Mitsubishi Electric PLFY-WP VBM-E, Data Book

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3. SYSTEM DESIGN GUIDE
2 - 64
WR2
MEE15K052
<Maintaining plate heat exchangers>
Plate heat exchangers must be maintained in a planned and periodical manner to prevent scale formation, which may
cause performance loss or decrease water flow rate that result in freeze damage to the plate heat exchanger.
 Check the following items before the operating season.
1. Check that the water quality meets the specified water quality.
2. Clean the strainers.
3. Check that the water flow rate is adequate.
4. Check for proper operation (e.g., pressure, flow rate, inlet/outlet temperatures).
 Plate heat exchangers cannot be disassembled for cleaning. Clean them in the following way.
1. Make sure that there is a pipe connection port on the water inlet pipe.
Use formic acid, citric acid, oxalic acid, acetic acid, or phosphoric acid diluted to 5% to clean plate heat exchangers.
Do not use highly corrosive acids, such as hydrochloric acid, sulfuric acid, or nitric acid.
2. Make sure that valves are installed before the inlet connection port and after the outlet connection port.
3. Connect a pipe for circulating cleaning solution to the inlet/outlet pipes of the plate heat exchanger, fill the plate heat
exchanger with cleaning solution at a temperature between 50 and 60°C, and circulate the cleaning solution with a
pump for 2 to 5 hours. The cleaning time will depend on the temperature of the cleaning solution and the degree of
scale formation. Use the color of the cleaning solution as a guide to determine how long the system needs to be
cleaned.
4. When done, discharge the cleaning solution out of the plate heat exchanger, fill it with sodium hydrate (NaOH) or
sodium bicarbonate (NaHCO
3
) diluted with water to 1 to 2%, and let the solution be circulated for 15 to 20 minutes
until the cleaning solution is neutralized.
5. After neutralizing the cleaning solution, thoroughly rinse the plate heat exchanger with clean water.
6. When using a commercially available cleaning solution, make sure to use a solution not corrosive to stainless steel
or copper.
7. Consult the cleaning solution manufacture for details.
 At the completion of cleaning, check the system for proper operation.
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