How to detect a heat exchanger leak?

Since you mentioned circulating water, what you probably want to ask about is the cooler. Generally, it is possible to make an approximate assessment based on the color and odor of the oil floating on the water’s surface. It is also possible to check by releasing air from the drain valve of the cooler’s return water valve to see if there is oil present; this should allow for an accurate determination!

Generally, it can be roughly determined from the water line drain of the cooler, but it becomes difficult to judge when there are multiple units. I’m afraid it’s just a minor leak. That’s exactly what’s worrying us right now, isn’t it? Our current secondary line is a condenser, and it cannot be disconnected. No problems were found with the other devices either; only a slight amount of oil was present in the secondary line drain. The circulating water was also replaced, but it still doesn’t work.

Close the inlet and outlet on the other side. Run it on the other side; by observing whether any medium comes out, a judgment can be made.

If a circulating water cooler is used, in the event of a leak, the outlet temperature should increase slightly!

Yes, the heat exchanger should be regularly drained to check for leaks, using the method mentioned above； If the outlet temperature rises, it means there must be a significant amount of leakage. So, does anyone have a better way to detect minor leaks in heat exchangers? For heat exchangers in which both the tube side and the shell side contain oil as the medium, how should one determine the appropriate approach for handling them? I would like to learn more about this as well

Generally, there are condensate guides at the inlet and outlet of circulating water; if it’s oil, turn on the return water condensate guide to check for any oil droplets

In general, for coolers that use water as the cooling medium, the pressure of the cooling fluid is higher than that of the circulating water. You can open the drain valve at the outlet of the circulating water in the cooler; if oil is discharged, it can be determined that there is a leak in the cooler

In heat exchangers where both the tube side and shell side are filled with oil, external leaks can be detected by visual inspection; for example, oil seepage can be seen at the flanges. Internal leakage occurs when high pressure leaks to low pressure; generally, the raw materials leak towards the product, resulting in substandard product quality, as well as issues with color and impurity levels.

Take samples from the circulating water for analysis to determine what substance is leaking, and then make a judgment based on the process flow

For heat exchangers, it is possible to determine whether there is a leak by taking condensate samples at the outlet of the low-pressure medium and analyzing their composition. For coolers, water can be drained directly from the cooling water outlet to visually observe changes in water quality.

Let’s start with an intuitive analysis: 1. Changes in pressure drop in the tube side or shell side can generally be detected by examining the difference between the pressure of the water used for heating or cooling and the pressure of the fluid itself, which helps to identify any leaks； If both the inlet and outlet are gas or liquid, it is more intuitive to consider the pressure drop. 2. If using water, observe the changes in its properties before and after use, including color and odor. 3. Direct pressure testing 4. Disassemble for inspection.

⒈In the case of water cooling, generally when the pressure of the circulating water is lower than that of the working medium, the return flow drain valve for the circulating water is opened to check for any gaseous or liquid components of the working medium； ⒉Make full use of the flow meter to check for any changes before and after heat exchange ； ⒊Check the test results to see if there are any special changes in the properties of the material ； ⒋Upon detecting the presence of foreign objects, use the process of elimination to locate the leak in the heat exchanger ； ⒌During maintenance, the heat exchanger is pressurized for leak testing.

Isolation method for individual pressure testing or observation.

For water coolers, it is necessary to check whether there is oil in the water and whether there is water in the oil. If the properties of the oils are similar, samples can be taken for analysis of their flash points, etc. For heavy oil heat exchangers, it is possible to check whether the light oil side has changed color and whether the heavy oil has become lighter. Pressure drop can also be used as an indicator

1. Whether the oil in the tube side and shell side is contaminated. 2. Steam is introduced into one path to determine whether there is significant steam discharge under pressure in the other path. 3. Add water to the system; the judgment is the same as above. 4. In the shutdown state, pressure testing can be carried out in two stages to check whether the pressure gauge remains stable (holds pressure).

1. Whether the oil in the tube side and shell side is contaminated. 2. Steam is introduced into one path to determine whether there is significant steam discharge under pressure in the other path. 3. Add water to the system; the judgment is the same as above. 4. In the shutdown state, pressure testing can be carried out in two stages to check whether the pressure gauge can maintain a stable pressure.

When internal leakage is severe, the effects are quite evident in terms of operation: both the exit temperature on the feed oil side of the heat exchanger and the exit temperature of the reaction heating furnace increase. The color of the produced oil deepens, and in some cases emulsification of the produced oil occurs, making it difficult to remove light and heavy fractions as well as causing significant water content in the feed used for distillation. If the internal leakage is not severe and difficult to detect during operations, it is possible to periodically compare the nitrogen content in the refined oil and the light fraction oil. If the nitrogen content in the light fraction oil is significantly higher than that in the refined oil, it can be concluded that there is internal leakage in the heat exchanger between the crude oil and the reaction products.

1. External leaks from coolers during operation are relatively easy to detect. (1) For minor leaks of low-toxicity fluids, soap water or a foaming agent can be applied directly for inspection. (2) For medium to highly toxic substances for which leakage is strictly prohibited, apply a coating that is highly sensitive to such toxic substances to the areas prone to leakage (such as flanges and connections); if a leakage occurs, a change in the color of the coating can indicate it. 2. Internal leakage occurs in the cooler during operation, which is determined by sampling at the cooling water outlet. Such as oil, flavor, etc.

Water quality can be tested, such as by measuring COD and oil content