Figure 1. Four different connection configurations are illustrated.
Condensate, of course, accumulates in the bottom of the jacket. Therefore, if the jump-over is at the top (Configuration A), then the jacket fills up with condensate, which has a much lower heat-transfer coefficient than condensing steam. Many applications will completely fail if the pipe fills with condensate.
Additionally, the condensate increases the pressure drop through the system. Steam pressure decreases dramatically toward the last pipe segment before the condensate return. At lower pressure, the condensate may not be able to enter the condensate return system or the steam may no longer be hot enough to meet process conditions.
Configurations C and D both take the steam and condensate mixture from the bottom and send it to the top of the next pipe. In the rising part of the jump-over, the two-phase mixture creates a static head. Downstream pressure may be lower than expected. As long as the pressure drops through the jacketing system are understood and have been allowed for, Configuration D works well.
However, the steam connections from one segment to another are rarely engineered to the same level as process systems. Often, these connections are left to field installers to fit. If the jump-over goes too high (as shown in Configuration C), the extra height increases the pressure drop through the system. This may not seem like much in a single jump-over, but five, 10 or 20 jump-overs like this in a row can have a big impact.
Configuration B, while less common, takes the steam and condensate mixture from the bottom of the pipe and returns it to the bottom of the next section. This works well and has few problems.
