IMechE seminar pre-empts deadline
With full implementation of ATEX 137 due to become law by July 2006, the Institution of Mechanical Engineers’ (IMechE) recent seminar ‘Existing plant - Meeting the ATEX deadline’ provided a timely opportunity to bring together both regulators and industry experts.
Most will be well aware that ATEX 137, ‘the user Directive’, is the second stage of the ATEX legislative framework and follows on from the July 2003 implementation of ATEX 95, ‘the equipment Directive’ - 137 concerns equipment users, focusing on the health and safety of workers operating in potentially explosive atmospheres, whereas 95 deals with the equipment operating in such areas.
Like all new legislation, industry has needed to clarify interpretation and applicability from the legislating authorities during the build up to full implementation. Indeed, discussions at the seminar indicate that there are still areas of concern in terms of labelling requirements for both equipment and hazardous areas, problems of overzoning and, in some instances, whether users are wrongly demanding ATEX approved equipment for applications where it is not really required.
One seminar speaker, John Pethullis, director and general manager, Portasilo Ltd, summed up the current situation most pertinently “...things will settle down and it (ATEX) will become second nature in the future...”.
Comments at the event appear to indicate that industry had been overloaded with ‘telephone books’ of documentation from different sources during the ATEX assessment process. This has tended to put industry under greater pressure, making it even more difficult to make risk assessments and diverting attention from the hazards that actually have to be dealt with.
One of the main pointers that delegates probably took away from the event was the need to use common sense and the right approach when implementing ATEX. If potentially hazardous dust clouds are likely to form in a plant, in the first instance, try and completely eliminate the particular material from the plant. If this is not possible, minimise the material’s interaction with the plant and put in a strict regime of housekeeping to ensure that any dust generated is not allowed to build up on surfaces.
Seminar chairman and speaker, Ron Sinclair, MD of Baseefa, a leading certification body concerned with electrical and mechanical equipment used in potentially explosive atmospheres, made the point that dust layers are outside the scope of ATEX except as a potential source of hazardous dust clouds. When you consider that a seemingly innocuous layer of dust can become airborne during a primary dust explosion and lead to a secondary explosion, you realise the gravity of any decisions you make. Dust is equally dangerous if it is allowed to lie on hot surfaces where smouldering might occur. Keeping the plant clean is therefore of utmost importance.
“Even if your plant complies with ATEX, it does not necessarily mean that your business is protected against dust explosion”, said Allan Macpherson, technical manager, FM Global UK Operations. It is worth looking beyond ATEX, he said, at the much wider implications of a dust explosion in terms of the effects on your company's business and reputation.
Another speaker, Declan Barry, MD, ATEX Explosion Hazards Ltd UK, said that when considering protection measures for a plant, to not look at a piece of equipment in isolation but consider the system as a whole when designing key items of protection. He said that protective equipment already installed could often be a double edged sword if misused eg badly sited explosion doors have the ability to not only damage other equipment but maim personnel during an explosion incident. Also important is the need to get up-to-date OEM information on items added later on to the system to ensure that all ATEX documentation is subsequently complied with.
The ATEX assessment process requires a thorough approach, said John Pethullis of Portasilo. It may become necessary to re-validate the plant further down the line if the situation changes. If the plant starts to have a dust problem in the future, retrofit costs could be high, so consider all eventualities now.
During the seminar presentations were given by:
John Hazeldean - HM Principal Specialist Inspector, Health & Safety Executive
John Walkington - Business Development Executive, Chilworth Technology Ltd
Vijay Varma - Intertek
Ron Sinclair - MD, Baseefa
Declan Barry - MD, ATEX Explosion Hazards Ltd UK
Allan Macpherson - Technical Manager, FM Global UK Operations
Alan Dempsey - Purchasing Manager, British Sugar Plc
John Pethullis - Director and General Manager, Portasilo Ltd
• For more details of future ATEX seminars or other IMechE seminars please contact: Taz Khatun Tel: 020 7973 1306 Fax: 020 7222 9881 Email: firstname.lastname@example.org
ATEX approved diaphragm pump
Following its recent agreement with REKO, Flux Pumps is now offering the new REKO-FLUX RFML series of heavy duty 100a-approved air operated diaphragm pumps in the UK. The series features a compact and rigid structure, with pump housings manufactured from conductive polypropylene or PTFE, with NBR, EPDM, FPM or PTFE diaphragms. These have a vulcanised support plate and, because of their short stroke, are said to deliver a high service life.
Units use a minimal number of component parts, providing fast stripdown and easy access to the air valve unit which is outside the pump housing, ensuring high reliability. Maintenance can be carried out inline without removing the pump from the work area.
Machined from solid materials and with a high chemical resistance, pumps are suited to continuous applications involving high temperatures and pressures. They are capable of handling liquids ranging from water to pastes, neutral or aggressive shear sensitive thixotropic, abrasive and corrosive liquids as well as sludge and gas/liquid mixtures. Capacities range up to 5 cu m per hr at up to 8 bar.
ATEX certified rotary valves
Rota Val’s HD range of rotary valves has been successfully tested under the requirements of Clause 126.96.36.199 ‘Functional tests for rotary valves’ of CEN/TC305/WG3/SG6 N9. This means that the valves can be used as an explosion/flame barrier under the ATEX/94/9/EC Directive.
Testing was provided through Rota Val’s notified body, Baseefa Ltd, and carried out by the Health & Safety Laboratory, Buxton, UK using zinc stearate as the test powder. This material possesses an explosibility rating of Kst293, with test procedures set to produce a minimum pressure peak of 11.1 barg, providing 10 bar certification. Normally, cornflour is used as the industry standard test material, but this only has a rating of Kst211 and is known to moisten and form cohesive agglomerations under an explosion condition, and is now seen as unlikely to provide accurate results due to the increased ‘blocking’ factor that results in the valve clearances.
Each of the valve sizes tested were subjected to a series of 20 full explosion tests which, on the largest 600 size unit, imposes a stress load on the rotor component in excess of 46t as well a shock factor each time. The test regime involves ten tests, conducted using visual recording instruments to try to detect spark/flame passage. Added to this are a further ten tests with the valves connected to a secondary explosion chamber to prove that there is no ignition energy transfer. All valves had to pass these tests.
Rota Val is now able to offer explosion/flame containment certificates for its relevant range of rotary valves covering the 100 to 600mm size range and hydrostatically tested before delivery.
Portasilo dischargers gain ATEX certification
Portasilo’s Rotoflo range of silo discharge systems has gained ATEX approval under Category I (Inherently safe) for use in potentially explosive environments. Independent certification work was carried out by SIRA, one of the DTI appointed Notified Bodies for the UK.
Certification covers use in Group II (non-mining) applications for Category I (Zone 20 - constantly dusty) internal hazard zones. It is further approved for Zone 21 (periodically dusty) and Zone 22 (infrequently dusty, such as when equipment malfunctions) external areas. With a temperature rating of 80 degrees C, the unit is suitable for most powder and granular material that could produce a potentially explosive atmosphere.
In addition, the company’s Augerflo screw bin dischargers and Osciflo oscillating bar bin dischargers now meet ATEX Category 2 (partly self-certified) standard, allowing use in Zone 21 and 22 environments. Test work is also ongoing with the objective of making the whole Portasilo discharge range of products certified to Category I.
The company point out that there has been significant confusion concerning internal and external environments and uptake and enforcement of the legislation has been slow. This has led to some difficulties for customers and systems integrators who may have categorised vessel internals as Zone 20 and been faced with a lack of suitably certified Category I equipment applicable for these hazard zones.
• Clarification recently issued by the EC indicates that the equipment category can be dictated by the internal environment of a vessel or machine. The internals of silos and other powder handling plant for use with potentially explosive products will often be categorised as Zone 20 which can necessitate the use of Category I approved equipment. This in turn requires equipment approval by a notified body appointed by the DTI.
ATEX guidelines for valve industry
The German Valve Manufacturers Association within VDMA (German Engineering Federation) has finalised its guidelines on the interpretation of the European ATEX Directive 94/9/EC ‘Equipment and protective systems intended for use in potentially explosive atmospheres’.
These are intended to support industrial valve manufacturers, users, as well as notified bodies dealing with the Directive.
• The guidelines are available free of charge as a pdf file by emailing email@example.com
Meeting demand for ATEX compliant conveyors
Since the ATEX Directive took effect on the 1st July 2003, bulk solids handling specialist, Flexicon (Europe) Ltd, has experienced a marked increase in requests for equipment to comply with the new regulations. Applicable to manufacturers and users of equipment in potentially explosive atmospheres, the Directive applies to both electrical and, importantly, mechanical equipment.
The company has therefore taken the initiative, getting ATEX approval for its flexible screw conveyors, a process that has involved extensive in-house testing and an ignition risk assessment submitted to BASEEFA (2001) Ltd, the DTI appointed Notified Body for ATEX.
The accreditation allows Flexicon to supply flexible screw conveyors for use in Zones 1, 2, 21 and 22 hazardous areas - covering gas/vapours/mist/dust hazards, ATEX category 2 – safe operation with one malfunction, and category 3 – safe operation in normal conditions.
HSE updates guidance on dust explosions
Revised and updated guidance for industries dealing with combustible dusts has been published by the Health and Safety Executive outlining the safest way of handling them. The publication, Safe Handling of Combustible Dusts, uses simple language to describe the tests used on dusts to assess their explosive properties, precautions that should be taken to control the risks and an outline of the health and safety law that applies.
The publication takes account of European Directive 99/92/EC on the Protection of Workers Potentially at Risk from Explosive Atmospheres (The ATEX Directive) which is implemented in the UK by the Dangerous Substances and Explosive Atmospheres Regulations. In particular, the guidance describes how the requirement for hazardous area classification, brought in by the Regulations, applies to dust handling plants, and explains which types of new equipment need to be 'ATEX compliant' ie be properly marked after undergoing specified tests and checks for their use in hazardous areas.
Alan Tyldesley, section head responsible for production of this guidance in HSE's Hazardous Installations Directorate, said: ‘Large dust explosions in the UK are fortunately few and far between, but the risk is present in many industries.... very simple failings can still lead to a major explosion if the risks are not understood at the workplace’. This point is graphically illustrated by two incidents earlier this year at polymer processing plants in the USA which resulted in 13 fatalities and over 50 injured employees. (20 November 2003)
• Copies of 'Safe handling of combustible dusts: precautions against explosions' HSG103, ISBN 0 7176 2726 8, price £10.95. Available from HSE Books, PO Box 1999, Sudbury, Suffolk, CO10 2WA, Tel: 01787-881165 Fax: 01787-313995
ATEX administration costs come under scrutiny
ATEX has added significantly to equipment manufacturers’ costs and, according to a special report by The Institute of Measurement and Control, the UK’s professional body for the instrumentation and automation industry, are, ‘difficult to justify in a market which generally accounts for only one third of the UK’s total output’.
The report, comprising a series of papers by leading industry experts, provides a comprehensive perspective on the impact of ATEX on manufacturers, installers, maintenance personnel and certifying bodies. From the UK manufacturers’ position, the added administration costs of ATEX compliance in what they see as an already well-regulated European market is disproportionate to its value globally.
Chris Towle of Measurement Technology points out that UK manufacturers of hazardous area equipment generally operate in three major sectors - Europe, the Americas and Asiatic countries, with other parts of the world providing a smaller but significant market. Europe, he states, accounts for about a third of the total output - ‘a factor which tends not to be recognised when Brussels is deciding what is good for manufacturers’.
Ian Clasper from GAMBICA, says that the additional costs to manufacturers ‘is difficult to justify when the world market can be more important’, with some specialist manufacturers of hazardous area equipment exporting up to 80% of their production outside the European Economic Area (EEA). However, the cost of regulatory compliance outside the EEA was also high and, with the need for multiple certification, ‘it is ultimately the customer who pays in unnecessarily high equipment costs’, says Mr Clasper.
Two directives - ATEX 95 equipment safety directive and ATEX 137 directive concerning the protection of workers in explosive atmospheres - include a new focus on ‘mechanical equipment’ in gas atmospheres and all equipment in dust atmospheres, where standards and practices are not so well developed as those for electrical and instrumentation in gas atmospheres.
David Stefanowicz of the Electrical Contractors’ Association comments: ‘I am not convinced that the mechanical fraternity is quite so conversant with the new requirement placed upon them. Many appear to think that ATEX is just an ‘electrical’ concern and does not affect them - and the Government does not appear to be doing much to dispel this theory’. There is also uncertainty for installers regarding pre-ATEX spares.
Equipment parts manufactured and placed in stock before 1 July are not required to be ATEX certified. However, Mr Stefanowicz warns installers to be vigilant in verifying the age of their equipment and to be aware that the law gives no dispensation for emergencies or loss of production.
The InstMC says that, although they recognise the positive elements embodied in the ATEX directives, they support the ideal of having one regulatory certificate acceptable worldwide. To this end, collaboration amongst UK manufacturers, end users and certification bodies has seen the development of the IECEx Certification Scheme which uses international standards. UK industry wants to see this adopted worldwide and, in particular, its full convergence with ATEX 95. In the meantime, industry will be looking to the legislators to resolve their differences.
Helping coffee producer to meet ATEX
Braby has supplied a vessel to a well known UK food processor designed to meet latest industry standards but in particular the requirements of ATEX. The client manufactures coffee powder and needed the vessel as a buffer hopper prior to transfer into tote bins and after powder had been processed.
The product is a light material with a bulk density half that of flour and does not move under its own weight. This, coupled with its sticky consistency due to warmth generated by the drying and transfer process, means that the powder sticks to the vessel sides and does not move easily. Discharge is therefore aided by a reverse cone, over which air is allowed to pass.
The ATEX element of the installation was important because of the potentially explosive nature of coffee powder and the vessel was designed in accordance with the VD13673 design code.
ATEX approved capacitive sensors
The DOL 40R series of capacitive sensors from SKOV A/S is now ATEX approved. Designed for use inside containers - eg with grain, feed and granulated material - where there is a dust explosion risk, sensors have their own amplifier and changeover relay, so no additional ATEX approved equipment is required. Units are already CE and C-UL approved.
Reliability is said to be a key feature using electronic rather than mechanical switching. Electronics are embedded in plastic to suit aggressive environments and units are immune to transient currents generated by motors or contactors.
Sensors have a 30mm diameter dust and waterproof cover and are easily mounted in an ATEX gland, with electric connection to the mounting surface via a conductive packing, with easy connection to earth.
Sensitivity and delay period are set by two press buttons, light emitting diodes indicating when they are activated. There is also the option of an integrated timer and two voltage ranges.
Couplings meet requirements
A range of couplings that comply with ATEX 94/9/EC is announced by Flender Power Transmission. Since the certificate of approval was gained in April 2002, the company has been supplying three approved coupling types - NEUPEX flexible jaw couplings, ARPEX torsionally rigid, all steel couplings and RUPEX flexible pin and buffer couplings.
Take-up in Europe has been fast says John Whitworth of Flender who commented that many enquiries had already been received from UK companies completing their risk assessments.
Flender anticipates a considerable increase in demand as the deadline approaches which some manufacturers may not be able to immediately fulfill. Many companies appear to be leaving compliance until the last minute.
A leaflet about the new ATEX requirements for couplings is freely available from the company by e-mailing firstname.lastname@example.org
Dust is equally dangerous
Explains Steve Meadows, product manager for process valve products at ASCO Joucomatic
The impending ATEX directive, which comes into force in July 2003, has concentrated the minds of plant engineers in all sectors of industry on the dangers of potentially explosive atmospheres. Although this is of necessity, it is also timely as research shows that there has been a substantial growth in hazardous areas in all sectors of manufacturing and the processing industries over last few years. It is estimated that 50 per cent of all industrial applications now contain a hazardous area of one type or another.
As well as being timely, ATEX is welcome for the focus that it provides on industrial dust as a potential source of explosions. Almost all types of industrial dust can be considered to be potentially explosive, so it comes as no surprise that the procedure for technically evaluating the safety measures used to avoid the risk of dust explosions is both complex and extensive. In order to determine the explosion risk posed by dust a number of factors need to be described. These include particle size, explosion limits, the maximum explosion pressure, the destructive power of the combustion, moisture content and minimum ignition energy required. Once the dust has been characterised, an examination then needs to be made of the industrial processes concerned, taking into account possible ignition sources, explosive volumes, operating temperatures and an assessment of the possibility of a dust explosion under given conditions.
Helpfully for engineers involved in safety evaluations of dust-laden atmospheres, ATEX simplifies explosion protection with a three-zone concept:
• Zone 20 the most critical of the three, is an area in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods, or frequently, typically conditions that would be encountered on the inside of containers or pipelines and enclosed conveying equipment.
• Zone 21 is a place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally eg. discharging and filling equipment.
• Zone 22 is a place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but - if it does occur - will persist for a short period only. Areas in which dust escapes and forms deposits are included in this category.
Whatever the zone, one of the biggest risks when it comes to preventing dust explosions, is posed by enclosures. The ATEX directive defines the type of protection provided by enclosures, based on limiting the maximum surface temperature of the enclosure and using dust-tight and dust-protected enclosures to prevent dust entry. The legislation covers two degrees of protection:
• Dust-tight - for use of equipment in Zone 20, 21 and even 22 in the case of the presence of conductive dust.
• Dust-protected - for use of equipment in Zone 22 areas in the presence of non-conductive dust.
The scope of the ATEX directive on enclosures is comprehensive, extending down to electrical actuators used on individual valve types. This is important due to the increasing use of solenoid valves in dust collector systems that reduce industrial air pollution. ASCO Joucomatic is a leading manufacturer of these valves including the Power Pulse range designed to optimise the performance of pulse Jet cleaning systems, one of the most effective techniques for removing dust from the atmosphere in cement plants, foundries, waste incinerators, power stations and food processing plants.
The company's enclosures, available in aluminium, cast iron, stainless steel and epoxy encapsulations, meet a range of ATEX certified categories including:
• d - flameproof. (ATEX Zone 21)
• e - increased safety. (ATEX Zone 21)
• m - encapsulation. (ATEX Zone 21)
• em- encapsulation with increased safety. (ATEX Zone 21]
• ia - intrinsically safe for use in continuously explosive atmospheres.
(ATEX Zone 20)
• ib - intrinsically safe for atmospheres where combustible dust is likely to
occur during normal operation, occasionally. (ATEX Zone 21).
• n - non-sparking. (ATEX Zone 22)
The range is employed in the Power Pulse Tank System, which provides a neater package for dust collector installations. The tank system is a fully integrated package designed to overcome the problem of CE certification for OEM's who traditionally build their own tank systems.