Industrial process plant: pressure vessels, tanks and pipework on a steel frame, overlaid with faint blueprint schematic lines.

EngiMetric Arena

Think. Solve. Design. Share.

Engineering challenges graded by the same authoritative engines that power the calculators. Not a quiz — a real problem, a defensible answer, and the reasoning behind it. No account, no sign-up, nothing stored on a server.

Browse the challenges Start with: Review this RO energy calculation: the credit is missing

6 challenges published
2 disciplines
5 challenge families live

Featured challenge

Spot the Error · Water Treatment & Desalination

Review this RO energy calculation: the credit is missing

A designer has issued an energy figure for a seawater RO plant with an energy recovery device fitted. Identify the mistake in the review.

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Showing 6 of 6 challenges.

Water & Desalination Quick Challenge foundation

How many RO elements can you actually buy?

The membrane area you need is not the number of elements you can procure. Work out how many elements a real vessel array must contain.

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Water & Desalination Spot the Error intermediate

Review this RO energy calculation: the credit is missing

A designer has issued an energy figure for a seawater RO plant with an energy recovery device fitted. Identify the mistake in the review.

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Water & Desalination Engineering Trade-off advanced

Choose a recovery rate that the plant can actually run

Two site limits constrain system recovery. Any recovery inside the feasible band is a defensible engineering choice — find one, and see the trade-off.

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Water & Desalination Diagnose the Failure intermediate

Diagnose a calcium-carbonate risk signal on RO feed

Feed chemistry returns a positive saturation index. Decide what that signal does and does not establish before you act on it.

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Water & Desalination Quick Challenge foundation

How long must the water stay in contact?

A chlorine residual and a required CT are given. Compute the contact time — and read carefully what that number does and does not prove.

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Mechanical & Fluids Design Challenge intermediate

Specify a pump efficiency that keeps the duty inside its budget

Static lift, friction and minor losses are known, and the duty is capped. Choose a pump efficiency that satisfies both constraints.

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Challenge families in progress

These families are part of the Arena design and each has at least one published challenge. Families with no evaluator yet are listed here as a roadmap rather than as empty cards, because a family that cannot be assessed must not look like one that can.

Project Scenario Work a realistic project situation through stated assumptions.

How Arena works

Every answer is computed. Challenges run the authoritative EngiMetric engine, so a graded answer cannot drift from what the corresponding tool produces.
Wrong answers are explained. Where a specific misconception can be identified, Arena names it instead of only marking it wrong.
Several answers can be right. A trade-off or design challenge is graded against explicit limits, so a defensible range of answers passes rather than one invented optimum.
Judgement has limits. Every challenge states what it does not establish, before you commit to an answer.
Nothing is stored remotely. Your attempt stays in this browser. There is no account and no result database.

Engineering notice

Arena challenges are teaching and self-check exercises built on EngiMetric's documented preliminary models. They are not design submissions. Any figure taken from a challenge into real work must be verified by a licensed professional engineer against project-specific criteria and the governing design codes.