About and methodology
How we build Long Seam, check our material and handle corrections.
Who we are
Long Seam is part of TrueGrade Prep. We make study resources for API 510, API 570, API 510 recert, API 653, API 571 candidates.
Operating company: Nori Software LLC.
What we build
We build free practice checks, calculators and guides to help you find gaps in your knowledge and plan your study time. The API 510, API 570, API 653 and API 571 exams also have a course: lessons, a question bank, timed practice exams and a study plan. The API 510 recert has a practice pack: a question bank and timed practice exams.
How we write and check questions
Questions are drafted with AI assistance from the exam body's published content outline, then each answer key is re-checked by a separate blind solve and against the code section or source it cites. Questions an expert reviewer has signed say so; every question, signed or not, is corrected as errors are reported.
We write each question from scratch. Each question is mapped to a domain and its published weight, so free check question selection follows the outline's balance. Code references cite section numbers only; we never reproduce code-book text. Use your own licensed copy of any code your exam requires. We never use real or recalled exam items, and reject questions that resemble them.
A question is removed from use if its answer is unreliable, its wording is ambiguous or its reference is out of date. Questions that cannot be corrected are retired, and corrections are recorded in the errata log.
How we check facts
Facts about fees, exam formats and rules link to the exam body's own pages and show the date checked. Those pages are the source to consult before booking or applying. Reported errors go through the corrections process below.
Who checks our questions
Outside experts sign off on question sets. We describe each reviewer by their background and do not publish names unless a reviewer has agreed to it. A reviewer is credited only on the questions they signed.
Our method
- Original questions, written to the exam body's published outline. Never real or recalled exam items.
- Every answer key is confirmed by a separate blind solve.
- Explanations cite the clause, table or figure they rest on, never code-book text.
- Reported errors are corrected within 2 business days and logged in the public errata log.
API 510
- 201 questions from the API 510 practice bank and course checks. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- one reworded API 510 course check question. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- The API 510 practice bank, course checks and free check as they stood that day. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 45 reworded questions in the API 510 practice bank and free check. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 36 API 510 code-lookup practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- The API 510 lessons, exam-day guide and sample lesson. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 40 more API 510 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 40 more API 510 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 80 more API 510 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 40 more API 510 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 120 API 510 flashcards. Signed by a pressure vessel inspection professional with 13 years in the industry, .
Practice bank: 614 of 617 questions carry an outside-expert sign-off.
Every question in the free 10-question check carries an outside-expert sign-off.
API 570
- 40 more API 570 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 39 more API 570 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 75 more API 570 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 40 more API 570 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 124 API 570 flashcards. Signed by a pressure vessel inspection professional with 13 years in the industry, .
- 15 more API 570 practice questions. Signed by a pressure vessel inspection professional with 13 years in the industry, .
Practice bank: 659 of 660 questions carry an outside-expert sign-off.
API 510 recert
Practice bank: 174 of 174 questions carry an outside-expert sign-off.
API 653
Practice bank: 347 of 347 questions carry an outside-expert sign-off.
API 571
Practice bank: 249 of 249 questions carry an outside-expert sign-off.
Sign-offs are recorded by month. This list shows only what has been signed so far.
Calculators
Our calculators use formulas and published reference data, cited on each tool alongside its assumptions and limits. They support study and preliminary checks; they are not a substitute for the project's engineer or authority having jurisdiction (AHJ).
Independence
Long Seam and TrueGrade Prep are independent and are not affiliated with or endorsed by American Petroleum Institute. Exam names are used descriptively to identify the exams our resources cover.
Corrections
Think an answer is wrong? Report it. We correct errors within 2 business days and log every change publicly.
Email hello@longseam.com with the page link, exam and question identifier where applicable, and what needs checking.
Errata log: no corrections logged as of 17 October 2026.