Disassembly and Inspection of Plate Heat Exchangers

Plate heat exchangers, known for their high efficiency, are widely used in industries such as chemical, pharmaceutical, and power generation. Their compact structure and excellent heat transfer performance make them a preferred choice. However, during prolonged use, plates may suffer from wear, scaling, or other damage, which is why regular disassembly, inspection, and maintenance are essential. This article provides a detailed guide on the precautions and steps for disassembling and inspecting plate heat exchangers, assisting operators in performing maintenance tasks safely and efficiently, ensuring the long-term stable operation of the equipment.

Preparation Before Plate Heat Exchanger Disassembly

 

Proper preparation before starting the disassembly process is crucial for a smooth operation and accurate reassembly.

1. Measure and Record the Compression Length

 

Before disassembly, measure the compression length of the plate bundle and record it. This dimension is critical when reassembling, as it ensures the plates return to their original compression force, maintaining the heat exchanger's heat transfer efficiency and sealing performance.

2. Handling Sealing Gaskets

 

If sealing gaskets are stuck in the grooves between the plates during disassembly, handle them carefully. A screwdriver can be inserted into the easy-to-peel areas of the gasket to gently separate it along the edges, ensuring no damage occurs to the plates or gaskets. If the gaskets are too rigid or adhesive, apply liquid nitrogen to rapidly cool and deform the gasket before removal.

3. Clean the Sealing Grooves

 

When replacing gaskets, the sealing grooves must be thoroughly cleaned. Acetone or other ketone-based solvents can be used to remove any residual adhesive, dirt, or old gasket remnants. Afterward, apply an even coat of adhesive with a brush to ensure good adhesion between the new gasket and the groove.

Plate Heat Exchanger Inspection and Cleaning

 

After disassembly, inspect and clean the various components of the plate heat exchanger. Address any issues promptly to maintain the equipment's optimal performance.

1. Plate Inspection

 

Examine each plate with a magnifying glass of at least five times magnification. Focus on checking for perforations, cracks, dents, or deformation. To further inspect, illuminate the plate surface or use a kerosene penetration method to check for potential leakage issues.

2. Check for Debris Accumulation

 

Inspect the inlet and outlet passages of the heat exchanger for any debris buildup, which could indicate a failure of the filter. In such cases, clean and replace the filter promptly to prevent any disruption in heat exchanger operation.

3. Plate Cleaning

 

Select the appropriate cleaning method based on the heat exchanger's operating conditions and the extent of fouling:

Backflushing: This method does not require disassembly and removes deposits by reverse flushing.

Manual Cleaning: After disassembling the exchanger, clean each plate individually. This method is suitable for light fouling.

Chemical Cleaning: For stubborn deposits, use specialized chemical solvents to clean the plates thoroughly.

For difficult-to-remove deposits, use a soft fiber or bristle brush to gently scrub the surfaces, avoiding any scratching.

4. Dealing with Hard Deposits

 

Hard deposits, such as oxides or carbides, may accumulate on the plate surfaces, particularly in dead zones where the medium flows. These deposits can be difficult to remove with manual cleaning, so chemical solvents specific to the plate material should be used. For stainless steel plates, avoid using wire brushes to prevent accelerating corrosion.

5. Water Quality Requirements

 

Ensure that the cleaning water is free from salts, sulfur, or other contaminants that may adversely affect the plate material. After cleaning, thoroughly rinse the plates with clean water and wipe them with fine cloth to ensure no water spots or residues remain.

Plate Heat Exchanger Disassembly Steps

 

Follow the proper sequence during disassembly to ensure each step is executed effectively without causing damage to any components.

Measure and Record Compression Length: Begin by measuring the compression length of the plate bundle and recording the data to support reassembly.

Remove Clamping Bolts and Plates: Proceed by removing the clamping bolts one by one and carefully separate the plates. Be cautious not to damage or lose any parts during this process.

Remove Sealing Gaskets: Use appropriate methods, such as liquid nitrogen treatment, to remove the sealing gaskets. Ensure that the plates and gaskets are not damaged during the removal.

Clean Adhesive Residues and Dirt: After gasket removal, clean the sealing grooves to remove any residual adhesive or dirt to ensure the new gasket will adhere properly.

Check Plate Conditions: Examine each plate for cracks, perforations, dents, or deformation. If any damage is found, repair or replace the plates to maintain proper heat exchanger function.

Plate Heat Exchanger Reassembly and Commissioning

 

After completing inspection and cleaning, begin reassembling the plate heat exchanger, paying particular attention to detail to ensure proper sealing and operational efficiency.

Sealing Groove Treatment: Before reassembly, clean the sealing grooves and apply the appropriate adhesive (e.g., Type 401 adhesive) to bond the new gaskets within the grooves.

Assemble Plates: Arrange the plates neatly in groups of 50 and compress them using 20-30mm wide steel plates. After assembly, cure the plates at a temperature of 30–35°C for 24 hours to ensure proper bonding of the gaskets.

Install End Covers and Bolts: Once the curing is complete, gently compress the end covers and install the fixing bolts. Use a torque wrench to tighten the bolts evenly, ensuring uniform compression of the plates.

Measure Total Compression Length: After reassembly, measure the total compression length of the plate bundle again to ensure it matches the pre-disassembly measurement and that the compression is uniform.

Install Inlet and Outlet Liner Sleeves: After securing the plates and end covers, install the inlet and outlet liner sleeves to ensure smooth fluid flow through the heat exchanger.

Pressure Test: Perform a pressure test by sealing one side of the fluid passage, filling it with water, and applying a pressure 1.5 times higher than the operating pressure for 30 minutes. If the pressure remains stable without issues, connect the external piping for further testing.

Plate Heat Exchanger Disassembly Precautions

 

During disassembly, cleaning, and reassembly, operators should pay special attention to the following:

Protecting Components: Protect all parts from damage or loss during disassembly and cleaning.

Cleaning and Maintenance: Ensure thorough cleaning and maintenance of all components to reduce the risk of future failure.

Special Material Handling: For plates made of special materials like titanium, avoid exposure to open flames during disassembly to prevent oxidation.

By strictly following the disassembly and inspection steps, the plate heat exchanger can be restored to its optimal condition after maintenance, improving its efficiency and service life.

Conclusion

 

Disassembly and inspection of plate heat exchangers are crucial for ensuring efficient operation and extending their service life. Accurate measurement of compression length, careful cleaning of sealing grooves, inspection for plate damage, and the selection of appropriate cleaning methods can enhance equipment performance and prevent failures. Proper reassembly, including the correct installation of all parts and pressure testing, ensures tight sealing and effective heat exchange. Regular inspection and maintenance can help detect issues early, minimize downtime, and reduce repair costs, ultimately increasing the return on investment for businesses.