The API open-book session: what you can look up

Candidates hear “open book” and relax. It is the wrong instinct, and the timing tells you why.

How is the API exam day structured?

One sitting, split in two. 110 closed-book questions in 2 hours 45 minutes, then a 45-minute break, then 60 open-book questions in 3 hours 45 minutes. The same shape applies to API 510, API 570 and API 653.

Work out the per-question budget and the intent becomes obvious: roughly 1.5 minutes each in the closed half, and about 3.75 minutes each in the open half. API is not being generous. It has allowed the time that locating a requirement and applying it actually takes.

What does “open book” mean in practice?

It means the reference documents appear as on-screen PDFs, during the open session only. You cannot bring your own copies, tabbed or otherwise.

This is the detail that quietly wrecks preparation. Months spent building a beautifully indexed paper set trains a retrieval skill you will not have access to. On the day you will be scrolling and using a search box, which is a different motion with a different failure mode — you will find forty matches for a common term and have to judge which one governs.

Rehearse on screen. It is less pleasant and it is the thing being tested.

What happens at the break?

Once you submit the closed-book section, you cannot return to it. Unanswered questions are scored as incorrect.

Both halves of that sentence matter. There is no partial credit for leaving something blank and no penalty for a wrong guess, so every closed-book question should carry an answer before you submit — even one you are unhappy with. The most expensive mistake available in the first session is running the clock down on question 94 and abandoning 95 to 110 unanswered.

What must you still know without the documents?

For API 653, the split is more interesting than “closed means memorise”.

Some formulas are supplied in the exam — the corrosion rate, remaining life, remaining corrosion allowance, maximum fill height and bottom-plate relationships. But certain API 653 tables must be known without access to the documents.

So the closed-book preparation is not formula memorisation. It is the judgement surrounding the formulas: which corrosion rate governs, which interval rule applies, which thickness goes into which variable, and which of the values in front of you is the one the question is actually about. Supplying the formula removes the arithmetic and leaves the decision, which is what was being examined all along.

How should you practise the open half?

Four things, in order:

1. On a screen, with a clock. Not on paper, not untimed. Both constraints are part of the exam.
2. Learn which document, then roughly where. You do not need to memorise clause numbers. You need to stop losing ninety seconds deciding whether something lives in 653 or 650.
3. Rehearse the whole rhythm at least twice. 2:45, a real 45-minute break, then 3:45. Fatigue in the final hour of the open session is a real factor and you cannot simulate it in forty-minute chunks.
4. Watch for edition drift. Which editions apply depends on the effectivity sheet for your window, and those sheets change. For API 653, windows from March 2027 move API 650 to its 14th Edition and ASME BPVC Sections V and IX to 2025 editions; the November 2026 window is the last on the older sheet.

Practise the real split

Our API banks mark every open-book question as such and present them in exam order — questions 1 to 110 closed, 111 to 170 open — so you can rehearse the actual 2:45 / break / 3:45 rhythm instead of a shuffled set.

• API 653 free sample — full guide
• API 510 free sample — full guide
• API 570 free sample — full guide
• Which API certification should you take first?