TL;DR

Rising pressure drop across the plate pack means fouling, partial blockage, or too many plates for the flow rate. Measure the delta P, run CIP, and verify the plate count against design.

What you might see

pump discharge pressure rising with constant flow
inlet-to-outlet differential above design spec
flow rate dropping with same pump speed
CIP did not restore normal delta P

Likely causes

Tap to mark as ruled out

Internal fouling or partial blockage narrowing the flow channels
Plate pack over-plated relative to the design flow, increasing channel velocity
Upstream particulate or fiber entering the port and bridging narrow channels
Gasket extrusion partially blocking a channel

Required tools

Differential pressure gauge or manometer
Torque wrench
CIP pump and cleaning chemicals
LOTO kit

Safety first

Depressurize and verify zero pressure on both sides before any mechanical disassembly.
Flushing channels under pressure requires controlled discharge. Direct the flush outlet to a safe drain.

Procedure

8 steps · ~60 min

1
Record the current pressure differential across each side. Compare to the commissioning or design baseline.
2
Check the upstream strainer or filter. A clogged strainer can mimic high PHE delta P. Clean and re-check.
3
Run the CIP cleaning procedure (see the reduced-heat-transfer guide on this machine). Record the delta P again after cleaning.
4
If CIP does not reduce the differential, isolate and de-plate the unit. Inspect each channel for visible particulate bridging or gasket extrusion.[1]
5
Flush each channel individually with clean water under low pressure to dislodge loose material.
6
Verify the plate count against the design document or original Alfa Laval order confirmation. An extra plate added in a previous reassembly increases the delta P.[1]
7
Re-assemble to the correct plate count and tighten to the frame dimension on the nameplate.
8
Commission with the process fluid and confirm the delta P returns to within 10% of the design value.

Sources

Alfa Laval M-Series Plate Heat Exchanger Instruction Manual, Alfa Laval
Alfa Laval M-Series PHE Instruction Manual, pressure drop troubleshooting and plate count verification (general)
View source

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