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Indeed, many companies are potentially at risk here. Why? Because combustible dusts are present in many manufacturing environments. Wood shavings, carbon dust, flour, grain, custard powder, sugar, coffee, tea, animal feed, plastic and aluminium dust are just some examples of highly combustible dusts. The problem is when these combustible dusts are left to gather on hot surfaces in a workplace, such as on an overheated electric motor or fan. This can cause smouldering fires to occur, or can cause an explosion when the dust is kicked up, for example, by a person opening a nearby window.
Dust explosions can have catastrophic consequences because the initial shock wave resulting from the explosion kicks up more dust, which triggers a chain reaction through the plant, often resulting in mass destruction of equipment and buildings, as well as causing possible death or injury to employees.
Therefore, as potential sources of ignition, all electrical equipment installed in these areas, including mixers, filling hoppers, conveyor systems, mills, silos, dust extraction plant, kilns and drying systems, need to be adequately protected and designed to operate under these conditions. Directors, company owners, plant managers and maintenance engineers, in fact anyone who is responsible for the health and safety of employees or for sourcing electrical equipment for hazardous areas - needs to be fully aware of the risks of dust explosions, the European Directives and standards relating to electrical equipment installed in hazardous areas and the measures that can be taken to eliminate the risk of dust explosions occurring. Therefore, the European Directive for hazardous equipment 94/9/EC pointed out that this was valid in the same way for dust explosion-protected equipment as well as for gas hazardous areas.
Owners of new equipment are governed by the compulsory European directive 1999/92/EC, implemented in the UK as the 'Dangerous Substances and Explosive Atmospheres Regulations 2002' (DSEAR). From 2006, this directive also includes 'old' as well as 'new' equipment. In summary, owners are required to identify the risks of explosion; implement explosion protection measures such as avoiding sources of ignition (secondary explosion protection); define zones in areas at risk from dust explosions; create an explosion protection document; use suitable production equipment; and to create a test plan.
The Standards for electrical equipment in areas at risk from dust explosions have seen a few changes in the last few years. EN61241-0 came into effect from 1st July 2007 and came into force on the 1st October 2008. This stricter standard superceded the old standard EN 50 281.
On 16th April 2010, the new version of the standard EN 60079-0:2009 was first published in the Official Journal and came into effect. In this standard, the requirement for explosive dust atmospheres now includes significant changes with respect to the previous edition limited only for explosive dust atmospheres are listed below:
Requirements for explosive dust atmospheres transferred from IEC 61241-0.
Dust groups defined as Group IIIA, IIIB and IIIC.
Equipment protection levels (EPL) introduced.
This new standard will supercede the old existing standard EN 60241-0 on 1st June 2012. Within this new series of standards, one of the main protection types for production equipment at risk from dust explosions in accordance with ATEX Directive 94/9/EC is the protection by enclosures type "tD" as given in IEC 61241-1. This protection type is where the electrical production equipment is equipped with an enclosure to prevent the penetration of dust and where measures to limit the surface temperature have been implemented.
On 7th July 2010, the new standard IEC 60079-31:2009 "Equipment - dust ignition protection by enclosures "t" comes into effect and will supercede the standard EN 61241-1:2004 on 1st October 2012.
There are a number of changes to the current and future standards, which you should be aware of. There are increased requirements, from the old 50281 series to the 61241 series and now to the 60079 series such as: impact energy - high demand on impact energy as in Zone 1; electrostatics - electrostatic conductance of the enclosure; and a geing resistance - high demand on the ageing resistance of the plastic enclosure associated with an ingress protection test after ageing. Customers need to be aware of these changes when sourcing or upgrading electrical equipment for hazardous dust areas, so that they can purchase equipment that fully complies with the new requirements.
Hazardous areas for explosive dust atmospheres are classified into three Zones: 20, 21 and 22. Zone 20 is an area in which an explosive atmosphere in the form of a cloud of combustible dust in the air is present continuously, or for long periods or frequently.
Zone 21 is an area in which an explosive atmosphere in the form of a cloud of combustible dust in the air is likely to occur in normal operation occasionally.
Zone 22 is an area in which an explosive atmosphere in the form of a cloud made up of combustible dust in the air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.
For the equipment to be used in explosive dust atmospheres, the sub-grouping system as known from the sub-grouping system for explosive gas atmospheres is now also implemented for explosive dust atmospheres. Electrical equipment of Group III is sub-divided according to the nature of the explosive dust atmosphere for which it is intended.
Group III sub-divisions:
IIIA: combustible flyings.
IIIB: non-conductive dust.
IIIC: conductive dust.
The equipment protection level (EPL), which is the level of protection assigned to equipment based on its likelihood of becoming a source of ignition and distinguishing the differences between explosive gas atmospheres, explosive dust atmospheres, and the explosive atmospheres in mines susceptible to firedamp, is now also implemented for explosive gas and for explosive dust atmospheres (details can be found in the standard EN 60079-0).
When can dust explode?
A dust explosion requires three ingredients: air, combustible dust and a source of ignition. Combustible dust-air mixtures have different ignition temperatures. The surface temperature of the equipment in areas where there is a risk of dust explosions is allowed to reach two-thirds of the minimum ignition temperature of the surrounding dust-air mixture. With a 5mm thick layer of dust, this surface temperature must be at least 75°K below the minimum ignition temperature of the dust (glow temperature).
It is therefore the equipment owner's responsibility to ensure that the cleaning and maintenance intervals of installed equipment with a dust explosion risk are scheduled so that no dust layers thicker than 5mm are allowed to form. At higher dust deposits, the minimum ignition (glow) temperature of the dust is reduced significantly.
The goal of the current European Directives is to protect operating plants from dust explosions and to prevent damage or personal injury. The explosion protection measures are divided into 'Owner' and 'Manufacturer' Directives. Again, the objective is to implement all necessary measures to ensure that explosion-protected products can only be operated if they do not pose any danger to health and safety and provided that they are correctly assembled, installed, maintained and used for their intended purpose.
COOPER Crouse-Hinds (UK) Ltd in profile
As part of the COOPER Industries Group, COOPER Crouse-Hinds (UK) Ltd is the number one company in the field of explosion protection. Committed to technological progress, the company develops and manufactures a range of products that cover all the requirements currently placed on modern, explosion-protected, electrical installation technology, including illumination, safeguarding, signalling, controlling, instrumentation and distribution of electrical energy in potentially explosive atmospheres. In the company's production plants in Germany, England and Spain, the company manufactures a wide range of products for explosion protection.
COOPER Crouse-Hinds supplies products that comply with all the latest directives and standards - worldwide. In addition to systems and components built to ATEX standards, the company also provides solutions that have been certified to both IEC and NEC standards. Moreover, the company also has a large number of other national approvals, e.g. for Eastern European countries, China and North America. With COOPER Crouse-Hinds you can get all you need from one source.
For further information, view website: www.ceag.de or e-mail: Gordon.Low@CooperIndustries.com Refer to page 399
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Marshall-Tufflex Energy Management is hitting the road in 2012, taking its market-leading technologically advanced energy savings solutions around the UK to showcase their proven effectiveness, ease of installation and attractive ROI timescales.
Kicking off the company's exhibition and conference calendar is the Scottish Energy & Environment Conference (SEEC) on February 7th at Ayr Racecourse. There MTEM will be exhibiting its recently launched domesic voltage optimisation system, Voltis Home, plus its growing portfolio of Sinergy fixed and portable sub-metering solutions, including its new wireless Pulse Plus system.
"SEEC attracts a wide variety of public and private sector delegates, from housing associations to police forces, FMCG manufacturers to fire brigades, hospitals and local authorities, all of whom can potentially benefit greatly from our voltage optimisation and sub-metering solutions," said Jeremy Dodge, MTEM Head of Marketing & Technical Services. "The conference is a great opportunity to meet clients, discuss their needs and talk them through the potential savings our products can help them achieve."
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Also in February the East Sussex-based manufacturer is attending the ESTA aM&T event (automatic Monitoring & Targeting) at the Ricoh Arena, Coventry, on February 23rd, exhibiting Voltis Home and Sinergy sub-metering solutions.
In May MTEM is making its inaugural appearance at Greenbuild Expo (May 9-10th, Manchester Central), again showcasing Voltis Home and Sinergy. Later that month it is returning to Nemex (part of Sustainabilitylive!) on May 22nd-24th at the NEC, Birmingham. At Nemex it will exhibit its full range of energy management systems, including the Voltis commercial voltage optimisation system, which can return power savings of up to 20%.
MTEM's full suite of products will also be on show at Energy Solutions (October 10th-11th) at London Olympia, the company's final event of the year.
Product Profile
* Voltis Home is the only 'intelligent' domestic voltage optimisation system on the market, giving householders peace of mind that they have selected the most efficient system available. All circuits in a typical house can be channelled through Voltis Home, which is rated up to 60Amps (40Amps continuous load and up to 100Amps in bypass mode). The automatic bypass mode allows the unit to handle higher loads without it tripping and cutting power to the property, as some domestic VO systems may do. The bypass function also means that Voltis Home turns itself off if the incoming load is not sufficient to warrant its operation, a further power saving feature. The system is suitable for installation in a property with photovoltaic panels and may boost the amount of electricity returned to the National Grid via the FiT. Voltis Home can be expected to pay for itself within three to four years.
* Sinergy sub-metering solutions enable users to monitor, and therefore manage, power consumption, identifying sources of energy waste and areas where savings could be made as well as checking bills and enabling accurate reporting of energy use. Sinergy has a range of solutions, from handheld portable monitors (such as e-Tracker and k-Wattch) to fixed solutions such as Escot, Klik and Pulse Plus, which monitor and record power usage to allow in-depth analysis. Pulse Plus has the added advantage of reporting its finding wirelessly, making it perfect for sub-metering across geographically dispersed sites such as retail outlets, hotels, sports facilities etc.
For further information, view website: www.marshall-tufflexenergy.com or www.savepowerathome.co.uk or e-mail: info@savepowerathome.co.uk
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