Hazardous area classification decides which motor you are allowed to install, and it happens before motor selection, not during it. The classification exercise divides a site into zones according to how often an explosive atmosphere is present. The zone then sets the equipment protection level, the protection level sets the acceptable protection concepts, and the gas present sets the gas group and temperature class. A motor is selected against all four. Skip any one and the certificate on the nameplate does not cover the installation.

One point before anything else. Area classification is the responsibility of the site operator, carried out by a competent person with access to the process data. It is not something a motor supplier can do for you, and no reputable supplier will offer to. What a supplier can do is tell you which motor matches the classification you provide, which is what this article is about.

TL;DR

• Classify the area first. Zone 0, Zone 1 and Zone 2 describe how often an explosive gas atmosphere is present, and each zone permits a different equipment protection level.

• Flameproof (Ex d) motors are for Zone 1 and Zone 2. They are not certified for Zone 0.

• Ex d contains an internal explosion. Ex e prevents one by design margin. Ex e is typically lower cost where the classification allows it.

• Gas group and temperature class are two separate checks. Hydrogen needs the most demanding gas group, IIC, but only a modest temperature class. Neither compensates for the other.

• The single most common buyer error is specifying “flameproof” without stating the gas group.

• IEC 60079-0 assumes standard atmospheric conditions of minus 20 to plus 60 degrees C and 80 kPa to 110 kPa. Hot Indian plant rooms and high-altitude African sites can fall outside that, and flameproof protection depends on flame quenching, which is pressure dependent.

What does hazardous area classification actually decide?

Hazardous area classification is the process of dividing a plant into zones based on the likelihood and duration of an explosive gas atmosphere being present, so that electrical equipment installed in each zone carries a level of protection appropriate to that risk. It produces a drawing and a schedule, not an equipment list, and everything downstream flows from it.

The chain runs in one direction:

1. The process defines the release sources. What substance, at what pressure, from which flange, vent, seal or drain.

2. The release sources and ventilation define the zones. Extent and grade, marked on a classification drawing.

3. The zone defines the equipment protection level (EPL). Ga, Gb or Gc for gas atmospheres, with Ga the highest level of protection.

4. The EPL defines the acceptable protection concepts. Flameproof, increased safety, intrinsic safety, pressurisation and others.

5. The substance defines gas group and temperature class. Independently of the zone.

A motor selection that starts at step 5 and works backwards is guesswork. A motor selection that starts at step 1 is engineering. The classification drawing is the document that must exist before an enquiry goes out.

Zone 0, Zone 1 and Zone 2: what each permits

The three gas zones describe frequency and duration of exposure, and each maps to an equipment protection level.

The point that catches people out is the first row. A flameproof motor is not a Zone 0 motor. Flameproof protection achieves EPL Gb, which suits Zone 1 and, by the hierarchy, Zone 2. Equipment for Zone 0 requires EPL Ga, which flameproof enclosures do not provide. If a classification drawing puts a Zone 0 boundary around a pump that needs a motor, the answer is to move the motor out of the zone or to change the process, not to buy a heavier enclosure.

The flameproof motors supplied by New India Electricals Ltd are stated for Zone I and Zone II for exactly this reason, and the range runs 0.09 to 200 kW across frames 63 to 355, at 220, 380, 415, 550 and 690 V, 50 or 60 Hz, in cage or wound rotor construction.

Ex d or Ex e: which protection concept belongs where

Flameproof, marked Ex d, contains an internal explosion. The enclosure is built to withstand the pressure of an explosion inside it and to cool the escaping gases through toleranced flame paths so that the flame is not transmitted to the surrounding atmosphere. It suits continuous or frequent presence of an explosive atmosphere.

Increased safety, marked Ex e, eliminates ignition sources by design margin rather than containment. Creepage and clearance distances, temperature limits and connection quality are all specified conservatively so that arcs, sparks and hot surfaces do not occur in normal operation. It is typically lower cost than Ex d where the area classification allows it.

Three practical consequences follow:

• Ex d cost sits in the casting and the machining. The enclosure and the flame paths are the expensive parts, which is why a flameproof motor is heavier and dearer than an equivalent standard machine at the same kW.

• Ex e cost sits in the derating and the protection. The design margin has to come from somewhere, and Ex e machines carry a specified maximum time from a locked-rotor condition, which the motor protection must be set to respect.

• Cable entry is part of the certification, not an accessory. On the flameproof range the terminal box is cast iron and forms a separate flameproof enclosure in its own right, capable of containing an internal explosion, and the enclosures are hydraulically tested to 10 kg per square centimetre. A non-certified gland fitted to that box invalidates the arrangement.

Gas group and temperature class are two separate checks

The most common customer error is specifying “flameproof” without stating the gas group. A motor marked Ex d with no gas group and no temperature class is not a specification, it is an aspiration.

Gas group and temperature class measure different physical properties and neither compensates for the other. Gas group describes how readily a flame propagates through a narrow gap. Group IIA covers gases such as propane, IIB covers ethylene, and IIC covers hydrogen and acetylene, which are the most demanding. The applications the flameproof range is built for reflect this spread: pumps in coal mines, fans in petrochemicals and on rigs, compressors in fertiliser, solvent extraction, paint and varnish, LPG bottling and pharmaceutical plants, and conveyors on oil mines and rigs. Equipment certified for a more demanding group covers the less demanding ones, so IIC equipment is acceptable in IIB and IIA atmospheres, but IIA equipment is not acceptable in IIB or IIC.

Temperature class describes the maximum surface temperature the equipment can reach, so that no surface can reach the auto-ignition temperature of the surrounding substance.

Confirm these values and the auto-ignition temperature of your specific substance against IEC 60079-0 and IEC 60079-20-1 and the substance safety data sheet before they enter a purchase order. Values circulating on the internet are not consistent, and this is not a table to take from a blog, including this one.

The illustration that makes the separation clear is hydrogen. Hydrogen sits in gas group IIC, the most demanding group, because it propagates a flame through a very small gap. Its auto-ignition temperature is high, so it needs only a modest temperature class. A supplier who reads “hydrogen” and reaches for T6 has understood half the problem. A supplier who reads “hydrogen” and reaches for IIA has understood none of it.

Gas group and temperature class must both match the actual hazardous substance on site. That means the substance has to be named in the enquiry.

Why site ambient and altitude can put you outside the certificate

IEC 60079-0:2017, the general requirements standard for equipment in explosive atmospheres, states the standard atmospheric conditions under which certified equipment may be assumed to operate: temperature minus 20 degrees C to plus 60 degrees C, pressure 80 kPa to 110 kPa, and air with normal oxygen content, typically 21 percent by volume. Operation outside that range needs further consideration and may need additional testing.

The standard is explicit that this matters most for protection concepts that depend on quenching a flame, which is precisely what a flameproof enclosure does. Two site conditions push against it:

• Ambient temperature. A certificate carries a stated ambient range, usually shown as Ta or Tamb. An enclosed pump house or a plant room next to a process heater can exceed the assumed ambient, and at higher ambient the equipment reaches its temperature class limit at lower dissipation. Measure the ambient where the motor breathes, not the outdoor shade temperature.

• Altitude and pressure. Atmospheric pressure falls with altitude, and 80 kPa is reached at roughly two thousand metres. Sites on the Zambian Copperbelt, in the Kenyan highlands and across Gauteng sit high enough that pressure deserves a check rather than an assumption. This is a question to put to the certifying body and the manufacturer, not one to resolve locally.

Neither point means a flameproof motor cannot be used at altitude or in a hot plant room. It means the certificate has boundaries, those boundaries are written down, and somebody has to confirm the site sits inside them.

What certification a flameproof motor needs in India

Flameproof equipment in India sits under a statutory approval regime rather than a purely voluntary one, and which authority applies depends on the industry. The flameproof range New India Electricals Ltd supplies is approved by Indian notified bodies including BIS, DGMS and PESO, and carries approvals from CMRI Dhanbad, DGMS Dhanbad, CCE Nagpur and DGFAS and LI Mumbai, alongside BASEFA and ATEX for export markets. The motors are built to IS 325 and IS 2148, with Class F or Class H insulation, IP55 enclosure and IC411 cooling.

Four rules govern what a buyer should accept:

1. Match the authority to the industry. Mining applications route through DGMS. Petroleum, LPG and other regulated substances route through PESO, historically the Chief Controller of Explosives. Confirm which applies to your installation before the enquiry, because a certificate from the wrong authority is not a certificate for your site.

2. Check the certificate covers the exact rating and configuration. A certificate is issued against a design and a rating. It does not automatically extend to a different frame, a different voltage or a modified terminal arrangement.

3. Check the certificate is current. Approvals carry validity conditions and are renewed. Ask for the current document, not a scan from a previous project.

4. Keep the certificate with the asset. The document is needed at inspection, at insurance renewal and at every future modification. Filing it with the purchase order rather than the equipment file is how it goes missing. Flameproof machines are built to order rather than held in ready stock, so certification questions belong at enquiry stage.

What we need from you before a flameproof motor can be quoted

A flameproof enquiry that arrives with the following can be quoted accurately. One that arrives without it cannot be quoted at all, only guessed at.

• The zone, from the classification drawing, with the drawing reference.

• The substance, named, with its gas group and auto-ignition temperature or the safety data sheet.

• The temperature class required.

• The ambient temperature at the motor location in the worst month, and the site altitude.

• kW, speed, duty, mounting and voltage, and whether the motor will be fed from a drive.

• The certifying authority required, and whether the end user or insurer imposes any additional regime.

• Cable entry details, since the gland arrangement is part of the certified enclosure.

Where the classification permits it, ask about non-sparking motors as well. On Zone 2 duty they are frequently the more economical answer, and the decision belongs at enquiry stage rather than after the flameproof quotation lands. Where the application involves lifting or holding, flameproof brake motors are a distinct product and the brake itself has to sit inside the certification.

A specification checklist

1. Obtain the current hazardous area classification drawing and confirm it has been prepared by a competent person with the process data.

2. Identify the zone at the exact motor location, not the zone of the general area.

3. Confirm Zone 0 does not apply. If it does, relocate the machine or change the process.

4. Name the substance and establish its gas group and auto-ignition temperature from the safety data sheet.

5. Derive the required temperature class from the auto-ignition temperature, and confirm it against IEC 60079-20-1.

6. Decide between Ex d and Ex e on the basis of the zone and the risk assessment, not on price alone.

7. Confirm the site ambient and altitude fall inside the certificate’s stated conditions, and raise it with the manufacturer if they do not.

8. Specify the certifying authority appropriate to the industry, and require the certificate for the exact rating.

9. Specify the cable entry and gland arrangement as part of the certified equipment.

10. Set the motor protection to respect any time limit stated on the certificate, and record the settings.

11. File the certificate with the equipment record, not the purchase order.

    Frequently asked questions

    What is hazardous area classification?

    Hazardous area classification is the process of dividing a plant into zones according to how likely an explosive gas atmosphere is to be present and for how long, so that electrical equipment installed in each zone carries a matching level of protection. For gas atmospheres the zones are Zone 0, where an explosive atmosphere is present continuously, for long periods or frequently; Zone 1, where it is likely in normal operation; and Zone 2, where it is not likely in normal operation and would only be present briefly. Each zone maps to an equipment protection level, Ga, Gb or Gc respectively, which in turn determines which protection concepts are acceptable. The classification is the responsibility of the site operator and must be carried out by a competent person with access to the process data.

    Can a flameproof motor be used in Zone 0?

    No. Flameproof protection achieves equipment protection level Gb, which covers Zone 1 and, by the hierarchy, Zone 2. Zone 0 requires EPL Ga, which flameproof enclosures do not provide. Rotating machines are not normally installed in Zone 0 at all. If a classification drawing places a Zone 0 boundary over a location that needs a motor, the correct responses are to relocate the machine outside the zone, to extend the shaft or use a magnetic coupling so the motor sits in a lower zone, or to revisit the process and ventilation so the classification changes. Specifying a heavier enclosure does not solve it.

    What is the difference between Ex d and Ex e?

    Ex d, flameproof, contains an internal explosion: the enclosure withstands the pressure and the flame paths cool escaping gases so the flame is not transmitted outside. Ex e, increased safety, prevents an explosion instead of containing one, by applying design margin to creepage, clearance, temperature and connection quality so that arcs, sparks and hot surfaces do not arise in normal operation. Ex d suits continuous or frequent presence of an explosive atmosphere. Ex e is typically lower cost where the area classification allows it, and is common on Zone 2 duty. The choice follows from the zone and the risk assessment, and Ex e machines require the motor protection to be set against the time limit on the certificate.

    What do IIA, IIB and IIC mean, and how do they relate to T1 to T6?

    IIA, IIB and IIC are gas groups, describing how readily a flame propagates through a narrow gap. IIA covers gases such as propane, IIB ethylene, and IIC hydrogen and acetylene. T1 to T6 are temperature classes, describing the maximum surface temperature the equipment may reach, from 450 degrees C at T1 down to 85 degrees C at T6. They are independent checks on different physical properties, and neither compensates for the other. Hydrogen illustrates this: it requires the most demanding gas group, IIC, but only a modest temperature class because its auto-ignition temperature is high. Equipment certified for a more demanding gas group covers the less demanding ones, so IIC covers IIB and IIA, but not the reverse.

    Which authority certifies flameproof motors in India?

    It depends on the industry. Mining applications route through the Directorate General of Mines Safety. Petroleum, LPG and other regulated substances route through the Petroleum and Explosives Safety Organisation, historically the Chief Controller of Explosives. BIS certification applies to the product standard. The flameproof motors supplied by New India Electricals Ltd are approved by Indian notified bodies including BIS, DGMS and PESO, and carry approvals from CMRI Dhanbad, DGMS Dhanbad, CCE Nagpur and DGFAS and LI Mumbai, with BASEFA and ATEX for export. Confirm which authority governs your installation before the enquiry goes out, and require the certificate for the exact rating and configuration being purchased.

    Does a hot or high-altitude site affect a flameproof certificate?

    It can. IEC 60079-0:2017 assumes standard atmospheric conditions of minus 20 to plus 60 degrees C, 80 kPa to 110 kPa pressure, and air at roughly 21 percent oxygen, and it notes that operation outside those conditions may need further consideration and testing, particularly for protection concepts that rely on quenching a flame, which is exactly how a flameproof enclosure works. Atmospheric pressure of 80 kPa corresponds to roughly two thousand metres, which is relevant on high-altitude sites in southern and eastern Africa. Certificates also carry a stated ambient range, usually marked Ta. Establish the real ambient at the motor and the site altitude, and put both to the manufacturer and the certifying body rather than assuming the standard case applies.
    Send the classification drawing and the substance data with the enquiry. New India Electricals Ltd can match a motor to a classification quickly. Nobody can match one to a guess.

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