Storage tank inspection services for API 653 and tank floors

These are planning ranges, not quotes. Tank diameter, height, product, access and the report you need change the real price, and several tanks at one site cost less per tank than a single call out.

API 653 covers the inspection, repair and alteration of aboveground steel storage tanks built to API 650 or API 12C. The tank owner or operator must have an authorized inspector (API 653 certified) sign off the records. The standard asks for routine in service checks by the owner, a formal external inspection at set intervals, and an internal inspection when the floor corrosion rate and the remaining thickness say it is due. The interval depends on measured corrosion rates, product and risk based inspection (RBI) results, so the thickness data you buy now decides how long you wait for the next internal. Ask the contractor to state which API 653 clause each scope item answers, and have the final report show remaining life by component.

Most of the cost and most of the risk sit in the floor, because the underside corrodes where nobody can see it. An out of service MFL scan covers the plates between the weld seams, flags thinned areas and pits, and the crew confirms the worst indications with UT. Edge zones near the shell, where scanners cannot reach, get hand UT. The result is a minimum remaining thickness and a map you can use to plan patch repairs or a new bottom. When opening the tank is hard to justify, acoustic emission screening ranks tanks by activity so the budget goes where the corrosion is. For the method background see ultrasonic testing services and magnetic particle inspection.

Shell thickness can be measured in service. Rope access or lift crews take UT readings on a grid, and crawler scanners cover whole courses faster with a record of every point. Weld seams and repair patches are checked with PAUT or magnetic particle testing. Floating roofs and tall shells are often screened first by drone, which cuts the time crews spend at height. The drone inspection services page shows what an aerial survey sees and what still needs contact methods. Girth welds on attached piping are covered under pipe weld testing.

Terminal and refinery reliability engineers buy API 653 inspections on a schedule set by their RBI program. Chemical plants order them before a change of service and after a leak or a settlement event. Fuel distributors and airports need them for regulatory and insurance records. Water, ethanol and biodiesel operators use them before extending a tank life or selling a site. Buyers of a terminal order a baseline inspection of every tank during due diligence. Engineering firms hire the NDT crew on behalf of an owner who has an outage window.

1. You send tank number, diameter, height, product, year built, last inspection date and what the last report found.
2. The inspection company proposes a plan: in service or out of service, methods, crew and access. For out of service work, the tank must be emptied, cleaned and gas free before anyone enters.
3. Crews mobilize, complete site safety and permit steps and inspect in the agreed window. Confined space entry needs a permit, an attendant and rescue plan.
4. Data is reviewed by a qualified technician and the API 653 inspector, who assigns remaining life and repair priorities.
5. You receive a report with thickness maps, floor scan results, defect list, corrosion rates, a recommended interval and repair recommendations. Urgent findings are called in the same day.

Cleaning and downtime often cost more than the inspection itself. Ask whether the quote includes them.

• External in service API 653 inspection. $2,500 to $9,000 per tank, depending on size and the number of thickness points.
• Out of service internal inspection with MFL floor scan. $8,000 to $40,000 per tank, plus cleaning, scaffolding and vapor control.
• Tank cleaning before entry. Often $10,000 to $100,000 or more for large crude or heavy product tanks, quoted by the cleaning contractor.
• Acoustic emission floor screening. $4,000 to $12,000 per tank.
• Vacuum box testing of repair welds. $800 to $3,000.
• Drone survey of a floating roof. $800 to $3,500 per tank.
• Mobilization and travel. $500 to $3,000 per trip for remote terminals.

Standby time during permits, night shifts and rush reports add to these numbers. Ask each contractor to list them separately so quotes compare like for like. The NDT inspection cost guide shows how crews price the underlying methods.

Check that the lead is an API 653 authorized inspector and that the MFL, UT and PAUT technicians hold ASNT SNT-TC-1A or CP-189 Level II certification. Ask for a sample floor scan report on a tank like yours and how they cover edge zones. Confirm the confined space program and injury record, insurance, and how quickly the first data is delivered after the crew leaves site. Quote comparisons only work when the scope, the code edition and the minimum thickness assumptions are the same in every response.