Regarding the installation of bypasses and inlet/outlet valves for heat exchangers, under what circumstances is a bypass necessary?

As title: 1. Ordinary bottom reboilers of types BIU and BKU do not have valves installed; in the event of an internal leak in the tube bundle, it cannot be isolated. 2. Generally, there are no valves at the air cooler inlets, so if any air cooler leaks, it cannot be isolated either, and the entire tower has to be purged along with it. 3. Typically, individual air coolers do not have bypass lines (there is a main heat bypass in some cases, but not in others). 4. In hydrogen-related systems, such as the heat exchangers at the inlet and outlet of hydrogenation reactors, there are no bypass lines either; in the event of an internal leak, operations must be stopped for repairs........................ Question: 1. Under what circumstances is it necessary to add isolation valves to heat exchange equipment? Cut-off valves are generally available; I don’t understand what you mean Another point is that there is no reboiler, and it cannot be added casually. 2. Under what circumstances is it necessary to add a bypass for cold exchange equipment? This is still determined by the design institute; additionally, it is designed and installed based on your own requirements. We design and install things according to our own actual conditions, and for any issues that require suspension of operations, we add auxiliary lines. As long as it’s possible to reduce production volume and carry out repairs promptly to restore normal operation, nothing else is needed. 3. Under what conditions is it necessary to add a thermal bypass for air cooling, and under what conditions is no thermal bypass needed? In such cases, is pressure controlled entirely by the fans and recirculation? What you mean is the air cooling for liquefied gas; nothing else, right?

Question: 1. Under what circumstances is it necessary to add a shut-off valve for cold exchange equipment? Cut-off valves generally have them ； The shell side of the reboiler, which is connected to the bottom of the tower, is driven by thermosiphon action and generally does not have valves. 2. Under what circumstances is it necessary to add a bypass for cold exchange equipment? If it can be cut out for processing, a bypass can be added. In other words, even bypasses that are cut to prevent operation and force a shutdown are useless. 3. Under what conditions is it necessary to add a thermal bypass for air cooling, and under what conditions is no thermal bypass needed? In such cases, is pressure controlled entirely by the fans and recirculation? Thermal bypass is mainly considered during the design phase.

This is still determined by the design institute; additionally, it is designed and installed based on your own requirements. We design and install things according to our own actual conditions, and for any issues that require suspension of operations, we add auxiliary lines. As long as it’s possible to reduce production volume and carry out repairs promptly to restore normal operation, nothing else is needed.

If there are 2 reboilers, is it necessary to install valves on the shell-side fluid?

The last edit to this post was made by longziyun on 2019-1-24 at 13:14. For reboilers that operate in a primary/backup configuration, there are generally two possibilities: First, both reboilers use the same heating source; since the medium can easily form scale or polymerize and block the tube bundles, if the heat exchange efficiency of one reboiler declines, it is possible to switch to the other one, while the problematic reboiler is taken out of service for repair； In another scenario, two reboilers use different heating sources; for example, one uses low-pressure steam while the other uses hot water. Due to differences in season or processing procedures, the temperature levels of these heat sources vary, which in turn results in different heat values. Using hot water for heating can help save steam, etc. The two heat exchangers are designed to be able to switch between different heat sources for energy-saving purposes. In such cases, to prevent uneven flow and ensure stable operation, it is also necessary to shut down the other reboiler. In either case, two reboilers, one in service and one as a backup, require isolation valves on both the tube side and the shell side.

It was taken off track by the moderator. I haven’t heard of bottom reboilers being equipped with cross-line designs, and top condensers, usually either individual units or in groups, also don’t have cross-lines installed ； As for whether cross-connections are used in other heat exchangers, they serve as means for adjusting process parameters such as flow rate, temperature, and pressure, with devices like three-way valves being the most typical examples. In most cases, cross-connections are used to prevent leaks of the medium (which may be toxic, harmful, highly heated, or flammable/explosive), both internal and external leaks. Under conditions where it has minimal impact on process operations and where production safety and product quality can be maintained under control, the heat exchanger can be disconnected for separate handling.