TL;DR
Reduced heat transfer almost always means fouling or scale on the plates. Run a CIP cleaning cycle, inspect the plates visually, and re-torque to the stamped dimension.
What you might see
- outlet temperature below setpoint
- heat duty dropping over weeks
- flow rate unchanged but performance lost
- higher pressure drop on one side
Likely causes
Scale or mineral deposit on plate surfaces, common with hard cooling water
Biofilm growth on low-temperature liquid sides
Oil or particulate fouling from upstream equipment
Gasket bypass allowing stream mixing and reducing effective plate area
Required tools
- CIP pump and hose connections
- pH meter or test strips
- Torque wrench sized to the frame bolts
- Soft nylon brush
- LOTO kit
Safety first
- Both sides can contain hot fluid and residual pressure. Verify zero pressure before opening any connection.
- Acid cleaning solutions are corrosive. Wear chemical-resistant gloves, face shield, and apron.
- Do not mix acid and alkaline cleaning chemicals in the same circuit without a full water flush between them.
Procedure
- 1
Isolate the heat exchanger from both process streams. Close the inlet and outlet isolation valves on the hot and cold sides.
- 2
Lock out and tag out both sides and verify zero pressure using installed pressure gauges before breaking any connection.
Warning: Both sides may contain hot process fluid under pressure. Verify pressure is zero before opening any connection. - 3
Connect the CIP supply and return lines per the Alfa Laval M-Series instruction manual CIP connection points.[1]
- 4
Circulate a cleaning solution appropriate for the fouling type: alkaline detergent for organic fouling, dilute nitric or citric acid for mineral scale. Follow the solution supplier's concentration and temperature guidelines.
- 5
After CIP, flush with clean water until the pH of the drain matches the inlet.
- 6
If CIP does not restore performance, de-plate the unit: loosen the tightening bolts in the alternating sequence and slide the plates out.[1]
- 7
Inspect each plate individually under good lighting. Look for pitting, cracks, bent corrugations, or gasket deterioration.
- 8
Clean persistent deposits mechanically with a soft nylon brush. Do not use steel brushes or abrasives on stainless plates.
- 9
Re-assemble plates in the correct chevron pattern. Tighten the frame bolts evenly in a cross pattern to the dimension stamped on the frame label.[1]
Sources
Alfa Laval M-Series Plate Heat Exchanger Instruction Manual, Alfa Laval
Alfa Laval M-Series PHE Instruction Manual, CIP procedures and frame tightening specifications (general)
View source
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