Samson 3241 Manual

Also see for 3241: Mounting and operating instructions Mounting and operating instructions Mounting and operating instructions Mounting and operating instructions

Contents

10Competence in Functional SafetyFunctional safety of globe valves, rotary plug valves, ball valves and butterfly valves5 Intended use of control valves insafety-instrumented systemsResponsibilityThe reliability of mechanical components is significantly affected by the operating condi-tions and, as a result, by systematic failures. This needs to be taken into account whenselecting and sizing devices.Safety-instrumented functionDuring normal operation, the signal pressure is applied to the pneumatic actuator. Tomeet the requirements of the safety-instrumented function, the actuator is usually ventedby a solenoid valve. The force of the actuator springs moves the valve to its end position,i.e. the valve is either completely opened or closed.The end position of the valve must not be impeded by mechanical equip-ment, such as travel stops or handwheels, under any circumstances.When the signal pressure is applied to the actuator again, the valve moves to the corre-sponding position. If the actuator is to be locked after a case of demand, this must beensured by the operator using suitable means.OperatorFeatures of final elements Contact with the process media may cause systematic failure and, as a result, affect thesafety-related availability of the safety-instrumented systems. The influence of specificprocess conditions must be analyzed and taken into account during sizing and main-tenance.These conditions arise from process requirements. To rule out systematic failure, we re-commend creating a loop data sheet according to the German standard VDI 2180-5,section 4 (recommendations for final elements).In case of doubt, consult the manufacturer for valve sizing.To reduce systematic failure, diverse redundancies may be advantageous (e.g. globevalve and ball valve).Operator