TL;DR
FDV fault diverts product to drain or stops the line. Confirm the valve position sensor and air supply before investigating the valve body.
What you might see
- FDV not returning to forward-flow position after hold time
- pasteurizer shutting down after FDV fault
- FDV position sensor alarm active
- product diverting to drain unexpectedly
Likely causes
Actuator air supply pressure below the minimum for reliable valve shift
Position sensor misaligned or displaced giving a false position fault
Valve stem or seat fouled with product deposits preventing full stroke
Solenoid valve fault preventing air supply to the actuator
Required tools
- Air pressure gauge
- Multimeter
- LOTO kit
- Replacement solenoid valve (same part number)
Safety first
- The FDV is a regulatory safety critical device on an HTST pasteurizer. Repairs must comply with the site's HTST operating permit and applicable regulatory requirements (PMO, 3-A). Document all FDV work.
- Product diverting to drain is a product loss event. Confirm upstream batches that ran during the fault are quarantined for regulatory review.
- Hot pasteurized product is present in the FDV valve body. Confirm CIP has been completed and the system is cool before disassembling the valve.
Procedure
- 1
Check the air supply pressure to the FDV actuator. Minimum supply is typically 5 barg for reliable actuation.[1]
- 2
Inspect the FDV position sensors. Confirm the target flag on the valve stem is within the sensor range.[1]
- 3
Command the FDV to divert and then to forward-flow using the HTST control panel manual test function. Observe whether the valve physically moves.
- 4
Check the solenoid valve coil resistance and supply voltage. A failed solenoid coil (open circuit) prevents valve movement.
Warning: The FDV is a food safety critical control point. Any fault repair must be followed by a full pasteurizer validation cycle or equivalent check per the site's HTST operating permit before releasing product. - 5
If the valve body itself is stuck, investigate for product fouling at the seat. Clean per the general valve maintenance procedure.
- 6
After any repair, run the FDV through at least 10 complete divert and forward-flow cycles and verify position sensor confirmation on each stroke.
- 7
Log the fault and repair in the pasteurizer maintenance record. FDV maintenance records are required by regulatory authorities.
Sources
Tetra Pak Tetra Pak A3 / Flex Pasteurizer / HTST System general technical documentation, Tetra Pak
Tetra Pak A3 / Flex HTST pasteurizer general flow diversion valve maintenance and regulatory procedures (general)
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Fouled heat exchanger plates reduce heat transfer and can prevent the pasteurizer from reaching the required temperature. Verify CIP effectiveness and plan a manual plate clean if needed.
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