Functional safety
8.2 Device-specific safety notes
SIPART PS2 with PROFIBUS communication
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Operating Instructions, 09/2007, A5E00127926-07
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The connected valve actuator must be single acting and switch the valve to its safe end
position by spring force in the following cases:
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Pressure failure
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At a chamber pressure (Y1 connection) up to a third of the maximum available inlet
pressure (Pz connection)
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The air outlet does not contain any additional cross-sectional contractions leading to an
increased dynamic pressure. In particular, a silencer is only allowed if icing or other
contamination is ruled out.
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The restrictor in the Y1 circuit may not be completely closed during operation.
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The auxiliary pneumatic power is free of oil, water and dirt in line with:
DIN/ISO 8573-1, maximum class 2
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The average temperature viewed over a long period is 40 °C.
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The MTTR after a device fault is 8 hours.
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In case of a fault, the pneumatic outlet of the positioner is depressurized. A spring in the
pneumatic drive must move the valve to the pre-defined, safe end position.
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A dangerous failure of the positioner is when the pressure outlet is not depressurized, or
the safety position is not reached, when the LOW signal is less than 4.5 V at the input for
the safety shutdown.
