1. ATEX Zone 1 and Zone 2 Classification
IEC 60079-10-1 defines three zones for areas where explosive gas, vapour, or mist atmospheres may be present. The zone classification is based on the frequency and duration of the explosive atmosphere occurrence, not on the toxicity or quantity of the material. Every motor installed in a hazardous area must be certified for the zone in which it is installed.
Inside tanks, vessels, and enclosed spaces where explosive vapour-air mixtures are present continuously or for long periods (more than 1,000 hours per year). Standard motors including explosion-proof motors are NOT suitable for Zone 0. Zone 0 requires intrinsically safe (Ex ia) equipment specifically certified for this zone. Chemical plant equipment installed inside enclosed process vessels falls in Zone 0; motors driving agitators inside vessels are installed outside the vessel and are typically in Zone 1.
Areas around vent openings, pump seals, flanged connections, and process equipment where explosive vapour may be released during normal operation (10 to 1,000 hours per year). Pump rooms handling flammable solvents, areas within 0.5 m of open drainage systems, and areas around sample points on process pipework are typically classified as Zone 1. All motors in Zone 1 must be ATEX or IECEx certified Ex d, Ex e, or equivalent for Group II gases and the specific temperature class of the location.
Areas where explosive vapour is not expected during normal operation but may occur infrequently or for short periods (below 10 hours per year) — typically the area surrounding Zone 1 extending 1 to 3 m from Zone 1 boundaries. General outdoor areas of a chemical plant where flammable material is processed are typically Zone 2. Motors in Zone 2 must be ATEX/IECEx certified Ex d or Ex e for Group II gases. A Zone 1 certified motor (Ex d IIB T4) is also suitable for Zone 2 installation.
Compliance requirement: using a standard non-explosion-proof motor in a Zone 1 or Zone 2 classified area is a violation of the ATEX Directive (EU 2014/34/EU), the IECEx scheme, and national safety legislation in most countries. It creates an ignition source in an area where explosive atmospheres may be present. The motor does not need to be running at the time of a spark event — internal arcing at contactor switch-on, brush sparking in wound-rotor motors, or static discharge from motor frames can all initiate an explosion in a Zone 1 or Zone 2 atmosphere. Only Ex-certified motors may be installed in classified zones.
2. Gas Group Classification: IIA, IIB, IIC
Group II gases are divided into three subgroups based on their maximum experimental safe gap (MESG) and minimum igniting current (MIC) ratio — both of which determine how likely a spark or hot surface inside the motor can propagate to an external explosive atmosphere through the flameproof enclosure joints. The motor must be certified for a gas group that covers the most hazardous gas present in the classified area.
| Gas Group | Typical Gases and Solvents | MESG | Motor Certification Required | YB2 Suitable? |
|---|---|---|---|---|
| IIA | Propane, butane, methane, acetone, ammonia, ethanol, toluene, xylene, methanol | > 0.9 mm | Ex d IIA or higher | Yes (IIB covers IIA) |
| IIB | Ethylene, diethyl ether, isopropyl alcohol, butadiene, vinyl chloride, styrene | 0.5–0.9 mm | Ex d IIB or higher | Yes (YB2 is IIB) |
| IIC | Hydrogen, acetylene, carbon disulphide — highest explosion risk | < 0.5 mm | Ex d IIC only | No (requires IIC motor) |
The Korea Ever-Power YB2 series is certified Ex d IIB T4, meaning it is suitable for all Group IIA and IIB gases and vapours — covering the vast majority of chemical plant atmospheres including most organic solvents, petroleum fractions, and process gases. For areas where hydrogen (Group IIC) is the hazardous material — electrolysis plants, hydrogen storage, and some battery facilities — a Group IIC certified motor is required and the YB2 IIB is not adequate. Please confirm the specific gas group with the area classification document before specifying the motor.
3. Temperature Class T4 Explained
The temperature class of an explosion-proof motor limits the maximum surface temperature of the motor enclosure to below the auto-ignition temperature of the hazardous atmosphere present. If the motor surface temperature exceeds the auto-ignition temperature of the surrounding explosive mixture, ignition can occur without any spark — hot surface ignition is as dangerous as electrical sparking in a hazardous area.
The T4 temperature class of the YB2 (135°C surface limit) covers ethylene (auto-ignition 490°C), diethyl ether (160°C), acetaldehyde (175°C), and most common organic solvents encountered in chemical manufacturing. The area hazardous area classification document must specify the temperature class required for the specific atmosphere — never assume the default class is adequate without checking the auto-ignition temperature of the most flammable material present.
4. Ex d Flameproof vs Ex e Increased Safety
Ex d motors are designed to contain any internal explosion within the motor housing and prevent propagation to the external atmosphere. The motor is not spark-free internally — instead, the housing is built to withstand the internal explosion pressure (typically 10 to 15 bar) and all external joints are designed with precise gap dimensions (MESG) that cool any escaping hot gas below the ignition temperature of the surrounding atmosphere before it exits. Ex d motors are suitable for Zone 1 and Zone 2.
Ex e motors prevent the occurrence of sparks, arcs, or hot surfaces under normal operation and under specified overload conditions, by applying enhanced construction standards to eliminate the internal ignition sources that Ex d merely contains. Ex e motors have no brush contacts, no commutator, and use enhanced winding insulation and temperature monitoring. Ex e squirrel-cage motors are often preferred in Zone 2 because their open enclosure (compared to the sealed heavy cast iron Ex d enclosure) provides better natural ventilation and cooling, improving efficiency and reducing weight. Ex e motors require mandatory winding temperature monitoring (PTC thermistors) connected to a certified protection relay.
5. Korea Ever-Power YB2 Series Specifications
The Korea Ever-Power YB2 series is a three-phase squirrel-cage induction motor certified to Ex d IIB T4 under both the ATEX Directive and the IECEx scheme. It is suitable for installation in Zone 1 and Zone 2 hazardous areas where the explosive atmosphere is classified as Group IIA or IIB (including most organic solvents, petroleum fractions, and chemical plant gases other than hydrogen and acetylene). The full YB2 range is available in the explosion-proof motors product section.
The YB2 is built on the same IEC 72-1 metric frame platform as the standard Y2 series, allowing it to replace a standard Y2 motor in an existing installation with no modification to the motor baseplate, coupling, or conduit entry positions. The heavy-duty cast iron enclosure provides IP55 protection for outdoor chemical plant installation exposed to rain and hose-down cleaning. The terminal box is sealed with an Ex d certified cable gland position for use with armoured cable or conduit systems in the hazardous area.
| Certification | ATEX + IECEx: Ex d IIB T4 |
| Zone suitability | Zone 1 and Zone 2 |
| Gas group | IIA and IIB (not IIC) |
| Surface temp limit | T4 = 135°C maximum |
| Power range | 0.55–200 kW |
| Enclosure | IP55, cast iron frame |
| Voltage / frequency | 380 V 50 Hz standard |
| Frame | IEC 72-1 (same as Y2) |
| Insulation | Class F |
6. Chemical Plant Applications
Solvent and Chemical Transfer Pumps
Centrifugal and gear pumps handling flammable solvents — ethanol, toluene, xylene, acetone, methanol, methylene chloride — are installed in Zone 1 around the pump seal and flanges. YB2 Ex d IIB T4 motors in 0.75 to 22 kW, 2-pole or 4-pole, provide the certified hazardous area protection required. The motor is direct-coupled to the pump via flexible coupling on a common baseplate outside the Zone 0 interior of the vessel or tank. IP55 for outdoor chemical plant installation; Ex d cable glands mandatory on all terminal box entries. |
Ventilation and Exhaust Fan Drives
Chemical plant ventilation fans and fume extraction systems handling flammable vapour-laden air are installed in Zone 1 at the duct connection and Zone 2 in the surrounding area. YB2 Ex d IIB T4 motors in 1.5 to 30 kW drive the fans through a V-belt or direct coupling. For paint spray booths, coating lines, and solvent recovery units where exhaust fans handle solvent-laden air at concentrations that may approach the lower explosive limit (LEL), Ex d certification to the appropriate gas group is mandatory regardless of the ambient zone classification of the surrounding area. |
External agitator motors driving stirrers inside chemical reactors through mechanical seals are in Zone 1. YB2 4-pole or 6-pole in 1.5 to 22 kW, typically paired with NMRV worm gearbox for slow agitation speed (10 to 60 rpm). Both motor and gearbox must be in Ex d enclosures.
Gas compressors and process air blowers in chemical plant areas handling flammable process gas require YB2 Ex d IIB T4 motors in 5.5 to 200 kW. The motor must be grounded to the compressor skid frame with an Earth bonding conductor sized to carry the full motor fault current for a time sufficient to operate the fuse or circuit breaker.
Liquid product loading pumps at tank farm bays handling petroleum products (petrol, diesel, jet fuel) are Zone 2 during normal operation and Zone 1 during loading. YB2 Ex d IIB T4 provides Zone 1 certification applicable to both normal and loading conditions without requiring two different motor specifications.
Chemical plant effluent pumps handling solvent-contaminated wastewater may be in Zone 2 if solvent concentrations above 25% LEL are possible. Where classified as Zone 2, YB2 Ex d IIB T4 provides the required certification with IP55 for outdoor sump and pit installation.
7. Installation Rules for Hazardous Area Motors
All cable entries into a YB2 terminal box must use Ex d certified cable glands of the correct type and diameter for the cable used. Standard IP68 or waterproof cable glands are not sufficient for Ex d applications — the gland must be specifically certified for use with Ex d enclosures and must be installed to maintain the Ex d integrity of the terminal box as defined in IEC 60079-0.
The YB2 motor frame must be connected to the plant earth bonding network with a dedicated earthing conductor connected to the external earth bonding bolt provided on the motor frame. Earth continuity must be verified as part of the pre-commissioning inspection and recorded in the area electrical inspection records.
In Zone 1 installations where the motor may experience extended overload conditions (such as pump blockage or cavitation), PTC winding thermistors should be installed and connected to a certified thermistor relay. An overloaded Ex d motor may develop surface temperatures above the T4 limit of 135°C before the motor overload relay trips, creating an ignition hazard even with a correctly sized motor.
Hazardous area electrical equipment (including Ex d motors) must be periodically inspected per IEC 60079-17 to verify that the Ex d integrity is maintained — that all fasteners are present, terminal box lid is correctly fitted, cable glands are tight, and the motor frame is not corroded. In Zone 1 areas, close inspection is typically required at least every 3 years; in Zone 2 every 5 years.
8. Frequently Asked Questions
Edited by Cxm
