The fault events that cause these four failures were identified, and their cause–effect connections were traced until they
reached the basic fault events (see Figures 4–7). Note the use of conditional events, which represent process controls that
restrict fault-event occurrence. Neglecting process controls exposes the process to failures stemming from basic events.
Figure 6: Packing-process fault tree showing the branch following from correspondence failure. QA is quality assurance. MUB
is multiple unit box.
Noncompliance with product-temperature requirements is considered the most critical of all possible process failures because
it can cause premature product deterioration. Because process history shows that these failures occur with a relatively low
frequency, the following actions should be sufficiently effective:
Figure 7: Packing-process fault tree showing the branch following from cleaning and line-clearance failure.
- Ensure cold-chamber qualification on at least a yearly basis to demonstrate consistency in keeping product temperature between
2 and 8 °C. Perform a similar study in the acclimatization room.
- Establish a metrological assurance plan, created by the QA department, to guarantee verification and adjustment of cold-chamber
temperature controllers on at least a yearly basis.
- Monitor cold chambers daily. Monitor acclimatization- and packing-room temperatures linked to standby and transfer follow-up
of each product batch. Standard operational procedures (SOPs) and supervision must be implemented accordingly.
- Implement an SOP to mitigate possible interruptions during the packaging of refrigerated products, and ensure that the quality
of these products is preserved.
Failures in the printing of primary information and in the correspondence between products, printed packing material, and
documentation are considered less critical because they have less impact on final product quality. Insufficient workstation
cleaning and line clearance are also considered less critical failures. All of these faults occur more frequently, however,
because of human error. The authors decided to create barriers in the packing-line configuration illustrated in Figure 2 for
detecting and eliminating faults throughout the process. The barriers are as follows:
- A first level to detect and eliminate possible faults in product-vial labeling and primary-information imprinting in which
the labeling-machine automatically senses and rejects unlabeled vials or nonimprinted vial labels.
- A second level to detect and eliminate possible faults in product-vial labeling and primary-information imprinting in which
a buffer operator visually inspects and rejects unlabeled vials, nonimprinted vials, badly pasted or wrinkled labels, and
illegible, misplaced, and erroneous imprints.
- A third level to detect and eliminate possible faults in product-vial labeling and primary-information imprinting (also for
previously prepared printed packing material) in which packing operators visually inspect and reject unlabeled vials, nonimprinted
vials, badly pasted or wrinkled labels, and labeled vials or cartons with illegible, misplaced, or erroneous imprints.
- A fourth level to check for MUB completion in which the first end-of-line operator looks for missing packed units, leaflets,
and vials by weighing. The second end-of-line operator performs visual inspection to verify proper MUB manual sealing and
correct primary-information printing on the corresponding label.
- A fifth level to check for shipping-box completion in which a handler operator looks for missing multiple boxes by weighing
and performs visual inspection to verify proper shipping-box sealing and correct primary information printing on the corresponding
- A documented, in-process control implemented at intervals by a supervisor who visually inspects printed packing materials
and their primary information. The supervisor also checks the appearance and completion of packed units by taking MUB samples
from the end of the line. A similar in-process control is also implemented for previously printed packing material during
the imprinting of cartons, MUBs, and shipping-box labels.
- Documented control performed by the supervisor to ensure the cleaning and line clearance for all involved areas at the beginning
and end of each process.