Does acceptance of a moisture-resistant equipment storage case always include a transmission test?

Answer: For series supply, yes. Pressure drop proves the seam is tight; wall or valve permeation needs the transmission figure.

Can the 3 kPa charge pressure be changed?

Answer: Yes, but keep it uniform within a batch. Lower pressure senses small leaks better; higher pressure can bed the gasket down and hide a defect.

Is 480 g of desiccant a fixed figure?

Answer: No. It matches a 60 litre interior at a 20 percent target. Double the volume and double the weight; relax the target to 40 percent and you may halve it.

How is gasket compression measured on a finished case?

Answer: Measure the seam gap with the lid closed, subtract it from the free thickness, divide by that thickness, then average three points.

Does a pass guarantee a dry year?

Answer: No. Acceptance covers the condition at dispatch; above 50 openings a year, or in a store held at 80 percent humidity, shorten the interval. ---

Moisture-Resistant Equipment Storage Case: Acceptance Tests

Quick answer: A moisture-resistant equipment storage case is accepted on four measurements, not on a badge: gasket compression with whole-case pressure drop, transmission rate, desiccant weight against the humidity target, and the annual load from opening cycles.

Acceptance Items a Moisture-Resistant Equipment Storage Case Must Pass
Seals and Vapor: Pressure Drop and Transmission Rate
Desiccant Weight and Target Humidity Inside the Case
Converting Opening Cycles into Annual Moisture Load
Sampling Ratios and the Judgement Record
FAQ

1. Acceptance Items a Moisture-Resistant Equipment Storage Case Must Pass

Disputes at goods-in start with a rating treated as a verdict. An IP rating answers water and particles, not vapor, and vapor attacks stored equipment.

The sheet lists gasket compression, whole-case pressure drop, transmission rate and desiccant weight against the humidity drop produced. The first two cover leakage, the last two absorption.

Item	Condition	Pass limit	Re-check
Gasket compression	seam gap, lid closed	25 to 32 percent	every batch
Permanent set	70 °C for 24 hours	20 percent or less	yearly
Pressure drop	3 kPa held 120 seconds	0.15 kPa or less	every batch
Transmission	38 °C, 90 percent RH	0.35 g per m² daily	yearly
Humidity drop	60 L, 480 g silica gel	below 20 percent at 48 hours	every batch

State the basis, foam deducted, or two inspectors measuring one moisture-resistant equipment storage case will differ by twenty percent.

2. Seals and Vapor: Pressure Drop and Transmission Rate

Pressure drop is the workshop test: plug the relief valve and cable port, charge to 3 kPa, hold for 120 seconds, accept 0.15 kPa or less.

Moisture-Resistant Equipment Storage Case: black lid corner close-up, two ribs forming the seal channel, grey foam pocket holding a flat black panel

Pressure proves gas does not escape, not that vapor stays out. Transmission is measured at 38 °C and 90 percent relative humidity, where water per square metre per 24 hours must stay at or below 0.35 g; a 4 mm polypropylene wall is near that figure.

Test	Load	Reading	Typical failure
Pressure drop	3 kPa, 120 seconds	loss in kPa	valve seat warp
Transmission	38 °C, 90 percent RH	grams per square metre	thin wall, insert edge
Immersion	300 mm, 10 minutes	humidity rise	latch lug cracking

Immersion: 300 mm for ten minutes, then humidity must not climb three points in two hours. Gaskets are judged at 25 to 32 percent.

3. Desiccant Weight and Target Humidity Inside the Case

Set the target first: electronics take 20 percent, optics 30 percent, general metal 40 percent, and each step down roughly doubles the desiccant.

A 60 litre interior takes 480 g of silica gel, about 8 g per litre; the same moisture-resistant equipment storage case given 240 g visibly slows its drop at 48 hours. Below 20 percent passes, while 25 to 30 percent means check the gasket, then ask whether the desiccant was already saturated.

4. Converting Opening Cycles into Annual Moisture Load

Ventilation is the item most often missing from the sheet. A moisture-resistant equipment storage case is never sealed for a year, and every opening exchanges air.

Moisture-Resistant Equipment Storage Case: navy case closed on a metal bench, round vent cap, two latches and folded handle on the front, factory wall behind

Air at 30 °C and 80 percent humidity carries about 24 g of water per cubic metre. A 60 litre interior opened for 60 seconds exchanges roughly 0.4 of its volume, bringing in 0.6 g; fifty openings a year totals 30 g, a tenth of the working capacity of 480 g of silica gel. Above that, add 10 percent desiccant or shorten the interval to six months. Leak paths also include the relief valve, cable port and label rivets.

5. Sampling Ratios and the Judgement Record

Sampling is defined per batch: one mould, one production run, one gasket lot. Two cases are drawn under 50 units, four up to 200, six up to 500, eight above.

One major defect rejects the batch; two minor are tolerated, provided no single moisture-resistant equipment storage case carries both. Record five fields per case: gasket lot, pressure drop, transmission, 48 hour humidity, opening-cycle figure.

Conclusion

Four numbers give acceptance a shared language: compression and pressure drop for leakage, transmission for permeation, desiccant for capacity, cycles for endurance. Fix the basis, sampling and record, and a moisture-resistant equipment storage case is accepted on evidence rather than a label.

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.