Third Party Inspection For Storage Tank: Comprehensive Surveillance & Quality Verification

The Third Party Inspection for Storage Tank article provides a sample procedure for storage tank inspection and testing in shop and site. You may review storage tank inspection and test plan with this procedure. 

This content guides about all necessary stages in the production of the storage Tanks from the examination of material, welding, fabrication, NDE, dimensional inspection to the final inspection, preservation and packing to despatch to site. This content is primarily for mill and prefabrication stages with site erection being covered in outline only.

You need to take this point in account this article is written for a typical storage Tank and might not be complete for special cases.

All storage Tank inspections and tests are carried out against the approved drawings, purchase order specifications, purchasers or company standards, and within the practices and rules of the country, state or province and any government decrees, laws, ordinance or regulation as may apply.

The applicable codes and specifications for the Storage Tank which is under construction process are:

• Design code
• Purchase order specification
• Purchaser’s standards
• Approved drawings

And the applicable codes and standards are:

• API 650
• API 620

The applicable codes and standard may be based other international standards such as BS 2654 and etc. This content is general and can be useful if even the design code is different from API Code.

Required Documents for Third Party Inspector Review:

The list of documents normally is agreed in the Pre Inspection meeting which is hold several weeks before actual commencement of inspection work. The parties which are participated in this meeting are manufacture, purchaser and third party inspection agency representatives.

These are the list of documents which are normally agreed to be presented to the inspector:

• Storage Tank Purchase Order or Contract
• Storage Tank Manufacture Quality Control Plan
• Storage Tank Inspection and test plan
• Storage Tank Data Sheet
• Storage Tank Approved Drawings
• Storage Tank Material Test Reports
• Storage Tank Welding Specification Procedures (WPS) and Procedure Qualification Records(PQR)
• Storage Tank Welding Map
• Storage Tank Welders Qualifications Reports
• Storage Tank NDE procedures i.e RT, UT, MT, PT and PMI
• Storage Tank NDE Personnel qualifications Reports
• Storage Tank Heat treatment procedure
• Calibration Certificates for Test Equipment
• Storage Tank Hydrostatic Testing Procedure and Water Quality Document
• Storage Tank Preparation and Painting Procedure
• Storage Tank Preservation, Packing and Shipping Procedure
• Storage Tank Packing List

Third Party Inspection for Storage Tank – Material Inspection

The first actual inspection work in the storage Tank is raw materials inspection.

The original or authenticated copies of mill test certificates of material normally are available at manufacturer’s premises.

The third party inspector examines these certificates for compliance with specifications and where appropriate, drawings.

The review includes checks on:

• Certificate No.
• Heat or cast No.
• Chemical composition.
• Mechanical properties.
• Heat treated condition.
• NDE applied and results.
• Surface finish

Then the inspector witnesses the materials identification on the certificates against materials marking. It is also necessary to check with storage Tank drawing datasheet, material list and other specification as appropriate.

The identification such as Heat No. needs to be transferred to cut off components.

Visual inspection for surface finish and probable defects are done and dimensional compliance with specification need also to be controlled.

When the third party inspector carried out the material inspection, then provides inspection visit report (IVR), the report contains following items:

• Confirmation of satisfactory document review
• Record of the endorsement of certification reviewed/witnessed
• Record of all non-conformities
• Record of any tests witnessed and the result

Third Party Inspection for Storage Tank- Fabrication Inspection

When the storage tank material inspection carried out and result was satisfactory or non-conformities closed by remedial action, then storage tank manufacture will be authorised to start fabrication.

The inspection scope is determined in ITP, some clients prefer to have stringent control and put the TPI inspector in more “hold points” in fabrication activities and some others may take lesser “hold points” and put TPI much more in the review document.

This depend to the inspection budget which client assign for inspection, much more inspection will have much more costs and less risks and conversely less more inspection will have less costs but more risks.

Third party Inspector is pays attention to the following points on a basis to be outlined in the purchaser’s documentation, quality plan, test and inspection plan, or other document, as notified to the inspector.

Third Party Inspection for Storage Tank- Plate Preparation

Third party inspection carries out visual and dimensional check to ensure compliance with WPS and specification. Where specified, weld bevels are examined by MT or PT after grinding/machining.

Edges and weld bevels need to be clean, dry and free from surface defects, laminations, cracks, voids, notches, etc.

These are causes for rejection unless suitable/satisfactory remedial action can be taken. Welding repairs to bevels are not permitted, without approval from the engineer/inspector. Inspectors needs report excessive or serious defects.

Plates subject to forming, rolling or dishing may require additional heat treatment and NDE to meet code requirements.

Third Party Inspection for Storage Tank- Shell Courses and Base Plates containing Welded Seams

This stage inspection is carried out when plates have been tacked using welding consumables and other parameters from an approved WPS.

Third party Inspector checks and report on:

• Cleanliness and fit up accuracy of weld preparation.
• Flatness of plates, methods of preventing distortion, e.g sequenced welding, strongbacks, backstep, etc.
• Application of preheat.
• Storage and handling of welding consumables.
• Interpass condition where welding is in progress.
• Cleaning of welds.
• Completion of test coupons, (where specified)
• NDE. Results need to meet specifications or code requirements.
• Hardness tests – when specified.
• Impact tests – when specified.

Weld repair may be permitted in accordance with the code requirements and is carried out only after investigation of the probable cause and in accordance with approved WPS documents.

All weld repairs need to be reported to the client by third party inspector.

Third Party Inspection for Storage Tank Post Weld Heat Treatment of Hot Formed Components

Third party Inspector carries out dimensional check and reviews furnace record chart to ensure heat treatment was carried out as specified.

Hardness measurement may be used to establish condition of material, heat affected zone or welds, as may be specified. Then the inspector checks dimensions, curvature, etc., after PWHT.

Third Party Inspection for Storage Tank – Assembly Inspection

Storage tanks may sometimes be assembled prior to despatch, this is witnessed and the results of any filling test recorded.

The number and thickness of the plates are checked if no trial assembly has been possible. Plates with access holes, manways and valve openings are visually and dimensionally checked.

Match marks, identification marks are checked to the drawing requirement. Name plates if attached need to be in accordance with the approved drawing.

Third Party Inspection for Storage Tank Painting and Coating

Surface preparation for painting is checked for the following points, according to specification by third party inspector:

• Cleaning method (commercial blast cleaning, near-white metal blast cleaning, etc. )
• Surface Preparation Level
• Freedom from weld spatter, blow-holes and other defects
• Dry film thickness is checked according to specification

Surface condition need to be free from pin-holes, runs damage and other discontinuity

Third Party Inspection for Storage Tank Spares and Accessories:

The third party inspector controls spares, tools and accessories and make visual and dimensional inspection for materials, workmanship and quantity according to purchase order specification and packing list.

Marking and/or Tag need to be checked for identification.

Third Party Inspection for Storage Tank- Reporting:

Third party inspector provides Inspection Visit Report (IVR) after each visit as well as a final report summarising the activities carried out during the storage tank production in accordance with the contract requirements and circulated within the time limits specified in the contract.

The report is in the format required by the client and clearly indicates final acceptance or rejection of the Storage Tank.

Third Party Inspection for Storage Tank Packing, Marking and Shipping:

The following points are checked by the third party inspector:

• Cleanliness and dryness of storage tank
• Rust prevention for all machined surfaces
• Protection for cover for all opening and protruding parts
• Spacing of plates
• Security from warping/transit damage
• Packing style and suitably for overseas transportation
• Shipping marks and other markings and notificationof welding prohibited, etc.

Third Party Inspection for Storage Tank – Fabrication Shop Documents

The following final documents are reviewed and signed off by third party inspector to the contract or purchase order requirement.

These may apply to both shop and site operations.

Component detail drawings, Manufacturer’s data reports, Material certificate or certified mill test reports, Material list or map, Welder record for each seam, Heat treatment records (Temperature-time record chart during PWHT), Dimensional record, NDE records, Hardness test record, Packing list, Spare parts and tool list.

Third Party Inspection for Storage Tank – Site Erection

The site third party inspector is responsible for all site operations up to and including final testing and certification of storage tanks.

Many operations are identical in nature to those already described for materials and fabrication inspection in the shops.

However, other factors which are likely to be more pertinent, include the necessity to closely watch for satisfactory climatic conditions and metal temperatures during welding and careful storage and handling of materials.

Site third party inspector carefully monitors Job site records of welders’ qualifications, approved weld procedures and site storage and handling of welding consumables.

The site third party inspector cross-checks all incoming plate, fabrications and material against certification. He ensures all material is clearly identified and during construction monitors transfer of markings, which is made to ensure all material of the completed tank is identifiable by such markings.

In the case of thin plates, marking need to be applied by painting or etching. All material need to be inspected prior to incorporation in the tank to ensure correct dimensions and freedom from unacceptable flaws, especially in edge preparations.

The inspector ensures that only approved procedures are used and that all welders and operators are suitably qualified. All welds are clearly identified with welder’s stamp or paint marking, as directed by the specification.

All welds need to be made to approved WPS and be inspected for conformity to finish profile.

Extent of NDE and all NDE requirements are monitored. Radiographs are reviewed and signed off by site third party inspector when they are satisfactory.

All defects requiring repair, are logged and reported and the inspector ensures that only approved weld procedures are utilised.

The inspector ensures that any required offsets or staggering of welds is correctly incorporated to code or project requirements. All fittings and fabrication are checked for conformity to tank curvature, prior to attachment. Major dimensional checks are witnessed to ensure compliance within specified tolerances of diameters, heights, circularity etc.

Third Party Inspection for Storage Tank – Site Erection Test

All pre-test procedures are monitored by third party inspector, including crack detection where required.

Hydrostatic and pneumatic tests are observed and reported, including vacuum box testing.

Third Party Inspection for Storage Tank – Site Erection Documentation

On completion of all aspects of tank construction and testing, the entire quality verification and construction documentation package are reviewed for accuracy and completeness prior to making a report of acceptance in accordance with the contract or purchase order requirement.

Third Party Inspection for Storage Tank Site Erection – Final Certification

Certification of completed tanks for compliance to code and specification requirements are prepared and countersigned by the site third party inspector prior to distribution, in accordance with project requirements.

Third Party Inspection for Storage Tank – Reporting:

Third party inspector provides Inspection Visit Report (IVR) after each visit as well as a final report summarising the activities carried out during the storage tank production in accordance with the contract requirements and circulated within the time limits specified in the contract.

The report is in the format required by the client and clearly indicates final acceptance or rejection of the storage tank.

Third Party Inspection for Storage Tank – Release Note:

When required by the contract or purchase order a release note is issued by third party inspection agency and given to the manufacturer when the Storage Tank have been finally accepted.

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