Can I take the wall to 10 mm instead of buying an explosion-proof case?

Answer: No. Wall thickness limits bulge, but the shell still carries the pressure and the seam still becomes the exit.

Where does the 120 litre line come from?

Answer: It follows the vent-area ratio. Larger cavities raise the rate of pressure rise at the same panel area, so past 120 litres two smaller cases cost less.

Does splitting into two cases not double the inspection?

Answer: It does, but each unit drops 1 mm of wall and runs four latches instead of six.

Which items should a supplier quote?

Answer: Wall and rib height, panel area and opening value, latch count and spacing, records per unit, tooling and lead time. ---

Explosion-Proof Case at 2x Price: 4 of 6 Duty Cases Skip It

Quick answer: An explosion-proof case usually quotes at twice the price of a plain protective case, with the gap spread over an 8 mm double wall, one independent vent panel and six evenly spaced latches. Of six common duty cases, only two need that structure; the other four are cheaper and better served by different hardware.

Where the 2x Price Sits
Six Duty Cases, Only Two Need It
The Four That Do Not: What to Buy Instead
Wall Thickness and Vent Area: How Far the Saving Goes
Three Costs Missing From the Quote
Four Steps to Recover the Difference
FAQ

1. Where the 2x Price Sits

A doubled quote means three items moved to dearer material, all measurable on a sample. A plain case carries a single 5 mm wall; an explosion-proof case uses a double 8 mm wall with 12 mm ribs. The vent panel is a separate 300 by 200 mm plate with a controlled opening value. Latches go from two plastic catches to six stainless ones at 240 mm, each marked 2.5 N·m.

Cost source	Plain case	Explosion-proof case	Share
Wall, ribs	Single 5 mm, flat	Double 8 mm, 12 mm ribs	40%
Vent panel	None	300 by 200 mm, controlled	35%
Latches, records	2 plastic, sampled	6 stainless, 240 mm, per unit	25%

Those rows carry nine tenths of the gap.

2. Six Duty Cases, Only Two Need It

Lay out the duty case first; the same box lands differently in different settings.

Explosion-Proof Case: dark grey body open on a bench, foam in the lid, one round vent valve centred, two latches back, cables beside, shelving behind

A pressure source inside, vent direction shifting as the case moves: required, panel facing an empty side.
Per-unit records and a permanent label: required, the paperwork is part of delivery.
Above 120 litres: split into two 60 litre units.
More than six openings a day: a hinged cabinet door outlasts a catch-and-lid design.
Surface above 70 °C: a 1.5 mm stainless shell distorts less than plastic.
Dust, water and impact only: a plain case is enough, and the panel adds a failure point.

The line sits in the first two rows. When either holds, no wall or gasket replaces that structure; when the last four hold, that margin is never used.

3. The Four That Do Not: What to Buy Instead

Each substitute moves the pressure duty off a single moulded shell.

Duty case	Better structure	What changes	Saving
Above 120 litres	Two 60 litre cases	Ratio doubles, wall drops 1 mm	About 15% cheaper
Above six openings	Hinged door	Latches stop carrying load, 5000 cycles	Six catches drop out
Above 70 °C surface	1.5 mm stainless	Salt spray 480 hours	Insert tooling drops out
Dust and water only	Plain case	Single 5 mm wall, 2 catches	Whole gap saved

The first three still carry pressure, just somewhere better: two shells share the load, a door hands it to hinges and frame, metal relies on thermal stability. The fourth carries nothing and needs no exit.

4. Wall Thickness and Vent Area: How Far the Saving Goes

Eight millimetres matches the bulge a shell shows as pressure rises. With 12 mm ribs, section height does the work, since bending capacity climbs with its cube, so the wall can stop at 8 mm rather than 12 mm.

Explosion-Proof Case: black body open on polished stone floor, radial ribs inside the lid, foam tray holding circuit boards and coiled cables, meters at right

The panel chooses which face pressure leaves through. A 300 by 200 mm plate covers about a fifth of the side wall on a 1.2 m cavity, so the shell only survives the rise before the panel acts. Block it with a shelf and the panel stops existing. Six latches at 240 mm add four restraint points over two catches, and 2.5 N·m marked on each ends the guessing.

Saving exists only inside that set: three-high stacking under 120 kg allows a 7 mm wall, five high forces 16 mm ribs.

5. Three Costs Missing From the Quote

Tooling comes first: a vent plate needs its own insert, about 40% above a plain mould and near CNY 26,000, so below 200 units it outweighs the wall.

Inspection is second, at roughly 12 minutes a unit once wall, torque and panel gap are measured one by one. Lead time is third: 45 days against 20, and the 25 between them is stock capital. None shows in the unit price, yet all three decide what an explosion-proof case costs.

6. Four Steps to Recover the Difference

First, ask about the pressure source. If it can pressurise in normal use or in a fault, the cheap option stops being one.

Second, ask about the exit. Which face does the panel point at, and can that direction stay clear? If not, change structure.

Third, ask about records. Per-unit files push the requirement onto panel area, latch spacing and torque marks.

Fourth, ask about price. For the explosion-proof case, compare wall, panel area, latch count and lead time, four items and nothing else.

Conclusion

The price gap in an explosion-proof case sits in three visible places, and whether they earn their keep depends on the duty case, not the budget. Two of six situations need it; the rest are better served by smaller units, a hinged door, a stainless shell or a plain case. Settle pressure source, exit direction and record demand first, and the answer follows for any explosion-proof case.

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.