended that the tank shell plates to be secured to ground level by means of guy wires.The number of guy wires to be used is dependent on the tank size. If the measured tank plumbness is not as per code requirements during any stage of erection work suitable measures to rectify the defects must be taken.i.e.locating defective area and pulling it either in or out by means of guy wires secured to the ground of the tank bottom and site erection tools. Site team to afford reasonable access for the x-ray team.They are part of the overall set up and are the only means of determining the welding quality.
Page 17 of 17
