Why test decay when the wall already passed?

Answer: Thickness covers material, not a flat sealing face or a split gasket corner. Decay measures the assembled seal.

Is 60 seconds long enough for a prop charge container?

Answer: It catches assembly faults; five minutes catches slow seepage, so add a ten minute hold at 2 kPa.

Why drop onto concrete instead of steel?

Answer: Concrete rebounds little, so the case absorbs nearly all the energy. Steel understates corner cracking.

What does 480 hours of salt spray represent?

Answer: Roughly three to five years of metal corrosion at a coastal site, a trend not a service life.

Beyond Wall Thickness: Prop Charge Container Acceptance Tests

Quick answer: A prop charge container passes on three independent sets of evidence, not a caliper reading. Dimensions, a 60 second hold at minus 30 kPa, and drops from 0.9 m and 1.5 m each stand alone.

Wall Thickness Is Not a Verdict
Appearance and Dimensions
Pressure Decay and Leak Location
Drop and Stack Tests on Site
Salt Spray and Thermal Cycling
Three Disposition Lines
FAQ

1. Wall Thickness Is Not a Verdict

The argument never changes: the caliper reads 3.5 mm, so why hold the batch. Thickness is a design input, not an acceptance result, and it says nothing about a flat sealing face.

A prop charge container passes on three independent groups of evidence: dimensions prove it closes, the seal proves it holds, the structure proves it survives a fall.

Group	Method	Criterion
Dimensions	CMM or go/no-go gauge	Cavity 158 mm, tolerance 0.5 mm, gap 0.8 mm max
Seal	Differential, minus 30 kPa, 60 s	Decay 0.8 kPa or less
Structure	Drops 0.9 m and 1.5 m, 5 high 72 h	No through crack, set 3 mm max

Sampling gets fixed first: 5 percent of a batch, floor of three cases, seal on every unit, drops at 2 per thousand.

2. Appearance and Dimensions

Three places never show on a thickness reading: parting line mismatch, gate marks, whitening near inserts. All sit near the sealing face.

Prop Charge Container: olive case open on a wooden table, egg-crate foam in the lid, a divided tray, a red valve knob, tools at right

Cavity 158 by 492 mm on a go/no-go gauge
Lid gap by feeler gauge at eight points, 0.8 mm max
Latch pull 350 N for 10 seconds, fitted at 8 N m
Seal groove 4 mm plus or minus 0.1 mm, no flash
Sealing face flat within 0.4 mm over 300 mm
Wall by ultrasonic gauge, five points per face, nothing under 3.3 mm

Flatness is the one that gets skipped. Four tenths sounds generous until you remember the gasket compresses 1.2 mm, so a 0.6 mm hollow eats half of it.

3. Pressure Decay and Leak Location

Most decay disputes come from temperature, not equipment.

A case needs four hours in the test room. Move a prop charge container from a 35 C floor into a 20 C room and the trapped air contracts, so the gauge climbs and a leaking unit looks fine; move one from 5 C into 20 C and a good unit fails.

Drift	Correction	Share of the 0.8 kPa limit
2 C	0.04 kPa	5 percent
5 C	0.10 kPa	12 percent
10 C	0.20 kPa	25 percent

When a unit fails, locating the leak beats scrapping it. Soap the groove for bubbles, pull the latches, check for a collapsed base, then suspect the body. Most trace to under-torqued latches or a split gasket corner.

4. Drop and Stack Tests on Site

Drops run at two levels: a single case and a pallet fail differently.

Prop Charge Container: khaki case in a grey tray on a steel counter, foam holding circuit boards, a handheld reader, a round valve

A single case falls 0.9 m onto concrete on corner, edge and face, checked for through cracks and popped latches. A pallet falls 1.5 m, where the contact zone takes twice that stress. Concrete barely rebounds, so the case absorbs the energy.

Stack five high for 72 hours at 40 C, months of creep in three days: the bottom lid sets 3 mm or less, recovering to 1 mm in 24 hours. Stack first, then drop.

5. Salt Spray and Thermal Cycling

Metal ages faster than polymer, so salt spray targets latches, hinges, valves.

Neutral salt spray for 480 hours, scribe creep under 2 mm per side, latches latching after 500 cycles, colour difference of 3 or less. Thermal cycling runs 4 hours at minus 40 C and 4 hours at plus 71 C for seven cycles. UV of 300 hours leaves no crazing.

Samples stay separate even in one order: latches and hinges for salt spray, a whole case for thermal cycling, plaques for UV.

6. Three Disposition Lines

Disposition belongs in the spec, not on the floor.

Defect	Line	Boundary
Gap 0.8 to 1.2 mm, decay 0.8 to 1.5 kPa	Rework	Gasket or latch fix, one rework only
Wall 3.0 to 3.3 mm, no cracking	Downgrade	Non-pressure duty, marked, kept apart
Through crack, decay above 1.5 kPa	Scrap	Destroyed on site, no return to stock

The lines do not cross: a prop charge container failing its single rework goes to downgrade or scrap, stored apart.

Conclusion

Acceptance is hard because the three groups stay independent: for a prop charge container, thickness, seal and structure each cover their own ground. Fix 158 mm, 0.8 kPa, 0.9 m, 1.5 m and 480 hours, and acceptance stops collapsing into a caliper reading.

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.