Industrial communication in explosion hazardous areas (with MTL components)

In some industrial companies explosion hazardous areas can occur. Explosion hazardous areas (Ex) are zones, in which there are substances which mixed with oxidizing gas e.g. air after ignition, makes the burning process spread to the whole substance.  

The concentration of the combustive compound in such area is within the range of explosiveness limits that are explained as follows:

• Lower limit of explosiveness is the intensity value of the combustive component in the compound with air or oxygen, above which the energy impulse can cause an explosion.
• Upper limit of explosiveness is the intensity value of the combustive component in the compound with air or oxygen, below which the energy impulse can cause an explosion.

Some types of the energy impulse - sources of ignition, include: electric sparks, sparks created mechanically, electrostatic sparks, or hot air.

According to § 5.1. Regulation by the Minister of Economy issued on 8th July 2010 “concerning the minimum requirements of safety and work hygiene, connected to the possibility of the explosion area occurrence in the workplace” (OJ 2010 no. 138 posit. 931) areas, in which explosive atmosphere can occur, are assigned according to the classification to explosive areas. According to the PN-EN-1127-7-2001 norm, we divide areas into the following groups:

Liquids and gases are classified into three areas - 0, 1 and 2:

• Area 0 is a space where the explosive atmosphere that includes air mixed with combustive substances like mist, steam, gases, occurs permanently, often or for long periods of time.
• Area 1 is a space where the explosive atmosphere that includes air mixed with combustive substances like mist, steam, gases, can occur during a typical operation.
• Area 2 is a space where the explosive atmosphere that includes air mixed with combustive substances like mist, steam, gases, does not occur during the typical operation, but if it does, it stays for a short period of time. 

Dusts, powders and fiber are classified into three areas - 20, 21, 22:

• Area 20 is a space where the explosive atmosphere in the form of combustive powder puff occurs permanently, often or for long periods of time.
• Area 21 is a space where the explosive atmosphere in the form of combustive powder puff can occur during a typical operation.
• Area 22 is a space where the explosive atmosphere in the form of combustive powder puff does not occur during a typical operation, and if it occurs, it remains for a short period of time.

The occurrence of explosive substances requires special devices intended for use in explosion hazardous areas, which can minimize the risk of ignition, thus also improve work safety. Eaton MTL offers the following two solution groups, which can be used for communication in explosion hazardous areas:

• Cable Ethernet
• MTL Industrial Wireless

Cable Ethernet is currently the most popular type used by companies. While designing an Ethernet network many power and communication methods should be taken into consideration e.g. communication standards of RS232 and RS485, and various outputs 4-20 mA, which makes it difficult to connect everything to the communication system. Additionally, Ethernet communication between drivers and input/output subsystems stretches also beyond control cabinets to the surface of the workshop. Remote input/output applications with requirements concerning video and phone communication brings Ethernet also to process areas.

Implementation of cable Ethernet to workshops is difficult due to harsh work conditions of the device, which operates in a given area e.g. work near explosive gases, accumulated dusts. High costs of protection of the general use Ethernet network in explosion risk areas, alongside with the maintenance limitations, decreased the usage of both cable and wireless Ethernet. Many final users prefer applying in hazardous areas intrinsically safe devices of small power, such as instrumentation, and after many investments, provide design, installation and maintenance personnel training in this technology.

Intrinsically safe Ethernet is currently used in two options: copper cables for short distances, and fiber- optic for long distances. It allows providing WLAN infrastructure, which makes it possible to use intrinsically safe computers and tablets. It decreases the costs of installation and simplifies the network’s architecture.

In the category of intrinsically safe Ethernet, Eaton MTL offers:

• Intrinsically safe power supply 
• Interfaces connecting Ethernet with intrinsically safe Ethernet 
• Cameras for controlling processes
• Instrumentation connected to Ethernet
• Ethernet interface
• Adapters from RS485/RS422/RS232 to intrinsically safe Ethernet

MTL offers a wide range of elements from wireless solutions: from simple replacement of the wire in sensors up to extensive 802.11 networks in explosion hazard areas. MTL wireless technology allows building reliable and safe systems, which can use standard connection and protocols, thus providing flexibility and decreasing storage costs. 

Benefits of wireless MTL devices:

• they enable work in harsh or protected  environments, where cables are continuously damaged because of difficult conditions,
• they also enable long distance communication, 
• they allow accessing measurement data for the personnel, which makes the result analysis faster,
• they are easier to install than cable ones,
• they are also easier to scale than the cable solutions,
• wireless networks can be tested before installation.

MTL offers a wide range of elements connected to designing and exploitation of wireless networks:

• antennas and elements needed for designing wireless network
• modems
• interfaces
• transmitters
• transducers

Author: Marek Piątkowski-Zajec

Contact:

[email protected]

+48 22 70 35 226