It’s all the plate exchanger that’s causing the problems!

It’s possible that when you parked the equipment in winter, the material from the plate heat exchanger ended up in the circulating water; or maybe one of the units leaked, causing that material to enter the circulating water system. Alternatively, thermal expansion and contraction of the plate heat exchanger might be the cause… As a result, the flow of material stopped and there was no pressure anymore. With the circulating water still running, how could any material get into the circulating water system?

The first items to consider should be the materials that have not been moved for a long time; while the circulating water continues to flow, thermal expansion and contraction can cause changes in the gap between the sealing surface of the circulating water and the materials, leading to leaks. When it is time to move the materials, large instantaneous temperature differences can cause this gap to widen further, resulting in increased leakage. Once thermal equilibrium is reached, the situation stabilizes within a certain range and the leaks cease. Here is a little of my analysis: loveliness:.

It’s equivalent to automatic repair after a leak occurs. Hehe, I really haven’t seen this happen before; if it’s missing, then it’s missing. It seems that your heat exchanger manufacturer has equipped the equipment with an automatic repair function.

My analysis is that when the medium flows on one side only, the pressure on that side is very high, which causes internal leakage; when the material flows on both sides, pressure exists on both sides as well, and the pressure difference decreases. In such cases, the plate exchanger may leak when the pressure on one side is high.

The issue of thermal expansion and contraction arises because the seals used in current plate exchangers are of the snap-type, rather than adhesive type. That’s why this kind of automatic repair-like situation occurs

Generally, the design pressure for plate exchangers is at least several dozen kilograms. In my opinion, it’s a bit far-fetched to think that leaks occur due to thermal expansion and contraction. I suspect that if there is a leak, it might be caused by the long period of use of the equipment, leading to the deterioration of the sealing rings (I’m not sure what type of sealing mechanism is used in the plate exchanger in question) As for the other one, is it possible that there’s no leakage, but rather a misjudgment due to the two units being connected in parallel? Once one is fixed, the other naturally won’t leak either!

The design pressure for plate exchangers currently does not exceed 3.5 MPa, neither in China nor abroad. Since no flow occurs on the material side while the circulating water continues to flow, this leads to a pressure imbalance between the hot and cold sides of the plate exchanger, causing water to leak onto the material side. It is recommended to stop both sides of the exchanger when it is shut down

I analyzed that it was likely the heat exchanger with a leak that caused an automatic backflow due to the pressure difference between the pipes; after it was repaired, the pressure balance was restored, so the other one did not need to be repaired

If there is a leak, it will recover automatically. I’m quite skeptical; in my opinion, the second unit doesn’t have any leaks at all

At that time, both plate heat exchangers were tested, and it’s undeniable that both of them leaked. For the second one, I removed the inlet and outlet ports for the fluid; even after doing that, leakage continued, though it gradually decreased until eventually there was no more leakage.

If the gasket is made of rubber, one thing that can explain this is that such gaskets have poor resistance to low temperatures. In winter, due to the low temperatures, the gaskets may harden and lose their elasticity, resulting in leaks. If the two heat exchangers are connected in series, once one starts operating, the temperature of the other also rises; as a result, the rubber gasket in that other unit regains its elasticity and its sealing ability is restored. Therefore, the leakage gradually decreases until it stops altogether.

LZ hasn’t described this issue very clearly, so it’s difficult to determine what caused the failure of the heat exchanger. Therefore, there are a few questions that the original poster needs to answer: 1. What exactly is the medium in question? 2. What material are the plates and gaskets made of? ； 3. What are the working pressures on each side? ； 4. What are the operating temperatures on each side? 5. How long has the rubber pad been in use? 6. How many times is it disassembled for maintenance per year? 7. What is the temperature in your area during winter? 8. How long was it parked in winter? Based on the problem you described, I would like to share my personal opinion here; please forgive me if there is anything wrong with it. 1. Since the side related to the circulating water isn’t closed, water flows between the plates; therefore I believe the water side won’t freeze and cause the plates to crack ； 2. Secondly, if water does not leak out but instead mixes with the material inside the chamber, this indicates that the gasket at the corner holes of the plates has failed to perform its sealing function, allowing the two media to mix within the chamber ； 3. After shutdown in winter, water continues to flow while the material flow has stopped; the large pressure difference on both sides can easily cause the gasket to fail ； 4. As for a unit that recovered automatically without the need for maintenance, I can only assume that it was because the pressures on both sides were equal after it started operating, resulting in a small pressure difference, which allowed the gasket to recover on its own.