How to Choose Tank Thickness Testing for U.S. Plant Owners

Choose a shell survey whose written scope commits to defined coverage, identifiable measurement positions, documented omissions and reusable records. Treat “thickness readings” and “corrosion mapping” as capability descriptions—not coverage specifications.

For a U.S. aboveground steel tank, frame the purchase around one question: will the delivered records let your engineer locate the measurements and assess whether they can be compared with the next survey? Use the checks below to define the work before accepting a quote.

Define coverage before choosing the technique

Acuren, for example, advertises manual thickness readings and manual or automated corrosion mapping for tank applications.[1] Its cited UT page does not specify a grid, point count, coverage percentage, location-selection rule or service area, so it establishes neither a defined survey scope nor availability at your U.S. site.[1]

Choose the coverage commitment, not the technique’s name. For selected readings, ask which locations will be measured and why. For mapping, request the defined areas and scan extent. Have your engineer assess the proposed coverage against the survey’s purpose rather than assuming either approach is preferable.

Put these details into the shell-survey scope:

• Boundaries: Identify the shell areas included and the proposed grid or scan boundaries.
• Location identification: Define the numbering convention connecting measurement positions to the delivered records.
• Extent and selection: State the planned point count or scan extent and the rule for choosing locations.
• Additions and exceptions: Explain how additional readings will be selected, identified and recorded, and how omitted areas will be listed.

Keep roof, floor, weld and engineering work separately identified so they do not blur the shell wall-loss scope. Agree numerical coverage with your engineer and bidder rather than treating an advertised mapping capability as a prescribed grid density.

A concise scope prompt is: “Survey these identified shell areas using the attached location plan; list planned coverage, additions and exceptions.”

Resolve coatings, access and unmeasured areas

Make coating condition and access responsibilities part of the scope before mobilization. Ask whether the proposed approach accommodates the existing coating, what preparation or removal is anticipated, who authorizes that work, and who restores affected surfaces.

Acuren describes UT as requiring access from one side.[1] Treat that as a test-access statement, not a commitment to reach and prepare every proposed shell location.

MISTRAS advertises crawlers that take ultrasonic wall-thickness measurements, rope access and surface-preparation services.[2] Ask Acuren and MISTRAS to specify a coating-treatment procedure for the proposed survey.[1][2] Confirm service at the tank’s U.S. location and identify which preparation and access services the quote includes.

Assign responsibilities explicitly:

• Access: Identify who supplies the agreed access equipment and coordinates work around operational restrictions.
• Preparation: Assign insulation removal and replacement, surface preparation, coating-removal authorization and restoration.
• Permissions: Identify who arranges applicable permits and operating approvals.
• Exceptions: Request a planned exclusions list and an as-surveyed register identifying each unmeasured location, the reason, the proposed alternative and any resulting scope change.

Ask: “If a planned location cannot be measured, how will you document the gap, propose an alternative, and explain the effect on coverage and price?”

Keep unmeasured locations visibly identified as unmeasured. Require a documented explanation and agreed scope change before accepting substitute locations or reduced coverage.

Specify a reusable map and traceable minima

Request a map linking each reported minimum thickness to an identifiable shell location and its supporting measurement record—not merely a highlighted low value.

Put the following deliverables into the scope as buyer requirements:

• Tank identity: A consistent tank identifier across the map, reading register and report.
• Location framework: A defined orientation reference, shell-course identification and location IDs, with dimensions or coordinates to locate each measurement position.
• Reading register: Each location ID linked to its measured thickness, stated units and supporting measurement-record reference.
• Minimum-reading links: Each reported minimum tied to its location ID and the defined surveyed area to which it applies.
• Coverage status: Separate markings for planned locations, completed measurements and unmeasured areas, preserving the difference between intended and achieved coverage.

Ask: “Does ‘minimum thickness’ mean the lowest measured value within this identified surveyed area, rather than the minimum for the entire tank?” Request report wording consistent with the answer.

As an example of advertised reporting, MISTRAS describes TankReporter as storing tank and inspection information and visually representing potential damage areas.[2] Ask MISTRAS or Acuren to commit to minimum-thickness coordinates, a complete reading table and a reusable location map with traceable minimum-reading positions.[1][2]

Request a sample deliverable showing how a minimum on the map connects to its register entry. Make that structure part of the agreed deliverables rather than relying on the reporting software’s name.

Request instrument records and usable files

Specify supporting records separately from the finished report. Ask which individual readings, native instrument files, exports and setup or calibration records you will receive. Ask Acuren or MISTRAS to confirm instrument serial numbers, calibration records, raw-data deliverables, file formats and retention periods in writing.[1][2]

Have your engineer approve the record request for the proposed survey, covering:

• Instrument identification: Manufacturer, model and serial number.
• Probe identification: Probe details and identifiers associated with the readings.
• Setup and calibration: Recorded settings, calibration references and supporting records.
• Measurement context: Relevant surface-condition or coating notes, survey date and operator identification.
• Data linkage: A connection between each delivered reading or file and the location IDs in the report.

For file delivery, ask: “Which exports can we read without proprietary software, which native files accompany them, and how are both linked to the location register?” Request a sample export and an explanation of its fields. Have your engineer confirm the proposed files contain the information needed for later review.

Agree a retention period, what the contractor will retain and how you can retrieve it. Assign responsibility within your organization for preserving the buyer’s copy, including native files and their location-ID links.

Check whether the locations can be revisited

Before award, have your engineer review the proposed map, register, exclusions and records package together. Ask the bidder: could a later inspector recover the same reference origin, orientation and measurement positions using the delivered records?

Make that review concrete by agreeing on:

• Location references: Which suitable datum references, grid identifiers and dimensions will locate each measurement position?
• Supporting identification: Which photographs, sketches or location marks will connect the register to recognizable tank features?
• Exceptions: How will the records distinguish measured positions from planned positions that could not be measured?
• Changes between surveys: How will changed coatings, repairs, revised location IDs or a different measurement setup be recorded and linked to the earlier survey?

Leave the choice and implementation of references to technical agreement; specify the identification outcome rather than how marks are installed. Ask Acuren or MISTRAS to define any permanent datum points, repeatable location marks, repeat-reading tolerance and procedure for reproducing the earlier setup in the scope.[1][2]

Treat repeatability as a scope and documentation objective, not a promise of identical readings. Ask your engineer and bidder to agree on any acceptance tolerance and how setup differences will be documented.

Separate measurement from engineering conclusions

Commission thickness measurement and engineering interpretation as separate scope items; do not assume a survey includes a fitness-for-service determination. MISTRAS lists ultrasonic thickness measurements alongside separately advertised engineering services, including allowable-pressure analysis, corrosion evaluations and fitness-for-service evaluations.[2]

Before approving the work, establish:

• Who interprets the results? Name the party responsible for evaluating the measurements.
• What engineering work is included? Specify the evaluation and written conclusions, identifying analysis requiring a separate agreement.
• What does the engineer need? Have the engineer identify the tank information, measurement deliverables and evaluation criteria before finalizing the survey scope.

Acuren cites ASME, API and AWS, while MISTRAS names API, STI, UL-142 and AWWA.[1][2] Ask the responsible engineer to identify the applicable standard, edition and evaluation criteria, including any mandatory survey-grid requirements. Keep the handoff explicit: who supplies the measurements, who evaluates them and who delivers the engineering conclusion.

Get the price structure and change terms

Ask bidders to price the measurement work, records and engineering handoff explicitly—not quote “tank thickness testing” without a defined scope. Request a pricing basis and separate identification of access, preparation, coverage, reporting, data delivery and engineering work where applicable.

Ask Acuren or MISTRAS for prices, minimum terms, service duration, cancellation terms and contractual turnaround commitments in writing.[1][2]

Request written answers to these commercial questions:

• What does the amount include? Tie the price to the agreed coverage and list excluded work or deliverables.
• What happens if conditions change? Address extra readings, access restrictions, return visits, and weather or operating delays, including price and schedule adjustments.
• Who authorizes changes? Agree a written approval process before additional work proceeds or coverage is reduced.
• Are records included? Confirm whether each requested map, reading table, data file and instrument record is included, and when it is due.
• What if work is postponed or canceled? Obtain the applicable terms before award.

Evaluate bids against the same requested scope. Ask bidders to identify and separately price alternatives so you can judge the tradeoff without silently giving up coverage or records.

Make the next-survey handoff part of acceptance

Agree how the delivered package will be checked, rather than waiting to judge the report’s appearance. Suggested acceptance wording to adapt with the bidder and engineer:

“Deliver the agreed location map, linked reading register, traceable reported minima, unmeasured-area register and specified instrument records in the agreed formats.”

Make the check practical: can the engineer identify the tank, understand what was and was not measured, locate each reported minimum and determine which records support it? Put the correction and acceptance process in the contract rather than assuming a right to rework or withheld payment.

Before award, confirm the scope covers shell coverage, coating and preparation, access and exclusions, linked locations and minima, instrument records, engineer review, and price-change terms. Approve a proposal that expressly commits to those deliverables; leave the technical judgment about later comparability to your engineer.

References

1. Ultrasonic Testing Services (UT) | Acuren (acuren.com)
2. ONE-SOURCE FOR (mistrasgroup.com)