New Ex-Encoders for Zone 2 and Zone 22 (PDF ... - Pepperl+Fuchs

PT2006_487e,_Drehgeber Zone 1 und Zone 2Pepperl+Fuchs GmbH – Königsberger Allee 87 – 68307 MannheimPlease quote the following contact information when publishing:Tel.: +49 621 776-1111, Fax: +49 621 776-27-1111, www.pepperl-fuchs.com, fa-info@de.pepperl-fuchs.comEditorial contact: Irmtraud Schmitt (extension: -1215, fax: -1667), ischmitt@de.pepperl-fuchs.comNo larger than the standard versions:New Ex-Encoders for Zone 2 and Zone 22As an extension of the existing Series 14 Ex encoders with flameproof enclosures forZones 1 and 21, Pepperl+Fuchs Drehgeber GmbH has now developed encoders forZones 2 and 22. A solid shaft version and a blind hole hollow shaft version are available.The incremental encoder RVI58X is contained in a 58 mm diameter housing with a 6 mmor 10 mm solid shaft. The RSI58X also has a 58 mm diameter housing and is intended forblind hole hollow shaft mounting on 10 mm or 12 mm shafts. Both models are availablewith pulse counting up to 5,000 pulses per revolution. The permissible ambienttemperature range covers up to 70 °C. On the output side these encoders are equippedwith either a 10...30 V push-pull output, 5 V supply and RS422 interface or 10...30 Vsupply and RS422 interface. Also available are Profibus encoders in single and multiturnversions, as absolute value encoders for application in Ex Zones 2 and 22. Other deviceswith field bus connections such as DeviceNet, CANopen and SSI interface are in thecourse of development. The special feature of all the new encoders is their compactconstruction in the 58 mm standard housing, which facilitates integration in plants whenthere is limited space for installation.In explosion protection a distinction is made between zones with different levels of risk.Because the cost of providing explosion protection increases as the risk increases, plantoperators tend to site as many plant components and machinery items as possible in the lessendangered areas categorised as Zone 2 (for gas) and Zone 22 (for dust). In these areasappropriate sensors are then required to control and monitor the speed of the rotatingcomponents. Pepperl+Fuchs Drehgeber GmbH has developed new Ex encoders for use inZone 2 and Zone 22 for this purpose. These sensors have standard 58 mm diameter housingsand thus occupy very little space on the plant.It is not only in the mining industry and in the chemical and petrochemical industries thatexplosion protection has an important role to play. The risk of explosion also has to becountered in the energy supply, paint, food and drink, milling and other industries.Page 1 of 5

In all these industries and others there is the routine possibility of the presence of mixtures ofgases and dust and accordingly explosion protection precautions are a must. Although theonset of an explosive atmosphere is avoided from the outset through the application of primaryexplosion protection measures, secondary explosion protection measures have to be taken tokeep danger zones free from sources of ignition, because it is not possible to fundamentallyexclude the existence of an atmosphere capable of supporting an explosion. In such dangerzones open flames, hot surfaces, the threat of sparking, etc., are not permissible.ATEX Directive defined danger zones, device classes and protection typesExplosion protection has been harmonised in the European Union since 2003 and set out in theso-called ATEX Directive. In accordance with the ATEX 95 Product Directive (Previously ATEX100a), after 30.06.2003 only those devices, components and protection systems that satisfy theDirective 94/9/EG (ATEX 100a) can be offered for sale. Depending on the category of device,either a test certificate from an approved test centre (EU prototype test) or a manufacturer’sdeclaration (EU certificate of conformity) is required, which provides information confirmingcompliance with the directive. A sub-division into danger zones and the definition of the classesof devices and categories specifies which requirements and protection classifications are set forthe individual apparatus and where these can be used.The ignition protection classifications describe the various options for the provision of devicesand apparatus for use in Ex areas. In the case of gas explosion protection there are increasedsafety, flameproof enclosures, pressurised enclosures, intrinsic safety, oil immersion, sandfilling and encapsulation. In intrinsically safe circuits, for example, the electrical energy is limitedvia current strengths and voltage levels, in such a way that the minimum ignition energyrequired to cause an explosion by the generation of sparks or heating is not attained. In thecase of devices in flameproof enclosures, all the components, which could trigger an explosion,are contained in a stable housing, so that in the event of an explosion inside the housing itcannot be transferred to the outside.Ex-Zone 2 and Ex-Zone 22In addition to the highest graded danger zones, Ex-Zones 0 and 1 for gas and 20 and 21 fordust, in which concentrations capable of supporting an explosion are either constantly oroccasionally present, there are the Zones 2 and 22 – the less endangered zones – which are ofspecial interest. It is in these zones that for reasons of cost in terms of explosion protection,plant operators site many items of plant and machinery. Here there are frequently to be foundgrinding and stirring apparatus, pumps and electric motors in general, revolving at speed, whichneed to be monitored and controlled. Zone 2 covers those areas, in which during normalPage 2 of 5

operation dangerous explosion-supporting atmospheres in the form of a mixture of air andcombustible gases, vapours and mists are not normally present or only present for short periodsof time. Correspondingly, Zone 22 relates to areas, in which dangerous explosion-supportingatmospheres in the form of a cloud of air containing combustible dust are either normally notpresent or are only present for short periods of time.Ex-Encoders with standard housingsAs an extension to the existing Ex encoders in the series 14, with flameproof enclosures forZones 1 and 21, Pepperl+Fuchs Drehgeber GmbH has now developed new encoders for Zones2 and 22. The ignition protection category “nA“ applies to gas explosion protection in Zone 2.This means that the protection is achieved by means of a “non-sparking apparatus”: The designminimises or prevents the occurrence of electric arcs, sparks and hot surfaces, which could leadto the danger of ignition during normal operation. Dust explosion protection for Zone 22 isachieved by the protection of the housing: The design provides protection from the ingress ofdust in quantities that are likely to represent a threat (At least IP5X protection) and ensures thatthe surface temperature of the encoder is always below the ignition temperature of dust-airmixtures and also below the glow temperature of dust deposits.The Type RVI58X incremental encoder is also contained in a 58 mm housing with a 6 mm or 10mm solid shaft. Versions are available with pulse counting up to 5,000 pulses per revolution.The maximum permissible ambient temperature is 70 °C and the radial shaft loading is 60 N.The incremental encoder with the designation RSI58X also has a 58 mm diameter housing andis intended for blind hole hollow shaft mounting on 10 mm or 12 mm shafts. It likewise featurespulse counting up to 5,000 pulses and an operating temperature range up to 70 °C. On theoutput side these encoders are equipped with either a 10...30 V push-pull output, 5 V supplyand RS422 interface or 10...30 V supply and RS422 interface. Also available are Profibusencoders in single and multiturn versions as absolute value encoders for application in Ex-Zones 2 and 22. Other devices with field bus connections such as DeviceNet, CANopen andSSI interface are in the course of development.Limited installation space demands compact sensorsThe special feature shared by all the new encoders for Zone 2 and Zone 22 is their compactconstruction. Despite their suitability for use in hazardous areas, they are no larger than theirstandard version counterparts. They are therefore strong favourites for integration into plantwhere space is at a premium. Another important factor is that a 58 mm diameter standardsensor can subsequently be replaced by the Ex version if the need arises, thus upgrading thesuitability of the machine or plant item concerned for the more stringent requirements of ExPage 3 of 5

operation. By contrast, the previous encoders with flameproof enclosures are an order ofmagnitude larger than the new versions. The sole external difference between the two versionsis that the new encoder is currently only available with a cable connection.Authors:Dipl.-Wirtsch.-Ing. Yvonne GrabowskiProduct Manager at Pepperl+Fuchs Drehgeber GmbH, TuttlingenDivision Factory AutomationDipl.-Ing (FH) Volker ParothTechnikredaktion LOGOSCharacters:7.072 without spacesCharacters summary: 1.022 without spacesPictures:Picture 1: No. 54_1123_03Picture 2: No. 54_1123_0203/2006For publication free-of-chargePage 4 of 5

Picture 1: (RV158X Solid Shaft Encoder)The 58 mm Ex encoder for Zone 2 and 22 satisfies ignition protection category “nA“and has a dust-tight housing, so that explosions due to the generation of sparks,heating up and dust deposits on the housing are excluded.Picture 2: (RS158X Blind Hole Hollow Shaft Encoder)This Ex encoder is designed for simple mounting on 10 mm and 12 mm shafts andprovides up to 5,000 pulses per revolution, either via a push-pull output or an RS422interface.Page 5 of 5