Explosion Proof Crane

Explosion Proof Crane Specs

Explosion Proof Classifications
Class Definitions
Class I Locations: Are those in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.
Class II Locations: Are those which are hazardous due to the presence of combustible dust.
Class III Locations: Are those which are hazardous due to the presence of easily ignitable fibers or flyings, but in which such fibers or flyings are not likely to be in suspension in the air in quantities to produce ignitable mixtures.
Division I Locations in which hazardous concentrations in the air exist continuously, intermittently, or periodically under normal operating conditions.
Division II Locations in which hazardous concentrations are handled, processed, or used but are normally within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown. 
Group (Class I)  
Group A Atmospheres containing acetylene.
Group B Atmospheres containing hydrogen, or gases (or vapors) of equivalent hazard, such as manufactured gas.
Group C

Atmospheres containing ethyl-ether vapors, ethylene or cyclo propane. 
Group D

Atmospheres containing gasoline, hexane, naptha, benzine, butane, alcohol, acetone, benzol, lacquer solvent vapors, or natural gas.
Group (Class II)  
Group E Atmospheres containing metal dust, including aluminum, magnesium and their commercial alloys and other metals of similarly hazardous characteristics.
Group F  Atmospheres containing carbon black, coal, or coke dust.
Group G Atmospheres containing flour, starch, or grain dust.

Hazardous locations are defined by these classes, divisions and groups, in accordance with National Electric Code (NEC). 

NEC does not specify mechanical features. The end user must specify if spark resistant features are required. Spark resistant features when applied to hoist equipment may decrease the lifting capacity and increase the cost.

Temperature classification

Another important consideration is the temperature classification of the electrical equipment. The surface temperature or any parts of the electrical equipment that may be exposed to the hazardous atmosphere should be tested that it does not exceed 80% of the auto-ignition temperature of the specific gas or vapor in the area where the equipment is intended to be used.

The temperature classification on the electrical equipment label will be one of the following (in degree Celsius):

USA °C UK °C Germany °C
Continuous - Short Time
T1 - 450 T3A - 180 T1 - 450 G1: 360 - 400
T2 - 300 T3B - 165 T2 - 300 G2: 240 - 270
T2A - 280 T3C - 160 T3 - 200 G3: 160 - 180
T2B - 260 T4 - 135 T4 - 135 G4: 110 - 125
T2C - 230 T4A - 120 T5 - 100 G5: 80 - 90
T2D - 215 T5 - 100 T6 - 85  
T3 - 200 T6 - 85    

The above table tells us that the surface temperature of a piece of electrical equipment with a temperature classification of T3 will not rise above 200 °C.

Auto-ignition temperatures

The auto-ignition temperature of a liquid, gas or vapor is the temperature at which the substance will ignite without any external heat source. The exact temperature value determined depends on the laboratory test conditions and apparatus. Such temperatures for common substances are:

Gas Temperature
Methane 580 °C
Hydrogen 560 °C
Propane 493 °C
Ethylene 425 °C
Acetylene 305 °C
Naphtha 290 °C
Carbon disulfide 102 °C

The surface of a high pressure steam pipe may be above the autoignition temperature of some fuel/air mixtures.

Auto-ignition temperatures (dust)

The auto-ignition temperature of a dust is usually higher than that of vapours & gases. Examples for common materials are:

Substance Temperature
Sugar 460 °C
Wood 340 °C
Flour 340 °C
Grain dust 300 °C
Tea 300 °C

Type of protection

To ensure safety in a given situation, equipment is placed into protection level categories according to manufacture method and suitability for different situations. Category 1 is the highest safety level and Category 3 the lowest. Although there are many types of protection, a few are detailed

 Type Ex Code Description Standard Location Use
Flameproof d Equipment construction is such that it can withstand an internal explosion and provide relief of the external pressure via flamegap(s) such as the labyrinth created by threaded fittings or machined flanges. The escaping (hot) gases must sufficiently cool down along the escape path that by the time they reach the outside of the enclosure not to be a source of ignition of the outside, potentially ignitable surroundings.

Equipment has flameproof gaps (max 0.006" propane/ethylene, 0.004" acetylene/hydrogen)

IEC/EN 60079-1 Zone 1 if gas group & temp. class correct Motors, lighting, junction boxes, electronics
Increased Safety e Equipment is very robust and components are made to a high quality IEC/EN 60079-7 Zone 2 or Zone 1 Motors, lighting, junction boxes
Oil Filled o Equipment components are completely submerged in oil IEC/EN 60079-6 Zone 2 or Zone 1 switchgear
Sand/Powder/Quartz Filled q Equipment components are completely covered with a layer of Sand, powder or quartz IEC/EN 60079-5 Zone 2 or Zone 1 Electronics, telephones, chokes
Encapsulated m Equipment components of the equipment are usually encased in a resin type material IEC/EN 60079-18 Zone 1 (Ex mb) or Zone 0 (Ex ma) Electronics (no heat)
Pressurised/purged p Equipment is pressurised to a positive pressure relative to the surrounding atmosphere with air or an inert gas, thus the surrounding ignitable atmosphere can not come in contact with energized parts of the apparatus. The overpressure is monitored, maintained and controlled. IEC/EN 60079-2 Zone 1 (px or py), or zone 2 (pz) Analysers, motors, control boxes, computers
Intrinsically safe i Any arcs or sparks in this equipment has insufficient energy (heat) to ignite a vapour

Equipment can be installed in ANY housing provided to IP54.
A 'Zener Barrier' or 'opto isol' or 'galvanic' unit may be used to assist with certification.
A special standard for instrumentation is IEC/EN 60079-27, describing requirements for Fieldbus Intrinsically Safe Concept (FISCO) (zone 0, 1 or 2)

IEC/EN 60079-25
IEC/EN 60079-11
'ia': Zone 0 &
'ib': Zone 1
'ic: zone 2
Instrumentation, measurement, control
Non Incendive n Equipment is non-incendive or non-sparking.

A special standard for instrumentation is IEC/EN 60079-27, describing requirements for Fieldbus Non-Incendive Concept (FNICO) (zone 2)

IEC/EN 60079-15
IEC/EN 60079-27
Zone 2 Motors, lighting, junction boxes, electronic equipment
Special Protection s This method, being by definition special, has no specific rules. In effect it is any method which can be shown to have the required degree of safety in use. Much early equipment having Ex s protection was designed with encapsulation and this has now been incorporated into IEC 60079-18 [Ex m]. Ex s is a coding referenced in IEC 60079-0. The use of EPL and ATEX Category directly is an alternative for “s” marking. The IEC standard EN 60079-33 is made public and is expected to become effective soon, so that the normal Ex certification will also be possible for Ex-s IEC/EN 60079-33 Zone depending upon Manufacturers Certification. As its certification states

The types of protection are subdivided into several sub classes, linked to EPL: ma and mb, px, py and pz, ia, ib and ic. The a subdivisions have the most stringent safety requirements, taking into account more the one independent component faults simultaneously.