Can the seal groove be cleaned with solvent?

Answer: No. Solvent swells the HDPE skin by 0.3 mm and the case seeps on the next closure.

When is the foam replaced as a whole block?

Answer: Below 27 mm residual thickness, crush over 2 mm, or offset over 3 mm — any one means a new block.

Can a latch be left until it breaks?

Answer: No. The line is 0.8 mm of free play on a closed missile box; by then the gasket has not seated for months.

How is desiccant failure detected?

Answer: By weight. A 32% gain means saturation, 2 hours at 120 °C regenerates it, and the 9th charge is replaced.

Does the relief valve need a schedule?

Answer: Yes, 24 months regardless of looks. A return slower than 5 seconds or a cracking pressure off 35 kPa also retires it.

15 Days to 360: Inspection Cycles for a Missile Box

Q: How often should a missile box be inspected?

Answer: Every 15 days for sealing faces and the valve, 90 days for foam and desiccant, 360 days for air tightness. Above a 20 °C swing, the first tier becomes 7 days.

Quick answer: A missile box runs on three clocks — 15 days for sealing faces and the relief valve, 90 days for foam and desiccant, 360 days for air tightness and stack load. Each clock carries one number that decides replacement, so the next shift does not re-invent the judgement.

Inspection Tiers for a Missile Box
Cleaning Sealing Faces and Pressure Valves
Foam Compression Set and the Replacement Line
Latch and Hinge Fatigue Counting
Desiccant Regeneration and Life Extension Records
FAQ

1. Inspection Tiers for a Missile Box

The interval follows the failure, not the calendar. A gasket degrades in weeks once humidity reaches the groove, foam takes a season to lose its set, and a rotomoulded shell chalks under UV over years. Three clocks on one page: 15 days, 90 days, 360 days, each faster than the failure it watches.

The store overrides the chart. Where the daily swing passes 20 °C, the sealing check on a missile box drops from 15 days to 7; at a coastal depot rated to 480 hours of salt spray, hinges join the monthly round.

Four columns are enough: interval, part, criterion. The criterion must be a number; feels gritty reads differently on the next shift.

Interval	Part	Criterion
15 days	Sealing face, valve port	Bubbles, or salt at the port
90 days	Foam, desiccant	Foam below 27 mm
360 days	Air tightness, stack load	Over 8% drop in 5 min

Keep the decay curve instead of a tick: 20 kPa falling to 18.2 kPa in 5 minutes is healthy, 15 kPa means a channel across the sealing face.

2. Cleaning Sealing Faces and Pressure Valves

Cleaning protects groove geometry, not gloss. The groove is 4.5 mm deep and the land 12 mm wide, and one grain of sand at the bottom can halve contact stress. Use a pH 7 cleaner at 40 °C, brush along the groove, rinse, and let the case stand 4 hours.

Missile Box: sand-coloured hard case standing upright on a warm beige backdrop, moulded top handle, two front latches, two bottom loops

Solvents are out. Acetone swells the HDPE skin by 0.3 mm, then seeps on the second closure. Salt bloom comes off with 5% citric acid dabbed on for 2 minutes at most.

The valve must pass air at 35 kPa and reseat within 3 seconds of release.

Part	Usual soil	Cleaning
Seal groove	Sand, old grease	Soft brush, neutral cleaner
Valve disc	Salt, oil film	5% citric acid dab

The disc is a calendar part on any missile box, swapped at 24 months whatever it looks like. Rubber in a -40 °C to 60 °C cycle gains 12 points of hardness and returns in over 5 seconds.

3. Foam Compression Set and the Replacement Line

Foam fails by thinning, not tearing. A 30 mm EVA block in a missile box, under 102 kg in a 40 °C store, typically measures 27.6 mm once the lid opens, a compression set near 12%.

Three limits run in parallel: residual thickness below 27 mm, local crush past 2 mm, block offset beyond 3 mm. The first two describe cushioning, the third describes location: a shifted block pushes load into one corner. Replace the whole block, never patch a corner: a glued offcut lifts peak acceleration from 45 g to 60 g.

4. Latch and Hinge Fatigue Counting

A latch is a fatigue part, counted in closures rather than years. Draw latches lose about 18% of preload after 6000 closures — 2.7 years at 6 openings a day, 7 months at 30. Two posts using the same missile box can differ 4x in interval.

Missile Box: sand-coloured case on a plank bench outside a corrugated shed, latches facing out, folded olive pad on the grass below

Judge a missile box latch by free play and torque. Push the latch body after closing: past 0.8 mm of travel the preload is gone. Hinge bolts re-torque to 6 N·m, and past 8 N·m the brass insert cracks.

Part	Count basis	Criterion	Action
Draw latch	6000 closures	Free play over 0.8 mm	Replace as a pair
Hinge pin	36 months	Gap over 0.15 mm	New pin and bush

Silicone grease, not engine oil. Oil stiffens at -40 °C and lifts hinge torque from 2 N·m to 6 N·m, so a winter lid takes two people.

5. Desiccant Regeneration and Life Extension Records

Half of life extension is humidity. Each missile box carries 800 g of silica gel, sized to hold the cavity under 45% RH. The gel nears saturation at a 32% weight gain, where 2 hours at 120 °C restores it; after 8 cycles capacity falls 15%, so the 9th charge is new stock.

Records follow the box number, not the batch: one card per missile box listing last inspection date, decay value and desiccant weight.

This routine moves service life from 8 years to 12, at 18 minutes of inspection per case per year and 2 planned stoppages.

Conclusion

What makes maintenance stick is numbers a storekeeper can read: 27 mm of foam, 0.8 mm of free play, a 32% weight gain, a 24-month disc. Set the clocks by failure speed, keep the card with the box number, and a missile box usually moves from 8 years to 12.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.