Equipment Sequence failures

Failures originate from two sources,

Equipment Phase

s and

Equipment Sequence

s. An

Equipment Phase

generates a failure by executing a Phase Failure (PFL) instruction, maintained by the Failure attribute. The

Equipment Sequence

generates a failure by detecting a problem that impairs its ability to coordinate active sequence elements, maintained by the Internal Failure attribute.

A failure propagates up the hierarchy of sequence elements from the point it originated;

Equipment Phase

s notify steps and steps notify the

Equipment Sequence

. Failure status is maintained at each of these layers:

A failure is considered a serious problem that warrants holding the execution of the sequence, all active elements, and any phases to which they are attached until the cause of the failure is corrected. This can occur in either Automatic or Manual mode.

Phase-generated failures

Phase-generated failures are the result of the phase logic executing a PFL instruction. The instruction includes a failure code created and managed by the user. The failure is stored on the Failure member of the phase’s backing tag. The failure is detected by the step, setting the Failure member on the step's backing tag. Finally, the failure on the step is detected by the sequence, setting the Failure member on the sequence.

Sequence-generated failures

Sequence-generated failures are detected by the sequencing engine as it executes. The failure is detected by the step and is stored on the Internal Failure member of the step’s backing tag. That failure is detected by the step, setting the Internal Failure member on its backing tag.

Clear failures

The Clear Failures command resets the failure and internal failure members of the sequence and step backing tags. If a phase failure is being cleared, the

Clear Failures

command is forwarded to the phase. Sequences, like phases, cannot be restarted until all their failures are cleared. Note that if the cause of the failure has not been resolved, the next scan of the

Equipment Sequence

engine will likely regenerate the failure.

You need to do the following sequence of actions in order to recover from an

Equipment Sequence

failure: