Explosion Proof Triangle

8/6/2019 Explosion Proof Triangle

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Gas Grouping

& IECEx update

Session 2 – Explosion Protection Fundamentals



The Explosion Triangle

In order to have an explosion, all three legs of the triangle need to be present...Our objective is to remove one or more of the legs of the triangle when we apply electrical

equipment in a potentially hazardous flammable atmosphere...

All theprotection

concepts thatare currentlyused in theworld today

address one ormore legs of this triangle



Sources of Ignition in Hazardous Areas

A in 10V. The voltage level has an influence on how incendive a spark will be. Flammable gases and vapor

Hot Surfaces

the surface temperature of the motor. If the motor is excessively overloaded and the thermal overload device i

Batteries

their terminals are short -circuited. Current of the order of 1000A can be enerated

equipment may only allow their use in hazardous areas if powered by low -power batteries. Replacement of batteri

Electrical Sparks






cleaning equipment. Bonding and earthing of aircraft or tankers during refueling prevents the buildup of electro

Excerpt from Maintenance Information on EEx e GRP enclosure

"Static Hazard

Glass Reinforced Polyester has a surface resistance of 10E9 ohms. They can

present a ha

zard from static electricity and should only be cleaned with a damp cloth.

ss reinforced, identified with the suffix "C" have a surface resistance of between 10E6 and 10E9 .

Ohms They do not present a hazard from

Static Electricity



Optical Radiation

Chemical eacton

R i

s that have different chemical reactions can and does create sinificant explosive

tly to ultrasound. Electrical hazards are also present and should be considered especially where any liquids are in

Ultrasound

Sources of Ignition in HazardousAreas

The use of optical fibres inparticular opens up many fields of application. This technique offers infact numerous ,

advantages however,the effect of the energy source

"light" as a potential ignitionsource in explosive atmospheres



must be given consideration.



2% -10% range while Acetylene and Hydrogen have much larger ranges, hence one reason they are grouped ve


Upper and Lower Flammable

Limits for Just like your automobile, the mixture needs to be in the proper range for an explosion to occur...



te

i as ari

nd there is little tendency for these gases to sink or move around.

hane, hydrogen) and have a tendency to disperse unless contained by a container or structure.

ring the types and gases that are typically going to be seen in the environment due to dispersion.

Specific Density of Flammablegases and

Density ration gases to air:

Some gases are generally denser than air (propane) and have atendency to creep over long distances and potentially ignite when exposedto an arc.



General Rules of Thumb in determininghazardous area

f 10 liters of explosive gases in a confined room is always considered to be a hazardous area irrespective of the size o

m or more of ignitable dust evenly distributed over an entire area is considered sufficient enough to create

ssel containing the material, much smaller volumes of gas should be considered as hazardous due to rupture f

Example of proper ventilation of a contained room with heavier than air mixtures.

A simple calculation is that if the volume of hazardous gas is 1/10,000ths of the volume of the room or greater, a potential for explosion can occur. This does not mean that theentire room would be classified as a hazardous area, but possibly only a part.



Temperature Identification Codes

Example of Temperature increasing factors in Ex terminal boxes



Temperature Identification Numbers -Gas Grouping

In general, if you can

produce aproduct that israted at T3 orbetter, (max.

surfacetemperature of

200?C or cooler)you will cover

approx. 90% of the flammable

gases andvapors seen inthe oil and gas

industry...



hat ?C

will never exceed 85 ?C. Elevated ambient temperatures can effect the T identification numerns to check with the manufacture to determine suitability of the product bein g used or considered.

Temperature Identification Numbers



h same ensty

Temperature Identification Numbers -Gas Grouping

Relevant EN/IEC standards for

Hazardous Locations



Gas

Dust

Hazardous AreaClassification....



Gas Grouping for EEx 'd' enclosures



Hazardous AreaClassification....



b dramacay.

Relevant IEC standards for Dust Hazardous

Locations



Dust Protection by Enclosure Updates (Ex tD)

EN 50281 -1-1:1998 will be withdrawn as a harmonised status under the ATEXDirective from the 1st of October 2008. The principal differences in EN 61241 -

0:2006 are listed below, minor differences are not listed. EN 61241 -0 is generalrequirements that requires either 61241 -1 to be used to acquire tD certification,ultimately, EN 61241 -0 will be merged into EN 60079 -0Additional testing for category 3 products particularly for non metallic materials

Increased requirements for batteries in line with gas standards in the EN60079 series

Thermal tests under specified dust layers required if the layer exceeds 50mmIntroduction of ‘practice A’ (similar to existing method) and ‘practice B’ (a newapproach) A is principally the same as the old standard max surface temp isdetermined with 5 mm of dust and end users need to de -rate it by 75K. To determinedust ingress by EN 60529. B determines the temp using a 12.5 mm layer of dust anda 25K off set is to be appe

li d in installation. The meoth d of determining dust ngress

i is by a heatcycling test. Type B has specific requirements for joints (plain, spigot, gasketed, shafts and rods).



Relevant IEC standards for DustHazardous

Locations



Updates on standards Hazardous Locations

The 4th edition of IEC 60079 -0 was published in May of 2004. This is not currently

harmonised but ‘can’ be considered ‘state of the art’. Significant changes to the

standard are as follows effective in 2008:

New type of protection “n” introduced (The standard for Type “n” was previously a

“stand -alone” standard that did not function as a sub -part of IEC 60079 -0. All the

“general” requirements have been moved from IEC 60079 -15 to IEC 60079 -0 and

adjusted as necessary).

Apparatus standards for caplights (IEC 62013 -1), intrinsically safe systems(IEC 60079 -25), Zone 0 apparatus (IEC 60079 -,

26) and trace heating (IEC 62086-1)introduced.

Clarification of the status of symbol “s” It has been clarified in a note that “s” is not arecognized type of protection, but is what SHOULD be used when equipment doesnot comply with the specific types of protection, but does present equivalent safety.

Temperature assessment has been re -written to address the influences of ambienttemperature, internal sources of heat, and external sources of heating or coolingRelative thermal index (RTI) added as an alternative to thermal index (TI)Impact test revised to specify drop height in lieu of energyClarification of application of 5 K and 10 K temperature margins to type -testedsamplesClarification of number of samples -

and order of tests for non metallic materials

Clarification of the order of protection concept marking (alphabetical)

Addition of a clause on instructions (As the installation, operation, and maintenancewas considered critical to the safe application of equipment in explosiveatmospheres, a new clause was added detailing the minimum information to be

prepared.)Some sac“ t ti ” requremens



Relevant IEC standards for DustHazardous

Locationsi t transerre

f d f rom IEC 60079-26



Harmonization of ATEX

& IECEx update



Harmonization of ATEX



Harmonization of ATEX& IECEx update

Properties of HazardousFlammable

Materials

All Electrical sparks are capable of igniting a gas/air mixture False

The glass surface of a light bulb will prevent ignition of gas/air mixtureFalse

Any concentration of flammable gas in air maybe ignited False

Acetylene has the widest flammable limit range True

Apparatus marked Gas Group II can be used in Gas Group IIA, IIB andIIC areas

True



False

True

Properties of HazardousFlammableMaterials

• All flammable vapors will rise in the atmosphereFalse

Apparatus marked IIA can be used in a IIC hazardous area False

A Zone 2 area indicates that a flammable atmosphere can occurduring normal operating conditions

The probability and duration of a gas leak in a hazardous area isindicated by the Zone

Generally, apparatus with a T3 temperature rating can be usedFalse

in place of apparatus rated T4

Documents

Explosion Proof Triangle