Sizing of condensate lines is calculated differently from sizing other fluids transferred in pipes. Although condensate is hot water, sizing a condensate line as if it were hot water would result in an undersized line. Undersized condensate lines will create excessive backpressure in the system, as well as maintenance and process problems throughout the system. The key item to remember is that there are two major differences between condensate and hot water. Condensate lines will contain two phases, condensate (liquid) and flash steam (gas.) Therefore, the correct size of a condensate line is somewhere between a hot water line and a steam line. With proper knowledge, a condensate line may be sized for the following:
Condensate liquid load
Flash steam load
This is defined as steam loss resulting from faulty steam traps or open bypass valves. This is more common in systems than typically acknowledged. Blow-by steam will add steam flow to the return line and must be included in the calculations. Condensate that is free of flash steam may be pumped and sized as liquid only (single phase flow). Condensate pipe velocities (liquid and flash steam) must be lower than 4500 feet per minute to prevent system waterhammer and other damaging effects. Condensate piping velocities (liquid only) must be lower than 7 feet per second.
Correct Identification of Condensate Type
The placement of condensate return lines is crucial to insure proper operation of the process equipment. The first step is to understand and identify the type of the condensate line.
The role of steam distribution lines is to reliably supply steam of the highest reasonable quality to the steam-using equipment. In order for this to be achieved, condensate must be removed quickly and efficiently through steam traps installed in proper condensate discharge location (CDL) installations.
Steam traps can't, however, simply be installed any which way and forgotten. There are certain guidelines to follow when installing them on steam lines. To ensure that steam traps operate properly, trap installation methods must be carefully respected and installation locations carefully chosen.
Steam traps should be installed in the following situations:
Every 30 to 50 meters (100 to 160 feet)
Traps should be installed at 30 to 50 meter (100 to 160 feet) intervals on a steam line.
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