How do you calculate good leak-test capacity?

Multiply stacks per cycle by planned cycles for gross capacity, then multiply by uptime and first-pass rate. Here 2 × 40 = 80 gross, × 88% × 95% = 66.88 good stacks.

What is the difference between gross and good capacity?

Gross capacity (80 stacks) is what the bench could test if nothing was lost. Good capacity (66.88) is what passes after subtracting 9.6 stacks to downtime and 3.52 to first-pass failures.

What is a good leak-test first-pass rate?

Strong stack lines run 95%+ first-pass at target test pressure, as in the example. Lower rates usually point to gasket seating, compression, or plate sealing-land issues that resurface in retest.

How much does tester uptime affect throughput?

A lot. At 88% uptime the example loses 9.6 stacks of capacity before any quality loss — more than the rework loss. Improving uptime often buys more capacity than chasing the last point of first-pass rate.

Why model first-pass rate instead of just final yield?

First-pass rate captures the stacks that pass without rework, which is what protects bench capacity. A stack that fails and is retested still ships, but it consumed two cycles, so it eats into the cycles available for new units.

How do I add leak-test capacity?

More cycles (extra shifts), more stacks per cycle (a multi-station fixture), higher uptime, or a higher first-pass rate all increase good capacity. The calculator lets you test each lever before committing capital.

Hydrogen Electrolyzer & Fuel Cell Manufacturing calculator

Leak Test Capacity Calculator

Leak testing is the gate every fuel cell and electrolyzer stack must pass before it ships — a pressure-decay or mass-flow test that confirms the stack holds gas at or above its target test pressure without crossing internal or external leak limits. This calculator estimates how many good, leak-tight stacks a tester can actually deliver in a period after you account for tester uptime and the first-pass rate at the test pressure. Production planners and test engineers use it to size leak-test capacity against build rate, because the leak bench is a common bottleneck: a stack that fails has to be diagnosed, resealed, and retested, consuming cycles that were planned for new units. Knowing your true good throughput keeps the leak bench from silently capping shipments.

What this calculator does

Estimate good-stack throughput on the leak test cell from stacks per leak-test cycle, planned cycles in the period, leak tester uptime, and leak-test pass rate at your target test pressure.
Use it when a test engineer or production planner needs to know whether the existing leak test bench can absorb a higher build rate, or whether a second helium or pressure-decay station is needed before the next build.
It computes gross capacity as stacks per cycle times planned cycles, then multiplies by tester uptime and first-pass rate to give good leak-tight stacks delivered.

Formula used

Gross leak test capacity = stacks per cycle × planned cycles
Good leak test capacity = gross capacity × leak tester uptime × first-pass rate

Inputs explained

Stacks per leak test cycle:
Planned leak test cycles in the period:
Leak tester uptime:
Leak test first-pass rate at the target test pressure:

How to use the result

Use it when planning leak-test capacity against build rate, justifying a second tester, or quantifying how uptime and first-pass losses erode throughput.
It assumes failed stacks consume a cycle but does not model retest queue dynamics, so the rework loss it shows is units lost from gross, not the added retest load on the bench.

Current U.S. benchmarks

Global copper trades at $13,484 per tonne (IMF via FRED, May 2026), up 41.5% in a year, and U.S. industrial electricity averages 8.66 cents per kWh. Both feed electrified-hardware unit economics.

Common questions

How do you calculate good leak-test capacity? Multiply stacks per cycle by planned cycles for gross capacity, then multiply by uptime and first-pass rate. Here 2 × 40 = 80 gross, × 88% × 95% = 66.88 good stacks.
What is the difference between gross and good capacity? Gross capacity (80 stacks) is what the bench could test if nothing was lost. Good capacity (66.88) is what passes after subtracting 9.6 stacks to downtime and 3.52 to first-pass failures.
What is a good leak-test first-pass rate? Strong stack lines run 95%+ first-pass at target test pressure, as in the example. Lower rates usually point to gasket seating, compression, or plate sealing-land issues that resurface in retest.
How much does tester uptime affect throughput? A lot. At 88% uptime the example loses 9.6 stacks of capacity before any quality loss — more than the rework loss. Improving uptime often buys more capacity than chasing the last point of first-pass rate.
Why model first-pass rate instead of just final yield? First-pass rate captures the stacks that pass without rework, which is what protects bench capacity. A stack that fails and is retested still ships, but it consumed two cycles, so it eats into the cycles available for new units.

Last reviewed 2026-05-12.