Disassembly and cleaning of a plate heat exchanger

Disassembling cleaning of a plate heat exchanger is performed when heavy deposits that are not soluble by chemical cleaning are present. Disassembling cleaning provides better cleaning compared to chemical cleaning and is considered more environmentally friendly.

The plates of the heat exchanger are covered with carbonate deposits (scale), rust, and sludge that enters with the flow. Pollution is determined by an increase in hydraulic resistance and a decrease in heat transfer.

The intensity of pollution and the frequency of cleaning depend on the design features and operating mode of the plate heat exchanger.

The degree of turbulence of the flow determines the intensity of pollution of the plates. Plates with a thermodynamically short channel (L-type) form a less turbulent flow compared to H-type plates, so they become dirty faster.

The operating mode of the heat exchanger at working fluid flows close to nominal contributes to the self-cleaning effect of the plates due to the undermining of formations by the turbulent flow. Deposits collection and metal corrosion begin in the corners of the heat exchanger plates 'dead zones', where the flow turbulence is slightly lower than in the central part of the heat exchange plate.

In water heating systems from a municipal water supply with a high content of hardness salts, the amount of deposits that precipitate increases exponentially with the temperature of the heated water above 60°C, which can lead to rapid fouling of the plate heat exchanger.

Procedure for disassembling and assembling a plate heat exchanger

1 Drain the liquid and disconnect the pipes connected to the heat exchanger with a visible gap.

2 Measure and record the size of the block of plates of the heat exchanger between the movable and main plate.

3 Use a marker to draw lines diagonally across the plate package, this will allow the plates to be assembled in the correct order without twisting.

4 Loosen all the bolts of the tension bolts diagonally. Unscrew and remove the tension bolts from the heat exchanger.

5 Push the movable plate and carefully, without damaging the interplate seals, without bending or scratching, push and remove the plates one by one.

6 Each plate removed from the heat exchanger should be numbered with a marker for further stacking in the block in the sequence in which they were installed.

7 The plates of the heat exchanger are cleaned one by one with a stream of water under high pressure. It is forbidden to use abrasive tools for cleaning the plates, which scratch the surface, and brushes with metal bristles.

8 The cleaned plates are stacked in a package one by one with the seal against the stationary plate, in the order in which they were removed from it.

9 Move the movable plate to the assembled plate block, install the tension bolts into the heat exchanger and tighten them diagonally until the package of plates reaches the size measured before disassembly.

10 Connect the inlet pipes and fill the heat exchanger with the working fluid. The pressure rise rate should not exceed 10 bar per minute.

11 After assembly, test the heat exchanger with a pressure of 1.25 times the operating pressure.