In a waterproof box standard, is pressure testing or immersion more important?

Answer: Pressure testing belongs to lots, immersion to type testing; pressure is fast and catches a missing gasket.

Why must gland torque be an inspection item?

Answer: Too little torque seeps along the thread, too much cracks it.

How is gasket compression calculated?

Answer: Cord diameter minus groove depth, divided by cord diameter. A 6 mm cord in a 4.5 mm groove gives 25 percent.

What if sampling finds one box with no gasket?

Answer: The lot is rejected regardless of Ac, since a missing part means the unit check failed.

How long should inspection records be kept?

Answer: Five years, with lot, cavity, torque value, pressure drop and inspector.

Waterproof Box Acceptance Standards: Items and Criteria

Quick answer: A waterproof box acceptance standard splits the word into measurable items: unit assembly checks, pressure drop, gasket compression, gland torque, IPX test conditions and sampling AQL. Each item needs a method and a threshold.

Three Inspection Layers Before Anything Else
Seal and Air-Tightness Thresholds
Ingress Ratings and Environmental Items
Dimensions and Fittings
Sampling and Rejected Lots
FAQ

1. Three Inspection Layers Before Anything Else

Every unit gets an assembly check: gasket in its groove, latch closed, gland torque confirmed. Every lot draws a sample for pressure and key dimensions. Type testing covers design at sign-off or material change.

A waterproof box is small and cheap, so plants settle for a glance at appearance, and leaks cluster in two places: a gasket that never seated and a cable gland never tightened.

Write the division into the inspection plan, or the plant drifts to testing everything, then to testing nothing.

Layer	Object	Main items
Unit check	Every box	Gasket seated, latch closed
Lot sampling	Every lot	Pressure drop, dimensions
Type test	Sign-off	IPX6 spray, IPX7 immersion

2. Seal and Air-Tightness Thresholds

Pressure testing is the most practical judgment for a waterproof box. Close and latch it, charge to 30 kPa, hold 60 seconds, accept a drop under 1.0 kPa. The negative method pulls to minus 8 kPa and allows 0.5 kPa of recovery.

Waterproof box: bright yellow box facing forward on a blue background, moulded top handle, two dark latches on the lid edge

A 6 mm gasket cord in a 4.5 mm groove closes at 25 percent, inside a 20 to 30 percent window. Material runs at 65 Shore A, harder than large-case rubber, because latches must spring back. Glands are torqued to 2.5 N·m, then held at 0.2 MPa water for 60 seconds without thread seepage.

Item	Method	Threshold
Pressure, both directions	30 kPa / −8 kPa, 60 s	≤1.0 / ≤0.5 kPa
Gasket compression	6 mm cord, 4.5 mm groove	20–30 percent
Gland torque and water	2.5 N·m, 0.2 MPa, 60 s	No thread seepage

3. Ingress Ratings and Environmental Items

For a waterproof box, IPX6 means 12.5 litres per minute at 100 kPa for 3 minutes from 2.5 to 3 metres, sprayed from four directions. IPX7 means one metre of water for 30 minutes, submerged, with the lid opened afterwards to check for standing water.

Thermal cycling runs from minus 25 °C to plus 55 °C, three hours at each end, six cycles. Salt spray is neutral, 240 hours at 35 °C, on metal only, so latches and screws show no red rust. UV runs 300 hours with ΔE under 3.0, and a 0.8 m drop onto six faces must not break the seal.

4. Dimensions and Fittings

Three dimensions matter: overall size within plus or minus 0.5 mm, mounting hole spacing within 0.3 mm, and lid-to-base gap no more than 0.2 mm. A box out of gap sits crooked on a panel and drags the seal with it.

Waterproof box: light grey box on a white surface, two black cable glands at the lower left, two front latches, one side handle

Hinges run 5,000 cycles with no sag beyond 1 mm, latches hold 150 N without releasing, and walls of a waterproof box measure 2.5 mm plus or minus 0.2 mm at six points. Colour stays within ΔE 2.0 and flash under 0.2 mm, with four markings: resin grade, ingress rating, month and cavity.

5. Sampling and Rejected Lots

Sampling follows ISO 2859-1, normal, single, level II. A lot of 151 to 280 boxes draws 32 samples, 281 to 500 draws 50, from different cartons.

Critical defects use Ac 0. Major defects run at AQL 2.5, giving Ac 2 and Re 3 at 32 samples; minor at AQL 4.0 gives Ac 3 and Re 4. A first failure allows a doubled sample, a second rejects the lot, and a lot that fails pressure testing may not be sorted and shipped.

Class	Examples	AQL	Ac / Re at n=32
Critical	Crack, missing gasket, seal failure	0	0 / 1
Major	Gland seepage, gap over 0.2 mm	2.5	2 / 3
Minor	Flash, ΔE over 2.0, marking	4.0	3 / 4

Conclusion

A waterproof box standard is not complicated; the work is pinning each item to a number: 30 kPa held for 60 seconds with a 1.0 kPa drop, 25 percent gasket compression, 2.5 N·m at the gland, 240 hours of salt spray without red rust, AQL 2.5 at Ac 2. With those thresholds on the inspection card, a missed assembly step stops inside the plant, which is what a waterproof box standard buys.

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.