What IP rating does an outdoor case need?

Answer: Match it to depth and time. Washdown takes IP67, one metre for thirty minutes; wading needs IP68 with the two metre, one hour condition in writing.

Is a pressure valve really necessary?

Answer: At altitude or in strong sun, yes. A 30 °C swing gives 0.2 bar and lifts the opening force past 200 N.

Will an outdoor case go brittle in three years?

Answer: It depends on the compound. After 1000 hours of xenon, strength should hold above eighty percent; unstabilised polypropylene often drops below sixty.

Answer: At 22 kg over several hundred metres, take 100 mm wheels; under 15 kg with stairs, straps work better.

Are dark outdoor cases more prone to sun damage?

Answer: Yes, 15 to 20 °C hotter at the surface and faster to age. At altitude, check for carbon black or a hindered amine stabiliser first.

How to Choose an Outdoor Case: Five Checks in Order

Quick answer: An outdoor case is selected by ingress protection, gasket and pressure valve, UV and thermal cycling, then wheels and harness. The rating is the item most often overstated, because one IP67 can hide two different tests.

How to choose an outdoor case: five checks in order
Ingress protection: two numbers behind the IP code
UV and thermal cycling: what shows in year three
Gasket and pressure valve: where the closing force goes
Wheels, harness and field access
FAQ

1. How to choose an outdoor case: five checks in order

An outdoor case lives in weather: sun at sixty degrees, a night at minus thirty, rain in between. Work backwards — water first, then whether the lid opens, then how the plastic ages.

Choose on wheels first and you buy thin walls with a narrow gasket; two kilometres later the wheels are fine and the inside is damp.

Check	Decide first	Typical	If wrong
Ingress protection	depth and time	IP67, 1 m for 30 minutes	water inside
Gasket and valve	swing, altitude	valve at 0.15 bar	lid sucked shut
UV and cycling	years in sun	1000 hours xenon	brittle in year three
Wheels and harness	weight, distance	100 mm, 22 kg	bent axle
Locks and access	last	two latches	slow on site

One item never appears in a brochure: the lid overlap. Below 8 mm driving rain climbs the joint; above 15 mm the rim stiffens.

2. Ingress protection: two numbers behind the IP code

IP67 means one metre of still water for thirty minutes. IP68 is agreed between buyer and supplier, commonly two metres for an hour.

Outdoor case: an olive-green case standing upright against a green gradient, moulded top handle, two pale side latches and small wheels at the base

Ask about gasket life, not the first dip: once compression set passes twenty percent, the second immersion leaks. Retest after 200 opening cycles.

Rating	Test condition	Typical use	Failure
IP65	jets from all directions	short rain	seeps under standing water
IP67	1 m still water, 30 minutes	drops, washdown	leaks as the gasket ages
IP68	2 m for 1 hour, agreed	wading, rafting	distortion opens the joint

Pressure also bends the body: at 4.5 mm the side panel bows about 1 mm at one metre, changing gasket compression, while a thin wall bows 2 mm.

3. UV and thermal cycling: what shows in year three

UV does not break a case on the day; it makes plastic brittle over years. A thousand hours of xenon is about two years outdoors, judged on colour within ΔE 3 and strength above eighty percent.

Thermal cycling is harsher than steady heat: ten cycles from −30 °C to +60 °C, two hours each, diagonal change within 1.5 mm.

Colour counts too: a dark case runs 15 to 20 °C hotter and ages faster. At altitude the additive package matters more than the shade.

4. Gasket and pressure valve: where the closing force goes

The gasket keeps water out; the valve lets you back in. A 30 °C rise or a 2000 m climb gives about 0.2 bar, and the opening force climbs from 80 N to over 200 N.

Outdoor case: olive-green body closed horizontally, two black latches at the front, recessed side handles, rubber corner caps, light grey background

Set the valve to open at 0.15 bar: lower trips in transit and lets dust in, higher leaves the lid hard work.

Latch force only counts if it reaches the gasket. Two latches should leave compression even within ten percent; a 0.2 mm feeler should not enter deeper than 20 mm.

5. Wheels, harness and field access

Wheels fail first because they take every impact. A 22 kg load on 100 mm wheels over 50 km of gravel should keep the axle straight.

A three-stage handle at 900 mm with no more than 3 mm of play stays put on gravel. An empty weight of 5.8 kg is the ceiling for a wheeled case.

Shoulder straps suit loads under 15 kg and the back panel needs channels. Side handles are accepted at 25 kg static.

Conclusion

The chain runs one way: both IP figures against the water the case will meet, a valve for the temperature and altitude swing, a UV package for the years in sun, then wheels or a harness by weight. Get depth, differential and sunlight right, and an outdoor case still closes cleanly in its third year.

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.