Repair of heat exchangers of brazed plate heat exchangers
In all situations, we strongly recommend monitoring the pressure drop on the heat exchangers and performing dry cleaning when the maximum pressure drop value corresponding to this installation is reached. It can be argued that the level of heat transfer characteristics depends on the frequency of cleaning.
Note! Preserve the environment: always use only environmentally friendly waste containers.
If we talk about the most effective way to clean the heat exchangers, then we should start with dry cleaning. Thanks to on-site cleaning, it is possible to achieve effective cleaning of the heat exchanger, without the need to open it. We should start by choosing a chemical for cleaning that can remove deposits and is compatible with the materials used to make the heat exchanger. The application of this method makes it possible to reuse the solution for cleaning and eliminate the need for disassembling heat exchangers, thereby reducing equipment downtime. The direction of the circulating solution during the cleaning process should be from bottom to top. The amount of the consumable solution should, if possible, be about 50 percent of the nominal value.
With regular cleaning, with equal intervals of time, the effectiveness of this type of washing will be the highest, and the removal of sediments will be optimal.
After completing the chemical cleaning procedure, it is necessary to take care of careful flushing of the heat exchanger and its drying.
Attention! It is forbidden to use hydrochloric acid for cleaning.
Due to too late cleaning, blocking or excessive clogging and extremely difficult or almost impossible restoration of the original thermal parameters can be encountered.
Mechanical cleaning procedure
If it is not possible to use chemicals for cleaning, it is necessary to start with the removal of the panels in order to provide access to the heat exchange surfaces.
Cleaning with water or steam under pressure (high-pressure jet can be used up to 1000 barg). It is not allowed to exceed 1000 barg.
The angle of inclination of the grooves is 45 degrees, therefore it is possible to reach the heat exchange surfaces by turning the washing device at the same angle equal to 45 degrees (it is talked about a washing rod or a nozzle of a jetting machine).
Attention! Before the opening of the brazed plate heat exchangers, it is necessary to make sure that there is no liquid in the unit. If liquid is present, it is necessary to take care of its removal in order not to pollute the atmosphere.
After completing the assembly, it is necessary to do hydraulic tests. If there was no repair of parts of the equipment, the level of test pressure can reach 1.1 of the nominal pressure, which is indicated on the brazed plate heat exchanger passport plate (leak test).
- Hydraulic testing is possible only with one empty circuit and another circuit filled in which the test pressure is provided.
- Reducing the pressure inside the test circuit is possible due to the easy fit of the plates or the compression of trapped gas. Leakage from the heat exchanger should not be allowed. It is necessary to monitor the test pressure, which will take about half an hour to stabilize.
Not tightness of the heat exchanger occurs at leakage between 2 circuits or leakage to the outside.
Attention! When performing hydraulic tests, it is necessary to fully install and tighten all 4 panels.
3. Works on troubleshooting.
4. Leak detection work.
5. Causes of external leakage.
External leakage is usually caused by faults associated with gaskets, panel cladding or core.
6. Leakage through gaskets
The leakage through the gaskets can be determined by the presence of dropping a liquid and accumulating it on the floor. It is necessary to make sure that the gasket is installed correctly, to tighten the panel if possible, or to replace the gasket.
7. Leakage through panel cladding
This leakage can be determined by the fluid that escapes through the hole for argon, which is located next to the butt weld on the flange tube. By leakage, it is possible to judge the occurrence of a crack or pinpoint incomplete penetration of the panel lining. Turning off the heat exchanger should be immediate. Carrying out color flaw detection will help confirm the source of the leak.
Often the reason for this is a complete vacuum or a sudden sharp partial vacuum. It is necessary to check the calculation of the heat exchanger for these parameters.
8. Leakage from the core
When confirming the tightness of the gasket and panel cladding, external leakage is possible in the core itself.
Problem with internal leakage
This leakage occurs when mixing both flows. This leads to cross contamination of both circuits. It is necessary to turn off the heat exchanger, drain all the contents, remove the panels. After that, it is necessary to study the color flaw detection of the welds, in order to determine the exact cause of the leakage.