How do you calculate vacuum jacket leak rate?

Divide the number of components failing the vacuum check by the total inspected, then multiply by 100. With 8 failures out of 250 inspected, that is 8 / 250 x 100 = 3.2% leaking.

What is a good vacuum jacket leak rate?

Lower is better; well-maintained cryogenic fleets often run a few percent or less. The acceptable level depends on service, but a 3.2% rate against a tight integrity standard signals a maintainable population that still needs the failures addressed.

Why is the 'leak rate above limit' value so large in the example?

Because the maximum acceptable rate was entered as 95%, the formula subtracts the 3.2% leak rate from 95 to give 91.8 points of headroom. If you intend the threshold as a low cap, enter the actual maximum allowable percent of failures, such as 2% or 5%.

What causes vacuum jacket failures?

Outgassing of the annulus, getter saturation, weld or seal micro-leaks, mechanical damage to the outer jacket, and thermal cycling fatigue. Each lets gas into the vacuum space, killing the insulating effect.

How many components should I inspect?

Enough to be representative — the 250-component sample in the example gives a stable rate. Small samples make the percentage jump sharply with each failure, so inspect a broad cross-section before trending.

Vacuum jacket leak rate vs. boil-off rate: how do they relate?

Leak rate is a cause; boil-off is an effect. A rising vacuum jacket leak rate predicts higher heat leak and therefore more boil-off, so tracking it lets you act before boil-off losses show up on the gauge.

Cryogenic Storage & LNG Equipment calculator

Vacuum Jacket Leak Rate Calculator

Vacuum jacket leak rate is the percentage of vacuum-insulated components — bayonets, transfer lines, tanks, and valves — that fail a vacuum-integrity check during an inspection campaign. Maintenance and integrity engineers on cryogenic and LNG systems track it because a lost vacuum annulus means the insulation collapses, heat leak spikes, and boil-off climbs. It is a fleet-level quality metric, not a single-vessel reading: it tells you what fraction of your vacuum-jacketed population is degrading. Watching the trend against an acceptable threshold flags when a re-evacuation program or component replacement campaign is overdue.

What this calculator does

Calculate the leak or failure rate for vacuum-jacketed pipe, valves, hoses, or vessel jackets from failed items versus inspected population.
Use it when vacuum jacket leak rate in cryogenic storage and lng equipment needs a clean rate and gap-to-target you can put on a tier board.
It computes the share of inspected vacuum-jacketed components that failed their vacuum check, expressed as a percent, and the gap between that rate and your maximum acceptable rate.

Formula used

Vacuum jacket leak rate = components failing vacuum check ÷ total components inspected × 100
Leak rate above limit = vacuum jacket leak rate − maximum acceptable jacket leak rate

Inputs explained

Vacuum-jacketed components failing check:
Total vacuum-jacketed components inspected:
Maximum acceptable jacket leak rate:

How to use the result

Use it after a vacuum-integrity inspection sweep to gauge fleet health and decide whether re-pumping or replacement is warranted.
It treats every component equally and as pass/fail; it does not weight by criticality, by how far each annulus has degraded, or by the heat-leak impact of a given failure.

Current U.S. benchmarks

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Common questions

How do you calculate vacuum jacket leak rate? Divide the number of components failing the vacuum check by the total inspected, then multiply by 100. With 8 failures out of 250 inspected, that is 8 / 250 x 100 = 3.2% leaking.
What is a good vacuum jacket leak rate? Lower is better; well-maintained cryogenic fleets often run a few percent or less. The acceptable level depends on service, but a 3.2% rate against a tight integrity standard signals a maintainable population that still needs the failures addressed.
Why is the 'leak rate above limit' value so large in the example? Because the maximum acceptable rate was entered as 95%, the formula subtracts the 3.2% leak rate from 95 to give 91.8 points of headroom. If you intend the threshold as a low cap, enter the actual maximum allowable percent of failures, such as 2% or 5%.
What causes vacuum jacket failures? Outgassing of the annulus, getter saturation, weld or seal micro-leaks, mechanical damage to the outer jacket, and thermal cycling fatigue. Each lets gas into the vacuum space, killing the insulating effect.
How many components should I inspect? Enough to be representative — the 250-component sample in the example gives a stable rate. Small samples make the percentage jump sharply with each failure, so inspect a broad cross-section before trending.

Last reviewed 2026-05-12.