Technical articles

As often happens, people's sensitivity to certain issues and events increases when accidents occur, even fatal, in proportion to the severity of the accident.

 

Recent news events lead us to a more than necessary reflection on the activities of loading and unloading fuels at petrol refuelling stations.

 

Everyone will have witnessed, during the refuelling operations of his car, the loading of tanks buried by self-propelled vehicles without paying attention to the procedures put in place during these operations nor to the clearly written instructions on each pump such as switch off the engine, do not smoke and last but not least, switch off the mobile phone.

  

 

The constant and continuous technical evolution consequently leads to the need to update reference standards of everything concerning the installation, operation and maintenance of the electro-instrumental equipment suitable for installation and operation in environments with the presence of explosive gases or dusts.

 

For these reasons, it is essential that the designer, the manager and maintenance operator of such equipment must have all the regulatory tools always present and constantly updated, in order to correctly design and size the electro-instrumental equipment and then to keep them constantly efficient, respecting the protection of people and things.

 

 

The following list of the regulations describes the fundamental criteria to be adopted for the construction, installation and maintenance of electro-instrumental equipment.

Dust explosions can occur in any activity in which solid materials are treated and finely divided (metals, organic substances, polymers, resins, coals, wood, etc.). Dust may be the end product of a process or an unwanted by-product. Even very common substances such as wheat flour, cocoa powder, icing sugar, tea, coffee, present an explosion hazard, often masked by their familiar appearance, when they are treated, in powder form, on industrial scale in milling, transport, separation, drying processes.

A myriad of small-sized particles is produced during the processes, thus creating dust. The particles with dimensions that are too large to remain suspended in the air are deposited, while the smaller ones remain suspended for an unlimited period.

 

The powders are measured in microns (μm). The micron is a unit of length equal to 10-4 (0,0001) centimeters or about 1/ 25,000 of an inch.

The electric energy in alternating current produced by thermal systems (coal-fired or oil power stations etc.) or by hydroelectric plants, is "non-accumulable" while the energy in direct current can be stored using devices called "Battery". This system allows to dispose of the energy over time and to be able to use it even in the absence or failure of the supply of traditional energy in alternating current.

 

With the rechargeable batteries, the charge can be completely re-established through the application of adequate electrical energy, with voltage/current control.

In the plant concept it has always been of primary importance the physical separation between safe area and classified area. This concept was applied in the electric energy transport systems by means of cables buried in sand bed and then derived to the user (an electric motor or a junction box or an end user) with the use of a conduit tube suitable for the insertion of electrical cables (Freez-Moon) free from internal ridges and terminated on the end user through a physical separation made with explosion-proof sealing device (for example a sealing fitting).

 

With the advent of the IEC/EN 61241-0 and IEC/EN 60079-0 standards, as well as the IEC/EN 60079-1 standard, changed the concept of cable entry in electrical and electronic equipment suitable for areas with danger of explosion, allowing to have the cable entry with appropriate sealing cable gland.