SAFETY STOP 1. Safety and scope check Assessment: Restricted analysis Reason: The conveyor is stopped, but the energy-isolation status is Not provided. No guard entry or hands-on inspection is authorized. A stopped machine must not be treated as safely isolated. Allowed scope: Administrative and remote evidence collection Review of HMI, PLC, drive, recipe, shift-log, and change records Review of the approved manufacturer documentation External observation from outside guarded or hazardous areas Planning of later checks for authorized, qualified personnel Required authorization before physical checks: Confirmation of isolation under the applicable local procedure Applicable permit or work authorization Qualified personnel assigned for the relevant technical discipline Approved manufacturer instructions for the conveyor, drive, controls, guarding, and changeover arrangement Prohibited actions under the present status: Guard entry or hands-on inspection Contact with moving or exposed equipment Energized diagnostic work Bypassing, bridging, simulating, defeating, or disabling any guard, interlock, alarm, permissive, emergency stop, or isolation control Restarting solely for diagnostic purposes without an approved risk assessment and authorization 2. Incident summary Field Summary Equipment function A generic case conveyor transfers sealed cartons from a packing machine to a labeling station. Observed deviation The conveyor stopped three times. During each reported event, the HMI no longer showed the run command. Operating context All three events reportedly occurred after a carton-size change and while using the new carton size. Recent change The carton-size recipe and guide setup were changed before the shift. This is a lead, not proof of causation. Timing Late shift. Exact event timestamps, stop durations, and sequence timing are Not provided. Frequency Three stops during the shift. Alarm information No persistent drive alarm remained after reset. Exact transient messages are unknown. Actions taken An authorized reset was performed after each event. Operation restarted temporarily. Impact Three production interruptions; exact downtime and production loss are Not provided. Current state Conveyor stopped. Energy-isolation status is Not provided. Physical inspection status No parts replaced and no hands-on inspection reported. 3. Information and evidence ledger ID Statement Class Source Relevance Reliability E01 The conveyor stopped three times during the late shift. Reported statement Incident description; shift log confirms three resets Establishes recurrence and event count Medium: stop count is supported indirectly by reset records, but exact event records are unavailable E02 The HMI stopped showing the run command. Reported statement Incident description Indicates that the commanded or displayed run state was absent during the event Medium: operator/HMI observation; no screenshot or PLC trend E03 No persistent drive alarm remained after an authorized reset. Observed fact Incident description Limits conclusions based on persistent drive faults Medium: post-reset condition only; transient history was not retained E04 Exact transient messages are unknown. Unknown Incident input Prevents alarm decoding and event-sequence reconstruction High: explicitly identified as unavailable E05 All three events happened with the new carton size. Reported statement Operator statement Supports investigation of size-dependent conditions Medium: consistent report, but no timestamped correlation data E06 The shift log confirms three resets. Observed fact Shift log Corroborates three recovery actions High for reset count; does not independently prove the cause of each reset E07 The carton-size recipe was changed before the shift. Observed fact Incident input Identifies a configuration change preceding the events Medium: no recipe version, parameter comparison, or audit export supplied E08 The guide setup was changed before the shift. Observed fact Incident input Identifies a mechanical setup change preceding the events Medium: no recorded positions, setup verification, or photographs E09 Authorized reset restored operation temporarily. Action/result Incident description Shows reset cleared the immediate stopped state but did not prevent recurrence Medium: restart occurred, but duration until recurrence is unknown E10 No parts were replaced. Observed fact Incident input Confirms no replacement action can be linked to the outcome High E11 No PLC trend is available. Unknown Incident input Prevents verification of commands, permissives, interlocks, and event order High E12 No drive history is available. Unknown Incident input Prevents verification of transient drive status or fault information High E13 No photographs or measurements are available. Unknown Incident input Prevents assessment of carton position, guide setup, and physical conditions High E14 No approved manual excerpt was supplied. Supplied manual information Incident input Alarm meanings and approved procedures cannot be established High E15 The conveyor is currently stopped. Observed fact Incident input Defines current operating state High E16 Energy-isolation status is not provided. Unknown Incident input Creates a safety restriction on physical work High E17 No guard entry or hands-on inspection is authorized. Observed fact Incident input Restricts the diagnostic scope High E18 Exact stop duration and sequence timing were not recorded. Unknown Incident input Prevents sequencing of command loss, permissive changes, and drive response High 4. Contradictions and missing information Material conflicts or ambiguities No direct contradiction is established in the supplied information. “No persistent alarm” does not establish that no transient alarm, warning, interlock, or permissive change occurred. “HMI stopped showing the run command” is ambiguous. It could describe a displayed command bit, an operator-button state, a sequence state, or another HMI indication. The tag or screen object is Not provided. Three resets are documented, but the exact relationship between each reset and each reported conveyor stop is not independently timestamped. The recipe and guide changes preceded the events, but no evidence currently establishes which change, if either, contributed. Prioritized questions Has the conveyor been isolated and verified under the applicable local procedure? Decision affected: Whether any authorized physical or technical checks may be planned beyond remote information review. What exact HMI object, label, or PLC tag stopped showing the run command, and what were its values immediately before and after each stop? Decision affected: Whether the investigation should focus first on command generation, sequence logic, permissives, or display interpretation. Can timestamped PLC event logs, diagnostic buffers, drive history, or HMI alarm history be recovered for the three events? Decision affected: Hypothesis ranking and reconstruction of the first state change. What exact recipe version and parameter values were active before and after the carton-size change, and was the approved changeover verification completed? Decision affected: Whether a recipe-dependent sequence or parameter condition remains a leading hypothesis. What guide settings were changed, how were they verified, and was any external carton misalignment, accumulation, contact, or abnormal movement observed? Decision affected: Whether a size-dependent mechanical or sensing condition should remain highly ranked. 5. Ranked hypotheses Rank Hypothesis and mechanism Supporting ledger IDs Contradicting or missing evidence Confidence band Rationale 1 Size-dependent permissive or sequence condition: With the new carton-size recipe or setup, a required control condition may cease to be satisfied, causing the run command to be removed without leaving a persistent drive alarm. E02, E05, E07, E08, E09 No PLC trend, tag identity, event sequence, recipe comparison, or decoded message: E04, E11, E14, E18 Plausible The reported loss of the run command and recurrence only with the new carton size fit this mechanism, but no control-state evidence establishes it. 2 Carton-position or guide interaction affecting a monitored condition: The changed guide setup or carton geometry may alter carton flow or a monitored state, resulting in removal of a run permissive or sequence command. E05, E08, E13 No photographs, measurements, external observations, sensor-state records, or setup verification are available: E11, E13, E18 Plausible The mechanical setup changed immediately before the events, but there is no direct evidence of contact, obstruction, misalignment, or sensor-state change. 3 Upstream or downstream coordination removes the conveyor command: A packing-machine, labeling-station, or line-control state may withdraw the conveyor run request during the new-size operating sequence. E02, E05, E07 No interface-state history, sequence timing, PLC trend, or equipment event logs: E11, E18 Weak Loss of the displayed run command could originate outside the conveyor drive. The supplied evidence contains no interface data. 4 Transient drive or control-power condition not retained after reset: A temporary drive, communications, or control-state event may stop operation and disappear from the active alarm display after reset. E03, E04, E09, E12 No drive history, transient code, electrical measurement, or timestamped event record: E04, E12, E18 Weak A non-persistent event remains possible, but the reported disappearance of the run command provides stronger support for investigating command and permissive logic first. 6. Diagnostic test plan Because isolation and authorization are not established, the present plan is limited to information review and safe external evidence gathering. Authorized technical checks may proceed only after all stated prerequisites are satisfied. Priority Hypothesis distinguished Check category Proposed check Prerequisites and authorization Observation that supports Observation that weakens Stop/escalation condition 1 All hypotheses Information review Preserve and export available PLC event logs, HMI alarm history, sequence-state history, drive diagnostic history, reset timestamps, and shift records. Correlate all records using their original timestamps. Authorized access to control records; approved data-handling procedure; no machine operation required A consistent first-changing signal, command, permissive, interface state, or transient drive event appears before each stop Records show no repeatable state change, or relevant history was overwritten Stop analysis and escalate if timestamps are inconsistent, records are incomplete, or access requires unauthorized system changes 2 Hypotheses 1 and 3 Information review Identify the exact HMI indication described as the “run command,” including screen name, displayed label, PLC tag, command source, and associated permissive logic from approved documentation. Approved PLC/HMI documentation and current controlled software reference; qualified controls personnel The indication maps to a command or permissive that was removed during the event The indication is only a display artifact or does not control conveyor operation Escalate to controls engineering or manufacturer support if the logic cannot be interpreted from controlled documentation 3 Hypothesis 1 Information review Compare the active new-size recipe with the previously used approved recipe and review the recipe audit trail, change record, and approved parameter definitions. Authorized read-only access; approved recipe documentation; qualified reviewer A changed parameter is directly associated with conveyor sequencing, permissives, timing, or line coordination No relevant recipe difference exists, or all changed values are verified as unrelated by approved documentation Stop and escalate if parameter meanings, valid ranges, or revision status are not available from the approved manufacturer or engineering source 4 Hypothesis 2 External observation From outside all guards and hazard zones, document the guide positions, visible carton path, accumulation, alignment, contact points, and condition of externally visible components while the equipment remains stopped. Area made safe under local procedure; no guard entry; no touching or adjustment; authorized observer Visible mismatch, contact, obstruction, displaced guide, or inconsistent setup is documented No visible abnormality is present from the permitted observation points Stop immediately if observation requires entry, reaching, guard opening, or proximity to an unverified energy source 5 Hypotheses 1–4 Authorized technical check After verified isolation and authorization, qualified personnel may inspect the changeover setup and relevant sensing, control, and drive interfaces using the exact approved manufacturer procedure. Verified isolation; permit; qualified personnel; approved manual including manufacturer, equipment identification, document number, and revision A repeatable physical or control condition is found that directly corresponds with the recorded command loss Inspection and approved static checks find no relevant deviation Stop and escalate for damaged safety equipment, uncertain isolation, stored energy, undocumented modifications, or absence of an applicable approved procedure 6 Hypotheses 1–3 Authorized technical check Any controlled functional reproduction must be defined through the local risk assessment and manufacturer procedure, with recording of command, permissive, sequence, interface, and drive states. Separate operational-test authorization; completed risk assessment; safeguards fully functional; qualified personnel; approved test plan The same state transition repeatedly precedes the stop under the new-size configuration and does not occur under an approved comparison condition The event cannot be reproduced and no repeatable signal sequence is observed Stop on any unexpected motion, protective-device event, abnormal noise, carton instability, undocumented alarm, or loss of controlled conditions Required manufacturer information Before alarm interpretation or detailed technical checks, obtain the applicable controlled documentation for: Conveyor and line-control operating sequence HMI screen and tag definitions PLC permissive and interlock descriptions Drive diagnostic and history retrieval Carton-size recipe parameter definitions Mechanical guide changeover and verification Guarding, isolation, stored-energy, and controlled test procedures The documentation must be identifiable by manufacturer or responsible engineering authority, equipment applicability, document number, and revision. 7. Root-cause assessment Status: Unresolved No Confirmed root cause is established. The current leading hypothesis is a size-dependent permissive or sequence condition, but it remains only a Leading hypothesis. The evidence shows temporal association between the carton-size change and the three events, together with reported disappearance of the HMI run command. It does not establish the causal mechanism. Confirmation would require: Timestamped evidence identifying the first relevant state change Identification of the exact run-command indication and its control source Controlled comparison of the applicable recipe and setup records Direct evidence linking a specific condition to removal of the run command Reasonable exclusion of material alternatives such as line coordination, mechanical carton interaction, and transient drive or control events 8. Immediate containment Keep the conveyor stopped until its isolation and authorization status are formally established. Preserve all remaining HMI, PLC, drive, recipe, audit, and shift-log records before they are overwritten. Record the active carton-size recipe identity and guide-setup state without changing them, where this can be done administratively or from an authorized safe location. Do not perform further resets solely to restore production without the applicable operational authorization and escalation process. Do not change recipe values, guide settings, sensors, wiring, or drive parameters before evidence preservation and approved review. Communicate that the equipment has experienced three recurrent stops and that the causal mechanism is unresolved. No hands-on containment measure can be proposed safely from the supplied information because verified isolation and physical-work authorization are absent. 9. Corrective and preventive actions Candidate corrective actions These are not approved repairs and must not be implemented until the corresponding mechanism is established. Linked cause or hypothesis Candidate action Required reviewer Verification evidence Leading hypothesis: size-dependent permissive or sequence condition Correct only the verified recipe, sequence, or configuration deviation in accordance with the controlled engineering or manufacturer procedure Qualified controls engineer and responsible operational authority Approved configuration comparison, documented change, controlled functional verification, and absence of recurrence during the defined acceptance check Alternative hypothesis: carton-position or guide interaction Correct only a documented guide, setup, alignment, or externally verified mechanical deviation using the approved changeover or maintenance procedure Qualified mechanical maintenance reviewer and responsible operational authority Recorded pre/post setup condition, approved dimensional or procedural verification, and controlled operating result Alternative hypothesis: upstream/downstream coordination Correct only the verified interface, permissive, or sequence-coordination defect under controlled software and change-management procedures Controls engineering and relevant line-equipment owner Timestamped interface test showing correct command transitions and successful controlled line sequence Alternative hypothesis: transient drive or control condition Address only the specific event identified through decoded diagnostics and approved manufacturer guidance Qualified electrical/drive specialist; manufacturer support where required Preserved diagnostic record, documented intervention, approved post-work checks, and no recurrence under the defined verification Preventive controls Preventive control Link Required reviewer Verification evidence Require recorded recipe identity and approved changeover verification for carton-size changes Leading hypothesis and Hypothesis 2 Operations and engineering authority Completed, traceable changeover record linked to the production run Enable or preserve timestamped PLC, HMI, and drive event history where approved All hypotheses Controls engineering and cybersecurity/change-control authority Verified event retention and successful retrieval test Record exact stop time, HMI indication, active alarm text, recipe, carton size, and reset time for recurrence All hypotheses Maintenance and operations management Complete incident record from the next event, without unsafe observation Maintain controlled documentation for recipe parameters, permissives, interfaces, drive diagnostics, and guide setup All hypotheses Engineering document owner Current approved documents available with applicability and revision confirmed Review repeated-reset practice through the applicable operational and safety process Recurrent unresolved event Operations, maintenance, and safety authority Approved escalation rule defining when further reset and restart are prohibited 10. Escalation criteria Escalate immediately to the applicable qualified role when any of the following applies: Safety personnel: isolation status cannot be confirmed; the required permit is absent; a guard, interlock, emergency stop, or protective device is involved; or an uncontrolled hazard is identified. Controls engineering: the run-command indication cannot be mapped to an approved PLC tag or sequence; event logs show unexplained permissive or command changes; or software/configuration differences require interpretation. Electrical or drive specialist: a transient drive, communications, control-power, or electrical event is recorded; drive history cannot be decoded; or inspection would involve electrical equipment. Mechanical maintenance specialist: an external observation identifies carton contact, obstruction, displaced guides, abnormal alignment, or a setup condition requiring physical inspection. Manufacturer or responsible engineering support: the applicable alarm meaning, sequence description, recipe definition, diagnostic method, valid setup method, or controlled test procedure is unavailable or ambiguous. Operations management: another stop occurs, another reset is proposed without captured evidence, or continued operation is considered while the causal mechanism remains unresolved. Quality personnel: the repeated stops or carton-size change may have affected carton condition, labeling flow, product traceability, or downstream grouping. Stop and escalate: any planned check requires guard entry, energized exposure, stored-energy release, bypassing a safeguard, or operation outside an approved risk assessment and procedure. 11. Maintenance log entry Context: Late shift; generic case conveyor transferring sealed cartons from a packing machine to a labeling station. Symptom: Conveyor reportedly stopped three times after a carton-size change. During the events, the HMI reportedly stopped showing the run command. Verified evidence: Shift log confirms three resets. The carton-size recipe and guide setup were changed before the shift. No persistent drive alarm remained after reset. Exact transient messages, event timestamps, stop durations, and sequence timing are not available. Actions completed: Authorized reset performed after each event. Operation restarted temporarily. No parts replaced and no physical inspection reported. Current status: Conveyor stopped. Energy-isolation status is not provided. No guard entry or hands-on inspection is authorized. Assessment: Cause unresolved. The association with the new carton size is an investigation lead and does not establish causation. Open questions: Exact run-command indication and PLC tag; recoverable PLC/HMI/drive records; active recipe version and parameter comparison; verified guide setup; confirmed isolation and work authorization. Next authorized step: Confirm safety isolation and authorization status. Preserve and review available PLC, HMI, drive, recipe, audit, and shift records. Obtain the applicable approved manufacturer or engineering documentation before technical interpretation or physical checks.