Design of safety guards Under observation of ISO 14119
Contents
1. m Ze l a Cuan f Dangerous movements Forces that occur at the The buildup of forces that Deliberately resilient stop at a distance that hazard spot are to be would lead to injuries is machine parts which cannot deform limbs deliberately limited so reliably interrupted before deform and absorb most as not to have any bodily reaching the limits of the deforming energy damaging effect m According to the image of the ISO 12100 the risks must be constructively eliminated first Inherent safety see ISO 12100 section 3 20 m nherent safety is understood to mean the elimination of risks by constructive measures 3 Technical protective measures SCHMEASAL f the identified risks cannot be eliminated by design measures or at least minimised to an acceptable level technical protective measures must be taken such as optoelectronic protective equipment tactile protective devices two hand controls etc refer to ISO 12100 section 3 21 Such a technical protective measure could for example be a movable safety guard This brochure concentrates on such measures SCHMERSAL 4 Determination of the safety function Table 8 of ISO 13849 1 defines safety functions that ensure that the identified risk is minimised also see ISO 12100 section 30 3 When implementing safety functions the entire safety circuit must be taken into consideration starting with the sensors input in our case the interlockin2. The position switches must be arranged and if necessary be protected in such a way to prevent damage by unforeseen external causes The movement caused by the mechanical operation or the distance to the actuating system of a non contact position switch must remain within the actuating area of the position switch specified by the switch manufacturer or the actuating system this is to ensure proper operation and or to prevent an overrun A position switch should not serve as a mechanical stop unless this is the intended use of the position switch according to the manufacturer Misalignment of the guard caused by an opening before the position switch state changes should not affect the protective effect of the safety device regarding access to hazardous areas see ISO 13855 and ISO 13857 m The receptacle and the mounting of the position switches must be sufficiently stable to maintain proper operation of the position switch Section 5 3 Arrangement and mounting of actuators Actuators must be secured so that the possibility of becoming loose or the possibility of modifying its intended position relative to the actuating system is reduced to a minimum over the intended service life B The fasteners of the actuators must be reliable and to move them a tool is required Gradual loosening must be prevented The actuators must be arranged and if necessary be protected in such a way to prevent damage by unforeseen external cause
3. Page 09 Page 09 Page 10 Page 15 Page 16 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 1 Risk assessment Risk assessment based on the defined limits and the intended use of the machine User information Protective measures to be made by the designer het hata Step 1 Inherently safe design Step 2 Technical protective measures and supplementary protective measures Designer information Step 3 User information Residual risk on the machine after the measu Warning signs Signals res taken by theif Warning equipment designer e in the user manual The MD and therefore the law requires each machine manufacturer to carry out a risk assessment The risk assessment consists of hazard identification risk estimation and evaluation The risk assessment takes into account the entire life cycle and all operating modes of the machine Instructions for conducting a risk assessment can be found in the ISO 12100 Only after completing the risk assessment the manufacturer knows where there are possible risks of injury on the machine and whether anything needs to be done about them ISO 12100 Risk assessment SCHMERSAL 2 Inherent safety M Minimum distances Limiting the effective Interrupting the flow of Elastic deformation S SCHMERSAL energy power a
4. must not exceed 150 N Cover mounting Guidance on rollers in form fitting custom runners Clamps prevent ejection of the cover if damaged The lower area of the cover should be designed that neither debris nor cooling lubricant can escape outwards D Controllers Functional safety Reliable fulfilling of safety functions within a defined period of time with the safety relevant part of the controller Defeat prevention Interlocking elements non accessibly mounted with tamperproof screws if necessary Safety concept harmonised with activity in all service life stages of the machine SCHMERSAL Principles and measures ISO 14119 Schedule 3 with high coding level according to 7 2 b 3 Type 2 and Type 4 interlocking device with low or middle coding level according to 7 2 b 1 or 7 2 b 2 with or without Type 2 and Type 4 Interlocking devices with or without solenoid latching solenoid latching and high coding level see note 2 Key transfer systems with middle D o9 23 SU a2 riu oo re ST EDL a OT o So a amp Die xe 2s o lt gt O 97 E x o o gt o p c T T o S E Type 1 Interlocking device operated only with hinge Mounting out the reach see 7 2 a 1 Barrier shielding see 7 2 a 2 Mounting in hidden location see 7 2 a 3 X Condition monitoring or periodic examination X see 7 2 d 1 i and ii Non releasable attachment of position switches an
5. of safety sensors 10 Product selection The selection of the appropriate product always depends of course on the real application i e operating conditions such as Temperature Humidity m Dirt m Shock vibration Explosive atmosphere 8 Necessary holding force Further details and application instructions for the different types described above are given in annexes A F of the standard The selection of a product also depends on the PL to be achieved see above page 7 ISO 14119 and ISO 13849 2 prescribe redundancy of Type 1 or Type 2 switches when the PL PLeis to be reached see ISO 14119 section 8 2 and ISO 13849 2 table D 8 If a safety sensor Type 3 or Type 4 is being used that allows to use only one to achieve PL e in contrast to Type 1 or Type 2 switches see above make sure that this sensor fulfills the requirements of the product specific standard IEC 60947 5 3 see ISO 14119 section 5 4 SCHMERSAL 3 GY S1 S12 PK 4 GNS21 p S22 YE 2 5 WH S31 S32 BN 6 If because of the stopping time described above an interlocking device with guard locking is required then Annex l is to be observed It informs about the maximum possible static action forces that may be posed on interlocking devices with guard locking feature As an informative annex and as an exemplary enumeration it is to be understood as a guideline of possible maximum force levels ie orders of ma
6. the PL of the interlocking device Reason The probability of the failure of the interlocking and simultaneous access of a person is very low ISO 14119 section 8 4 Note 2 Nevertheless inadvertent unlocking of the locking device must be included in the risk assessment ISO 14119 takes into account the characteristics and requirements on the sensor input of the safety circuit Their sensor is part of the interlocking device of a safety guard described in the standard SCHMERSAL ISO 14119 Safety function 5 Design of the safety circuit i j i mEn ia T a o a EHI m Ss E 3 After the safety function has been determined it is now necessary to design the appropriate safety circuit SS m m n mL i e mu taji l The design is to be in accordance with the requirements of the PLr see ISO 13849 1 section 6 This means it must meet the requirements of the EE GNE Monitoring Monitoring n SPINE Input Output signa signal 3 Input Output 2E Ja Bx Output signal signal i i signal f HET 2 2 81 Second o ISO 13849 1 5 8 shutdown 9 Monitoring Safety pem a or architecture Eus ar Dar Input Output reporting signal signal path Categories B and 1 Category 2 Categories 3 and 4 m expected service life of the components used until the first occurrence of a dangerous fault MTTF or Biog m test quality which means the quality of
7. Design of safety guards he m Em AUS UE ER XC So UON gt uo a a ee St Se e S Treoin Yt Cy NUS a a At SSA SS 3S a UU is X X sa nei ot Vas Geto cry Am M A a LO wage amp oo PRO D Cc eL As EAT AS a E uad AUSSI 7 EE AE ICON PICO IU LC EE EU IACC XL AUO USES Cum RU YS S aso Lm e Ea a rua m m lt gt ADUSI nmm _ i a i Ta PEN dom ome me See X a ono hh ks SS Dux XO ACOA CUR PN OS dagana i EC ri MEA ee Stoo Arna o PX ein D M I 1 Ses AR E ES radi eet Am Sys tott E Lee e e i s we Ate qe TE TER orum X CURA Ce ES n a ee uo T M i ET E a te ien l WDR UAM US TENT re AN M EE EO ACIE UNDAE UE _ ee Tt ge m Eu E uS Es A n csl aX LER CSDL DOR UR E mN m md A i e AT Th M SS Sage 7S a A Ah Re o amp SCHMERSAL Safe solutions for your industry Introduction With the Machinery Directive MD 2006 42 EC and its associated standards the European Union has created a set of rules that needs to be considered when designing machinery and plants This set of rules is also considered and adapted in markets outside the EU as a basis for machine safety It contains amongst other statements concerning the design of the moveable safety guards Position monitoring of moveable guards is described in detail in ISO 14119 Safety of machinery Inte
8. Standards Committee NA 095 Safety principles and Protective devices safety measures and interlocks Reading the brochure does not exempt you from your own study and interpretation of the standard An initial note on terminology The term interlocking device used in the standard is synonymous for safety switchgear and often leads to confusion because the term interlocking device is generally associated with a component which actually does keep the safety guard locked From the standard s point of view this component is referred to as interlocking device with guard locking The interlocking devices themselves by definition of the standard only monitor the position open closed of the safety guard This task can be fulfilled by electromechanical safety switches or non contact safety sensors SCHMERSAL Content SCHMERSAL Introduction Risk assessment Inherent safety Technical protective measures Determination of the safety function Design of the safety circuits Safety guards Choosing the locking principle Rate defeat incentives cC ON OO A W PY Interlocking devices with and without guard locking 10 Product selection 11 Interlocking devices with guard locking with Power to lock or Power to unlock working principle 12 Fault exclusions to ISO 13849 2 13 Verification 14 Validation 15 User information 16 List of Standards Page 02 Page 04 Page 05 Page 05 Page 06 Page 08
9. ck of all conditions and parameters is mandatory see ISO 13849 1 image 3 How to proceed with the validation is described in ISO 13849 2 The procedure shown there is as follows SCHMEASAL Considerations for designing SS 7 Fault list Aeon Documents v6 Fault exclusion criteria Verification plan Eu Validation guidelines Y Analysis ISO 13849 2 Validation Specification of the Is the analysis No en safety functions sufficient a Safety functions x m m um mm am EN EE ES Em um PL and categories Yes Determining the category No Yes MTTF DC CCF ad es Systematic error Category 2 3 4 c passed gt Software Verification of the PL for Yes Y No Y the SRP CS Combination of SRP CS Check of the safety functions Changes in Ambient conditions under failure conditions the design Maintenance related requirements Technical specification Validation report user information Y Were all safety functions validated No Yes Y SCHMERSAL Hence it does not only depend on the theoretical analysis but depending on the complexity of the machine also on the practical check of the safety function For a practical check of a two channel machine it can be useful to deliberately disconnect one channel and then test the reaction of the syste
10. d actuators see 7 2 C Non releasable attachment of the position switch M M see 7 2 Non releasable attachment of the actuating element M M M M see 7 2 C Additional interlocking device and plausibility checks R R see 7 2 d 2 X The application of at least one of these measures is mandatory M Mandatory measure R Recommended measures additional SCHMERSAL 14 In ISO 14119 section 5 very general requirements for the installation and mounting of interlocking devices are described which must be observed regardless of the measures described in Table 3 above Section 5 2 Arrangement and mounting of position switches Position switches must be arranged so that they are adequately secured against their position be changed To achieve this the following requirements must be met The fasteners of the position switches must be reliable and to remove them a tool is required m Type 1 position switches must have a method to permanently secure the position after adjustment such as bolts or dowel pins The facilities required for access to the position switches for maintenance and verification of the correct operation must be ensured Avoidance of dealing in reasonably foreseeable way is also to be considered when designing the access Gradual loosening must be prevented Bypassing the position switch in a reasonably foreseeable way must be prevented see section 7
11. e H 1 Of course this table is to be adapted to the respective application or machine SCHMERSAL 12 primary hazardous area If it is determined that defeat incentives exist then these must first be eliminated by design see ISO 14119 section 7 1 c Examples of purely constructive measures are A Ergonomics Height adjustment of the control panel Arrangement and design of the display and operating elements Position of the emergency stop switch Observability of the working zone Dimensions and location of the handles Manual forces for displacing B Viewing window Window construction Polycarbonate window must be protected against chemical and abrasive influences from inside with a safety glass pane and from the outside should be protected with a non splintering plastic pane or splintering prevention foil Window mounting The mounting should be able to withstand high impact reaction forces allow considerable deforming and at the same time the ends of the polycarbonate window should be hermitically sealed against chemical reaction C Protective cover Cover structure With sandwich construction the inner skin must be extremely deformable and the outer skin designed to be extremely resistant and stiff Main closing edge With power operated safety doors the kinetic energy and speed when closing must be limited so that no dangerous pinching point is created at the main closing edge The effective closing force
12. er new paths for the transmission and evaluation of the information provided by these principles Furthermore the set of ever more complex standards regulations and directives relating to machinery safety also requires a change in thinking from the manufacturers and users of machines These are the challenges which the Schmersal Group in partnership with machinery manufacturers is tackling and will continue to tackle in the future Competences WS 1 aie Fa pn Services Industries Product ranges Safe switching and monitoring Guard door monitoring safety switches Command devices with safety function Tactile safety devices Optoelectronic safety devices Safe signal processing m Safety monitoring modules m Safety controllers Safety bus systems Automation B Position detection Command and signalling devices B Elevators and escalators B Packaging B Food m Machine tools m Heavy industry Application advice CE conformity assessment m Risk assessment in accordance with the Machinery Directive Stop time measurements B raining courses Machine safety m Automation Explosion protection m Hygienic design Precautions have been taken to assure accuracy of the information in this catalogue www schmersal com 3 000 L W 09 2014 Teile Nr 103008190 EN Ausgabe 01 Typographic or pictorial errors that are brought to our attention will be corrected in subseque
13. ety of machinery Safety related parts of control systems Part 1 General principles for design Safety of machinery Safety related parts of control systems Part 2 Validation Safety of machinery Positioning of safeguards with respect to the approach speeds of parts of the human body Safety of machinery Safety distances to prevent hazard zones being reached by upper and lower limbs Safety of machinery Interlocking devices associated with guards Principles for design and selection Safety of machinery Guards General requirements for the design and construction of fixed and movable guards Safety of machinery Evaluation of fault masking serial connection of guard interlocking devices with potential free contacts draft Low voltage switchgear and control gear Part 5 1 Control circuit devices and switching elements Electromechanical control circuit devices Low voltage switchgear and control gear Part 5 3 Control circuit devices and switching elements Requirements for proximity devices with defined behaviour under fault conditions PDDB Preparation of instructions for use Structuring content and presentation Part 1 General principles and detailed requirements Finally with this brochure we hope to have given you helpful tips with the standard compliant construction of protective devices We have created the content of this brochure and the poster to the best of our knowledge and belief but assume no respo
14. fety guard indicating when they are to be used At a frequency of more than once a week a movable guard should be used with an interlocking device to ISO 14119 m ISO 13857 Safety distances to prevent hazard areas being reached by the upper and lower limbs This standard describes the sizes of limbs and consequently the necessary ISO 14120 F ISO 13857 safety distances to hazardous areas It states amongst others in section 4 3 that guards L Safety d _ Safety should not exceed a ground clearance of 180 mm because this would allow the whole guards JO ee body to access the hazardous area 7 Choosing the locking principle The type of locking device that should be used i e with or without guard locking can be determined by using the flow chart of the ISO 14119 Start SCHMEASAL Overall system stopping performance 2 entry access time ISO 14119 Yes Y No Y Locking l i rincipl Interlocking guard with guard locking Interlocking guard without guard locking BS de see section 5 can be sufficient see 5 1 to 5 6 End Information to answer the question whether the stop time of the whole system is 2 entry access time is given in the standard ISO 13855 section 9 i F ISO 13855 m This given standard calculates the safety distance from behind the safety guard to the Entry and danger zone with an entry speed of 1600 mm s or an access speed of 2000 m
15. g device the monitoring device logic and the actuator output SCHMEASAL Every safety function or circuit includes the following components Sub systems ISO 13849 1 Safety for example function SCHMERSAL By using the risk graph of ISO 13849 1 Annex A the required performance level 2 PL can be determined for this safety function Required perfor S Severity of injury Low risk mance S1 Slight normally reversible injury level PL S2 Serious normally irreversible injury or death FF Frequency and or exposure to hazard F1 rarely up to less often and or time of exposure to the hazard is short F2 Frequently up to permanently and or time of exposure to the hazard is long P Possibility of preventing the hazard or limiting the damage P1 possible under certain conditions P2 barely possible Starting point for estimating the High risk risk reduction The relevant safety functions of movable safety guards are see ISO 14119 section 3 2 m Switching off the dangerous machine function when opening the safety guard m Protection against unexpected start up f necessary locking the safety door until the dangerous machine function is completed f necessary unlocking the guard locking device The safety function unlocking the guard locking device is new However the standard assumes see remarks 1 and 2 of section 8 4 that the PL of the locking device is less than
16. gnitude are represented The locking forces actually required in a real application cannot and will of course not be prescribed by the standard Here either the machine manufacturer or a type C standard also see section 6 2 2 Note 2 should be consulted If an interlocking device with a guard locking is used a manual deliberate deactivation of the guard locking device should be considered for installation maintenance or repair work purposes on the machine Such types of release are defined in the standard ISO 14119 section 3 25 to section 3 27 Qe m Emergency release m Auxiliary release for B Escape release mounted mounted outside unlocking during setup within the hazardous zone the hazardous area no emergency to be able to leave the area for emergency use independently in the event of danger SCHMERSAL 18 SCHMEASAL 11 Power to lock or Power to unlock working principle Depending on whether energy is needed to lock or unlock the safety door one distinguishes between m Power to unlock mechanically locked unlocked by applying energy see A Power to lock energy required to keep locked release by removing the energy see B and D For safety reasons the power to unlock quiescent current principle is preferable After a proper risk assessment the power to lock principle may also be applied Accordingly interlocks are often used with the power to unlock princi
17. m Here it is again important to record the results validation report 15 User information If in spite of all protection measures there are still remaining risks at the safety guard available such as with certain operating modes e g maintenance operations setting up it is essential that A m the user is informed ig ow m pa l This can take place in two different ways on the safety guard itself and in the operating instruc SSS tions for the machine EE IH n 3 SCHMERSAL However at this point it must be made clear that this is the last possibility for risk reduction that may be used after the inherent construction see page 5 of this brochure and also the technical protection measure ie locking the safety guard have been exploited ISO 12100 Information on creating standardised operating instructions can be found in ISO 12100 section 6 4 Operating IEC 82079 1 and also in IEC 82079 1 instructions 22 SCHMERSAL 16 List of Standards MD 2006 42 EC ISO 12100 2010 ISO 13849 1 2006 ISO 13849 2 2012 ISO 13855 2010 ISO 13857 2008 ISO 14119 2013 ISO DIS 14120 2013 ISO DTR 24119 IEC 60947 5 1 2003 IEC 60947 5 3 2013 IEC 82079 1 2012 Machinery Directive of the European Parliament and of the Council of 17 May 2006 on machinery and amending Directive 95 16 EC General principles for design Risk assessment and risk reduction Saf
18. m s access speed The safety distance is also dependent on the size of the body parts that obtain access to the danger zone when the safety guard is opened Therefore the standard ISO 13857 is also to be considered when calculating the stopping time SCHMERSAL 9 10 8 Rate defeat incentives An investigation has showed that accidents are often the result of protective equipment being defeated Therefore an essential focus of ISO 14119 is the prevention of the interlocking devices from being tampered with To prevent this the standard suggests a certain method in the form of a flowchart Start SCHMERSAL Y Implementing basic measures see 7 1a Is there an incentive to _Is there an incentive to bypass see 7 1b and annex H see 7 1b and annex H Yes Ooo Is it possible to eliminate or to minimise the incentive to bypass interlocking devices see 7 1c ISO 14119 Manipulation incentives no V Yes Y Implementation of measures against a bypass on reasonably Q foreseeable manner required by Table 3 see 7 1c Elimination of minimising the incentive to bypass by implementing design measures or alternative operating modes see 7 1c End The goal of this method is to recognise the defeat incentive and to reduce or eliminate it The ISO 14119 also supports the designer with determining the defeat incentive It s
19. nnections are sufficiently resistant to systematic and random errors that would result in the loss of the safety function This is accomplished using a PL calculation that must also include the corresponding monitoring device and the actuator This calculation process is described in ISO 13849 1 Calculation of the safety function oes Structure Category 3 DC 29996 Structure Category 4 Biog 2 000 000 so 13849 1 CCF 80 points Biog 2 000 000 so 13849 1 F 1 h PFH 5 0 x 10 h F 1 h MTTF 2 283a MTTF 2 283a MTTF gt 100 a High MTTF gt 100 a High 90 Low 60 Low 80 points gt 65 80 points gt 65 PL d PL e PL e Assessment in accordance with Table 11 of ISO 13849 1 PLachieved PLd PL Such calculations can be performed on the computer with the SISTEMA software tool provided free of charge by the BIA The software is available for download at http sistema en schmersal net Many manufacturers of safety components make the data of their components available in so called SISTEMA libraries The Schmersal library is available at www schmersal net Further information and calculation examples can be found in 1 Our brochure Background information to EN ISO 13849 1 2006 http iso13849 en schmersal net 2 BIA Report for 13849 1 http bia en schmersal net 3 In the SISTEMA Cookbooks http sistema book schmersal net SCHMERSAL 14 Validation Despite all care a final che
20. nsibility for their content We also wish to point out the standardisation in European and at international level are in constant change in order to keep in line with the technical progress and to adapt the standards and regulations to this new technology If you have any questions or suggestions we would be happy that you contact us If you require more information please refer to our current event and training program which can be viewed under www tecnicum schmersal com Additionally our staff are available with further information SCHMERSAL 23 The Schmersal Group For many years the privately owned Schmersal Group has been developing and manufacturing products to enhance occupational safety What started out with the development and manufacture of a very wide variety of mechanical and non contact switchgear has now become the world s largest range of safety systems and solutions for the protection of man and machine Over 1 500 employees in more than 50 countries around the world are developing safety technology solutions in close cooperation with our customers thus contributing to a safer world Motivated by the vision of a safe working environment the Schmersal Group s engineers are constantly working on the development of new devices and systems for every imaginable application and requirement of the different industries New safety concepts require new solutions and it is necessary to integrate new detection principles and to discov
21. nt issues SCHMERSAL Safe solutions for your industry
22. ple for personal protection and interlocks with the power to lock principle for process protection also see section 3 28 and section 3 29 Power to unlock Locked A Energy ON unlocked Unlocked Energy ON locked Locked B Power to lock Unlocked Energy ON locked Locked C Energy ON unlocked Unlocked D Energy ON locked Locked SCHMERSAL 12 Fault exclusions Machine safety requires the correct functioning of the safety circuit It is therefore of utmost importance that any errors that could occur leading to a loss of safety are excluded The central standard that deals with possible errors in the components of a safety circuit is the ISO 13849 2 In the annexes possible errors and possible exclusions due to the application of certain tecniques are described in tabular form For example The non opening of an electro mechanical contact can be excluded by using a switch with positive break contacts It is important to study the applicable tables of the standard especially Annex D Validation tools for electrical systems and document possible fault exclusions SCHMERSAL SCHMERSAL ISO 13849 2 Fault exclusions 19 E oo a et ox ig g m ilaji z SCHMEASAL ISO 13849 1 Verification eT n ESAE E 2d iat 1 2 3 20 13 Verification The verification is used to provide evidence that the selected components and their inter co
23. rlocking devices associated with guards Principles for design and selection German version DIN EN ISO 14119 2013 This new standard replaces the currently valid EN 1088 and was published on 11 April 2014 in the Official Journal of the European Commission as an European standard harmonised under the MD As an ISO standard it is also valid beyond the European Union Since the transition period for the implementation of the new standard ends on 30 April 2015 you should already consider this standard during the design of new machines and plants This brochure s objective is to aid designers of machinery and plants with standard compliant design of moveable guards taking into consideration the ISO 14119 and other relevant regulations In the centre of the brochure there is an accompanying poster that gives a quick overview of the technically correct design of moveable safety guards and represents the whole process of their standard compliant selection and design in the form of a flowchart This brochure outlines the enclosed poster and gives detailed information on the individual process steps of the flowchart The page numbers noted on the poster refer to the relevant page in this brochure where the process step is described The contents of this brochure reflect the interpretation of the Schmersal Group and is also based on the experience gained as a member of the Deutschen Institut f r Normung e V German institute for standardisation
24. s B An actuator should not serve as a mechanical stop unless this is the intended use of the actuator according to the manufacturer m The receptacle and the mounting of the actuator must be sufficiently stable to maintain proper operation of the actuator SCHMERSAL Given the procedure described above and the protective purpose of this standard it is Our opinion that a position switch may be mounted with standard screws if neither a defeat incentive exists nor a standard screwdriver belongs to the normal operating tool of the machine 9 Interlocking devices with and without guard locking The standard distinguishes four different types of interlocking systems inv I Type 1 Type 2 Type 3 Type 4 i uncoded coded uncoded coded NENNEN IEEE The coding level is not important When considering the designs the first consideration is whether the interlocking device is at all coded or not The following coding levels are defined in the standard see section 3 13 1 to 3 13 3 low Coding options 1 9 medium Coding options 10 1 000 high Coding options gt 1 000 This definition is independent of the locking function of the interlocking device SCHMERSAL 15 16 LM TT y E Ec i ig m ilaji S SCHMEASAL ISO 14119 ISO 13849 2 Redundancy IEC 60947 5 3 Product standard
25. the dangerous fault detection DC awg B measures against common cause failures CCF Note to DC n many applications the interlocking devices are electrically connected in series Because of the possibility that dangerous faults that occur may not be detected the DC must be correspondingly reduced B A technical report currently being prepared ISO TR 24119 will give relevant information on series connections of interlocking devices and their effect on the DC Currently we recommend that you set the following DC m Series connection of interlocking devices with positive break contacts DC 60 which still allows a max performance level of PL d m Series connection of magnetic interlocking devices DC dependent on distance of the safety guards and their frequency of operation m Series connection of self monitoring electronic interlocking devices DC 99 which allows a max performance level of PL e Further details on these values see our information sheet Estimation of diagnosis degree in series connections of electromechanical safety switches and safety sensors under http series connection schmersal net SCHMERSAL 6 Safety guards The mechanical design of the safety guard is also described by requirements in the following standards SCHMERSAL m ISO 14120 Safety guards There is a reference in section 6 4 4 1 on the access or frequency of access with a movable sa
26. uggests a matrix that shows the task to be carried out on the machine and the consideration of easing the task through corresponding defeat SCHMERSAL Thus it is readily apparent at what point and in which task or operating mode of the machine there is a risk of defeat Flexibility such as with larger work pieces Cc Ke fe E ce i cd Q e 2 ie m o m 7 o i z a i lt Tasks possible without bypassing Operating mode 1 Operating mode 2 Operating mode 3 Operating mode 4 Operating mode 5 Easier more convenient Quicker high productivity Higher level of precision Improved visibility Improved audibility Less physical effort Larger freedom of movement Better flow of movement Prevention of interruptions Less travel Commissioning Program test Test run Installation adjustment modifcation equipping Proccessing Manual intervention for removal of debris Manual changing of work pieces Manual intervention with troubleshooting Check random sampling Manual intervention with measurement fine adjustment Manual tool change Maintenance Repair Fault rectification on machine Cleaning e g removing debris Tab 2 Example of an assessment of incentives to bypass interlocking devices Source ISO DIS 14 119 Tabl
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