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?

The formula subtracts the leak rate from your maximum allowable rate, so 2% minus 3.2% reads -1.2: the batch is 1.2 points over the cap. Enter the threshold as the maximum allowable percent of failures, not as a pass rate.

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? The formula subtracts the leak rate from your maximum allowable rate, so 2% minus 3.2% reads -1.2: the batch is 1.2 points over the cap. Enter the threshold as the maximum allowable percent of failures, not as a pass rate.
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 2026-08-12.