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Revealing Failures By Proof Tests
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All other tests are called Proof Tests.
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They are
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Not automatic, OR
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Their frequency is too low
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A proof test is
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Initiated by human action
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Usually not “built-in”, additional equipment is necessary to carry out the test
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For example an operator performs a Partial Stroke Test (PST) on a safety valve
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Note: not subject to the rules in IEC 61508 for development of H/W and S/W
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