Energy is supplied for starting the movement of a mechanism. Guide on the use and application of EN Further information on cookies is available in our data protection statement. For proportional flow valves: Clogging blockage Yes, for hose assemblies in the power circuit.
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The extent of the accumulation of faults considered shall be in accordance with the design rationale.
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Oriented failure mode Oriented failure mode components or systems should be used wherever practicable [see EN —2: After the completion of validation by testing the safety functions shall continue to be in accordance with the specifications for the safety requirements, or the safety-related parts of the control system shall provide output s for a safe state.
Transient suppression Use of a suppression device RC, diode, varistor parallel to the load, but not parallel to the contacts. Components can be io as being well—tried if they comply with the description given in EN Positive mechanical action The positive mechanical action is used for moving parts inside hydraulic components, see also Table A. The greater the risk, the higher the requirements of the control systems.
The drive is shut down via two contactors with positive-guided contacts. Change of the pressure djn behaviour without changing the setting device see remark 1 Yes, for directly actuated pressure limiting valves and pressure switching valves if the installed spring s are well—tried see Table A. See primary action for starting in EN —2: Remarks 1 By using ferrules or other suitable means for multi— stranded wires.
Two basic types of techniques exist: Size px x x x x Changes in flow rate due to changes in the pressure differences and viscosity are physically limited in this type of valve and are not covered by this assumed fault. Bursting of the housing or fracture of the cover or 113849-2 elements Yes, if construction, dimensioning and installation are in accordance with good engineering practice.
Where applicable validation shall address: Such arguments can be constructed on the basis of simple, well—understood concepts, such as the correctness of a mechanical interlock.
EN ISO 13849-1: Performance Level (PL)
Overloading can be avoided by applying adequate torque loading technology. The achieved PL must be greater than or equal to the PL r required from the risk assessment.
Fault considered Fault exclusion Remarks Change of switching times None Non-opening, incomplete opening, non-closure or incomplete closure sticking at an end position or at an arbitrary intermediate position Yes, if the guidance system for the moving component s is designed in a manner similar to that for a non—controlled ball seat valve without a damping system see remark 1 and if well-tried springs are used see Table A.
Step 1 – Define the requirements of the safety functions. Cam All factors influencing the cam arrangement e.
None — high resistance at Interruption in power supply No operation of mechanical failure switch due to Short—circuit between the three connections djn a change—over switch measures Table D. The precise instant at which a fault is injected into a system can be critical.
Insulation monitoring Use of isolation monitoring device which either indicates an earth fault or interrupts the circuit automatically after an earth fault [see EN More information on analysis methods is given in EN EN a other influences are taken into account, e. Cross—reference may be made to previous validation records, provided they are properly identified.
Unintended unscrewing of the operating element of the setting device Yes, if an effective positive locking device against unscrewing is provided. It presents the UK view on standards in Europe and at the international level.
Spring See Table A. When testing is necessary to determine compliance with the environmental requirements the procedures outlined in the relevant standards shall be followed as far as required for the application. Protection against unexpected start—up Consider 138499-2 start—up caused by stored energy and don power supply restoration for different modes, e.
This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by Februaryand conflicting national standards shall be withdrawn at the latest by February Documents containing sufficient information e the list below shall be included in the validation process to demonstrate the category ies and the safety function s of the safety-related parts which have been achieved: For safety gate guarding on a machine, for example, hazardous movements must be shut down when the safety gate is opened.