In “What is ATEX?" is explains what ATEX is, but to find the right ATEX certified sensor, a basic knowledge about the different ATEX zones is important. This article explains which ATEX zones there are and when which ATEX certification applies.
Which ATEX zones are there?
An ATEX environment can be divided into zones, each with its own specific risks and regulations for the use of equipment. Of the six EX zones three gas zones and three dust zones specified where an explosive atmosphere is or may be present.
Gas zones: there is an explosive liquid, vapor or gas in the atmosphere, or there is a risk of this.
Dust zones:explosive solids, fibers or dust particles are present or there is a risk of this. Examples include: Granulates, wood fiber and saw dust, or powdered food ingredients, animal feed, etc.
Classification of the different ATEX zones
ATEX gas zones
In ATEX zone 0, or Ex zone 0, there is a high to permanent risk of an explosion hazard, because an (almost) always explosive gas mixture is present for longer periods. To classify an Ex zone as ATEX zone 0, an explosive atmosphere is present for more than 10% of the operating time. A common Zone 0 application is level measurement in an enclosed oil storage at refineries, oil drilling platforms or in bulk transport such as on LNG tankers or oil tankers. Another common application is monitoring the temperature of an explosive mixture. In zone 0 applications, our optically safe laser sensors and pyrometers can be found in particular. This is possible with the expolsion safe ExTemp temperature sensors from Calex.
In an Ex zone 1 gas environment, the risk of the presence of an explosive gas mixture is less great, the frequency of its presence lower and the duration on average shorter. However, the risk of the presence of an explosion hazard is still very real. When an explosive atmosphere is present between 0.1% and 10% of the time, an area is classified as Ex zone 1. This does not mean that when an explosive atmosphere is present, it is less dangerous than in a Zone 0 application. Because during normal use there is still a great risk of the presence of an explosive gas or dust mixture, very strict requirements are also set for zone 1 Ex sensors. Common zone 1 applications are distance measurements to an oil tanker or presence detection from a helicopter on the heli-deck of an oil drilling platform. Ex-compliant laser distance sensors are often used for this, such as the LAM 50 Ex d distance laser. All our ATEX lasers are certified as optically safe. Other common applications are monitoring the explosive atmosphere using thermal imaging cameras or monitoring the temperature in the process using pyrometers. In addition, various sensor applications can be found in Zone 1, such as measuring up to an object, object detection in zone 1, positioning and monitoring of products and processes, via ultrasonic sensors, photoelectric and laser sensors. A very capable set of photoelectric sensors are the LT G 30 EX 15 (transmitter) and LR G 30 EX 15 (receiver) from the LT/LR series.
Finally, an Ex gas environment can be referred to as Ex zone 2. In a zone 2 gas environment, in normal use, the chance that an explosive atmosphere is present is very small and if it is present, this will only be for very short periods. For Ex zone 2, it is assumed that the risk of the presence of an explosive atmosphere is less than 0.1% of the operating time. The least stringent requirements are imposed on equipment for use in ATEX zone 2, because the risk of the presence of an explosive atmosphere is very small and hardly or never occur in normal operation. An Ex zone 2 is the most common Ex gas zone. Sensor Partners offers a wide range of contactless sensor solutions for the Ex zone 2 environment. An example is the very versatile LAM 300 Ex d distance laser from Sensor Partners which is equipped for both detection and measurements in environments with and without explosion risk!
ATEX fabric zones
The ATEX dust zones are classified in Ex zone 20, Ex zone 21 and Ex zone 22. The zoning of dust zones is done in a similar way as the zoning of the Ex gas zones 0 = 20, 1 = 21 and 2 = 22. The main difference is in the technical requirements for the sensors. The use in Ex dust environments and thus the way in which they are certified is different. As a result, it is possible that a sensor is suitable for use in an Ex zone 22, but may not be used in an ATEX zone 2 application. However, in practice it appears that a product will be suitable for both zones in a large part of the situation.
Finally, it is important to know that on an ATEX certified product it is mandatory to affix an Ex mark. Strict requirements are attached to this marking to ensure that the correct information is displayed in the correct manner.
Requirements for equipment in various ATEX zones
Ex equipment (sensors) is divided into the following groups and categories:
ATEX equipment Group I: Equipment intended for underground use in mining and in above-ground mining installations. Gases and / or flammable substances can be released here, because an explosive atmosphere is present or can be.
ATEX equipment Group II: All other environments where there is a risk of explosion due to the (possible) presence of an explosive dust and / or gas mixture.
Categories within group II are:
Device category 1:
Device category 2:
Device category 3:
Applicable for ATEX Zone 0 (gas) or ATEX Zone 20 (dust). An explosive atmosphere is present continuously, long or repeatedly. The same requirements apply to Zone 1 and Zone 21 equipment, with the following additional requirement. The protection method of the device must be double and independent of each other. In addition, safety must be guaranteed if two faults occur independently of one another, or if one of the two types of protection is lost.
Applicable for ATEX Zone 1 (gas) or ATEX Zone 21 (dust). In normal operation it is likely that an explosive atmosphere is occasionally created. Think of the inside of a silo, or the deck of an oil tanker. The same requirements apply to Ex Zone 1 and Ex Zone 21 equipment as for Ex Zone 2 and Ex Zone 22, with the additional requirement that in the event of frequent faults and defects in the device, which normally have to be taken into account, no explosive atmosphere may ignite.
Applicable for ATEX Zone 2 (gas) or ATEX Zone 22 (dust). An explosive atmosphere will seldom and will only be present for a short time. In normal operation, this equipment must not be able to ignite an explosive atmosphere. The Ex zones 2 and 22 are the most common zones, in about 95% of the cases it concerns a zone 2 or 22 application. It makes sense that category 3 is the most common device category within the ATEX Sensors package. A Zone 2 or 22 situation occurs in a wide range of applications, including paint factories, sawmills, bulk warehouses, chemical and petrochemical, oil and gas, F&B (food & beverage), animal husbandry, biogas plants, recycling machinery, petrol stations et cetera.