Revealing Enclosures

Design flexibility, lightweight materials, and environmental concerns are among factors most influencing purchase and use of these protective structures. Dick Johnson reports.

"To protect and serve" appears on

countless police and public safety

vehicles in the United States.

Although taken for granted by many,

it is a serious motto for those in law enforcement,

fire protection, and security fields. This same motto

could appear on industrial enclosures as well. Their

function is also to protect and serve. It is a job

taken very seriously by enclosure manufacturers:

providing users with a way to protect electrical and

control components from a variety of problems,

including environmental contaminants, moisture,

temperature changes, shock/physical damage, and

tampering. Enclosures also serve as a terminus and/

or mounting site for electronic or control devices and

their wiring.

The right protection

According to a recent on-line survey by Reed

Research Group and Control Engineering magazine,

enclosures are widely applied. The majority (51%)

are used for in-plant requirements , with 30% used

for OEM (resale) requirements. The remaining 19%

were bought for both in-plant and OEM uses.

Primary applications vary widely

(see accompanying graphic). Responses put

supervisory control and data acquisition (SCADA)

applications at the top of the list, followed closely by

machine control/CNC and motion control/robotics

applications, which are common (almost generic) in

discrete manufacturing operations. Continuous and

combined continuous/batch processes also account

for a large share of the applications, coming in

fourth and seventh in the list of uses. Compared to a

year earlier in 2005, most applications remained in

essentially the same or close to the same order.

Although protection varies with the item

(workstations, PLCs, DCSs, instrumentation,

HMIs), respondents listed the following attributes

as necessary when specifying an enclosure

(in descending order): dustproof,waterproof, washdown

resistance, A/C cooling capability, EMI/RFI

shielding, office-level/non-hardened capabilities,

explosion-proof, heating capability, and UV

protection. Dustproof, waterproof, wash-down

resistance, cooling, and EMI/RFI resistance were

invariably tagged for typical in-plant uses. Non-hardened

enclosures were most used in standard

computer/workstation applications.

Applications were further broken down

by enclosure environments/location. The majority

found their way to the plant floor, which included

sanitary/wash-down and hazardous/dusty

environments. Less than half that amount were used

in an office environment and a small number (less

than 2%) ended up out-of-doors.

Respondents chose availability from stock and

cost as the most important factors when selecting

enclosure suppliers. Other criteria affecting choice

includes ease of use, the ability to customize (for

example, add cutouts, colors, rack, rack locations),

modular design, and the availability of technical

support. The only change in the listing from previous

surveys (and eclipsing tech support for the first time)

was an increased preference for modular enclosure

design.

A modular enclosure system is designed to be

flexible and easy to expand in capabilities or size.

According to Troy Miesee, Industrial Business and

Product Development manager at Rittal Corp., “With more and more companies providing

to the global market, it has become

important to be able to adapt a standard

design, whether it be an enclosure or a

complete system, to the application or

requested need. These designs can easily

have accessories such as shelves, brackets,

and mounting panels added, as well as the

ability to bay multiple enclosures together to

increase the size of the system.”

Modularity allows designers and builders

to configure and build various systems

from a standard platform, which can

reduce engineering and assembly time and

enclosure inventory. Bill Geese, Product

Manager for CCS-Inc. suggests another

reasons for the rise in the popularity of

modularity: “In most production-floor

system rollouts, the enclosure is seen by

the customer as the component with the

least risk. For this reason, the selection of

an enclosure system is not attended to until

late in the project, when the requirements

are fully understood. By then the project

schedule does not allow for customization

in the traditional sense, so customers turn to

enclosure lines that support customization

through modularity,” he says.

The survey says the greatest percentage

of enclosures are specified in carbon steel

or stainless steel. These materials shared

the lead in earlier surveys. Most recently,

aluminum enclosures took over third place

from fiberglass/engineered plastic for the

first time.

Lighten up with aluminum

Any number of applications require the

rigidity, strength, and fire-resistance of

steel enclosures. Although stainless steel

can provide the corrosion protection that

carbon steel cannot, both are

heavy and may be ill-suited to

an application when larger size,

mobility, or ease of installation

are required. Aluminum

offers lightweight construction

(similar to both fiberglass and

engineered plastics), with many

of the benefits of steel.

The high cost of stainless

steel and fiberglass/plastics

has also made aluminum more

attractive. Rittal’s Miesse

says his company has seen

an increase in requests for

aluminum. “However, Rittal

sees this only as a next best

alternative to stainless and fiberglass when

price is a major issue,” he adds.

CCS-Inc.’s Geese adds that the rising cost

of petroleum products present in most, if

not all, non-metallic solutions may also be

partly to blame. “Couple this with the fact

that it is very difficult and costly to do true customization in non-metallic solutions, and

one can easily accept that aluminum has

become more popular than non-metallic

enclosures,” he adds.

For enclosures used indoors, this survey

asked about respondents’ familiarity

with RoHS (Restriction of Hazardous

Substances) requirements affecting

enclosures and consoles. Most (>90%)

said they were not very familiar or not

familiar at all with them. According to

Ron Rotondo, product manager for

Hoffman, RoHS relates to enclosure

construction materials, specifically to

corrosion-resistant plating (hexavalent

chromium, for instance) and nonmetallic

materials (some compounds in fiberglass

materials). RoHS regulations restrict the

use of some substances in manufacturing

to try to prevent hazardouns material from

leaching into the environment.

Environmental concerns

When properly disposed of, RoHS-compliant enclosures have limited

environmental impact. The legislative

environment around RoHS is changing.

The European Union RoHS Directive

took effect July 1, 2006. China and

California are both considering similar

directives. Users’ knowledge varies with

business environments. Machine builders

that export to Europe have already been

impacted. Additional legislation will force

everyone to become familiar with such

regulations. Rotondo points outs that

Hoffman’s online catalog marks compliant

products with a RoHS emblem. “Currently,

we are 92% compliant for all products.

Additionally, customers will be able to

request and download RoHS compliance

certificates to build their technical file

through our Website in early 2007,”

he adds.

Users may take enclosure capabilities for

granted because most products have met

changing market needs seamlessly, living up

to the motto: protect and serve. CEA

The high cost of stainless steel and fiberglass/plastics has made aluminum more attractive

RoHS relates to enclosure construction materials