A storage tank tender turns on a single standard reference that changes the entire job: API 650 for atmospheric welded tanks, API 620 for low-pressure tanks including refrigerated and cryogenic service. Confusing the two, or missing which one governs, means designing and pricing the wrong tank. API 620 work carries heavier design, materials, and inspection demands than API 650, so a fabricator who assumes 650 against a 620 requirement underprices and under-scopes a tank it then cannot deliver to specification.
What Each Standard Demands
API 650 governs vertical, atmospheric, welded storage tanks, with appendices for specific services such as Appendix A for small tanks or Annex requirements for seismic and wind. API 620 covers larger, lower-pressure tanks and the colder, more demanding services, with stricter materials and design rules. The tender also layers in foundation interface, roof type (fixed, floating, internal floating), coating, and inspection. The governing standard sets the baseline; the appendices and project specifics set the rest. Reading the wrong baseline invalidates everything built on it.
Why the Standard Gets Confused
The tender names the standard in the design basis, but the service description, refrigerated, cryogenic, low-pressure, is what actually determines which one applies, and that description can sit in the process data rather than next to the standard reference. A fabricator scanning for tank size and capacity can default to API 650, the more common standard, and miss that the cold or low-pressure service pushes the job into API 620 territory. The error is structural and it is priced in from the first estimate.
How an AI Bid Response Agent Confirms the Governing Standard
An AI bid response agent reads the design basis and the process and service description together, confirms whether API 650 or API 620 governs, and surfaces the roof type, appendices, materials, and inspection requirements that follow. It flags a low-pressure or cryogenic service that pushes the tank into API 620 before you estimate. You design and price against the standard the tender actually requires, not the one you assumed.
You can see the full workflow running, the requirements check, the Go or No-Go read, the draft assembled from past winning bids, and the red-team score, in our AI bid response agent demo for oil and gas equipment tenders. The same AI bid response agent runs for any oil and gas equipment supplier, against any tender they are eligible to pursue.