Tough boxes for tough places

Finding an enclosure that can survive in difficult environments that can cope with wet and/or corrosive environments, sunlight and generally harsh conditions can be difficult.

IP ratings of boxes range from IP65 to IP66, which means that they are dust tight and can withstand jets of water sprayed at them. Submersion for long periods at depth and varying pressures will define the need for an IP67 or IP68 enclosure.

For most quick, near surface, temporary submersions, rainstorms, hose cleaning, etc, an IP65 or IP66 rated box will be fine.

Materials vary between ordinary diecast aluminium, thick-walled diecast aluminium, stainless steel, polycarbonate, glass reinforced polyester and flame-retardant ABS plastic.

Environments are usually harsh in more than one aspect, hence a material must be able to cope with a combination of undesirable factors like high UV, salt/sand laden winds and heat.

Anyone who has looked at structures by a beach will have seen signs of rust and the bubbles of corrosion.

Ability to withstand a particular situation will also be influenced by the stress that is to be placed on the material. An enclosure in a sheltered position is going to be sturdier than one that is constantly being showered with debris - all other factors being equal.

Here is a quick summary of materials and their use in some tough situations.

Aluminium is suitable for indoor and outdoor applications, marine environments as well as areas with solvents, petrochemicals, some acids and most sulfates and nitrates. Generally, resistance to corrosion is improved if painted.

Hammond Electronics has the 1590 series, a thin-walled diecast aluminium enclosure ranging in size from the 1590H at 52.5 x 38 x 31 mm to the largest at 187.5 x 187.5 x 67 mm. These boxes are all available as waterproof with an IP65 rating. Most are available with flanged lid or base, painted or unpainted versions.

The 1590Z series is a thick-walled aluminium ranging in size from 50 x 45 x 30 mm to 360 x 160 x 90 mm. IP65 rating is available in painted or unpainted versions. These are suitable for high impact situations like those in mining, construction and the transport industries.

Stainless steel is suitable for indoor and outdoor applications, food/water treatment areas and good for most environments.

Type 316 aluminium has 2% molybdenum content and is more resistant to saline environments than Type 304.

Stainless steel enclosures are not cheap but they supply a need where no other material may be suitable for an application.

Two enclosure types made of stainless steel are available.

The EJ (Eclipse) series ranges in size from 150 x 100 x 100 mm to 400 x 360 x 250 mm. They are IP66 rated and made from 304 stainless steel.

The EN (Eclipse) series ranging in size from 300 x 300 x 150 mm to 910 x 910 x 300 mm is available in 316 stainless steel and is rated IP66.

Polycarbonate is one of the strongest of the non-metal materials used for enclosures. Ratings for hardness, tensile strength and elongation and resistance to impact and heat are higher than for most other plastic materials.

It is also flame resistant - UL94-V0. It is, however, susceptible to chemicals, especially organic solvents. Its other disadvantage is that it is more expensive than other plastics.

Glass reinforced polyester in the smaller enclosures is normally hot compression moulded resin with at least 20% addition of fibreglass by weight.

Additives can ensure flame resistance ie, UL94-V0 rating.

The surface of fibreglass enclosures may be affected by weathering but this does not affect the physical strengths of the enclosure.

It is susceptible to attack by ketones, esters and alkalis. GRP gives strength and lightness and is suitable for outdoor applications, particularly in saline or oily environments.

The company has the 1590ZGRP series that consists of thick-walled IP65 rated boxes for use where a robust non-metallic enclosure is required. They range in size from 80 x 75 x 55 mm to 260 x 160 x 90 mm.

The PJ series is designed more for electrical/electronic use and available with a variety of lid types. Rated IP66.

Flame-retardant ABS plastic is suitable for indoor use where flaming may occur from electrical shorting. UL 94-V0 rating ensures that the plastic used will not burn for longer than 10 seconds and will not emit burning particles.

It is not advisable to use it where ambient heat exceeds about 60°C, ie, the dashboard of a car, as melting/distortion may occur.

It does have resistance to alkalis, diesel oil and salt water.

The meet this demand Hammond has the 1594xWBK series, a thick-walled flame-retardant black enclosure where a sturdy low cost housing is required. Rated IP65. Sizes range from 56 x 56 x 40 mm to 167 x 107 x 65 mm.