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IDE GENERAL PURPOSE

ENCLOSURESGENERAL PURPOSE ENCLOSURES

THIRD EDITION

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INDEX

Introduction 2

The Right Enclosure 3

IP Ratings (Ingress Protection) 4

Mechanical Impacts (IK Code) 7

Materials 8

Surface Finishes 13

Construction 16

Internal Fittings 18

Lock & Hinges 20

Lifting Arrangements 21

Earthing & Bonding 23

Gaskets 24

Compartmented Enclosures 25

Environmental Considerations 26

Hazardous Areas 28

Thermal Management 32

RFI/EMI Shielding 34

Installation & Maintenance 35

Standards see GAMBICA website

Members of GAMBICA Enclosures Group see GAMBICA website

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INTRODUCTION

This GAMBICA handbook is intended as aguide to specifiers and users of Enclosuresfor electrical and electronics applications. It has been produced recognizing that theEnclosure can form the most important partof any system. It protects the equipmentwithin from the effects of the environmentand the environment itself, including people,from the effects of the equipment.

This handbook has been produced bymembers of the Enclosures Group ofGAMBICA, Association for Instrumentation,Control, Automation and LaboratoryTechnology. GAMBICA's Enclosures Groupis the UK's professional organisation formanufacturers and suppliers of Enclosureproducts. Members aim to apply the mostup to date industry standards in design,quality and production, to promote theprofessional use of Enclosures throughoutindustry and to support development ofinternational standards for Enclosuresthrough participation in StandardsCommittees.

In addition to Enclosures, GAMBICA coversIndustrial Control Components and Systems,Power Electronics, ProgrammableControllers and Systems Integrators,Hazardous Area Equipment, LaboratoryAnalytical and Nucleonic Instruments,Electronic Test and Measurement andAutomatic Test Equipment, ProcessMeasurement and Control Instruments and Systems, Environmental PollutionMonitoring and Control, Fluid Measurementand Control Valves. Guides to member'sproducts in some of these areas areavailable on request.

A list of members of GAMBICA'SEnclosures Group, together with a productguide to suppliers of various types ofenclosures, can be found on the web atwww.gambica.org.uk together with hot links,to member's web sites. Contact themembers directly for details of theirproducts and applications.

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THE RIGHT ENCLOSURE FOR YOURAPPLICATION

CCoonnssiiddeerr ::

� Where it will be installed

� What it will be used for

� How it will be mounted

� The type of environment

� The degree of ingress protection required

� The weight of internal equipment

� Aesthetics

� The risk of physical damage

� Internal accessibility

� Which standards apply

� The maintenance requirements

� EMC or protection

� Controlling the operating temperature

� Accessories

� Security requirements

� Safety requirements

Standard general-purpose enclosures normally range in size from around 50 mm square up toa maximum height of around 2400 mm. It should not be difficult to find an enclosure to fiteven the most awkward site, or to house the required equipment with maximum economy of space, avoiding the expense of unnecessarily large enclosures.

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IP RATINGS - INGRESS PROTECTION

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The IP code defined in the standards BS EN 60529: 1992, EN 60529: 1991, IEC 60529: 1989Specification for degrees of protection provided by enclosures (IP code) provides a means ofspecifying the ability of an enclosure to protect its contents from external objects. Thestandard applies to enclosures for electrical equipment with a rated voltage not exceeding72.5 kV.

The standard provides Definitions, Designation and Requirements for degrees of protectionprovided by enclosures for electrical equipment for:

protection of equipment inside the enclosure against ingress of solid foreign objects; protection of persons against access to hazardous parts inside the enclosure;protection of equipment inside the enclosure against the ingress of water.

The following extract from BS EN 60529: 1992 is reproduced with the permission of BSI andexplains the arrangement of the Code, which consists of 2 numerals and optional letters.Complete editions of the standard can be obtained by post from BSI Customer Services, 389 Chiswick High Road, London W4 4AL.

4.1 Arrangement of the IP Code

IP 2 3 C HCode letters (International Protection)

First characteristic numeral (numerals 0 to 6, or letter X)

Second characteristic numeral (numerals 0 to 8, or letter X

Additional letter (optional)(letters A,B,C,D)

Supplementary letter (optional)(letters H,M,S,W)

Where a characteristic numeral is not required to be specified, it shall be replaced by theletter �X� (�XX�) if both numerals are omitted).Additional letters and/or supplementary letters may be omitted without replacement. Where more than one supplementary letter is used, the alphabetic sequence shall apply. If an enclosure provides different degrees of protection for different intended mountingarrangements, the relevant degrees of protection shall be indicated by the manufacturer in the instructions related to the respective mounting arrangements. Details for the marking of an enclosure are given in Clause 10.

4.2 Elements of the IP Code and their meanings

- A brief description of the IP Code elements is given in the following chart. Full details are specified in the clauses indicated in the last column.

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Code letters IP

Firstcharacteristicnumeral

Secondcharacteristicnumeral

0123456

Against ingress of solidforeign objects

(non-protected)≥ 50 mm diameter≥ 12.5 mm diameter≥ 2.5 mm diameter≥ 1.0 mm diameterdust-protecteddust-tight

Against accessto hazardousparts with(non-protected)back of handfingertoolwirewirewire

C1.5

012345678

Against ingress of waterwith harmful effects(non-protected) vertically drippingdripping (15° tilted)sprayingsplashingjettingpowerful jettingtemporary immersioncontinuous immersion

C1.6

Additional letter(optional)

ABCD

Against accessto hazardous parts withback of handfingertoolwire

C1.7

C1.8Supplementary informationspecific to:

High voltage apparatusMotion during water testStationary during water testWeather conditions

HMS

W

SupplementaryLetter(optional)

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4.3 Examples for the use of letters in the IP CodeThe following examples are to explain the use and arrangements of letters in the IP Code.For more comprehensive examples see Clause 9.

IP44 - no letters, no options;

IPX5 - omitting first characteristic numeral;

IP2X - omitting second characteristic numeral;

IP20C - using additional letter;

IPXXC - omitting both characteristic numerals, using additional letter;

IPXlC - omitting first characteristic numeral, using additional letter;

IP3XD - omitting second characteristic numeral, using additional letter;

IP23S - using supplementary letter;

IP21CM - using additional letter and supplementary letter;

IPX5/IPX7 - giving two different degrees of protection by an enclosure against both water jets and temporary immersion for �versatile� application.

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When deciding which IP rating to specify for a particular application,care should be taken not to over specify as the cost of an enclosureoften increases with the rise in IP rating.

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MECHANICAL IMPACTS (IK CODE)

The IK code defined in the standard BS EN 50102: 1995 Degrees of protectionprovided by enclosures for electricalequipment against external mechanicalimpacts (IK code) provides a means ofspecifying the capacity of an enclosure toprotect its contents from external impacts.

Before the advent of EN 50102 a thirdnumeral was added to the IP code toindicate the level of impact protection - e.g.IP66(9). Non standard use of this systemwas one of the factors leading to thedevelopment of the standard, which

uses a separate two numeral code todistinguish it from the old differing systems.The standard came into effect in October1995 and conflicting national standards hadto be withdrawn by April 1997.

EN 50102 specifies the way enclosuresshould be mounted when tests are carriedout, the atmospheric conditions that shouldprevail, the number of impacts (5) and their(even) distribution, and the size, style,material, dimensions etc. of the varioustypes of hammer, designed to produce theenergy levels required.

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IKcode IK00 IK01 IK02 IK03 IK04 IK05 IK06 IK07 IK08 IK09 IK10Impact energy (joules) * 0.14 0.2 0.35 0.5 0.7 1 2 5 10 20

To test for resistance to higher impacts an energy of 50 joules is recommended

IK code and impact energy (Values changed in Amd 1: 1998)

Impact test characteristics

IK codeImpact energy(joules)R mm (radius of striking element)MaterialMass kgPendulum hammerSpring hammerFree fall hammer

IK00*

*

*****

IK01 to IK05<1

10

polyamide 1)

0.2YESYESNO

IK061

10

polamide 2)

0.5YESYESNO

IK072

25

steel 2)

0.5YESYESYES

IK085

25

steel 2)

1.7YESNOYES

IK0910

50

steel 2)

5YESNOYES

IK1020

50

steel 2)

5YESNOYES

* not protected according to the standard

1) R100 Rockwell hardness according to ISO 2039/2

2) Fc 490-2, Rockwell hardness according to ISO 1052

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MATERIALS FOR ENCLOSURES

A variety of different materials are used inthe manufacture of enclosures. Those incommon use are listed below, together withtheir advantages and limitations. Choice ofmaterial clearly has a major bearing on thedegree of protection afforded by theenclosure.

Mild SteelMild steel is the most widely used materialfor general-purpose indoor or outdoorapplications. Standard enclosures aremanufactured from steel up to 2 mm thick.

Mild steel sheet is an ideal medium forfabrication, hole punching and forming intoshape. It is easily welded to form apermanent bond and component parts areeasily joined together. The two mostcommon grades of steel used in theenclosure industry are CR4 and CR2.

CR4 is easy to form into angles andcommonly used in the construction of wallmounted and floor standing enclosures.CR2 is a ductile material, which lends itselfto be pressed into shape reducing the needfor welding. Pressed enclosures are limitedto smaller sizes.

Different gauges (thickness) are availablefrom 0.75 mm. However, it is not alwaysthe thickness of the material that determinesthe strength of the enclosure but rather theconstruction and how the material isformed. For example, the position andnumber of return folds makes a significantdifference. Good design may allow for areduction in enclosure cost and weight.

Stainless SteelStainless steel is commonly used in areaswhere hygiene, cleanliness or corrosionresistance are important. Grades 304 and316 are the most common and a thicknessof 0.75 mm to 2 mm is suitable for mostenclosure applications. Stainless steelenclosures are an effective protectionagainst more aggressive environments. Care should be taken to ensure the correctgrade of material is selected.

Grade 304 is used for standard stockenclosures covering the majority of industrialapplications, in particular for the food,beverage and dairy industries. Grade 316 is a more expensive option, covering thoseapplications where the enclosure is to besited in a highly corrosive environment, inparticular, salt laden atmospheres.

Advantages

� May be used in many aggressive environments

� Provides excellent corrosion resistance

� May be less expensive than surface treated mild steel

� Does not deteriorate when subjectto exposure to sun light (ultra-violet radiation)

� Alternative grades and finishes available to enhance appearance and corrosion resistance

� Low maintenance

Disadvantages

� More expensive than mild steel� More difficult to work

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Pre-Plated SteelZinc is the most common pre-plated steelfor enclosures and is usually available in thesame thickness and size as mild steel.

It is often used in the manufacture of EMCenclosures.

Pre-CoatedThere are many plastic coated steels whichare typically used in the production ofelectronic housings and racks.

Aluminium Aluminium is used in either sheet, extruded,sand or die cast forms. A thickness of 1mm to 4 mm is typical.

Die casting is the most common methodused in the production of enclosures.Molten aluminium is forced into a steel dieat high pressure by the action of hydraulicrams. The process produces componentswith good mechanical properties and closetolerances.

LM6 (Al Si 12) is a medium strength castingalloy with excellent foundry characteristics,high ductility, impact strength and shockresistance, together with high resistance tocorrosion. The alloy can be used to

produce castings of intricate shape and withthin varying wall thicknesses. It is howeverdifficult to machine and results in rapid toolwear caused by its high silicon content.

Corrosion ResistanceThe corrosion resistance of aluminium andits alloys is due to their ability to form a thinbut protective coating in the presence ofoxygen or water. This oxide, unlike rust onsteel, is continuous and adherent. Shouldthe surface be damaged, the oxide film isimmediately reformed. In aggressiveenvironments localised corrosion may occurbut structural integrity is unlikely to beaffected.

Where two dissimilar metals are in electricalcontact with each other in the presence ofan electrolyte, they adopt a potential and acurrent flows in the electrolyte from themetal having the negative potential to thepositive. This results in increased corrosionof the former metal; an important factorwhen components such as fixings or cableglands made of other unprotected metalsare used with aluminium enclosures.

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Aluminium Enclosures in Hazardous Areas The use of aluminium alloys for someapplications of equipment is controlled bylegislation derived from the concern ofincentive sparking achievable from theimpact between aluminium and rusty steel.BS5501: Parts 1-9 Atmospheres. Generalrequirements restrict the use of aluminiumin enclosures for mining applications toalloys containing not more than 6%magnesium and titanium. For potentiallyexplosive atmospheres other than mines,the alloy must not contain more than 6% byweight of magnesium but with no limit onaluminium content.

Use in Marine EnvironmentsThe correct choice of aluminium alloy isessential and it is recommended that onewith a higher silicon content is selected.Avoid possible corrosion caused byelectrolytic action from dissimilar metals.Insulation materials should be used forseparation purposes when installing theboxes on steel structures. Metal parts lyingoutside the enclosure, such as fixing screws,should be manufactured from austeniticstainless steel. Cable glands made of brasswith chrome or nickel finish give no causefor concern.

Cast IronThe use of this material for enclosures ismostly restricted to outside use, where highstrength and protection from vandalism arerequired. It is also used for enclosures inhazardous areas where there is a risk ofexplosion.

Cast iron is not a single material but a termapplied to a large family of materials. Castirons have many attributes, some of whichare of particular value for the production ofenclosures for electrical and electronicequipment. Foremost is their high strengthand fire resistance when compared withmaterials such as mild steel or GRP. Thisenables them to be used in severe serviceconditions, such as in process plants andmines. Ductile irons are particularly valuablewhen the enclosures have to be flame-proofor explosion proof. Of all the cast metals,cast iron has the best foundingcharacteristics, which means that it is wellsuited for making components, which mustbe pressure-tight.

A wide range of cast irons is available foruse in both benign and aggressiveenvironments. Further protection mayreadily be given through the applications ofcoatings, such as hot dipped galvanising orelectro-plating. Alloying allows good lowand high temperature performance to beachieved, whilst maintaining all theadvantages of a cast product.

The casting process is a most energyefficient and cost effective way of makingcomplex-shaped components, includingenclosures. It offers the designer almostlimitless freedom to place metal where it isrequired and is suitable for producing bothone-offs and long production runs, and bothsmall and large components.

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enclosure with an ABS base and apolycarbonate lid. When exposed to flame,it is not necessarily self-extinguishing.

GRP (Glass ReinforcedPolyester)The good mechanical properties of thismaterial include insulation, strength, hardnessand stability over the temperature range -50°C to + 150°C. Its self-finishing qualityand durability have widened its range ofapplications.

The electrical advantage of GRP is that it isan excellent insulator and can offer doubleinsulation properties. Its use reduces the riskof electric shock in the event of impact.Where busbars are being fitted, use of GRPenclosures may allow reduction of theclearance between the bars and theenclosure, offering benefits of size reduction.

It should be noted that when any work iscarried out on the enclosure, cut or exposedsurfaces, holes or edges should be treated toavoid moisture ingress. Damage to thesurface may also result in moisture ingressinto the material through the exposed glassfibres.

GRPs with a range of properties are available.Manufacturers can supply more detailedinformation on the grades of materials usedin the construction of individual enclosuresand the results of tests to which they havebeen subjected. Engineering specifications,details of mechanical, electrical and physicalproperties, as well as flame and chemicalresistance are normally available.

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Plastic MaterialsPlastics are capable of providing a toughdurable product of excellent appearance.The properties of a number of materialsmay be varied by means of additives. Thefollowing descriptions relate to standardmaterials and for further information onperformances in a particular situation, themanufacturer should be consulted.

PolycarbonateMany different types are used for producingenclosures and with the correct choice, itmay be used in a variety of locations.

This material has good impact resistancewhich varies only marginally over thetemperature range - 50°C to + 120°C. Inthe long term it should not be exposed totemperatures higher than 80°C. Outdoorexposure may cause some loss ofmechanical strength and yellowing inappearance. An agent to combat the effectsof ultraviolet light can be added in themanufacture of the raw material. Exposedto flame it is self-extinguishing.Polycarbonate releases no toxic gases onburning. Contact with methyl alcohol,alkaline solutions, amines, gaseous ammoniaand its solution should be avoided.

ABS (Acrylonitrile Butadiene Styrene)Usually produced in the same designs aspolycarbonate enclosures, ABS is a cheapermaterial with characteristics similar topolycarbonate but not suitable for suchextremes of temperature and having alower impact strength. ABS andpolycarbonate may be combined offering an

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In its unfilled state - without its glass fibres,polyester is brittle but offers crystal cleartransparency, making it suitable for windowsor clear fronted enclosures. It may bewiped clean with soap and water. If adetergent is used, it should be rinsed wellwith clean water: Solvents and abrasivesshould not be used. Deep scratches are noteasily removed and should be filled.

GRP is resistant to mineral acids, manyorganic acids, oxidants and reducing agents,neural and acid salt solutions, greases andoils, and some alcohols. Resistant, does notmean that it is entirely impervious - over aperiod of time, for example, some machinetool oils can affect its integrity.

PVC (Poly Vinyl Chloride)PVC is used for moulding small plasticboxes. It has excellent resistance to mineralacids (both dilute and concentrated), alkalisand detergents. Resistance to alcohol-basedsolvents is good but poor to ketones,aromatic bases and hydrocarbons. Althoughit is a self-extinguishing material, PVC doesgive off toxic and corrosive gases whenburned. PVC has a low UV resistance andcan be brittle.

NylonNylon is used for moulding small boxes andcan become brittle in dry atmospheres. Itcan be affected by moisture and has poorresistance to acids although good resistanceto alkalis.

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SURFACE FINISHES

The type and quality of finish required on anenclosure depends very much on itsultimate environment and application.Other considerations are appearance andlife expectancy.

Is the enclosure to be used indoors oroutside? Within these two areas there arestill many variations. Indoors may mean afarm building, a dairy, a chemical plant, apower station. Outdoors can meananything from the North Sea to tropicalAfrica, with many other climates andenvironments between.

How important is appearance, not just oninstallation but over the longer term?Where the enclosure is strictly functional,the fading of colour may not be a cause forconcern. Scratches can easily be retouchedwith standard paint. In another applicationscratch resistance may be vital to avoid ashabby appearance or prevent corrosion.

Manufacturers offer a variety of treatments,some as standard, others as specials.

No Additional FinishWhere the material of the enclosure has itsown, suitable �natural� finish, no furthertreatment is necessary. This eliminatesmaintenance costs. An obvious example isstainless steel, brush polished for a grainedfinish or shot-blasted for a satin finish, bothof which are intended not to show fingermarks, or electro-polished for a higher shine.Because of its natural corrosion resistance,glass reinforced polyester needs noadditional finish.

It is important that enclosuressupplied primed or otherwise in needof further treatment are properlyfinished before they are taken intoservice. Not to do so is falseeconomy.

Aluminium For industrial use aluminium enclosures arenormally painted. They may be anodised or'alochromed' but these finishes are not veryhard and scratch easily. Anodised finish isnon-conductive whereas alochrome isconductive. Other forms of treatment areavailable.

Pre-Treatment for PaintingPaints suitable for protecting steel aregenerally suitable for aluminium, therequirements being that the paint be lead-free to avoid galvanic attack of aluminium.

The presence of air-formed aluminiumoxide on the surface can result in poor paintadhesion. One method of addressing this isto use an etch primer containing phosphoricacid and zinc chromate. An alternative toetch-primers is a conversion coating. This isproduced from solutions containingchromates and either fluorides orphosphates applied by dipping thecomponent in hot solutions.

Paint with special properties such as stovedfactory-applied polyurethane paint providesincreased wear and scuff resistance. Plasticcoating of either thermo-setting or thermo-plastic type can be used but good pre-treatment to ensure adhesion is necessary.

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Metal spraying provides a high quality finishand protection of welded joints. Tin andzinc coatings are used to improve theelectromagnetic shielding effectiveness ofthe enclosure.

AnodizingThe anodizing process consists of convertingthe surface layers to a hard oxide coating byelectrolytic means. For maximumprotection, the thickness applied should be25 microns. Anodizing is of benefit whereappearance is required to be maintained andweathering prevented.

Stainless SteelA wide range of finishes are available:

Mechanical PolishingThe products are available in grained(brushed) or glass bead (satin) finish.

ElectropolishingProduces an exceptionally bright lustre andimproved evenness of the surface byimmersion in an electrolytic bath.

CoatingsStainless steels are durable and resistant tocorrosion. They will however, acceptchemically produced coatings, vitreousenamels and conventional paint.

SteelVarious methods are used, depending uponthe location and duty of the enclosure.

Some manufacturers still prefer traditionalwet paint. Acrylic, polyurethane, and someunspecified types are all offered. Theirdurability depends upon a number of factors

such as the preparation procedure, type of paint, and number of coats applied.

In recent years many manufacturers haveswitched from wet paint to thermosettingpowders (powder coating) which offerprotection against a variety of environments.Typically, powder coating film thickness is 60-80 microns and does not normally require aprimer or undercoat. The powder is appliedto the chemically prepared surfaceelectrostatically and the object passes directlyinto the curing oven. It then liquefies to givea continuous uniform bonded finish.

Powder can be divided into three categories;polyester, epoxy and epoxy/pol. Polyesterpowder should be specified whereprotection against ultra-violet light is required.Epoxy powder should be specified whereprotection against mechanical damage orchemicals is required although it should benoted that this surface will quickly lose itsgloss and deteriorate to leave a dustyresidue. Where resistance to all of theabove is required a hybrid referred to asEpoxy/Pol is available which offers goodgeneral protection in the majority ofapplications.

Off the shelf, powder coatedenclosures are usually finished in grey (RAL 7032) but they can beoverpainted using two pack air drying finishes.

For more severe, wet or corrosiveenvironments, zinc coating by spray or dipcan be used but this is dependent on thethickness of the material as processdeformation can often occur.

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Iron or phosphate can be applied in anumber of film thicknesses with zincgenerally giving the best protection.

The majority of enclosure manufacturers donot recommend the use of a hot-dipgalvanising process because distortion canoccur.

ColoursProducers of steel enclosures tend to offerthe same basic colours. This has anadvantage to users in that they can mixequipment from different manufacturers andstill preserve a colour scheme. However,care must be taken as shades and texturesmay vary slightly. Special colours aregenerally available, but may incur a surchargeand a delay in supply.

Most manufacturers have highly automatedpainting lines geared to standard finishes.Leaving an enclosure unfinished may causean interruption in the normal process andtakes time. Hence the anomaly that aprimed enclosure may cost more than a standard paint finish.

The economic moulding of plasticenclosures in non-standard colours demandslong runs. Typically this is based

on a minimum quantity of mouldingmaterial.

If an alternative to the self-colour injectionmoulded plastic enclosure is required, or atextured finish, then paint can be used inaccordance with the manufacturer'srecommendations. Compression mouldedGRP can be painted with two-packpolyurethane paints but surface preparationto form an adequate key can be expensive.

Colour finishes can be provided to either BSor RAL colour standards, with additionalquantities of the appropriate paint (e.g. RAL7032 grey) available in an aerosol or tin.Colour charts are produced by paintmanufacturers.

Note that BS and RAL colour standards arenot fully cross-referenced.

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CONSTRUCTION

There are many differing types of enclosureconstruction. The list below gives someindication of the construction techniques.

DesignAs with car design the strength of themodern enclosure comes more from theattention the manufacturer has paid to thedesign than from the material thickness.

Most wall and floor mounted metalenclosures available today are producedfrom sheet of 0.75 mm to 2 mm thicknesswith the folding and welding techniquesused providing rigidity and strength. Thethicker the material the higher the potentialcost of the enclosure. In addition thedifficulty of making cut-outs or holes forcomponents increases with thickness.

Mounting plates are thicker to allow fordrilling and tapping holes for components.These are also available with variousmounting systems to overcome the needfor drilling.

Other design features allow for theenvironment in which the enclosure is to beinstalled, for example, gutters to ensure anywater runs away from the gasketed areas.

Enclosures are often manufactured usingmore than one technique, for example afloor standing enclosure could have a rolledframe, folder and welded doors and panels,die cast hinges and fixing parts. Plastic topand bottom covers could be added toextruded aluminium side walls to give anaesthetically pleasing enclosure.

WeldingOne of the most common methods ofconstruction is to cut the basic componentsfrom sheet steel and form into shapes priorto welding. Dependent on the specificationof the enclosure various types of weldingcan be used.

An enclosure with a need to achieve only alow ingress protection could be producedusing simple spot welding techniques. Themost common approach today as thedemand for more tightly sealed enclosuresgrows is to seam weld all the sections soensuring no penetration risk between thevarious welded elements of the enclosure.

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Self Assembly and BoltedConstructionModular self assembly systems transfer theassembly process from the manufacturer tothe customer and offer speedy delivery ofenclosures and busbar systems. Theequipment is delivered in kit form withresultant savings in delivery and storagecosts. The customer should confirm thatadequate training and back-up are availablefrom the manufacturer to ensure that thesystem is assembled correctly and efficiently.By its nature, this type of construction willallow modifications to panel layouts to beaccommodated after delivery/assembly,whilst keeping associated costs and delays toa minimum.

Casting Various materials are suitable for casting ordie-casting. Die-casting is used for highvolume production runs. Sand casting canbe used for one offs. Casting can introducedesign features into the enclosure such asinternal fittings.

Vacuum FormingThis system is used for plastic materials orthin metals. The material is drawn over amoulding form to give the finished shape.

ExtrudingPlastics and metals such as aluminium can beextruded to shape. The raw material inmolten or semi-molten state is pushedthrough a die to give the desired shape ofthe component. Large production quantitiesare required to compensate for the cost ofthe die.

Glass Fibre MouldingGRP enclosures can be manufactured on aone off basis by hand 'lay-up' of the fibremats. However, it is more usual forproduction quantities to be manufactured bya hot press method with heated materialsand a form of punch and die or a vacuumforming technique.

Injection MouldingThe process of injection mouldingenclosures involves the conversion ofplastics granules into a moulded form. Thematerial is heated to its molten state andinjected, under pressure, into the formingtool. This process is suitable for boththermo-plastic and thermo-setting plasticmaterials.

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INTERNAL FITTINGS

An enclosure provides a housing forequipment, generally for reasons of safety,security, environmental protection orcombinations of all three. A variety offittings may be incorporated within theenclosure to assist in the mounting of thisequipment, including:

Mounting Plates These are usually in the form of plated orpainted sheet steel, sometimes folded alongtwo or more edges to give extra rigidity andattached to the enclosure with nuts andbolts, studs or fixing rails. The fixing railmethod normally allows the mounting plateposition to be adjusted between the frontand rear of the enclosure.

Mounting plates are available in othermaterials such as aluminium, fibreboard, andstainless steel dependent on the supplierand application. Also available are pre-punched mounting plates that allow captivenuts to be fitted to hold equipment soobviating the need to drill and/or tap theplate. On larger enclosures partial heightmounting plates are now available.

Mounting Studs/InsertsThis method of fixing equipment is normallyreserved for wall mounting enclosures ornon-metallic products. The studs andinserts are traditionally positioned toaccommodate the manufacturer's standardaccessories.

Mounting RailsMore common in mainland Europe, thesesystems are readily available and take theform of various standard lengths of 'DIN'rail or top hat shaped profiles and bracketsystems that allow them to be fittedanywhere in the enclosures. These systemsare fitted as accessories and therefore tendto pick up their main fixing positions fromthe mounting plate fixing studs, bolts or rails.

The rails may also be fitted to the doors ofthe enclosures.

Racking Techniques19 inch rack enclosures have been designedespecially for the electronics industry toallow 'prepacked' modules such as modems,video equipment etc., to be fitted easily andquickly. A standard width between frontfixing holes has been established at 482.6mm (19 inch - hence the name) althoughother dimensions such as 515 mm - IEC60917 Series and 600 mm are used. Newstandards such as ETSI and metric modularare becoming more popular.

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These racks have many fixing optionsincluding drawers, sliding rails and fixed orsliding trays. The normal 'racks' are oftendesigned without ingress protection in minddue to the benign environment in whichthey are installed. In order to offer an IPfacility, enclosure manufacturers havedesigned accessories to allow rack mountingsystems to be installed in an ingressprotected product.

In its simplest form this could be twovertical rails that when fitted to a 600 mmwide enclosure offers the 482.6 mm (19inch) front fixing option. Variants on theseinclude variable depth versions, partial heightrails and swing frames.

Swing frames are in essence a simple framewith the two vertical rails to provide the482.6 mm (19 inch) punchings. Theseframes may be full or partial height and arefitted with hinges and brackets that allowthem to act as an inner door and hinge outto offer access to the rear for servicing.

Special BracketsMany manufacturers offer accessory bracketsto assist users with the installation ofequipment. These may range from simpleangled brackets to allow the fitting of aprofile rail for terminals to a full system tosupport monitors or other equipment. Fulldetails can be found in manufacturersliterature.

AccessoriesMany other useful accessories are available,including drawing pockets, earthing bars andcables, internal lighting, power distributionpanels, door switches, door stays and cableretaining rails.

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LOCKS & HINGES

Enclosures are fitted with locks and hingesfor two main reasons - to enable easyaccess to the interior and to preventunauthorised access.

However, with tampering, vandalism andunauthorised use of equipment on theincrease, there is a need for moresophisticated security measures to be builtinto products and systems. Enclosuremanufacturers offer a number of options.

The simplest form is probably the insertlock, when operated by a key rotates asimple cam or tab to engage behind theenclosure body.

Various lock inserts can be fitted forincreased security.

With larger enclosures, the lockingmechanism has to perform other functionsapart from just securing the door.Depending upon the IP rating of theenclosure, a gasket may be fitted to providea seal. It may be necessary to have a designof lock that will secure the door at morethan one place. This can give rise to awhole range of rod-latch systems. Any lockfitted must not degrade the designed sealingcapability of the enclosure. If the enclosureis sealed to IP65 it is important that the lockis no less in specification, or water and dirtmay enter the enclosure.

The need to secure against unauthorisedaccess is not the only reason for fittingsophisticated locking systems. Manyenclosures contain high voltage electricalequipment and it may be essential that thisis isolated prior to opening the access

doors, a need that leads to interlockingsystems which isolate the supply to theinternal equipment before the door can beopened. In considering this, it is alsoimportant to respect any other safety needsof the apparatus. Can the supply simply beturned off without any hazards arising fromthe effects of the disconnection ofassociated equipment? Is there a sequenceto the shut down procedure, which must befollowed?

Much of the above relates to the largerenclosure, but particularly in the Electronicsindustry there is a need for smaller, butnone the less secure, locking systems. Inthis sector a range of quarter turn fasteners,pawl latches, push and slide action fastenersand similar devices have been developed.

Just as it is important that any lock ensuresthat doors locate correctly on to theirgaskets, so it is necessary to ensure that thehinge design is such that the lid or door fitsproperly at that edge. A simple 'pianohinge' type of approach can result in leaks.A hinge design that in itself pulls theappropriate edge of the door tightly into thegasket needs to be used. When consideringlarger, sheet metal cabinets, care must betaken to ensure that the hinge does notallow or cause distortion.

Locks and hinges are essential partsof the enclosure system and it isimportant that they are given properconsideration when selecting theenclosure, if the design integrity ofthe completed installation is to bepreserved.

ENCLOSURES

21

ENCLOSURES

LIFTING ARRANGEMENTS

An important feature of any large enclosureis the facility to allow it to be lifted andtransported.

EyeboltsThe most common method of lifting largeor heavy enclosures is by eyebolts screwedto the top surface of the enclosure. Various methods of fixing the eyebolts are employed. The most common is acollar/nut in a strengthened section on the underside of the top of the enclosure.

Eyebolts manufactured in accordance withthe relevant national or internationalstandard and certified accordingly should beused, the thread diameter dictating the safework load (SWL) from tables in thestandard.

An eyebolt should not be surface finishedafter it has been tested and stamped as theprocess could anneal the metal, affecting itsstrength.

Safe working loads are given assuming avertical lift on the eyebolt, although by theuse of slings with links (shackles) attached tothe fixed eyebolts it is possible to lift from asingle hook. The angle of sling reduces thesafe working load of the eyebolt by as muchas 75%.

A preferred method is to use a parallellifting beam as shown below:

ENCLOSURES

22

ENCLOSURES

Practical Advice

� Personnel performing lifting operations should be suitably qualified, trained and familiar with the relevant standards. They should also be aware of their responsibilities under health and safety legislation.

� Reduce the risk of the enclosure becoming unstable while being lifted by designing to ensure, where practicably possible, the weight distribution is evenly dispersed. Maintain a low centre of gravity by positioning heavy items towards the bottom of the enclosure.

� For a suite of enclosures intended to be bolted together, try to design the

joints within the suite to reduce the size and weight of each lifted section to help transportation.

� Where possible, before lifting, remove heavy items such as large transformers from the enclosure and transport separately.

� Use dedicated lifting points as indicated in manufacturer's literature.

� Consult manufacturer for purpose designed lifting aids.

� Always check that the thread size on the eyebolt corresponds to the thread size at the lifting point on the enclosure.

ENCLOSURES

23

ENCLOSURES

EARTHING & BONDING

In the interests of electrical safety, all metal parts should be bonded and then earthed.Traditionally, this has applied to doors, panels, mounting plates and gland plates. Facilities forthe connection of an earth conductor are usually provided on these components and themain body of the enclosure.

The manufacturer's dedicated earth points should be positioned such that bonding to themain body can be achieved by short conductors, which reduce the probability of damage tothe conductor by snagging. If a dedicated earth point is not provided and a fixing is madethrough a hole in a panel or gland plate, then a suitable means must be used to ensure thatadequate metal-to-metal contact is achieved.

Dedicated earth points on enclosures can be identified by the use of Symbol 417 - IEC 5019-a:

Protection against electric shock can also be achieved by total insulation against indirectcontact. The enclosure should be made of insulating material eg. GRP and carry the Symbol417 - IEC 5172-a visible from the outside to indicate 'Double Insulation'.

ENCLOSURES

24

ENCLOSURES

GASKETS

Gaskets are fitted to enclosures to provide aseal against ingress of solid objects ormoisture to conform to a chosen protectionrating. Some enclosures have no gasketsbecause the conditions in which they arerequired to perform do not demand thefitting of one.

Gaskets are usually applied by four differentmethods:

� Use of an adhesive strip on the rear faceof the gasket which is then placed on the enclosure.

� Use of a gasket material which foams and sets, as part of the manufacturing process.

� Use of gaskets moulded and designed to fit a particular location in the enclosure, fitted by the customer and mechanically sandwiched in place between the gland plate and the enclosure.

� Use of an extruded shaped gasket, which is fitted to an edge or flat surface and has particular physical properties.

Electromagnetic Compatibility(EMC)Special electrically conductive gaskets areavailable to provide protection against radiofrequency interference (RFI). These gasketsmay or may not protect against the ingressof particles and moisture. They may takethe form of:

� carbon filled silicon elastomers,

� silver filled silicon elastomers,

� carbon composite gaskets,

� conductive wires in a silicon material,

� wire meshes over elastomer cores,

� copper beryllium finger strips,

� wire mesh strips.

The choice of EMC gaskets should bediscussed with the manufacturer withregard to the application.

ENCLOSURES

25

ENCLOSURES

COMPARTMENTED ENCLOSURES

The majority of compartmented enclosuresare produced in mild-steel but stainless steeland aluminium options are also available.

Various methods may be employed toachieve the division of enclosure sections(columns) into sub-sections orcompartments:-

a) Enclosures bolted together to form sections sub-divided by horizontal barriers, individual doors being provided for the sub-sections or compartments formed within each section.

b) Enclosures welded together to form the individual sections, the sub-division of the sections being achieved by the inclusion of horizontal insert plates.

c) Enclosures of fully welded constructionwith all sub-divisions formed at the fabrication stage.

In the switchgear and controlgear industry inparticular, further divisions within a suite ofenclosures are often required in order, forexample, to segregate busbars, individualincoming or outgoing circuits, and theterminals for external conductors.

In Type-tested assemblies to BS EN 60439-1:1994 Specification for type-tested and partiallytype-tested and partially type-testedassemblies these separation arrangementsare classified in terms of various �Forms ofinternal separation�.

Increasingly, attention is given to the mannerin which cables enter or leave this type ofenclosure since users may require thatexternal cables can be connected orreplaced without the need to shut downthe entire enclosure assembly. BS EN604439-1: 1994 includes an informativeannex (Annex NC): Guide to the internalseparation of assemblies which givesadditional information about the typicalmethods of construction which may beempolyed to achieve varying levels ofsegregation. However, it emphasises that the form of separation is still subject toagreement between the manufacturer.

More information on this subject iscontained in the GAMBICA technical guide,A Guide to the Specification for Low VoltageSwitchgear and Controlgear Assemblies - BSEN 60439-1: 1999 which is available fromGAMBICA.

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26

ENCLOSURES

ENVIRONMENTAL CONSIDERATIONS

OutdoorsWhen an enclosure is used outdoorsconsideration must be given to theprevailing weather conditions and extremesof temperature.

These conditions will determine choice ofmaterial e.g. GRP, stainless steel, aluminium;the design of the enclosure e.g.requirements for improved sealing, venting,rainhoods; the addition of extra equipmente.g. heaters, vents, thermal managementsystems; and special finishes e.g. anti-condensation paint.

Standard steel enclosures generally aredesigned to meet the demands of industrialenvironments. Failure to take account ofother conditions can result in damage to theenclosure and contents.

The Cooling EffectA standard enclosure will probably allowrainfall to run around the outside of variousgasketed areas. If the internal temperatureis reduced rapidly the pressure inside a highIP rating enclosure may be significantly lowerthan the ambient pressure outside, therebyinducing a suction effect through thegasketed areas. This could result inmoisture around the gaskets being drawninto the enclosure.

This effect may be avoided by reducing thenumber of gasketed areas in contact withthe rain by choosing an enclosure withgutters and/or fitting a rainhood.Alternatively it may be possible for thepressure to equalise quickly by allowing the

enclosure to breath (through controlledventilation) although this may reduce the IPrating.

CondensationCondensation is often mistaken for wateringress. It is caused by a difference intemperature between the inner and outersurfaces of an enclosure and normally formson the same side as the prevailing wind.The most common solutions are to fit anti-condensation heaters, controlled ventilationor use of anti-condensation paint.

Apart from water lying in the bottom of theenclosure, moisture may condense on thecomponents causing electrical 'leakage' and'tracking' as well as component corrosionand degradation of insulation.

Remember the temperature effect. Watervapour is always present in the air and whenair is cooled the 'dew point' is reached, theair is then saturated and further coolingresults in condensation. Looking for thecause of moisture in an enclosure on a'warm' day may mean that the obvious ismissed and the condensation hasevaporated, only to return when thetemperature drops again.

Corrosive Environments In certain applications enclosures will needprotection from chemicals and selection ofthe right material is determined by thechemicals involved. The most likely choiceis stainless steel but even then care must betaken to ensure the correct grade isselected.

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ENCLOSURES

Some non-metallic materials have excellentresistance to certain chemicals and poorresistance to others. Advice should beobtained when selecting a suitable materialand construction as, for example, thecomponents within the enclosure may needprotecting from harmful gases.

Marine, Coastal and Off-shoreCoastal, external applications can usually becovered by referring to the previous'Outdoors' element of this section and thenpaying particular attention to the treatmentsor materials chosen to address the extracorrosion likely from the salt ladenatmosphere.

Off-shore specifications depend on theintended location of the enclosure e.g. arelatively low IP rating enclosure in anaccommodation area through to a very high rating on a ship's deck.

Some users have very clearspecifications for such equipment but if in doubt contact a GAMBICAEnclosure Group member.

Hosedown AreasEnclosures in these areas are usually inprocessing plants when the environment issubject to special regulations. Theenclosures chosen are usually free of surfacetreatment to avoid contamination, for

example by paint flakes entering theproduction process.

In practice most users choose stainless steeldesigns which have few external features,for ease of cleaning. Various non-metallicproducts offer the same benefits but astainless steel enclosure will maintain thebest appearance.

Care must be taken when using ahose to clean the enclosure andsurrounding area. Often very high-pressure hoses exceed the IP ratingof the enclosure, resulting inunexpected ingress. Condensationcan also be a problem in cool areas(see below).

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28

ENCLOSURES

HAZARDOUS AREAS

Hazardous Areas are those locations wherea potentially explosive atmosphere mayexist. This is an atmosphere in whichdangerous quantities of flammablesubstances may occur in the form of gas,vapour, haze, dust or fibre capable ofcombining with air to form potentiallyexplosive mixtures.

Use of equipment (including enclosures) inHazardous Areas is highly regulated, withequipment generally requiring third partcertification, whether mandatory or not.Selection of equipment must take intoaccount the regulations of the country inwhich it is to be used and the acceptabilityof the third party certificate to that country.

Prior to selecting equipment (includingenclosures) for Hazardous Area use, theGas Grouping, Zone Classification andTemperature Classification assessments must be made.

Gas GroupingIn Europe hazards are classified and groupedas follows:

Group 1 - Those found in MiningOnly (underground firedamp methane)

Group II - Those found in Surface industry and �Off-shore� installations

11A - Typically butane11B - Typically formaldehyde11C - Typically hydrogen or

acetylene

Zone ClassificationHaving established the hazardoussubstances, the likelihood of the explosionrisk also needs to be considered. This issimplified by a zoning method inInternational and European standards asfollows:

Zone 0 - Hazard continuously present orpresent for long periods

Zone 1 - Hazard likely to be present

Zone 2 - Hazard unlikely to be present or only present for short periods of time, for example under fault conditions

Temperature ClassificationIn order to establish the suitability ofapparatus for use in a hazardous area fromthe view point of hot surfaces, apparatus isawarded a T-rating, corresponding to itsmaximum surface temperature under certainconditions: EN50014 or IEC 60079-0. TheT-rating or T-class, can then easily becompared to the Auto Ignition Temperatureor Spontaneous Ignition Temperature of thehazard in which it is to be used, thusestablishing safety from ignition from hotsurfaces. For example T6 = 85°C which isthe highest temperature the apparatus willreach when operated under the mostonerous conditions.

Protection ConceptVarious concepts of Hazardous Areaprotection are available to suit a particularapplication. The �Enclosure Specification�chart shows suitability of each concept andthe type of enclosure that is applicable.

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29

ENCLOSURES

European RegulationsIn the European Economic Area (EEA*),applicable regulations are in the form ofDirectives. These are not applied directlybut implemented by national regulations ineach country.

For electrical equipment in hazardous areasthe Directives currently in force are:

� 76/117/EEC (as last amended by 97/53/EC) and 79/196/EEC (also at last amended by 97/53/EC): Electrical Equipment for use in Potentially Explosive Atmospheres, with the latter relating to 'Equipment Employing Certain Types of Protection'.

� 82/130/EEC (as last amended by 98/65/EC): Electrical Equipment for Use in Potentially Explosive Atmospheres in Mines Susceptible to Firedamp

These 'old approach' Directives remain inforce until 30 June 2003 and refer to specifictechnical standards (the EN 50014 series)and their issues and amendments. Theyrequire specific information to be presenton the product's certification labels, forexample:

EEx ... de�11�C�T6

EEx = Equipment conforms to types of protection standardised by CENELEC (European Standards EN 50014)

de = Type of protection used:

d = flameproof enclosure

e = increased safety

11 = Gas grouping:11 = surface industry an �Off-shore�

C = Gas subdivision, most critical category, including hydrogen,acetylene and carbon disulphide

T6 = Temperature class:T6 = maximum 85°C

A 'new approach' Directive becomesmandatory from 1 July 2003 but becameavailable for use as an alternative to the 'oldapproach' Directives from 1 March 1996.Called the ATEX Directive, 94/9/EEC, itcovers both mine and surface industries andintroduces, for the first time in Europe,requirements for mechanical hazards andpotentially explosive atmospheres arisingfrom dusts. The Directive gives the essentialsafety requirements that must be met byequipment, including enclosures andprotective systems, for use in hazardousareas. European Harmonised standards(EN's) may then be used for demonstrationof compliance with the essentialrequirements of the Directive.

The ATEX Directive introduces thefollowing changes:

Equipment is classified by group andcategory according to its intended use:

Apparatus group 1 (mines)�.Equipment category M1 and M2

Apparatus group 11 (surface) �..Equipment category 1,2 and 3

* EEA comprises the 15 countries of the EuropeanUnion (EU), Iceland, Liechenstein and Norway.Switzerland is not part of the EEA but because of itsmembership of the European Standards Organisations,uses the same technical standards.

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ENCLOSURES

Under this Directive apparatus is marked asfollows:

CE � Ex �11�2�G and D

CE = CE marking, which has to be in a specific format

Ex = Use of equipment in potentially explosive atmospheres, again in a specific format

11 = Equipment group:11 = surface industry

2 = Equipment category

G = Gas

D = Dust

In Great Britain the ATEX Directive isImplemented by Statutory Instrument1996 No. 192, The Equipment andProtective Systems Intended for Use inPotentially Explosive AtmospheresRegulations 1996. Northern Ireland has itsown regulations, but both will use the BSEN's, the UK harmonised standards, as away of demonstrating compliance.

Both the 'old approach' and 'new approach'Directives require the use of a specificexplosion protection mark, the 'Epsilon x'symbol. CE marking may not necessarily bean indication of compliance with the ATEXDirective, since it can also mean compliancewith other applicable 'new approach'Directives.

ENCLOSURES

31

ENCLOSURESEN

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32

ENCLOSURES

THERMAL MANAGEMENT

The management of the operatingtemperature of the enclosure can be a verycomplex matter. Equipment may need to beheated to protect it from frost or maintain aworking temperature when the system isshut down to prevent condensation.Alternatively equipment may need to becooled to prevent malfunction.

Below are given some types of thermalmanagement devices and their typical usage.

Thermostats Used to switch thermal managementdevices at predefined temperature limits.

HeatersThese can be installed in enclosures tomaintain working temperature or preventcondensation. A fan may be used toincrease the thermal power output andassist the flow of warmed air.

LouvresRaised covers, louvres, louvre plates or bolton grilles are used to give a natural air flow.The IP rating of the enclosure may beaffected by the method used. Any coolingwill only be to the level of the ambienttemperature and there could be heatpockets formed within the enclosure due tothe absence of a forced air system.

FansFans used with louvres, louvre plates orgrilles give an air throughput for theenclosure. Unless filters are used,contaminated air may be brought into theenclosure.

Fans may vary in size, power, design and airflow characteristics. Some high air flow fansmay have a low pressure stall limit. Fans canbe used to draw air in or out of theenclosure and should be used with aninlet/exhaust louvre or grille. If any intakefan is used without an exhaust or with anundersized or restricted exhaust a positivepressure will result. In special circumstancesthis can be used to help prevent ingress ofparticles. Fans will only cool to aroundambient temperature and are therefore oflimited use in high temperatures. Anadvantage of fans and units containing morethan one fan is that they can be used for thecooling of hot spots.

Heat ExchangersAir to air heat exchangers work on theprinciple of two separate air circuits passingeach other in opposite directions andseparated by a thin (usually aluminium)dividing wall.

Heat exchangers allow a higher degree of IPprotection due to the use of separated aircircuits. The enclosure temperature will becooled to just above the ambienttemperature.

Where the ambient temperature is high anair/water heat exchanger may be used withthe water being used as the coolingmedium. However, a prerequisite of thissystem is the availability of a continuouswater supply.

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ENCLOSURES

Coolers These are based on the principle of arefrigerator. The internal air of theenclosure is kept to a sealed air circuit,which passes through the cooler. Coolerscan be roof mounted, 19 inch rackmounted, door or side panel mounted andmay incorporate a microprocessor forfunction indication and control as well as belinked to a central process computer.

The cost of coolers is high when comparedwith other forms of thermal managementbut may be the only solution to problems inhigh ambient temperatures. The IP rating isgenerally unaffected.

Many manufacturers offer expert guidanceand information in the field of thermalmanagement control.

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34

ENCLOSURES

RFI/EMI SHIELDING FOR ENCLOSURES

Radio frequency interference (RFI) andElectromagnetic interference (EMI) can beprevented from penetrating or escapingfrom an enclosure by ensuring it acts as aFaraday Cage. This means providing aelectrically conductive shield over all thesurfaces. Doors and ports have to beelectrically sealed to their apertures. Inpractice this need not be continuousprovided the frequencies being shieldedcannot escape. Some manufacturers offersolutions using dual function gaskets thatboth shield and retain a level of IP rating butthis is often less effective than two separategaskets dedicated to their own function.

The overall levels of attenuation varydependent upon design, gasketing used andmaintenance. The latter is very important as

contaminants build up on the conductivesurfaces over a period of time so reducingthe conductive effect. This is morecommon in designs with �butt� joints.Gaskets sealing with a wiping action offer alevel of self cleaning and so retain theirshielding levels without maintenance forlonger.

Shielding windows can be provided by usinga material with a lamination of conductivemesh but this will need connecting to thedoor or aperture continuously around itsedge.

In January 1996 the European Directive onElectromagnetic Compatibility (EMC) cameinto force. This Directive demands that allproducts susceptible to or capable ofemitting EMI must be designed so that theirfunction is not unduly degraded in thepresence of EMI and that they do not emitinterference that would unduly affectequipment in their environment. TheDirective has caused an increased demandfor shielding products and filters. If you arein any doubt about the effect of thisDirective contact a GAMBICA EnclosureGroup member for clarification.

Enclosures themselves are outside the scopeof the EMC Directive since they neitherproduce nor are susceptible to EMI. Theydo not have to carry the CE mark as far as

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35

ENCLOSURES

INSTALLATION & MAINTENANCE

It is important that users of electricalequipment, including enclosures, ensure thatthe equipment is given proper care andattention by competent personnel. Thefollowing notes are intended to provideguidance on a general level only. Anyregulations or manufacturer's instructionsconcerning installation, safety or specifichazardous area applications must be strictlyadhered to.

InstallationBefore commencing the work of installingthe equipment, study the installationinstructions supplied by the manufacturer.

If the equipment is to be lifted, use all of thelifting points supplied, ensuring that thesecuring bolts or eye bolts are of thecorrect size and thread. Check that thelifting equipment used is adequate to handlethe load and do not lift in any otherdirection or from any other point other thanthat intended in the design. During liftingdo not induce additional stress by rapidacceleration or deceleration. Set downgently to avoid mechanical shock.

Heavy or awkward equipment should bemoved into position with the aid of skates,such that the weight is distributed evenly toavoid deformation. It should not bedragged into position or moved on rollers assuch handling can result in damage to thesurface finish or the structure itself.

The following are common sense tips whichcan help to ensure a successful installation:

� Inspect outer packaging on delivery as damaged wrapping may mean the

enclosure itself has been damaged in transit.

� Do not insert a knife into the packaging to cut tape or other wrapping material as you risk scoring the paint finish and creating a potential rust site.

� Do not drag enclosures - use approvedlifting methods.

� Clear swarf from work and make sure work surfaces are free from debris before working on enclosures.

� Empty the enclosure of any debris before installation as it may form a focusfor condensation which may cause corrosion.

� When marking out do not score paint surfaces outside drilling sites.

� Use sharp cutting tools to avoid cracking paint and repaint bared hole edges.

� Use punches in preference to drills on steel enclosures.

� Seek manufacturers advice on care of seal and paint selection before removingseals or over-spraying.

� Remember that all work on the enclosure should seek to maintain the IPintegrity. For example, cable entries should have glands with similar or higherIP rating.

� Check the loading of equipment to be fitted as distortion of mountings or doors may affect the sealing.

�� Check wall mounting brackets are sufficiently robust for the purpose.

� Final inspection should be conducted before transportation from the workshop.

ENCLOSURES

36

ENCLOSURES

Site Installation� Ensure adequate site access is available

for the size and weight of the enclosure.

� Ensure walls/floors are plumb, level and in good condition. On external locations, site on the lee (out of the wind) side of building where possible.

� Canopies are recommended to deflect direct rainfall, as are pedestals to raise enclosures from wet floors.

� Floor standing enclosures which are not designed to be free standing should be bolted back to a wall or stanchion for stability.

� Cable entries must be supported outside the box, so that no stress is caused to the enclosure, as deformation may degrade the sealing.

� Earthing continuity should conform to local standards.

� Check loads on doors and swing frames as opening them may cause the enclosure to become unbalanced and tip over.

MountingIt is essential that the equipment is mountedon a level surface. If the enclosure is boltedto an uneven surface, the doors or coversmay not fit correctly and the integrity of theenclosure will be degraded.

For wall mounting enclosures, ensure thatthe designed fixing method i.e. internal holesor external fixing brackets are used. Thesize of fixing should fit comfortably into thehole or bracket provided.

For floor fixing enclosures, it is essential thatadjacent sections of an assembly are boltedtogether and aligned prior to final tighteningon the floor fixings. Any swarf or dust thathas accumulated within the enclosure mustbe removed and any doors or covers thatwere taken off must now be reassembled.

CablingAll external cabling associated with theenclosure should be firmly supported so asnot to increase stress on either theenclosure fixings or the enclosure itself. Any damage caused to the surface finishedby the cutting of gland holes must berectified prior to the fitting of the gland.

InspectionBefore putting the equipment into service,ensure that the enclosure has been fullyreassembled and all gaskets are in place. All external surfaces should be inspected forscratches and damage with the purpose ofrepairing such damage.

The installation should comply with therelevant standards as specified by the user.Selection of the enclosure should conformto the required BS or equivalent.

MaintenanceA planned maintenance programme isadvisable, checking gaskets, paintwork,hinges, locks, etc, for signs of physicaldamage, tampering and corrosion.

ENCLOSURES