What is a Flow Diagram?
A flow diagram is a graphical overview that shows the sequence and interaction of process activities within the scope of the HACCP study/plan2. The first process step or module usually begins with receiving raw materials and continues until the product is no longer under direct control of the operation2. A flow diagram can be used for a specific product or grouped products that follow similar processing steps2.
The flow diagram should be clear, accurate and provide sufficient detail to support the foundation of the hazard analysis2. Information should indicate all inputs, outputs, transfer steps and where applicable any rework or recycling. Inputs that enter the flow include raw materials, intermediate products, processing aids, packaging materials, and utilities (e.g. water)2. Outputs that are released or removed during the process include finished or intermediate products, waste and by-products4.The flow diagram should also indicate any transfer steps and outsourced processes1,2.
Linear or Modular?
There are two different approaches to consider in the construction of a flow diagram. You can choose a linear or modular format1. Linear is the simplest approach to constructing a flow diagram in which one step follows the next1. Modular is more suitable for complex food operations where products follow similar processing steps1. This particular method creates a top-level diagram depicting distinct stages in the overall process with additional diagrams showing further steps of the process within each module2..The MyHACCP website provides excellent examples of linear and modular flow diagrams.
Construct the Flow Diagram (Codex Step 4)
Construction of the flow diagram will require knowledge of all process activities and steps within the scope of the HACCP study. Supporting technical information will also be required in advance to help the HACCP team accurately construct the flow diagram. This usually includes the following:
- schematic plan of the factory and layout of equipment
- details on raw materials, processing aids, packaging and intermediate or finished products
- any utility inputs (e.g. water, air and steam)
- sequence and interaction of process steps2.
- segregation of low-risk, high-risk, high-care and ambient high-care areas
- time and/or temperature profiles
- storage/holding conditions
- details on any reworking or recycling
- potential delay(s) during or in between process steps
- any outsourced processes or sub-contracted work2
- waste removal routes
Documenting your process diagram will follow some standard principles. The document should communicate inputs, process sequence and interactions, outputs and any transfer and/or backward steps (e.g. rework). Each module and/or process step should be numbered in the correct sequence to aid easy reference. If possible, connected lines and arrows should not cross. The process flow diagram should clearly state where product moves through segregated areas along the process, for example low-risk to high-care. Critical control points identified in the second principle of HACCP can also be highlighted at the appropriate step on the flow diagram2.
Onsite Confirmation of the Flow Diagram (Codex Step 5)
The flow diagram must be checked to confirm it represents current processing activities during all stages and hours of the operation2. A missed step in the process could result in a hazard not being identified and controlled during later stages of the HACCP study. Checking accuracy of the flow diagram should be carried out by a person or persons with sufficient knowledge of the processing operation2.On-site confirmation can be done by going into the process area and comparing the documented flow diagram in hand against what actually happens in practice. This may require numerous visits until all relevant information has been gathered. Checking accuracy should also determine if processing activities are the same for all shift patterns, high and low production volumes and seasonal patterns2.
The original flow diagram must be amended if any deviation to the actual process activities is observed during onsite confirmation2. Justification for amendment must be documented. The finalised flow diagram must be dated and signed by an appropriate person or persons to confirm accuracy. Previous versions of flow diagrams must be retained as they might be required for future reference.
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