Third-Party Inspection for Storage Tanks

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

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

You need to consider that this article is written for a typical storage Tank and might not be complete for exceptional 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, or regulations 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

Required Documents for Third Party Inspector Review:

The list of documents is typically agreed upon in the Pre-Inspection meeting, held several weeks before the actual commencement of inspection work. The parties participating in this meeting are the manufacturer, purchaser, and?third-party inspection agency?representatives.?

These are the list of documents that are typically 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 types are available at the 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 the storage Tank drawing datasheet, material list, and other specifications as appropriate.

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

Visual inspection for surface finish and probable defects is done, and dimensional compliance with a specification must be controlled.

When the third-party inspector carries out the material inspection, then provides an inspection report (IR) the report contains the following items:

·?????Confirmation of satisfactory document review

·?????Record of the endorsement of certification reviewed/witnessed

·?????Record of all non-conformities

·?????Record of any tests seen and the result

Third-Party Inspection for Storage Tank- Fabrication Inspection

When the storage tank material inspection is carried out, and the result is satisfactory or non-conformities closed by remedial action, the storage tank manufacturer will be authorized to start fabrication.

The inspection scope is determined in ITP. Some clients prefer stringent control and put the TPI inspector in more "hold points" in fabrication activities. Others may take lesser "hold points" and put much more TPI in the review document.

This depends on the inspection budget that the client assigns for inspection, much more assessment will have much more costs and fewer risks, and conversely, less inspection will have less costs but more risks.

Third-party Inspector pays attention to the following points to be outlined in the purchaser's documentation, quality plan, test and inspection plan, or other documents, as notified to the inspector.

Third-Party Inspection for Storage Tank- Plate Preparation

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

Edges and weld bevels must 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 need to report severe or excessive 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 reports on:

·?????Cleanliness and fit-up accuracy of weld preparation.

·?????The flatness of plates, methods of preventing distortion, e.g., sequenced welding, strong backs, backstep, etc.

·?????Application of preheating.

·?????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 per the code requirements and is carried out only after investigation of the probable cause and per approved WPS documents.

A third-party inspector must report all weld repairs that need to be written to the client by a 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 the 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 before dispatch, this is witnessed, and the results of any filling test are recorded.

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

Match marks and identification marks are checked to the drawing requirement. Nameplates, if attached, need to be per 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 a third-party inspector:

·?????Cleaning method (commercial blast cleaning,?near-white metal blast cleaning, etc. )

·?????Surface Preparation Level

·?????Freedom from weld spatter, blowholes, and other defects

·?????Dry film thickness?is checked according to?specification

Surface condition need to be free from pinholes, runs damage, and other discontinuity

Third-Party Inspection for Storage Tank Spares and Accessories:

The third-party inspector controls spares, tools, and accessories and makes visual and dimensional inspections for materials, workmanship, and quantity according to purchase order specifications and packing list.

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

Third-Party Inspection for Storage Tank- Reporting:

A third-party inspector provides Inspection Report (IR) after each visit. A final report summarizes the activities carried out during the storage tank production per the contract requirements and circulated within the contract's specified time limits.

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

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

The third-party inspector checks the following points:

·?????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 notification of welding prohibited, etc.

Third-Party Inspection for Storage Tank - Fabrication Shop Documents

A third-party inspector reviewed the following final documents and signed off on 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 third-party site inspector is responsible for all site operations, including the final testing and certification of storage tanks.

Many operations are identical 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 third-party site inspector cross-checks all incoming plates, fabrications, and material against certification. He ensures all material is identified and, during construction, monitors the 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 needs to be applied by painting or etching. All material needs to be inspected before 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. In addition, all welds are identified with the welder's stamp or paint marking, as directed by the specification.

All welds must be made to approved WPS and inspected for conformity to the finished profile.

The extent of NDE and all NDE requirements are monitored. Radiographs are reviewed and signed off by a 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 utilized.

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

Third-Party Inspection for Storage Tank - Site Erection Test

A third-party inspector monitors all pre-test procedures, 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 before making a report of acceptance per the contract or purchase order requirement.

Third-Party Inspection for Storage Tank Site Erection - Final Certification

Per project requirements, certification of completed tanks for compliance to code and specification requirements are prepared and countersigned by the third-party site inspector before distribution.

Third-Party Inspection for Storage Tank - Reporting:

A third-party inspector provides Inspection Report (IR) after each visit and a final report summarizing the activities carried out during the storage tank production per the contract requirements and circulated within the time limits specified in the contract.

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

Third-Party Inspection for Storage Tank - Release Note:

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