Jacketed piping features a core pipe which is completely surrounded by a jacket pipe. Process flows through the core pipe, while a heating medium (or cooling medium) flows in the annular space between the core and jacket pipes. This allows the heating medium to directly contact the entire surface of the process pipe, providing maximum surface area and heat transfer to the process pipe.
Since the heating medium is in direct contact with the entire process pipe surface area, jacketed pipe provides maximum heat transfer to the process. Heat transfer to the process is only limited by the process convection coefficient. For these reasons, jacketed piping possesses maximum thermal capability for bulk temperature maintenance, wall temperature maintenance, and heat exchanger applications (including melt out).
Safety and Reliability
Jacketed pipe offers the highest thermal reliability due to its ultimate thermal capability. However, its operational reliability is also affected by the fabrication quality. There are many concealed welds in jacketed piping, and if any of these welds fail, cross contamination can occur between the heating medium and the process. This can create costly production issues due to product contamination as well as the time spent trying to find the leak source. Some plants have prohibited the use of jacketed pipe due to safety concerns resulting from cross contamination. In one particular plant, a jacket weld failed allowing steam to mix with an H2S vapor stream. This contamination went undetected until the plant came down for a turnaround. With the steam flow to the jacket turned off, residual H2S in the core piping was able to enter the jacketing and resulted in a serious safety incident for an employee who was working downstream on the steam system.
Jacketed piping systems are generally the most expensive due to increased material (over twice the material required for process piping), significantly more fabrication labor than process piping, and additional pipe routing required for thermal expansion. Since the core and jacket must be built concurrently (because the jacket cannot be slipped completely over core fittings and flanges), and additional NDE is often required for the concealed welds, jacketed pipe can require 5-8X more fabrication labor than process piping. Also, as the core pipe size increases, non-standard wall thicknesses are often required to withstand the external pressure on the core pipe (from the jacket), and this can become cost-prohibitive. Finally, due to its maximum heat transfer rates, jacketed piping results in large heating medium consumption rates, and this increases the ongoing energy costs required to support the system.