I. Complete Plate Heat Exchanger Cleaning Process - 6 Steps
① Shut Down and Disassemble the Plate Heat Exchanger
Close all inlet and outlet valves of the plate heat exchanger and drain the fluid remaining inside the unit. For floor-mounted plate heat exchangers, the unit can be removed from the system. Replace the original clamping bolts with specially prepared extended disassembly bolts, then loosen the clamping bolts evenly to disassemble the equipment for cleaning.
② Remove the Heat Transfer Plates
For frame-type plate heat exchangers, the unit can be removed from the system. Loosen the clamping bolts evenly and remove them. Move the movable pressure plate toward one end of the support frame. Tilt the upper end of each heat transfer plate toward the movable pressure plate, then remove the plate from the suspension opening on the upper guide bar. The lower end of the heat transfer plate can then be separated from the lower guide bar before the plates are completely removed.
③ Clean the Heat Transfer Plates
When cleaning the heat transfer plates, use copper wire brushes or fiber brushes. Steel wire brushes must never be used, as they may damage the surface of the plates and reduce their corrosion resistance.
Care should also be taken not to damage the gaskets during cleaning. After the heat transfer plates have been thoroughly cleaned, rinse them with clean water and wipe the gaskets with a clean cloth or cotton fabric.
④ Replace Aged Gaskets
Aged or deteriorated gaskets should be replaced. For gaskets that need to be bonded with adhesive, first remove the old gasket and thoroughly clean the gasket groove on the plate.
Then, secure the new gasket in place with an appropriate adhesive and keep it flat while allowing it to cure for 24 hours. After the adhesive has fully cured, the heat exchanger can be reassembled and clamped to the specified L dimension.
⑤ Loosen the Bolts During Long-Term Storage
If the plate heat exchanger will remain out of service for an extended period, loosen the clamping bolts until the dimension reaches 1.1–1.2L. After the heat exchanger is put back into operation, tighten the bolts again according to the specified requirements.
During normal operation, if any medium is found leaking from the signal holes, the cause should be investigated.
If the leakage is caused by loose clamping bolts or elongation of the bolts due to long-term heat exchange operation, the heat exchanger should be re-tightened according to the specified requirements. However, do not overtighten the bolts, as excessive compression may damage the heat transfer plates.
If the leakage is caused by aged or deteriorated gaskets, the gaskets should be replaced.
II. Plate Heat Exchanger Cleaning Methods
There are three main methods for cleaning the plates of a heat exchanger:
Backflushing / reverse flushing without disassembly,Manual cleaning with the heat exchanger disassembled,Chemical cleaning without disassembly.
(I) Cleaning Methods
① Manual Cleaning
When the scale or deposits on the heat transfer plates are relatively thin and insoluble in water, the plates can be removed and cleaned individually.
Use pressurized water at 0.1–0.2 MPa or low-pressure steam with water to flush away the deposits.
For deposits that are difficult to remove with water, use a soft fiber brush or soft-bristle brush for cleaning.
② Chemical Cleaning
Hard deposits, such as oxides or carbon deposits, may accumulate on the surface of the heat transfer plates, especially in dead zones where the medium has limited flow.
When these deposits cannot be effectively removed by manual cleaning, an appropriate chemical cleaning solution can be selected according to the material of the heat transfer plates.
(II) Selection of Cleaning Agents
Acid cleaning is currently one of the most commonly used chemical cleaning methods. Both organic and inorganic acids can be used.
Common organic acids include:
- Oxalic acid
- Formic acid
Common inorganic acids include:
- Hydrochloric acid
- Nitric acid
① Pre-Flushing
Before acid cleaning, flush the heat exchanger thoroughly with clean water to remove mud, dirt, and other impurities from inside the unit.
This can improve the effectiveness of the acid cleaning process while reducing acid consumption.
② Fill the Heat Exchanger with Cleaning Solution
Introduce the cleaning solution into the equipment and then fill the heat exchanger completely with the cleaning solution.
③ Acid Cleaning
After the heat exchanger has been filled with the acid cleaning solution, allow it to soak for 2 hours.
Then perform dynamic circulation cleaning for 3–4 hours, with the flow direction alternated between forward and reverse circulation at 30-minute intervals.
After acid cleaning, if the pH value of the remaining cleaning solution is greater than 2, the solution can be reused. Otherwise, the solution should be neutralized and properly diluted before disposal.
④ Alkaline Cleaning
After acid cleaning is completed, prepare an alkaline cleaning solution using NaOH, sodium compounds, phosphate, and softened water in the appropriate proportions.
Circulate the alkaline solution dynamically through the heat exchanger to neutralize any remaining acid and prevent corrosion of the heat transfer plates.
⑤ Water Rinsing
After alkaline cleaning, repeatedly rinse the heat exchanger with clean softened water.
Continue rinsing for approximately 0.5 hours to ensure that all remaining cleaning agents, residues, and deposits are completely removed from inside the heat exchanger.
⑥ Record the Cleaning Process
During the cleaning process, record the duration of each cleaning stage accurately so that the effectiveness of the cleaning process can be evaluated.
In simple terms, the heat exchanger should undergo a pressure test after cleaning. It should only be returned to service after the test confirms that the equipment meets the required standards.
(III) Measures to Prevent Scale Formation
(1) Strictly Control Water Quality During Operation
Water quality must be strictly controlled during operation.
The water circulating within the system and the softened water in the softening tank should be regularly tested. Only water that meets the required quality standards should be allowed to enter the piping network.
(2) Isolate the Heat Exchanger When Starting a New System
When a new system is put into operation, the heat exchanger should initially be isolated from the system.
After the system has been circulating for a certain period of time, the heat exchanger can then be connected to the system.
This helps prevent impurities and debris from entering the heat exchanger and causing blockage.
(3) Keep the Entire System Clean
In addition to regularly cleaning strainers and filters, the entire piping network should be kept clean.
Regular maintenance and cleaning can help prevent impurities from entering the plate heat exchanger, reducing the risk of blockage and scale buildup.
