How do you calculate protected days of supply for spares?

Divide inventory on hand by average daily usage and adjust for the lead-time safety factor. With 1,200 parts on hand and 85 parts/day usage, unprotected coverage is about 14.1 days and protected coverage about 12.8 days after the factor.

What is the difference between protected and unprotected days?

Unprotected days is raw inventory divided by usage, here 14.1 days. Protected days, about 12.8, applies the safety factor to leave margin for demand spikes and lead-time variability, so it is the conservative number you plan against.

How much cryogenic spare buffer is enough?

Your protected days should exceed your worst realistic supplier or repair lead time for the part. If a vacuum-jacketed valve takes 20 days to source, 12.8 protected days is short and you need to raise stock or qualify a second supplier.

Why do cryogenic spares need a bigger buffer than ordinary parts?

Cold-service components are specialized and low-volume, so lead times are long and erratic, and a stockout can idle a whole tank or vaporizer. The safety factor and a deliberate buffer absorb that variability instead of betting on the supplier.

Should critical insurance spares use this calculator?

Not on their own. A relief valve that fails once in years has effectively zero average daily usage, so a usage-based buffer will not size it. Hold those as dedicated insurance spares and use this tool for parts with steady consumption.

How does the safety factor change the result?

The factor discounts raw coverage to leave headroom for variability, pulling 14.1 unprotected days down to 12.8 protected days in the example. A larger factor means a more conservative plan and a higher reorder point.

Cryogenic Storage & LNG Equipment calculator

Cryogenic Spare Parts Buffer Calculator

The cryogenic spare parts buffer tells you how many days of protected supply your on-hand inventory of cold-service spares actually covers once you account for a lead-time safety factor. Maintenance and supply-chain planners on LNG and cryogenic storage sites use it because the critical spares, vacuum-jacketed valves, cryogenic seals, relief devices, and pump components, often carry long, unpredictable lead times. Run short on a relief valve or seal and a tank can be down for weeks. This calculator shows whether your shelf stock buys enough runway to survive a supplier or repair delay.

What this calculator does

Calculate spare-parts inventory needed to cover cryogenic equipment usage through supplier lead time plus safety stock.
Use it when cryogenic spare parts buffer in cryogenic storage and lng equipment is being sized for a buffer or safety stock review.
It computes protected days of supply from spare inventory on hand and average daily usage, scaled by a lead-time safety factor.

Formula used

Lead-time spare demand = average cryogenic spare usage × supplier or repair lead time
Required cryogenic spare inventory = lead-time spare demand + critical spare safety stock

Inputs explained

Cryogenic spare inventory on hand:
Average cryogenic spare usage:
Supplier or repair lead-time safety factor:

How to use the result

Use it when setting reorder points for cryogenic spares, reviewing stock for long-lead critical items, or stress-testing inventory against a supplier delay.
It assumes steady average usage; a single failure of a critical, rarely-used part can outrun a buffer sized on average demand, so treat insurance spares separately.

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.
Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate protected days of supply for spares? Divide inventory on hand by average daily usage and adjust for the lead-time safety factor. With 1,200 parts on hand and 85 parts/day usage, unprotected coverage is about 14.1 days and protected coverage about 12.8 days after the factor.
What is the difference between protected and unprotected days? Unprotected days is raw inventory divided by usage, here 14.1 days. Protected days, about 12.8, applies the safety factor to leave margin for demand spikes and lead-time variability, so it is the conservative number you plan against.
How much cryogenic spare buffer is enough? Your protected days should exceed your worst realistic supplier or repair lead time for the part. If a vacuum-jacketed valve takes 20 days to source, 12.8 protected days is short and you need to raise stock or qualify a second supplier.
Why do cryogenic spares need a bigger buffer than ordinary parts? Cold-service components are specialized and low-volume, so lead times are long and erratic, and a stockout can idle a whole tank or vaporizer. The safety factor and a deliberate buffer absorb that variability instead of betting on the supplier.
Should critical insurance spares use this calculator? Not on their own. A relief valve that fails once in years has effectively zero average daily usage, so a usage-based buffer will not size it. Hold those as dedicated insurance spares and use this tool for parts with steady consumption.

Last reviewed 2026-05-12.