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CompEx - Basic Principles Standards Since the early 1920`s many standards have

CompEx - Basic Principles Standards Since the early 1920`s many standards have evolved both in Britain and all over the world. Most of these standards are now obsolete so there is one international standard that is really important to remember - IEC 60079. IEC 60079-10 - Classification of Hazardous Areas IEC 60079-14 - Construction of electrical installations IEC 60079-17 - Inspection and maintenance ATEX Directives ATEX is the European Directive 94/9/EC which applies to all equipment, both electrical and mechanical, used in hazardous atmospheres (both dust and gas). It came in to effect on 1th July 2003. ATEX 95 - deals with all equipment and protective systems in use in potentially explosive environments. ATEX 137 - workplace directive that sets the minimum requirements for the safety and health protection of workers in potentially explosive environments. Definitions Spark - a form of electrostatic discharge; it can occur in various types (short circuit, lightning, static electricity, operation of switches and relays). It is important to remember that there can be two types of sparks - incentive spark and non-incentive spark. An Incentive spark has sufficient energy to cause an explosion in a hazardous environment (i.e. Ignite a gas source). A non-incentive spark does not have the sufficient energy to cause an explosion in a hazardous environment. Flashpoint - the lowest temperature at which sufficient vapour is given off a liquid, to form a flammable mixture with air that can be ignited by an arc, spark or naked flame. Ignition temperature - the minimum temperature at which a flammable material will spontaneously ignite. Ambient temperature - from -20 celsius to 40 celsius. Zones Area classification is a method of analysing and classifying the environment where explosive gas atmospheres may occur. The main purpose is to give guidance in the selection and installation of apparatus to be used in that environment, taking into account the properties of the flammable materials that will be present. Hazardous areas are classified into zones based on an assessment of the frequency of the occurrence and duration of an explosive gas atmosphere. Zone 0 - an area in which an explosive atmosphere is present continuously, or for long periods, or frequently (more than 1000 hours per year). Zone 1 - an area in which an explosive atmosphere is likely to occur in normal operation occasionally (more than 10, but less than 1000 hours per year). Zone 2 - an area in which an explosive atmosphere is not likely to occur in normal operation, but if it does occur, will persist for a short period only (less than 10 hours per year). Explosive atmosphere equipment groups Group I - Mining activities - equipment designed for use below ground and associated areas where methane is the flammable gas (not covered in the CompEx course). Group II - Surface industries - Gas - Sub-divided IIA, IIB, IIC (types of gases) - equipment that is used primarily used above ground where any other flammable gas may be present. Group III - Surface industries - Dust - Sub-divided IIIA, IIIB, IIIC - equipment that is used where flammable dust may be present. Equipment Protection Levels (EPL) EPL`s are the IEC`s equivalent of the ATEX categories. It is a complicated and illogical concept, but the candidate must be able to remember the table below in order to successfully complete the CompEx course. Zone ATEX Category IEC EPL 0 1G Ga 1 2G Gb 2 3G Gc It is important to understand that equipment designed for a higher level of protection (i.e. Zone 0) can be used in areas of lower requirements (i.e. Zone 1 or Zone 2). However, equipment designed for lower levels of protection (i.e. Zone 1) must never be used in areas with higher levels of protection requirements (i.e. Zone 0). Gas sub-division groups Gas sub-division Gas Ignition Temp. °C IIA Benzene Butane Gasoline Propane 555 365 280 470 IIB Ethylene 425 IIC Hydrogen Acetylene 560 305 Note: this table consists only of the most important gases and their ignition temperatures. During the course you will learn about more gases in each group. In order to successfully complete the CompEx course the candidate will have to memorise the contents of this table. Temperature Classification Temperature classification is based on the maximum temperature reached by any part of the equipment that could be in contact with a flammable gas. T Class Max . surface temp. T1 450 °C T2 300 °C T3 200 °C T4 135 °C T5 100 °C T6 85 °C In order to successfully complete the CompEx course the candidate will have to memorise the contents of this table. CompEx - Explosion Protection Concepts There are several methods and concepts which may be used in potentially explosive environments. The table below identifies the types of protection based on the Zone/EPL/Category requirements. It is absolutely essential to memorise this table in order to successfully complete the CompEx course. Zone/EPL/Category Types of protection Zone 0 or EPL Ga or Cat 1 Ia, ma Zone 1 or EPL Gb or Cat 2 d, e, mb, o, p, q, ib Zone 2 or EPL Gc or Cat 3 n, s, ic, mc Types of protection: i - Intrinsic safety (ia, ib, or ic) m - Encapsulation (ma, mb, mc) d - Flameproof or explosion proof enclosure e - Increased safety o - Oil immersion p - Pressurisation q - Powder filling n - Reduced risk s - Special A full CompEx course for a practising electrician covers all of these types, but only i, d, e, and n types will be covered in full detail, simply because these are the most common protection types in the UK. Our guide for the electricians CompEx course will therefore only cover these most common protection types. Once again we emphasize that our guide is only a good orientation tool for the actual CompEx course, the scope of which is much wider, with a great deal of important details not mentioned here. This guide focuses on the absolutely essential, by learning which the candidate will get a good head start for the actual course, which otherwise could be surprisingly demanding. CompEx `d` - Flameproof Enclosure Ex d type of protection is a type of protection in which the parts that can ignite an explosive atmosphere are placed in an enclosure that can withstand the explosion developed within the enclosure, and prevent the transmission of the explosion to the outside environment. Area of usage: - Zone 1 or Category 2 or EPL Gb - Zone 2 or Category 2 or EPL Gc - All gas groups. Gaps in the enclosure Since these enclosures are not hermetically sealed, all gaps, cover flanges, cable inlets and other places where a gas could enter or leave the enclosure are not to exceed these specified values: - 0.1 mm with group IIC gases - 0.15 mm with group IIA or IIB gases. Threaded joints The treaded part must be at least 8 mm long, with 6 threads of which 5 threads must be engaged. Minimum distances to other objects next to the enclosure These values will depend on the type of the hazardous gas potentially surrounding the enclosure: Group Minimum distance IIA 10 mm IIB 30 mm IIC 40 mm Glands All glands used for cable entry to an Ex `d` enclosure have to be Ex `d` or Ex `de` certified. A barrier gland may be required if one of these is true: - Cable outside body not round (some old types of cables, usually not in use any more). - Not a Compact Cable (some old types of cables, usually not in use any more). - Hygroscopic fillers (some old types of cables, usually not in use any more). - Group IIC gases. - Group IIA and IIB gases and enclosure internal volume greater than 2 litres. Ex `d` type enclosures are always made of metal, because of that there is no need for locknuts, serrated washers, IP washers, or shrouds of any type. Blanks used to cover any unused entry holes must be Ex `d` or Ex `de` certified! CompEx `e` - Increased Safety CompEx type of protection `e` is a type of protection in which additional measures are applied in order to give increased protection against the possibility of excessive temperatures, and against the possibility of the occurrence of arcs and sparks in normal conditions or under specified fault conditions. Areas of usage: - Zone 1 or Category 2 or EPL Gb - Zone 2 or Category 2 or EPL GC - All gas groups. Ingress protection CompEx type of protection `e` requires IP54 as a minimum. Terminations Type of protection `e` requires the use of certified terminals in every case. The following rules apply: - One conductor per terminal. - Wires must be crimped. - Soldering is not allowed. - 50mm separation between `normal` and `IS (intrinsically safe)` terminals. - All (even unused) terminals must be tight. Accessories Accessories Required type Glands Certified glands only:  Ex `d`  Ex uploads/Philosophie/ compex-guide.pdf