selection of equipment & type of ex protection for dust ... · selection of equipment &...

Selection of Equipment &

Type of Ex Protection for

Dust locations. Aug. 2010

Mike Scott : EXB Electric (Pty) Ltd.

www.exbelectric.co.za

Tel. + 27 11 887 8941

Fax. + 27 11 887 8945

EXB Electric (Pty) Ltd.

Thank You

Peter Turnherr, CEO of thuba and a

member of numerous working groups and

committees (IEC) associated with Explosion

Protection.

Peter has made available a lot of information and

material used in this presentation.

The thuba group of companies are mainly

concerned with various aspects of Explosion

Protection.

Disclaimer

All information in this presentation is given in good

faith and does NOT replace standards, codes of

practice and any other requirements of industry or

other.

EXB Electric (Pty) Ltd and / or the writer / presenter

will / are NOT responsible for any errors / miss-

understandings.

IEC 60079-14

International Standards

IEC 60079-17 IEC 60079-19

Qualifications of personnel

The design of the installation, the selection of

equipment and the erection covered by this

standard shall be carried out only by persons

whose training has included instruction on the

various types of protection and installation

practices, relevant rules and regulations and

on the general principles of area classification.

The competency of the person shall be relevant to

the type of work to be undertaken.

Information required

• Classification of the hazardous area including

the equipment protection level requirements

where applicable

• Where applicable, dust classification in relation

to the subgroup of the electrical equipment

• Surface temperature of the dust involved

Information required

• Minimum ignition temperature of the

combustible dust cloud, minimum ignition

temperature of the combustible dust layer

and minimum ignition energy of the

combustible dust cloud

• External influences and ambient temperature

General requirements

Hazardous areas are classified into Zones 20, 21

and 22 for combustible dusts according to

IEC 60079-10-2 in order to facilitate the selection

of appropriate electrical equipment and the design

of suitable electrical installations.

Electrical installations in hazardous areas shall

also comply with the appropriate requirements

for installations in non-hazardous areas.SANS 10142 in RSA

However the requirements for non-hazardous

areas are insufficient for installations in

hazardous areas.

SANS 10086 in RSA

Equipment shall be installed in accordance with

its documentation.

Installations should be designed and equipment

and materials installed with a view to providing

ease of access for inspection and maintenance

(IEC 60079-17).

Selection of repaired, second hand

or existing equipment

When it is intended that existing, second hand or

repaired equipment is to be installed in a new

installation, it shall only be reused if:

a) it can be verified that the equipment is

unmodified and is in a condition that meets the

content of the original certificate (including any

repair or overhaul)

b) any changes to equipment standards relevant to

the item considered do not require additional

safety precautions.

Use of equipment that is not certified

simple electrical apparatus used within an

intrinsically safe circuit. (The I S loop needs

certification)

Equipment Protection Level (EPL)

Equipment Protection Level (EPL)Zone

Dc, Db and Da

Db and Da

Comparison of Dust Zones and Gas Zones.

Dust (Zone 20) ~ Gas (Zone 0)

(NB: approximately)

Type of protection and EPL

Type of protection

Protection by enclosure

IEC 60079-31

IEC 60079-0

Standard

IEC 61241-11Protection by intrinsic safety

Protection by encapsulation ma IEC 60079-18

Type of protection

Type of protection „pD“

Protection by encapsulation

IEC 61241-11

IEC 60079-31

Standard

IEC 61241-4

IEC 60079-18

Protection by intrinsic safety

Type of protection

IEC 60079-31

IEC 61241-4

Standard

IEC 60079-18Protection by encapsulation

Type of protection „pD“

Suitability of apparatus for less hazardous

locations.

DUST Hazardous Locations

EPL level Da : Suitable for Zones 20 & 21 & 22

EPL level Db : Suitable for Zones 21 & 22

EPL level Dc : Suitable for Zone 22 ONLY

GAS Hazardous Locations

EPL level Ga : Suitable for Zones 0 & 1 & 2

EPL level Gb : Suitable for Zones 1 & 2

EPL level Gc : Suitable for Zone 2 ONLY

Group III (Dust)

Equipment groups (dust)

Conductive dust

Non-conductive dust

Fibres

Comparison of Equipment Groups.

Group I : Fiery Mines, (Firedamp (Methane / Coal Dust))

Group II : Industries other than mines. (surface industries)

Group II A : Propane for Example

Group II B : Ethylene for Example

Group II C : Hydrogen gas for Example

Group III : Dusts.

Group III A : Fibres. Polyester / cotton for example

Group III B : Non Conductive dust. Grain for example

Group III C : Conductive dust. Aluminum for example

Dust clouds

Temperature limitations because of the presence

of dust clouds

The maximum surface temperature of the

apparatus shall not exceed two-thirds of the

minimum ignition temperature in degrees Celsius

(C) of the dust/air mixture concerned:

Tmax ≤ ⅔ TCL

where TCL is the minimum ignition temperature of the cloud of

Dust layers

• Temperature limitation because of the presence

of dust layers

– up to 5 mm thickness

– above 5 mm up to 50 mm

– dust layers above 50 mm

Dust layers

Plugs and socket outlets for dust

• Socket outlets shall be installed so that dust will

not enter the socket outlet with or without a plug

in place.

• To minimize the ingress of dust in the event of a

dust cap being accidentally left off, socket outlets

shall be positioned at an angle, which is not more

than 60 degrees to the vertical, and the opening

facing downwards.

Plugs and socket outlets for dust

≤ 60°

External factors

• Thermal effects

• Chemical effects

• Mechanical effects

• Varying pressure conditions

• Effects of movement and vibration

• Electrical effects

• Moisture

• Ingress of process liquids

• Corrosion

• Small animals, rodents and insects

Equipment shall normally be designed

for use in an ambient temperature range

between –20 ºC and 40 ºC; in this case,

no additional ambient temperature

marking

is required.

Example of extended ambient temperature

range Tamb

Tamb –30C to 65C.

Ambient temperature

EN 60079 – 0 : 2009 - 08 General Requirements

IEC 61241-2-1

Methods for determining the minimum

ignition temperatures of dust

IEC 61241-2-2

Method for determining the electrical

resistivity of dust in layers

IEC 61241-20-3

Method for determining minimum ignition

energy of dust/air mixtures

EN 60079-31:2008

Protection by Enclosure «t»

EN 61241- 4:2006

Protection by Pressurization «pD»

EN 61241-11:2006

Intrinsic Safety «iD»

EN 60079-18:2008

Protection by Encapsulation «m»

EN 60079-10-2:2009

Area classification

EN 60079-14:2009

Electrical installation design,

selection and erection

EN 60079-17:2007

Inspection and maintenance

EN 60079-19:2007

Repair and Overhaul

Standards for dust

Protection by Enclosure «t»

Group III

Equipment groups (dust)

conductive dust

non-conductive dust

fibres

EXB Electric (Pty) Ltd. 36

2.Aging resistance testing

(thermal endurance)

Hot and cold

storage tests

3.Testing for mechanical

strengthImpact test

4.Testing for dust

protectionIngress test in

dust test chamber

5. ElectrostaticsTake appropriate

measures

1.Limiting surface

temperatureThermal

Protection by enclosure «t»

Sequence of tests

Testing for aging resistance

Testing for mechanical strength

Testing for dust protection

Evaluation of dust protection taking into

consideration aging and mechanical

influences

Dust ingress protection IP 6X

Equipment for Zones 20 and 21

Equipment for Zone 22 with conductive dust

Dust ingress protection IP 5X

Equipment for Zone 22 with non-conductive

Intrinsic Safety «iD»

Intrinsic safety «iD»

• Energy limitation (current and voltage)

• Equipotential bonding

• Isolation of non-intrinsically-safe circuits

• Marking

• Verification of the safety of the interconnection

(equipment parameters, including conductor

length)

Marking

• Text inscription «Intrinsically safe circuit»

• If coloured marking, only light blue such as

RAL 5012

Simple apparatus

• No internal cells or batteries

(exception: thermocouples, photocells, etc.,)

limited to 1.5 V, 100 mA and 25 mW

• Connection to a single source only

• No internal voltage/current transformation

Simple apparatus

• If these conditions are met, the protection

against spark ignition is afforded primarily by

the source – the «associated apparatus».

• This associated apparatus must be tested and

certified.

Marking simple apparatus

No ATEX mark may be applied to the apparatus!

Simple Apparatus

Associated apparatus

• apparatus must not be installed in the Ex area

• apparatus has an intrinsically safe output

(observe the interconnection parameters!)

• designation [Ex iD] IIIC

[Ex iD] IIIC

NOTE the square brackets used in the marking.

Hazardous area

Switching contacte.g. pressure switch, thermostat

Non-hazardous area

Output

Pressurized enclosure «p»

Pressurized enclosure «pD»

• Enclosure containing components that are not

Explosion Protected. (Standard Ignition Capable

components)

• Continuous monitoring for minimum pressure

Minimum requirement 0.5 mbar (power switched off at

≤ 0.8 mbar if a leak occurs)

• Switching off means isolating from power supply

(max. rating 1.5 V, 100 mA, 25 mW)

• Prepurging not permitted

Blue [is]

Ex tD [ibD] [pD] A21 IP65 T70°C

Ex e mb [ib] [px] IIC T4

Thank you for your attentiveness.

Thank you to SAFA for this

opportunity.

Questions?

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