You don’t need to be an expert technician to troubleshoot a plate heat exchanger (PHE). PHEs are reliable, but they occasionally experience performance issues. The three most common problems with PHE are leakage outside the cell, leakage within the cell, and pressure drop. Most of these problems are easy to identify and fix.
This article will help you identify the issues with your plate heat exchanger and guide you on how to fix them. Most problems are caused by plate fouling or gasket failure, so it’s important to determine if it’s a one-time problem or a system defect. The first step is to identify the cause of the heat exchanger failure.
Identify symptoms
Here are some of the most common symptoms:
- The pressure drop from the inlet to the outlet increases.
- Heat transfer efficiency is deteriorating.
- Both flow rate and performance are affected.
- Leakage during operation.
The first three symptoms are usually caused by plate fouling, while the last one is caused by gasket failure. However, any of these four symptoms can be caused by either gasket failure or a rare plate crack. Therefore, it’s crucial to follow some basic procedures to identify the issue accurately.
Differential Leaks and Gasket Failure
When troubleshooting, it’s usually best to start with the most likely problem, as it has the simplest and cheapest solution. Gasket failure is easy to spot: if a gasket fails, the pressure will force fluid to leak, and you’ll see fluid dripping from the PHE. You can easily detect the failure by checking for seepage from the faulty gasket. Disassemble your PHE and remove the plate with the failing gasket, as well as the adjacent plate. If you have new parts available, simply replace them, reassemble the PHE, and tighten it to the specified specifications before putting it back into service. If you don’t have replacement components on hand and can’t wait for them to arrive, you can temporarily close your plate heat exchanger and put it back into service while you wait. The loss of two plates will have minimal impact on performance. However, be cautious and ensure you know how much to tighten the PHE since there are two fewer plates. This information should be in your manual or available from the manufacturer.
A differential leak occurs when two fluids mix in the PHE due to a device failure. Incompatible fluids and/or high pressure are the most common causes of gasket failure. Make sure your pressures are within the specified limits (and that your system is free from potential water hammers) and that your gaskets are suitable for the materials you’re using. If your gaskets develop holes, it’s likely that your fluid is too hot or corrosive. In this case, you’ll need to replace the gaskets with new ones that are better suited for your operation.
External leakage
Damaged gaskets or errors in unit assembly are the most common causes of fluid leakage. Start by measuring the distance between the front plate and the pressure plate. The device’s instructions should provide you with this measurement. If the measurement is larger than usual, you need to tighten the unit by ensuring that all bolts are tightened evenly. If the unit continues to leak after tightening, mark the plates that are leaking if the measurement is accurate. After removing the heat exchanger, check the designated plate and replace the gasket. You can find instructions on how to replace the gasket in our heat exchanger brochure.
Leakage inside the unit (liquid mixing)
If the fluids inside the device start to mix, it’s likely that the plates within the device are leaking. The plate is most likely to be blamed. You can verify this through a stress test. Fill the unit halfway with water and pressurize only one side. If there is an unpressurized side of the perforated plate, it will overflow. Apply consistent water pressure on one side of the unit to get started (never use compressed air in a PHE). Fill the other side of the device with water, but do not apply pressure on that side. If the plate is perforated, the compressed side will seep into the uncompressed side, causing overflow. If the heat exchanger has two sections, each section must be tested independently. If the plate is perforated, disassemble the machine and inspect the plate with gap detection fluid.
ACE brewery with plate heat exchanger
Corrosion and Plate Fouling
Plate fouling is the most common problem with PHEs, but it’s difficult to fix because it’s usually not covered by warranty. If your PHE frequently becomes fouled due to the characteristics of your process fluid, there isn’t much you can do except clean it regularly. You can consult your manufacturer about adding plates with wider spacing, but this solution has performance and cost limitations and may not be suitable in all situations. In general, the best approach is to establish a regular cleaning plan. The most convenient method is cleaning in place (CIP), but manual disassembly and cleaning are also options.
Corrosion of the plates is a more serious problem than simple fouling. A differential leak is also present in this case. You can continue to use your plate heat exchanger in the same way, but a cracked or corroded plate indicates that one of your fluids is excessively corrosive, and you may encounter the same problem again. Make sure your PHE is correctly specified for your application by checking with your manufacturer. If everything seems to be in order, the crack or rust is most likely a manufacturing defect that will be covered by warranty.
Abnormal Heat Transfer and/or Pressure Drop Performance of the PHE
There are a few tests you can run to determine why your heat exchanger is not performing as well as it should. The most common problem with heat exchangers is poor performance, which can be caused by various factors such as plugging errors, insufficient water flow, debris buildup inside the device, or improper connection.
Plugging errors:
If the plates are incorrectly joined, a dead zone can form, causing the unit to bypass a portion of the plates. Examine the plates to ensure they are arranged in a honeycomb design. It may be difficult to spot the pattern change at first, so watch out for any plates placed in the wrong direction. If a plate is out of place, you need to open the heat exchanger and rotate the plate to the correct position. Close the device and retest the pressure once all plates have been adjusted.
Insufficient water flow:
The heat exchanger will experience reduced efficiency if the water flowing into the unit is insufficient. Check the water pressure and flow rate to ensure they are within the specified limits.
Debris in the unit:
Debris inside the unit can reduce performance. To remove any excess debris, run a regular CIP cycle. If the debris persists, manual cleaning may be required. Cleaning a heat exchanger by hand is relatively simple, and the Heat Exchanger Manual provides detailed instructions.
Faulty connection:
If the connection is incorrect, the unit will operate at very low efficiency. Check the operating and setup instructions to ensure that it’s functioning properly. Remember that countercurrent flow is essential.
Things to remember
Plate heat exchangers can be challenging to assemble if you’re not familiar with the plate configuration. Before removing the plates from the unit, make sure to number them accordingly.
